ARCHIVED - Priority Substances List Assessment Report for Releases from Primary and Secondary Copper Smelters, Refineries - Releases from Primary and Secondary Zinc Smelters and Refineries

Environment Canada
Health Canada
2001
ISBN: 0-662-29871-3
Cat. No.: En40-215/62E

Canadian Environmental Protection Act 1999

Table of Contents

• List of Acronyms and Abbreviations
• Synopsis
• 1.0 Introduction
• 2.0 Summary of Information Critical to Assessment of "Toxic" Under CEPA 1999
  • 2.1 Identity
    • 2.1.1 Definitions and scope
      • 2.1.1.1 Smelters and refineries
      • 2.1.1.2 Releases
    • 2.1.2 Facilities included in assessments
    • 2.1.3 Release constituents examined
  • 2.2 Entry characterization
    • 2.2.1 Releases to air
      • 2.2.1.1 Sulphur dioxide
      • 2.2.1.2 Metals
      • 2.2.1.3 Particulate matter
      • 2.2.1.4 Carbon dioxide, nitrous oxide, methane and volatile organic compounds
    • 2.2.2 Releases to water
      • 2.2.2.1 Canadian Copper Refinery
      • 2.2.2.2 Canadian Electrolytic Zinc
      • 2.2.2.3 Cominco Trail Operations
  • 2.3 Exposure characterization
    • 2.3.1 Releases to air
      • 2.3.1.1 Sulphur dioxide
        • 2.3.1.1.1 Fate of sulphur dioxide in air
        • 2.3.1.1.2 Concentrations of sulphur dioxide in air
        • 2.3.1.1.3 Deposition of sulphate from air
      • 2.3.1.2 Metals
        • 2.3.1.2.1 Fate of metals in air
        • 2.3.1.2.2 Deposition of metals from air - empirical
        • 2.3.1.2.3 Deposition of metals from air - modelled
        • 2.3.1.2.4 Concentrations of metals in ambient air
      • 2.3.1.3 Particulate matter
        • 2.3.1.3.1 Fate of particulate matter in air
        • 2.3.1.3.2 Concentrations of particulate matter in ambient air
    • 2.3.2 Releases to water
      • 2.3.2.1 Fate and concentrations
        • 2.3.2.1.1 Canadian Copper Refinery
        • 2.3.2.1.2 Canadian Electrolytic Zinc
        • 2.3.2.1.3 Cominco-Trail Operations
  • 2.4 Effects characterization
    • 2.4.1 Ecotoxicology
      • 2.4.1.1 Releases to air
        • 2.4.1.1.1 Sulphur dioxide
        • 2.4.1.1.2 Sulphate deposition
        • 2.4.1.1.3 Metals (Cu, Zn, Ni, Pb, Cd, As)
      • 2.4.1.2 Releases to water
        • 2.4.1.2.1 Whole-effluent toxicity
        • 2.4.1.2.2 Derivation of CTVs and ENEVs
        • 2.4.1.2.3 Environmental effects monitoring
    • 2.4.2 Abiotic atmospheric effects
      • 2.4.2.1 Photochemical ozone creation
      • 2.4.2.2 Stratospheric ozone depletion
      • 2.4.2.3 Climate change
    • 2.4.3 Effects on human health - epidemiological studies of populations in the vicinity of copper smelters and refineries and zinc plants
      • 2.4.3.1 Studies of mortality and of cancer incidence
      • 2.4.3.2 Non-neoplastic effects
      • 2.4.3.3 Effects on reproduction and development
• 3.0 Aseessment oF "TOXIC" Under CEPA 1999
  • 3.1 CEPA 1999 64(a): Environment
    • 3.1.1 Copper smelters and refineries
      • 3.1.1.1 Releases to air
        • 3.1.1.1.1 Sulphur dioxide
        • 3.1.1.1.2 Deposited sulphate
        • 3.1.1.1.3 Deposited metals
      • 3.1.1.2 Releases to water (Noranda-CCR)
    • 3.1.2 Zinc plants
      • 3.1.2.1 Releases to air
        • 3.1.2.1.1 Sulphur dioxide
        • 3.1.2.1.2 Deposited sulphate
        • 3.1.2.1.3 Deposited metals
      • 3.1.2.2 Releases to water (Noranda-CEZinc and Cominco-Trail)
  • 3.2 CEPA 1999 64(b): Environment upon which life depends
  • 3.3 CEPA 1999 64(c): Human health
    • 3.3.1 Exposure assessment
    • 3.3.2 Effects assessment
      • 3.3.2.1 Exposure-response characterization for selected components of emissions from copper smelters and refineries and zinc plants
        • 3.3.2.1.1 Arsenic
        • 3.3.2.1.2 Cadmium
        • 3.3.2.1.3 Chromium
        • 3.3.2.1.4 Nickel
        • 3.3.2.1.5 Lead
        • 3.3.2.1.6 Sulphur dioxide
        • 3.3.2.1.7 Respirable particulate matter (PM₁₀)
    • 3.3.3 Risk characterization
      • 3.3.3.1 Arsenic, cadmium, chromium and nickel
      • 3.3.3.2 Lead
      • 3.3.3.3 Sulphur dioxide
      • 3.3.3.4 Particulate matter
    • 3.3.4 Uncertainties and degree of confidence in human health risk characterization
  • 3.4 Conclusions
    • 3.4.1 Releases from copper smelters and refineries
    • 3.4.2 Releases from zinc plants
  • 3.5 Considerations for follow-up (further action)
• 4.0 References
• Appendix A Search Strategies Employed for Identification of Relevant Data

List of Tables

• Table 1 Copper production facilities whose releases were assessed
• Table 2 Zinc production facilities whose releases were assessed
• Table 3 Releases of SO₂ to the atmosphere in 1995
• Table 4 Releases of metals to the atmosphere in 1995
• Table 5 Releases of total particulate (TP) matter, particulate matter less than or equal to 10 mm (PM₁₀) and particulate matter less than or equal to 2.5 mm (PM_2.5) to the atmosphere in 1995
• Table 6 Releases of carbon dioxide (C_O2), nitrous oxide (N₂O), methane (CH₄) and other volatile organic compounds (VOCs) to the atmosphere in 1995
• Table 7 Annual loading rates of effluent components
• Table 8 Factors applied to annual effluent loadings to estimate maximum short-term loading rates (maximum monthly and four-day mean loadings)
• Table 9 Concentrations of metals and other constituents in undiluted effluents
• Table 10 Growing season average SO₂ concentrations at monitoring stations located near copper and zinc production facilities
• Table 11 One-hour average SO₂ concentrations during the growing season at monitoring stations located near copper and zinc production facilities
• Table 12 Annual summary of 24-hour ambient air concentrations of SO₂ near copper smelters and refineries and zinc plants in Canada
• Table 13 Wet sulphate deposition rates in selected regions of eastern Canada for 1990-1993 estimated using the Integrated Assessment Model (IAM)
• Table 14 Wet sulphate deposition rates at monitoring stations located near two of the receptor areas considered in deposition modelling
• Table 15 Deposition of soluble metals in the vicinity of copper and zinc production facilities - based on dustfall sampling
• Table 16 Percent contribution of dry metal deposition to total metal deposition
• Table 17 Deposition of soluble metals in the vicinity of copper and zinc production facilities - based on total suspended particulate sampling
• Table 18 Deposition of soluble metals in the vicinity of copper and zinc production facilities - based on snowpack and combined ("wet plus dry") deposition sampling
• Table 19 Water-soluble metal fractions used in the estimation of bioavailable deposited metals
• Table 20 Estimation of annual regional background soluble metal deposition for the Canadian Shield
• Table 21 Mass emission rates of trace metals used in dispersion modelling assessment of releases to air from generic facilities
• Table 22 Trace metal release partitioning among high- and low-elevation and fugitive releases to air
• Table 23Maximum distance from facility where the modelled total soluble deposition rate exceeds the critical load
• Table 24 Annual average concentration of As, Cd, Cr, Ni and Pb in ambient air near copper smelters and refineries and zinc plants in Canada
• Table 25 Summary of estimated or measured concentrations of PM₁₀ (m g/m³) near copper smelters and refineries and zinc plants in Canada
• Table 26 Modelled annual average exposure concentrations for 1995 effluent discharges from the MUC-WWTP, and the percentage of each concentration attributable to CCR
• Table 27 Modelled maximum short-term exposure concentrations for 1995 effluent discharges from CEZinc, and the percentage of each concentration attributable to CEZinc
• Table 28 Modelled maximum short-term exposure concentrations for 1998 effluent discharges from Cominco-Trail, and the percentage of each concentration attributable to Cominco-Trail zinc operations
• Table 29 Acute and chronic CTVs and ENEVs for SO₂ derived for terrestrial vegetation
• Table 30 Background soil pore water metal concentrations and ENEVs derived for terrestrial endpoints
• Table 31 Critical loads of soluble metal for different terrestrial assessment endpoints
• Table 32 Background surface water metal concentrations and ENEVs derived for aquatic endpoints
• Table 33 Critical loads of soluble metal for different aquatic assessment endpoints
• Table 34 Results of whole-effluent toxicity tests
• Table 35 Estimated No-Effects Values (ENEVs) for aquatic organisms exposed to effluents
• Table 36 Risk quotients for exposure of vegetation to ambient SO₂ as a function of distance from copper and zinc production facilities
• Table 37 Risk quotients for wet sulphate deposition for four receptor areas in eastern Canada
• Table 38 Risk quotients for metal deposition as a function of distance from copper and zinc production facilities
• Table 39 Risk quotients for biota in the St. Lawrence River based on exposures calculated for annual average loadings from the MUC-WWTP, which receives effluent from the Noranda-CCR facility
• Table 40 Risk quotients for aquatic biota based on exposures calculated for maximum monthly or four-day average effluent loadings from the Noranda CEZinc facility to the Beauharnois Canal
• Table 41 Risk quotients for aquatic biota based on exposures calculated for maximum monthly or four-day average effluent loadings from the Cominco-Trail facility to the Columbia River
• Table 42 Summary of adverse health effects associated with particulate matter (epidemiological studies)
• Table 43 Total Exposure Potency Index for lung cancer mortality at sites near Canadian copper smelters and refineries and zinc plants

List of Figures

• Figure 1 Map of Trail, B.C., showing the outfalls and sampling locations considered in the assessment of aquatic releases from the Cominco facility
• Figure 2 Fiftieth percentile of total soluble deposition rates (mg/m²/a) estimated by dispersion modelling for copper emitted from a generic copper smelter
• Figure 3 Ninety-fifth percentile of total soluble deposition rates (mg/m²/a) estimated by dispersion modelling for copper emitted from a generic copper smelter

List of Acronyms and Abbreviations

a

annum (year)

Ag

Silver

As

Arsenic

CCR

Canadian Copper Refinery (Noranda)

Cd

Cadmium

CEPA

Canadian Environmental Protection Act

CEPA 1999

Canadian Environmental Protection Act, 1999

CEZinc

Canadian Electrolytic Zinc (Noranda)

CH ₄

methane

CL

critical load

CL ₂₅

25th percentile critical load

CL ₅₀

median critical load

C _O2

carbon dioxide

COPD

chronic obstructive pulmonary disease

Cr

chromium

CTO

Cominco Trail Operations

CTV

Critical Toxicity Value

Cu

copper

d/s

downstream

EC ₅₀

median effective concentration

EEM

environmental effects monitoring

EEV

Estimated Exposure Value

ENEV

Estimated No-Effects Value

EPA

Environmental Protection Agency

EPI

Exposure Potency Index

ERG

Environmental Resource Group

FIAM

free-ion activity model

GSC

Geological Survey of Canada

GSD

geometric standard deviation

HBM&S

Hudson Bay Mining and Smelting

Hg

mercury

IADN

Integrated Atmospheric Deposition Network

IAM

Integrated Assessment Model

K _d

distribution coefficient (ratio of bound:dissolved metal)

LC ₅₀

median lethal concentration

LD ₅₀

median lethal dose

LEL

Lowest-Effect Level

LOAEL

Lowest-Observed-Adverse-Effect Level

MEF

Ministère de l'Environnement et de la Faune du Québec

MMER

Metal Mining Effluent Regulations

MMLER

Metal Mining Liquid Effluent Regulations

MOE

Ministry of Environment

MUC

Montreal Urban Community

MWTP

municipal wastewater treatment plant

N ₂O

nitrous oxide

NAPS

National Air Pollution Surveillance network

Ni

nickel

NPRI

National Pollutant Release Inventory

OME

Ontario Ministry of the Environment

Pb

lead

PEL

Probable Effect Level

PLE

pressure-leach-electrowin process

PM

particulate matter

PM ₁₀

particulate matter less than or equal to 10 µm

PM _2.5

particulate matter less than or equal to 2.5 µm

PSL

Priority Substances List

RDIS

Residual Discharge Information System

RLE

roast-leach-electrowin process

RQ

risk quotient

Se

selenium

SEL

Severe-Effect Level

SMAV

Species Mean Acute Value

SO ₂

sulphur dioxide

SO ₄ ^2-

sulphate

TC ₀₅

tumorigenic concentration associated with a 5% increase in incidence of or mortality due to cancer

TD ₀₅

tumorigenic dose associated with a 5% increase in incidence of or mortality due to cancer

TEL

Threshold Effect Level

Tl

thallium

TP

total particulate

TSP

total suspended particulate

TU

toxic unit

VOC

volatile organic compound

WHO

World Health Organization

WWTP

wastewater treatment plant

Zn

zinc

Synopsis

Assessments of the two substances "Releases from primary and secondary copper smelters and copper refineries" and "Releases from primary and secondary zinc smelters and zinc refineries" have been conducted and reported together due to the similar nature of the two types of facilities and the common approach used in assessing their releases. For the purposes of these assessments, a smelter is defined as a facility that uses high-temperature chemical processes to recover base metals, while a refinery is a plant in which impurities are separated from metals using thermal or electrolytic processes. Zinc operations use integrated processes that are a combination of smelting and refining and are conventionally referred to as "zinc plants." The six copper smelters, four copper refineries and four zinc plants currently operating in Canada were considered in the assessments.

Releases from copper smelters/refineries and zinc plants are complex mixtures, containing varying amounts of numerous substances. Since most releases (on a mass basis) are discharged to air, and releases to air have the greatest potential for causing widespread effects, these assessments have focused on environmental and human health risks of air emissions. The components of releases to air that were examined most closely are sulphur dioxide (SO₂), the metals (largely in the form of particulate matter) copper, zinc, nickel, lead, cadmium, chromium and arsenic, and particulate matter less than or equal to 10 microns (PM₁₀). For facilities having multiple operations, source emission attribution was evaluated to estimate the fraction of ambient and deposited contaminants attributable to those operations that are the subject of these assessments.

Risk due to SO₂ released from copper smelters/refineries and zinc plants was assessed based on both direct exposure to SO₂ and associated acidic deposition. Effects thresholds for direct exposure to SO₂ were based on vegetation exposed for periods of 1 hour (acute) and one growing season (chronic). Results for direct exposure indicate that there is a risk to vegetation over varying areas near both copper smelters/ refineries and zinc plants, to a maximum distance of about 10 km. For acidic deposition, it was determined that copper smelters contributed up to 8% (relative to all anthropogenic and natural sources) of the SO₂ resulting in acidic deposition at the four eastern Canadian receptor areas considered. Copper refineries and zinc plants were responsible for significantly lower fractions (up to 0.1% and 0.2%, respectively). U.S. sources were the largest contributors at all four receptor sites.

Endpoint organisms were identified for exposure to each metal examined in both aquatic and terrestrial environments (relating to deposition to surface waters and land, respectively). The 95th percentiles of natural background metal concentrations were used as lower limits for the effects thresholds. The transport and fate of metals deposited on surface waters and soils were modelled to permit estimation of critical metal deposition values ("critical loads") - defined as the amount of annual deposition required for steady-state metal concentrations to reach these low effect concentrations in receiving surface waters and soils. Probabilistic modelling was based on the range of receptor conditions (soil types, pH, lake size, etc.) encountered on the Canadian Shield. Estimated free metal ion concentrations were assumed to be representative of the concentration of biologically available metal.

Estimated annual metal deposition rates were compared with 25th percentile critical loads representative of effects on sensitive organisms under 25% of conditions in sandy soils or acidic lake water of the Canadian Shield. It was concluded that there is potential for effects on aquatic and/or soil-dwelling organisms from exposure to steady-state concentrations of metals in the vicinity of copper smelters/refineries and zinc plants resulting from emissions (especially of copper and zinc, respectively) from these facilities. Impacted areas were estimated to extend up to about 13-14 km from the facilities. In all cases, it is recognized that the range of impact is dependent on the emissions of the individual facilities as well as on local meteorology and geography. Range of impact is also dependent on the percentile of the critical load on which the comparisons are based. A lower percentile critical load, representing risk under a smaller fraction of Canadian Shield conditions, would result in estimation of impacts to greater distances. It is also recognized that emissions from zinc plants using exclusively pressure-leach technology will be significantly less than those from plants using roasting processes.

Screening-level evaluations of the environmental effects of aquatic releases from the three facilities (namely Cominco-Trail, Noranda-CCR and Noranda-CEZinc) that are not currently required to report their aquatic releases under the Metal Mining Liquid Effluent Regulations of the Fisheries Act were conducted. Constituents of releases to water considered in these assessments include all metal contaminants reported to be present, as well as ammonia, fluoride and pH. The results of the assessments of these three facilities indicated the potential for detrimental effects on the environment. However, the indicators of risk were fairly low, especially given the slightly conservative nature of the assessment.

The assessed facilities are also sources of carbon dioxide, nitrous oxide, methane and volatile organic compound (VOC) emissions. The former three contribute to global climate change, while VOCs contribute to tropospheric photochemical ozone creation, and some VOCs contribute to stratospheric ozone depletion. Emissions of all of these substances from copper smelters and refineries and zinc plants are, however, minor in comparison to those from other emission sources.

The health assessment addressed potential risks to nearby populations from current releases from copper smelters/refineries and zinc plants in Canada. Based on recent data, concentrations of arsenic, cadmium, chromium, nickel, lead, SO₂ and particulate matter in air are generally increased in the vicinity of most Canadian copper smelters/refineries and zinc plants in relation both to proximity to the facilities and background concentrations at remote sites.

The results of available epidemiological studies of human populations resident near copper smelters/refineries and zinc plants are inadequate to characterize the potential for both cancer and non-cancer effects from releases from such facilities. Based on assessments conducted previously on the Priority Substances List under the Canadian Environmental Protection Act (CEPA), carcinogenicity is considered to be the critical effect for arsenic, cadmium, chromium and nickel, in light of the sufficient weight of evidence for lung tumours in occupational populations or experimental animals following inhalation of compounds of each of these metals. The range of annual mean concentrations of PM₁₀ near Canadian copper smelters/refineries and zinc plants overlaps those associated with increased cardiorespiratory morbidity and mortality in recent extensive epidemiological studies of the general population exposed to ambient air pollution in various countries, including Canada. The concentrations of SO₂ in ambient air in the vicinity of all Canadian copper smelters/ refineries and zinc plants occasionally exceed health-based guidelines intended to protect against cardiorespiratory effects. Although not directly considered in this assessment, it is also recognized that SO₂ is an important precursor in the secondary formation of respirable particulate matter, especially the fine fraction (PM_2.5). Levels of airborne lead also exceed health-based guidelines near certain of the Canadian facilities involved in smelting copper, indicating potential for lead-induced health effects.

Based on available data, it has been concluded that emissions from copper smelters and refineries and from zinc plants of metals (largely in the form of particulates) and of sulphur dioxide are entering the environment in quantities or concentrations or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. Based on available data, it has been concluded that emissions from copper smelters and refineries and emissions from zinc plants are not entering the environment in quantities or concentrations or under conditions that constitute or may constitute a danger to the environment on which life depends. Based on available data concerning the effects of PM₁₀, sulphur dioxide and compounds of arsenic, cadmium, chromium, lead and nickel, it has been concluded that emissions from copper smelters and refineries and from zinc plants of PM₁₀, of metals (largely in the form of particulates) and of sulphur dioxide are entering the environment in quantities or concentrations or under conditions that constitute or may constitute a danger in Canada to human life or health. Therefore, metals (largely in the form of particulates) contained in emissions from copper smelters and refineries, metals (largely in the form of particulates) contained in emissions from zinc plants, PM₁₀ and sulphur dioxide are considered "toxic" as deflned in Section 64 of the Canadian Environmental Protection Act, 1999 (CEPA 1999).

There are a number of ongoing initiatives that address different release components of copper smelters/refineries and zinc plants. These include activities resulting from the Base Metals Smelting Sector Strategic Options Process, the Canada-wide Standards initiative for PM₁₀ and PM_2.5, and the Canada-wide Acid Rain Strategy for Post-2000. There are also activities resulting from the addition of PM₁₀ to Schedule 1 of CEPA 1999. Any investigations of options to reduce exposure as a result of these assessments should be integrated with these initiatives.

Comparison of estimated exposure to arsenic, cadmium, chromium and nickel in the vicinity of Canadian copper smelters/refineries and zinc plants with the tumorigenic potency indicates that the priority for investigation of options to reduce human exposure to releases from these facilities is considered to be in the high range for copper smelters, to range from low to high for copper refineries, and to range from low to high for zinc plants. Comparison of levels of lead, SO₂ and PM₁₀ in ambient air with health- based guidelines or with concentrations at which health effects have been observed also suggests that the priority for options analysis is high, especially for facilities where copper is smelted.

Given existing controls on effluents put in place by the companies or imposed by Provincial governments or other authorities, Federal prevention or control actions under the Canadian Environmental Protection Act, 1999 (CEPA, 1999) are not recommended at this time. It is believed, however, that an increase in contaminant concentrations or loadings or changes in conditions affecting bioavailability (such as pH) have the potential to significantly increase risk to the environment. It is important that facility operators recognize that if information, such as monitoring data, shows a significant increase in contaminant concentrations or loadings or changes in conditions affecting bioavailability, such information may be subject to reporting under Section 70 of CEPA, 1999.

Assessment of releases from copper smelters/refineries and zinc plants necessitated evaluation of a limited number of components from the complex mixture of substances released. The constituents of emissions to air examined generally represent the substances released in the greatest quantity. This selection does not imply that other release constituents do not pose a risk. Investigations of options for risk management should also take into consideration other substances of potential concern, some examples of which include mercury, selenium, dioxins and furans.

1.0 Introduction

The Canadian Environmental Protection Act, 1999 (CEPA 1999) requires the federal Ministers of the Environment and of Health to prepare and publish a Priority Substances List (PSL) that identifies substances, including chemicals, groups of chemicals, effluents and wastes, that may be harmful to the environment or constitute a danger to human health. The Act also requires both Ministers to assess these substances and determine whether they are "toxic" or capable of becoming "toxic" as defined in Section 64 of the Act, which states:

...a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that

1. have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
2. constitute or may constitute a danger to the environment on which life depends; or
3. constitute or may constitute a danger in Canada to human life or health.

Substances that are assessed as "toxic" as defined in Section 64 may be placed on Schedule 1 of the Act and considered for possible risk management measures, such as regulations, guidelines, pollution prevention plans or codes of practice to control any aspect of their life cycle, from the research and development stage through manufacture, use, storage, transport and ultimate disposal.

Based on initial screening of readily accessible information, the rationale for assessing "Releases from primary and secondary copper smelters and copper refineries" provided by the Ministers' Expert Advisory Panel on the Second Priority Substances List (Ministers' Expert Advisory Panel, 1995) was as follows:

A wide variety of substances is released into the Canadian environment from primary and secondary copper smelters and refineries. The individual chemical components of releases from these facilities include particulate matter, copper, lead, arsenic and sulphuric acid. The Panel recognizes that assessing the effects of these releases will be difficult from a human health perspective. Releases are often very complex, containing variable mixtures of individual compounds. Often there are no epidemiological studies on populations living near such point sources. For populations at some distance, it may be difficult to attribute effects to the source under examination since other sources can contribute to exposure. Nonetheless, given the large volumes released and the persistent and hazardous nature of some of those substances, an assessment is required to determine the nature and extent of local and long-range ecological and health effects.

The rationale provided by the Panel for assessing "Releases from primary and secondary zinc smelters and zinc refineries" was the same, except that the individual components identified were particulate matter, zinc and sulphuric acid.

Because of their similarities, assessments of whether these two PSL substances are "toxic" under Section 64 of CEPA 1999 were conducted in parallel, and the findings are reported together in this Assessment Report. Since most releases (on a mass basis) are discharged to air and releases to air have the greatest potential for causing widespread effects, these assessments have focused on environmental and human health risks of air emissions. Levels in air were also expected to better reflect current releases than is the case for other environmental media, which can be strongly influenced by high historical emissions. Releases to water from several Canadian copper smelters and refineries and zinc smelters and refineries (more conventionally "zinc plants") will be included in the effluents regulated under the revised Metal Mining Liquid Effluent Regulations (MMLER) and Guidelines of the Fisheries Act.¹ Releases subject to the Fisheries Act² were not examined in these assessments.

Although potential impacts on both the environment and human health are considered in these assessments, the focus of the assessment is on environmental effects. This is due primarily to limitations of available epidemiological studies of human populations near copper smelters and refineries and zinc plants, which are exposed directly to releases from these facilities, and difficulties in assessing the effects of mixtures based on data from mammalian toxicity studies on individual compounds. These limitations were recognized in the rationale for these assessments provided by the Ministers' Expert Advisory Panel.

Since the entries included on the second Priority Substances List relate to "releases" from copper smelters and refineries and zinc plants, the human health assessment was focused on populations in the vicinity of these facilities, which are expected to be most exposed to substances emitted from them, and on evaluating the potential impacts of current releases. Consequently, the health-related sections of this report contain a summary of recent environmental levels of a number of substances near these facilities in Canada, obtained in response to a questionnaire sent to the companies. A review of available epidemiological studies of populations in the vicinity of copper smelters and refineries and zinc plants is also included. Given the number and variety of substances released from copper smelters and refineries and zinc plants, the health assessment builds on previous work for information on health effects and exposure-response for individual substances, relying on other assessments conducted under the PSL assessment program and other programs.

Descriptions of the approaches to assessment of the effects of Priority Substances on the environment and human health are available in published companion documents. The document entitled "Environmental Assessments of Priority Substances under the Canadian Environmental Protection Act. Guidance Manual Version 1.0 - March 1997" (Environment Canada, 1997a) provides guidance for conducting environmental assessments of Priority Substances in Canada. This document may be purchased from:

• Environmental Protection Publications
  Environmental Technology Advancement Directorate
  Environment Canada
  Ottawa, Ontario
  K1A 0H3

It is also available on the  Commercial Chemicals Evaluation Branch web site at www.ec.gc.ca under the heading "Guidance Manual." It should be noted that the approach outlined therein has evolved to incorporate recent developments in risk assessment methodology, which will be addressed in future releases of the guidance manual for environmental assessments of Priority Substances.

The approach to assessment of effects on human health is outlined in the following publication of the Environmental Health Directorate of Health Canada: "Canadian Environmental Protection Act - Human Health Risk Assessment for Priority Substances" (Health Canada, 1994), copies of which are available from:

• HECS Publishing
  Healthy Environments and Consumer Safety Branch
  Health Canada
  Tunney's Pasture
  Address Locator: 3100A
  Ottawa, Ontario
  K1A 0L2

or on the Environmental Health Program publications web site (www.hc-sc.gc.ca/ewh-semt/pubs/contaminants/index-eng.php). The approach is also described in an article published in the Journal of Environmental Science and Health -Environmental Carcinogenesis & Ecotoxicology Reviews (Meek et al., 1994). It should be noted that the approach outlined therein has evolved to incorporate recent developments in risk assessment methodology, which are described on the Existing Substances Division web site (www.hc-sc.gc.ca/ewh-semt/pubs/contaminants/index-eng.php#existsub) and which will be addressed in future releases of the approach paper for the assessment of effects on human health.

Informal questionnaires were used to obtain the most recent information available from Canadian industry on releases, environmental concentrations and the ecological effects of their releases. The search strategies employed in the identification of additional data relevant to assessment of potential effects on the environment (prior to fall 1999) and on human health (prior to March 2000 for monitoring and epidemiological data on nearby populations only) are presented in Appendix A. Review articles were consulted where appropriate. However, all original studies that form the basis for determining whether releases from copper and zinc smelters and refineries are "toxic" under CEPA 1999 have been critically evaluated by staff of Environment Canada (entry and environmental exposure and effects) and Health Canada (human exposure and effects on human health). In addition, a number of reports were prepared under contract in support of the environmental component of these assessments; these are also listed in Appendix A.

The environmental components of these assessments were led by P. Doyle and D. Gutzman, with support from D. Caldbick, A. El-Shaarawi, C. Fortin, A. Green, M. Lapointe, D. Morin and J. Sanderson on behalf of Environment Canada. Sections of the Assessment Report and the supporting documentation related to the environmental assessment of copper and zinc smelters and refineries were prepared or reviewed by the members of the Environmental Resource Group (ERG), established by Environment Canada in August 1997 to support the environmental assessment. ERG members were selected based on their expertise in fields of particular significance to these assessments, including releases from the base metal smelting sector, aquatic and terrestrial effects, atmospheric dispersion modelling, metal transport and fate, metal speciation, critical loads, ambient sulphur dioxide (SO₂) and acid deposition. Members include:

• J. Ayres, Environment Canada
• G. Bird, Canadian Nuclear Safety Commission
• U. Borgmann, Environment Canada
• S. Daggupaty, Environment Canada
• W. de Vries, DLO Winand Staring Centre, The Netherlands
• M. Diamond, University of Toronto
• G. Dixon, University of Waterloo
• R. Garrett, Natural Resources Canada
• B. Hale, University of Guelph
• D. Hart, Beak International Inc.
• K. Hedley, Environment Canada
• W. Hendershot, McGill University
• R. Hoff, University of Maryland Baltimore County
• D. Hrebenyk, SENES Consultants Ltd.
• T. Jackson, Environment Canada
• P.K. Leung, Environment Canada
• S. Linzon, Phytotoxicology Consultant Services Ltd.
• K. Lloyd, Environment Canada
• M. Sheppard, ECOMatters Inc.
• S. Sheppard, ECOMatters Inc.
• J. Skeaff, Natural Resources Canada
• A. Tessier, University of Quebec
• P. Thompson, Canadian Nuclear Safety Commission

Industry representatives on the ERG who monitored the assessment process include:

• Cominco Ltd. - M. Edwards and G. Kenyon
• Falconbridge Ltd. - R. Telewiak
• Hudson Bay Mining and Smelting (HBM&S) Ltd. - W. Fraser
• Inco Ltd. - T. Burnett, C. Ferguson and W. Szumylo
• Noranda Ltd. - J. Moulin and H. Veldhuizen

In addition to members of the ERG, the following individuals reviewed and provided comments on environmental sections of the supporting documentation:

• H. Allen, University of Delaware
• B. Antcliffe, Department of Fisheries and Oceans
• N. Belzile, Laurentian University
• G. Bonham-Carter, Natural Resources Canada
• T. Burnett, Inco Ltd.
• D. Chambers, SENES Consultants Ltd.
• P. Chapman, EVS Environmental Consultants
• B. Duncan, Cominco Ltd.
• L. Evans, University of Guelph
• D. Gamble, Agriculture and Agri-Food Canada
• A. Germain, Environment Canada
• M. McLaughlin, CSIRO, Australia
• M. Moran, Environment Canada
• M. Power, University of Waterloo
• R. Prairie, Noranda Ltd.
• M. Sadiq, University of Guelph
• R. Stager, SENES Consultants Ltd.
• H. Veldhuizen, Noranda Ltd.

Individuals who reviewed and provided substantive comments on the draft environmental assessment report and who have not been recognized above include:

• Bezak, Manitoba Conservation Department
• P. Campbell, Institut National de la Recherche Scientifique - Eau
• V. Chapados, Noranda Ltd.
• D. Daoust, Noranda Ltd.
• M. Edwards, Cominco Ltd.
• W. Fraser, HBM&S Ltd.
• B. Keller, Laurentian University
• J. Leclerc, Noranda Ltd.
• K. Taylor, Environment Canada

Supporting documentation and sections of this Assessment Report related to human health were prepared by the following staff of Health Canada:

• K. Byrne
• H. Hirtle
• M.E. Meek
• R. Newhook

The health-related supporting documentation was circulated for comment to the following representatives of the smelting and refining companies who are members of the ERG for this assessment, primarily to ensure the accuracy of the information contained therein concerning the copper smelters and refineries and zinc plants that their companies operate:

• M. Edwards, Cominco Ltd.
• W. Fraser, HBM&S Ltd.
• R. Prairie, Noranda Ltd.
• W. Szumylo, Inco Ltd.
• R. Telewiak, Falconbridge Ltd.

Due to reliance on measures of exposure-response derived from peer-reviewed sources for comparison with ambient levels of components of releases, external review of the health-related sections of the assessment was less extensive than for other assessments on Priority Substances. The health-related sections in the Assessment Report were reviewed externally by M. Younes, World Health Organization (WHO) International Programme on Chemical Safety and M. Dourson, Toxicology Excellence for Risk Assessment.

The health-related sections of the Assessment Report were reviewed and approved by the Health Protection Branch Risk Management meeting of Health Canada.

The entire Assessment Report was reviewed and approved by the Environment Canada/Health Canada CEPA Management Committee.

A draft of the Assessment Report was made available for a 60-day public comment period (July 1 to August 30, 2000) (EC/HC, 2000b). Following consideration of comments received, the Assessment Report was revised as appropriate. A summary of the comments and responses is available on the Internet at:

 Public Comment on Draft Assessment Reports
www.ec.gc.ca

The text of the Assessment Report has been structured to address environmental effects initially (relevant to determination of "toxic" under Paragraphs 64(a) and (b)), followed by effects on human health (relevant to determination of "toxic" under Paragraph 64(c)).

Copies of this Assessment Report are available upon request from:

• Inquiry Centre
  Environment Canada
  Main Floor, Place Vincent Massey
  351 St. Joseph Blvd.
  Hull, Quebec
  K1A 0H3

or on the Internet at:

 Priority Substance Assessment Program Assessment Reports
www.ec.gc.ca

Unpublished supporting documentation, which presents additional information, is available upon request from:

• Existing Substances Branch
  Environment Canada
  14th Floor, Place Vincent Massey
  351 St. Joseph Blvd.
  Hull, Quebec
  K1A 0H3

or

• Existing Substances Division
  Health Canada
  Environmental Health Centre
  Tunney's Pasture
  Address Locator: 0801C2
  Ottawa, Ontario
  K1A 0L2

2.0 Summary of Information Critical to Assessment of "Toxic" under CEPA 1999 (Continued)

2.1 Identity

2.1.1 Definitions and scope

2.1.1.1 Smelters and refineries

For the purposes of these assessments, a smelter is defined as a facility that uses high-temperature chemical processes to recover base metals (MAC, 1995). A refinery is understood to be a facility in which impurities are separated from metals using thermal or electrolytic processes (MAC, 1995). In these assessments, both electrorefineries and electrowinning facilities are considered to be refineries.

Since several metals are recovered from individual smelters and refineries, for the purposes of these assessments a "copper" smelter or refinery is understood to be a facility in which one of its primary commercial products is more or less pure copper metal. Similarly, a "zinc" smelter or refinery has more or less pure zinc metal as one of its primary products.

Primary smelting and refining produce metal directly from ores and concentrates, while secondary smelting and refining produce metal from scrap and/or process waste (Environment Canada, 1997b). The distinction between primary and secondary smelting is not always clear in practice, however, since some predominantly primary smelters use recycled metals to supplement their primary feed.

In a typical copper smelter, a sulphide concentrate or calcine is heated with fluxing agents to about 1200° C, to effect a phase separation into a molten sulphide matte containing copper and iron and an overlying molten slag containing iron oxide, silica and lime. The matte is then subjected to converting and fire refining to produce an impure copper metal known as anode copper, which contains about 99% copper, and minor and trace elements (Skeaff, 1997). Casting of the impure metal into anodes, the configuration suitable for electrorefining, may take place in either the smelter or refinery. A copper refinery then electrolytically refines the anode copper to produce pure copper.

Zinc may be produced using either a roast-leach-electrowin (RLE) process or a pressure-leach-electrowin (PLE) process. Roasting refers to the heating of concentrate to oxidize and drive off sulphur oxide gases. In roasters, zinc and iron sulphides in the concentrate are converted to oxides, and the resulting solid product (calcine) is sent to leaching. Leaching can be under acidic conditions, neutral conditions or a combination. Zinc and non-ferrous metals are extracted, producing a zinc sulphate leach liquor. In the pressure-leach process, zinc concentrate is reground and agitated in an autoclave with oxygen and sulphuric acid. Iron and zinc sulphides are thereby converted to iron and zinc sulphate and dissolved in the leachate. Leach liquor from either the roast-leach or pressure-leach process is purified and directed to electrowinning. In electrowinning, an electric current is passed through the purified liquor, causing the zinc sulphate to chemically decompose and zinc metal to deposit on the cathode. Cathodes are stripped mechanically, and the zinc is melted and cast.

Since the RLE process is a high-temperature chemical process, facilities using it to recover zinc may be considered to be, at least in part, "smelters" as defined previously. However, zinc production facilities may also be considered "refineries" as defined previously, in that they include an electrowinning step. Because of the ambiguity concerning their classification, these facilities are commonly referred to as "zinc plants". The term "zinc plants" is used in this report to describe facilities involved in recovering zinc using RLE or PLE or a combination of the two.

2.1.1.2 Releases

For the purposes of these assessments, a release is considered to be any current discharge to the ambient environment. Past releases, which were often larger and less well controlled than at present, are not included.

Releases considered in these assessments include all current on-site discharges to air and water from Canadian copper smelters and refineries and zinc plants. Releases to air include emissions from "point" (e.g., tall stack) and "area" sources (e.g., low stacks or fugitive emissions from concentrates stored on-site). Effluents considered include both process and cooling waters that are entering surface waters either directly or indirectly (e.g., after passage through a municipal water treatment plant).

As noted in Section 1.0, releases to water from copper smelters and refineries and zinc plants that will be included in effluents regulated under the revised Metal Mining Effluent Regulations (MMER) of the Fisheries Act are not examined in these assessments. Releases from off-site activities related to copper and zinc smelting and refining (e.g., releases from the shipment of feed materials or wastes and landfilling of wastes) were also not considered in these assessments.

Direct impacts of the storage of smelter or refinery wastes (e.g., slags) on lands within the boundaries of facilities were also not examined, since land owned by the facilities is not considered part of the ambient environment. However, leachate or runoff from such wastes that enters ambient off-site waters and wind-blown fugitive emissions from such wastes that are transported off-site were in principle included.

2.1.2 Facilities included in assessments

All copper smelters and refineries and zinc plants currently operating in Canada were included in these assessments.³ Using the definitions presented in Section 2.1.1, six copper smelters, four copper refineries and four zinc plants were identified (Tables 1 and 2). Those with effluents that will be regulated under the revised MMER of the Fisheries Act are identified in these tables. As noted in Section 1.0, risks associated with direct releases to water from these facilities were not assessed. Screening-level assessments of the risk to the environment of aquatic releases were conducted for the Noranda-Canadian Copper Refinery (CCR), Noranda-Canadian Electrolytic Zinc (CEZinc) and Cominco-Trail Operations (CTO).

The Falconbridge-Kidd Creek and HBM&S copper smelters are primary smelters. No currently active stand-alone secondary copper smelters were identified. However, a relatively small portion of the feed entering the Noranda-Horne facility, and to a lesser extent the Noranda-Gaspé facility, is recycled copper-bearing material (Hatch Associates, 1997). These smelters could be considered to be predominantly primary copper smelters that engage in some secondary smelting.

Two primary nickel/copper smelters were also assessed. They are the Falconbridge-Sudbury and Inco-Copper Cliff plants. The Inco plant produces impure copper as well as nickel products. The Falconbridge operation produces only a nickel/copper matte, which is shipped to Norway for further processing (Environment Canada, 1997b). The Falconbridge smelter has been included in these assessments because the operations carried out at Sudbury are the first step of a smelting process that ultimately leads to the production of copper metal.

Copper production facilities whose releases were assessed

1. Environment Canada, 1997b.
2. Hatch Associates, 1997.
3. Approximate recent figures, Skeaff, 1997.

Of the four copper refineries identified, three are electrorefineries (Noranda-CCR, Falconbridge-Kidd Creek and Inco-Copper Cliff) and one is an electrowinning plant (Inco-Copper Cliff). Throughout the balance of this report, the Inco-Copper Cliff copper refineries will be referred to as a single operation.

Of the four zinc plants identified, one uses a RLE process (Noranda-CEZinc), one uses a PLE process (HBM&S), and two use both processes (Cominco-Trail and Falconbridge-Kidd Creek). All process only concentrates from zinc ores and hence are "primary" plants. No secondary zinc production plants were identified in Canada.

2.1.3 Release constituents examined

Constituents of releases to water considered in these assessments include all metal contaminants reported to be present, as well as selenium (Se), fluoride, ammonia and pH (hydrogen ion activity).

The components of releases to air that were examined most closely are SO₂, particulate matter (PM) and seven metals (copper-Cu, zinc-Zn, nickel-Ni, lead-Pb, cadmium-Cd, chromium-Cr and arsenic-As⁴). These include the vast majority (on a mass basis) of substances released to air from Canadian copper smelters and refineries and zinc plants (e.g., NPRI, 1995, 1996; RDIS, 1995). Past emissions of both SO₂ and several of these metals from Canadian copper smelters and refineries and zinc plants have been reported to cause environmental harm (e.g., Sanderson, 1998). Hexavalent Cr compounds, inorganic As compounds, inorganic Cd compounds, and oxidic, sulphidic and soluble inorganic Ni compounds were assessed under PSL1 and were found to be CEPA toxic. It should be pointed out, however, that these assessments were not specific to copper smelters and refineries and zinc plants - they considered all sources of entry of the compounds into the environment and therefore do not on their own satisfy the mandate of the current assessments. Other components of releases to air that were examined in the environmental assessment are carbon dioxide (C_O2), nitrous oxide (N₂O) and volatile organic compounds (VOCs).

1. Environment Canada, 1997b.
2. Hatch Associates, 1997.

Among the substances reported in releases to the atmosphere from Canadian copper smelters and refineries and zinc plants that were not examined in these assessments are mercury (Hg) and, in the case of at least one copper smelter, dioxins and furans (Environment Canada, 1997b). While it is recognized that releases of such substances have the potential to harm the environment and human health, their fate in the environment (including accumulation pathways in organisms) is complex and uncertain. The decision not to consider such substances in these assessments was in part a practical one, taking into consideration the anticipated uncertainties associated with estimating their fate (including long-range transport, bioaccumulation and biomagnification) in the environment.⁵ As noted in Section 3.1.1.1.3, this decision contributes to the uncertainty of the overall risk characterization. Polychlorinated dibenzodioxins and polychlorinated dibenzofurans were on the first PSL and were found to be CEPA toxic. Mercury is also on the list of CEPA toxic substances (Schedule I). As pointed out above, however, these conclusions were not based specifically on copper smelters and refineries and zinc plants as the sources of entry to the environment.

2.2 Entry characterization

Voluntary questionnaires were sent to industry in 1998 to verify and update existing information on the chemical constituents of releases, the amounts (expressed as rates) of substances released, the conditions of release (e.g., stack heights and temperatures), the physical and chemical forms of substances released, and concentrations in waste streams (e.g., effluents) and in environmental media near Canadian copper smelters and refineries and zinc plants. Other information collected included the configuration of effluent waste streams and source apportionment of emissions for facilities having multiple operations.

The most recent empirical data available for a complete calendar year were generally used for estimating exposure to metals and ambient SO₂. Data for 1995 were used for atmospheric metal dispersion modelling and for SO₂ source-receptor modelling. All empirical data used in these assessments are for 1995 or a more recent year.

2.2.1 Releases to air

2.2.1.1 Sulphur dioxide

Information on emissions of gaseous SO₂ from copper and zinc facilities is summarized below. Data described are for 1995, since these were the most recent available at the time of information collection. Further detail is provided in SENES Consultants (1999a).

Approximately 99% of the SO₂ emissions from copper and zinc facilities in 1995 were derived from copper smelters, as compared to 1% from copper refineries and zinc plants (see Table 3). Approximately 85% of the SO₂ emissions from these facilities were generated by three copper smelters: Inco's nickel/copper smelter complex in Sudbury, Ontario; Noranda's Horne copper smelter in Rouyn-Noranda, Quebec; and the HBM&S copper smelter in Flin Flon, Manitoba. By 1995, total SO₂ emissions from the copper smelters listed in Table 3 had been reduced by over 61% from 1980 emission levels, and by a total of 63% from copper smelters and refineries and zinc plants as an industry group. Emissions from zinc plants had been reduced by 94%, mainly due to the elimination of SO₂ emissions from the HBM&S zinc plant after 1993. Trend analyses for SO₂ emissions from copper refineries over this period were unavailable because emissions from the Noranda-CCR refinery were incomplete, while emissions from the Inco refinery at Sudbury and the Falconbridge refinery at Kidd Creek were included in the total SO₂ emission inventories from their associated smelters over this period. Although some data on refinery emissions were obtained for the Inco and Falconbridge-Kidd Creek refineries (personal communication with facility operators), the inconsistent consideration of anode casting as either a smelter process or a refinery process complicates their interpretation.

1 Data presented are based on unpublished emissions data from the Residual Discharge Information System (RDIS, 1995), the 1995 annual report for the Eastern Canada Acid Rain Program (Environment Canada, 1995) and additional information provided by facility operators.

In 1995, emissions from copper and zinc facilities accounted for approximately 37% of SO₂ emissions from sources in eastern Canada. However, total SO₂ emissions in eastern North America are dominated by emissions from the United States, with SO₂ emissions in the eastern United States accounting for about 86% of total emissions in eastern North America (Environment Canada, 1997c). Consequently, as a source group, copper and zinc facility emissions represent a much smaller component of total SO₂ emissions in eastern North America. For example, in 1995, SO₂ emissions from Canadian copper smelters and refineries and zinc plants represented only about 5% of the total SO₂ emissions in this region.

2.2.1.2 Metals

The following discussion focuses on metal emissions in 1995, as the dispersion modelling used data from that year. The year 1995 was selected for use as it was the most recent year for which detailed data were available at the time the modelling was begun. No data were identified on the chemical or physical forms of the emitted metals. Most emissions of the metals considered below may, however, be assumed to be in particulate form.

The total annual releases of Cu, Zn, Ni, Pb, Cd and As from the copper and zinc facilities in 1995 are summarized in Table 4. Data in this table are based largely on 1995 data from the NPRI (1995), supplemented with information obtained directly from the facility operators. A more detailed discussion of these releases is provided in SENES Consultants (2000).

The total amount of trace metals released by a facility depends to some extent on the concentration of that element in the raw material fed into the process, as well as on the type of process used, the facility production rate and the efficiency of control equipment at the point of release. If the smelter derives a large proportion of its raw materials from a variety of mining operations, the variability in the concentration of trace elements can result in large fluctuations in trace element release rates, depending on which concentrate is being processed at any given time. Further, for any given trace element, the quantity released in the process exhaust stream will also depend on the temperature of the smelting or the refining process in use. The more volatile elements, such as As, Cd, Pb and Zn, are more likely to be liberated during the process if the temperature is high than are less volatile elements, such as Cu and Ni. Finally, the quantity of each element released is also dependent on the efficiency of the emission control equipment in use at each facility (i.e., multi-cyclones, electrostatic precipitators or baghouses). For all of these reasons, it is not surprising that the data in Table 4 display a high degree of variability in the emission rates among the facilities. The differences range over two to three orders of magnitude for most of the trace metals within each of the three facility categories (i.e., copper smelters, copper refineries and zinc plants).

Among copper smelters, the Inco-Copper Cliff facility ranked highest in 1995 for emissions of trace Cu, Ni and As releases. The Noranda-Horne smelter was a close second for both Cu and As. Noranda-Horne also had the highest emission rates for both Zn and Pb. The highest emission rate for Cd was reported by the HBM&S copper smelter at Flin Flon, followed closely by both Noranda-Horne and Falconbridge-Sudbury.

As with the copper smelters, the trace metal emission rates from copper refineries also vary significantly among the various facilities. As was the case with SO₂ (Section 2.2.1.1), a lack of consistency for inclusion of anode casting as a smelter or a refinery operation complicates interpretation of these data.

ND - Not determined; neg. - negligible

1. Emission values for Cu, Zn, Ni, Pb, Cd and As were used for dispersion modelling. Chromium was considered only in the assessment of risk to human health. Trace metal emission data were based largely on NPRI data (NPRI, 1995) with additional information provided by facility operators. Values have been rounded for presentation.
2. Values shown are based on the average of results from two samplings of the main Inco stack, one from 1994 and the other from 1996. It should be noted that these values differ significantly from those reported to the NPRI in 1995 for the smelter complex (Inco reports releases from the copper refinery separately). NPRI (1995) values for the smelter complex were: Cu-107.04; Zn-15.65; Ni-417.76; Pb-68.23; Cd-ND; As-7.32 tonnes.
3. Cominco-Trail is a combined facility, including both a zinc plant and a lead plant. NPRI data are reported for the overall facility and do not distinguish between the plants. Therefore, the values shown in the table were based on 1995 source attribution data provided by facility operators in response to a questionnaire from Environment Canada. It is believed that the provided list of emission sources reportedly associated with the zinc plant was incomplete, resulting in underestimation of emissions from this operation. For comparison, more accurate metal emission estimates for the Cominco zinc plant in 1998 (personal communication with facility operators) were: Zn-125; Pb-0.36; Cd-0.124; As-0 tonnes. The facility operators point out that the 1998 estimates are based on releases for the point sources associated with each operation (zinc and lead). This is an oversimplification because of the numerous recycle streams between zinc and lead operations. Therefore, there is considerable uncertainty associated with these values.

Emission rates for trace metals from zinc plants also vary by two to three orders of magnitude. Among zinc plants, the Noranda-CEZinc facility had the highest emission rates for Cu, Zn, Pb and Cd. In fact, the Zn emission rate from this facility exceeded that from all other copper and zinc facilities, including the emissions from the Noranda-Horne copper smelter. However, as discussed in the footnote to Table 4, it is believed that the emissions attributed to the Cominco zinc plant in 1995 may have been significantly underestimated. For comparison, Zn emission values attributed to the Cominco zinc plant for 1998 were estimated at 125 tonnes (personal communication with facility operators), greater than those from any of the other copper or zinc facility operations for 1995. The Falconbridge-Kidd Creek plant had the highest emission rate for As among the zinc plants and was the only zinc plant to report Ni emissions, although the rate is very low. Releases of all metals from the HBM&S zinc plant were reported to be very low, since, in contrast to the others, this plant does not use a high-temperature roasting process.

2.2.1.3 Particulate matter

Table 5 summarizes 1995 emissions of total particulate (TP) matter for the copper and zinc facilities as contained in the Residual Discharge Information System (RDIS, 1995). The table also includes emission data for the size fraction less than or equal to 10 mm (PM₁₀) and the fraction less than or equal to 2.5 mm (PM_2.5).

These data indicate that the Inco copper smelter at Copper Cliff had the highest TP emission rate at 7052 tonnes per year in 1995. Note that this total includes TP emissions from the copper refinery and nickel refinery as well as from the smelter. The Noranda-Horne copper smelter ranks second at 1339 tonnes per year, followed by the Falconbridge copper smelter at Sudbury, with 1181 tonnes per year. The lowest reported TP emission rate for the copper smelters is 430 tonnes per year at the Noranda-Gaspé facility.

TP data for two of the three copper refineries are included in the TP emissions from the copper smelters (Inco at Copper Cliff and Falconbridge-Kidd Creek). Only the Noranda-CCR facility is listed as a separate copper refinery source, at 7.1 tonnes per year.

Among the zinc plants, the highest TP emission rates listed in the RDIS (1995) are for the Noranda-CEZinc and Cominco-Trail facilities, both of which emit about 150 tonnes per year. TP emissions from the Falconbridge- Kidd Creek zinc plant are not listed separately and are included with emissions from the copper smelter and refinery located at this site.

TP emissions from RDIS (1995) may be subdivided into three categories (Table 5):

• fugitive sources - consisting of dust from roads, wind erosion of exposed surfaces, and releases from material handling and storage on-site;
• low-elevation sources - consisting of releases from short stacks (defined as less than 30 m high); and
• high-elevation sources - consisting of all releases from stacks greater than 30 m high.

There are some anomalous features associated with these TP emissions. For example, three copper smelters list identical estimates of fugitive emissions of 500 tonnes per year. These appear to be notional numbers, and are unlikely to have been based on detailed emission calculations. In addition, fugitive emissions are not reported for any of the Noranda facilities, or for Cominco-Trail. Because of these anomalies, and the fact that trace metal to TP mass ratios at several sites appear to be unusually high, TP emission data in Table 5 must be interpreted with particular caution. It should be noted that there are some inconsistencies between facilities in the reporting of both TP and metals emissions. Among the sources irregularly reported are fugitive emissions from the production, storage and handling of concentrates, exhaust from baghouses and wind-blown dust from uncovered tailings. The emissions sources reported by four zinc and copper processing facilities have been evaluated and are detailed in SENES Consultants (1999b).

Although data on the size of the particles released were very limited, it is expected that fugitive releases are relatively coarse (>2 mm). Results of preliminary work on particle size distributions of PM obtained from the stack of the Inco smelter indicate that the particles are extremely fine, with 80% less than 3 mm (Burnett, 1998).

1. Data obtained from RDIS (1995). Values have been rounded for presentation. As the reliability of some of these data has not been established, there is considerable uncertainty associated with some values.
2. Some emission values include sources that are associated with and reported by the facilities, but which are not the subject of these assessments. Owing to questions on the reliability of the data, more rigorous evaluation of source attribution was not warranted and was in some cases precluded.
3. It should also be noted that PM (mostly in the form of PM_2.5) can form from condensation of smelter gases after release to the atmosphere. Therefore, attribution of ambient PM_2.5 based on emissions could underestimate the proportion due to smelting processes.
4. "High stacks" are defined in this assessment as being more than 30 m in height.
5. TP values for Inco-Copper Cliff include emissions from the smelter complex, the copper refinery and the nickel refinery.

The values for TP emissions discussed above do not take into account the secondary formation of PM. Secondary processes involve the formation of PM (usually PM_2.5) in the atmosphere as a result of physical and chemical transformation of gases. Sulphur dioxide, nitrogen oxides and VOCs are among the major contributors to the formation of PM_2.5 (EC/HC, 2000a).

2.2.1.4 Carbon dioxide, nitrous oxide, methane and volatile organic compounds

Emissions of gaseous C_O2, N₂O, methane (CH₄)⁶ and VOCs from copper and zinc processing facilities are summarized in Table 6. These compounds are of significance due to their influence on abiotic atmospheric effects such as climate change and the formation of ground-level ozone.

As mentioned in the previous section, both VOCs and nitrogen oxides are significant precursors in the secondary formation of PM_2.5. Total emissions of the oxides of nitrogen from the facilities being considered in these assessments were about 1800 tonnes in 1995 (RDIS, 1995).

2.2.2 Releases to water

Information on releases to water from CCR, CEZinc and CTO is summarized below. Further details are provided in Beak International (1999).

Annual average loading rates from the three facilities into their receiving environments are shown in Table 7. Factors applied to annual averages to estimate maximum short-term (monthly and four-day mean) loading rates are summarized in Table 8. These factors are based on empirical loading information. Concentrations of release components in undiluted effluents are shown in Table 9.

2.2.2.1 Canadian Copper Refinery

The waste metal loadings from CCR (Table 7) are released to the Montreal Urban Community (MUC) wastewater treatment plant (WWTP), which discharges in turn to the mid-channel St. Lawrence River east of l'Île aux Vaches. On a volume basis, approximately 7% of the wastewater leaving CCR is treated process water, and the remainder is untreated cooling water drawn from the St. Lawrence River. On a mass basis, Cu and Se are the two most significant loadings. In 1995, these metal loadings comprised 0.82 and 3.58 tonnes, respectively. Loadings of most metals increased significantly in 1996.

The MUC-WWTP removes much of the CCR loading prior to entry into the St. Lawrence River. Typical removal rates at the MUC-WWTP and the total annual loadings of pertinent metals to the St. Lawrence River in MUC-WWTP treated effluent were taken from Deschamps et al. (1998). There is considerable uncertainty in both removal rates and loadings for certain metals, such as As and Se, that are measured at the MUC-WWTP at concentrations close to the analytical detection limit.

The subsequent assessment of biological exposures to metal in the St. Lawrence River and associated effects on aquatic biota must be based upon the loadings from the MUC-WWTP (not CCR), since these are the loadings actually received by the St. Lawrence River. However, it is important for the purposes of this assessment to identify the proportional contribution that CCR makes to the release of metals in MUC-WWTP effluent. This proportion is calculated for each metal as follows:

P_CCR = L_CCR/[(C_MUC/[1- R_MUC])*Q_MUC]

where:

• P_CCR = proportional contribution of CCR
  (fraction),
• L_CCR = metal loading from CCR to MUC-WWTP (mg/s),
• R_MUC = metal removal rate at MUC-WWTP
  (fraction),
• C_MUC = metal concentration in MUC-WWTP effluent (mg/L), and
• Q_MUC = volume of MUC-WWTP effluent (L/s).

NR - Releases not reported

1. Data obtained from the Residual Discharge Information System (RDIS, 1995).
2. To facilitate their interpretation in terms of potential influence on climate change, values for N₂O and CH₄ have been converted to equivalents of C_O2 using global warming potential multipliers of 310 and 21, respectively (Jaques et al., 1997).

The proportional contribution that CCR makes to the metal loading from the MUC-WWTP to the St. Lawrence River (Table 7) ranges from approximately 0.1% for metals such as Cd and Cr to approximately 1% for Cu and Ni, 10% for As and approaching 100% for Se.

Most of the metals released at the MUC-WWTP outfall are presumed to be in dissolved or adsorbed form. The total metal release was assumed to be available to partition with suspended solids in receiving water, and to contribute accordingly to exposures of aquatic biota.

Temporal variability in the MUC-WWTP loadings is uncertain. Neither monthly mean nor daily loading data were available.

Annual loading rates of effluent components (tonnes/year)

1. NPRI (1995, 1996) and Noranda-CCR data.
2. Deschamps et al. (1998) and (1) above.
3. NPRI (1995, 1996) and Noranda-CEZinc data.
4. NPRI (1995, 1996) and Cominco-Trail data.
5. Cominco-Trail, loading and sewer flow data.

1. Noranda-CEZinc data (1995).
2. Cominco-Trail data (1998).
3. Driven by a Tl upset event in April 1998.

2.2.2.2 Canadian Electrolytic Zinc

The waste metal and ammonia loadings from CEZinc (Table 7) are released to the Beauharnois Canal in the St. Lawrence River. On a volume basis, approximately 4% of the wastewater leaving CEZinc is treated process water, and the remainder is untreated cooling water drawn from the Beauharnois Canal. On a mass basis, for the combined effluent, ammonia, Zn and Se are the three most significant loadings. In 1995, these loadings comprised 24.0, 3.24 and 2.5 tonnes, respectively. Process changes in 1999 have resulted in significant reductions in Se loadings from 1995 levels.

1. Percentage of total concentration that is dissolved, plus the adsorbed portion of that which is particulate, according to K_d and suspended solids in effluent.
2. Annual means are based on weekly composite samples (Deschamps et al., 1998). Maximum monthly and 4-day average concentrations have been estimated from maximum monthly or 4-day mean loading and flow for the corresponding period.
3. Concentrations calculated as annual loading (NPRI) ÷ annual discharge, based on weekly composite samples analysed in two effluent streams. Maximum monthly and 4-day average concentrations have been estimated from maximum monthly or 4-day mean loading and flow for the corresponding period.
4. Concentrations calculated as mean daily loading (Cominco data) ÷ mean daily discharge.

The treated process water (UNA) effluent and the cooling water (Principal) effluent have historically been discharged at separate points, about 1 km apart, on the Beauharnois Canal. However, they are now being (or will soon be) released together at the Principal effluent location. For the purpose of the assessment of biological exposures to effluent constituents in the Canal and associated effects on aquatic biota, the two effluents are considered here together as a combined effluent at a single point of release. As compared to a separate UNA discharge, this makes for a larger point source loading, lower end-of-pipe concentrations and less rapid near-field dilution.

Virtually all of the ammonia released at CEZinc will be dissolved, and most of the metal released will be in dissolved or adsorbed form (labile). However, some 5-10% of the zinc may be in a fine particulate metal oxide or hydroxide form. This conclusion is based on CEZinc observations that approximately 60% of Zn in the UNA effluent is not dissolved. With an average 13 mg/L of suspended solids, we might expect 15% of Zn to be adsorbed based on distribution coefficients (Beak International, 1999), but the remaining 45% of Zn in UNA effluent must have a more integral association with PM. Metal oxide particles, formed in the roasting process, are unlikely to dissolve later if released. Metal hydroxide particles, formed in the water treatment process, may dissolve later, although slowly. Here it is assumed that 20%x45% = 9% of the total Zn loading is in such relatively inert forms. Only the portion of loading estimated to be in dissolved or adsorbed form (91%, Table 9) was considered to be available to partition with suspended solids in receiving water, and hence to contribute to exposures of aquatic biota.

Temporal variability in metal loading from CEZinc (Table 8) is based on 1995 monthly composite data for most metals and on daily data, which were available only for Zn. Maximum monthly average loadings range from 1.7 times the annual average to 6.2 times the annual average, depending on the metal. Factors for 4-day average loadings would be higher.

2.2.2.3 Cominco Trail Operations

CTO includes zinc and lead refinery operations, as well as a fertilizer plant. There are three main combined effluent outfalls that contribute chemical loadings to the Columbia River, as well as some residual drainage from a historical landfill area via Stoney Creek. Most of the landfill drainage toward Stoney Creek is now collected and treated.

The Combined IV outfall (C-IV) and Stoney Creek are furthest upstream (Figure 1). The C-IV outfall, associated with the fertilizer plant, is the dominant source of ammonia, but a minor source of metal loadings. Stoney Creek is a significant source of metal loadings.

The Combined III outfall (C-III), approximately 1.3 km downstream from C-IV, is primarily associated with zinc operations. It is a source of ammonia and a significant source of metals and fluoride (Table 7). The C-II outfall, a further 0.8 km downstream, includes contributions from zinc sulphide leaching, as well as lead and other operations. It, too, is a significant source of metals.

A blast pond discharge (C-I) once existed further downstream, and was a very minor source of metal loadings, primarily associated with lead operations. This discharge no longer exists.

Recent (1998) loadings from CTO and specifically from the C-II and C-III outfalls are summarized in Table 7, along with 1995 and 1996 loadings for all CTO as reported in NPRI (1995, 1996). The average 1998 loadings from C-II and C-III were utilized in this assessment to represent the zinc smelting/refining operations at CTO.

The proportion of loading attributed to zinc operations (Table 7) was estimated for each metal in each outfall, based on an evaluation of toxic unit contributions from different sewers to each outfall (Duncan and Antcliffe, 1996). For C-II, only sewer #6 is associated with zinc operations (it drains the zinc sulphide leaching plant and cadmium plant). For C-III, all contributing sewers are associated with zinc operations, except for the contributions from the effluent treatment plant, which were apportioned to lead and zinc operations based on inflow from these areas (60% from zinc operations). Table 7 shows that most of the C-III loadings (77-99% for metals) are related to zinc operations, while for C-II the proportion ranges from 25-91%, depending on the metal.

Figure 1 Map of Trail, B.C., showing the outfalls and sampling locations considered in the assessment of aquatic releases from the Cominco facility

Virtually all of the ammonia and fluoride released from CTO will be in dissolved form. However, a significant portion of the metal loading, particularly for Zn and Pb, is evidently not in dissolved form, based on analysis of filtered and unfiltered effluent samples. With an average of 2-3 mg/L suspended solids in these samples, we might expect up to 5% of some metals to be adsorbed based on distribution coefficients (Beak International, 1999), but this cannot account for all of the undissolved fraction. Thus, the undissolved fraction may be substantially composed of metal oxides, hydroxides or other relatively inert forms. Only the portion of loading estimated to be in dissolved or adsorbed form (as shown in Table 9) was considered to be available to partition with suspended solids in receiving water, and hence to contribute to exposures of aquatic biota.

Temporal variability in chemical loadings from CTO (Table 8) is based on 1998 daily data for all chemicals. Maximum monthly loadings range from 1.2 times the annual average to 3 times the annual average, depending on the metal and outfall. Four-day average loadings may be as high as 2.2-6.8 times the annual average, depending on the metal and outfall.

2.3 Exposure characterization

2.3.1 Releases to air

For releases to air, exposure is quantified both as concentrations in ambient air and as rates of deposition from air. Results for both empirical monitoring and model calculations are presented when available.

2.3.1.1 Sulphur dioxide

2.3.1.1.1 Fate of sulphur dioxide in air

The fate of SO₂ released to air, discussed briefly here, is considered in more detail in SENES Consultants (1999a).

The conversion of SO₂ to sulphate (SO₄^2-) and its subsequent deposition are governed by a complex series of interactions that include transport and diffusion (i.e., dispersion), gas-phase and aqueous-phase chemistry, meteorology, cloud physics, and dry and wet scavenging processes. Field studies of oxidation rates in clouds suggest that aqueous-phase oxidation mechanisms are considerably faster at converting SO₂ to SO₄^2- than gas-phase reactions. Aqueous- phase oxidation of SO₂ in the atmosphere can occur in cloudwater, fogwater and rainwater, in deliquescent aerosol droplets at high relative humidity and in the liquid surface film condensed on aerosol particles (Radojevic, 1992).

Sulphate formed from oxidation of SO₂ often takes the form of fine PM (PM_2.5). For example, for samples collected at 14 urban sites in the National Air Pollution Surveillance (NAPS) network operating from 1986 to 1994, an average of 17% and up to 95% of PM_2.5 collected at each site was composed of SO₄^2- (Brook et al., 1997, as summarized in EC/HC, 2000a).

According to Hidy (1994), SO₂ concentration patterns tend to be consistent with the observed distribution of SO₄^2- concentrations (as a secondary pollutant) in air and rainwater, except that SO₄^2- is more widely and uniformly distributed than SO₂ due to the time required for 2-the transformation of SO₂ to airborne SO4 (about 1 day) and the efficient scavenging of SO₄^2- by precipitation.

Regional airborne SO₄^2- concentrations exhibit episodic behaviour which is linked to stagnant high-pressure systems (Hidy, 1994). In general, high SO₄^2- concentrations in eastern North America are associated with high temperatures, high absolute humidity, moderately low atmospheric pressures and wind speeds, and high ozone concentrations indicative of high oxidation potential. Thus, the year-to-year spatial variability of high SO₂ and SO₄^2- episodes is closely related to the path and frequency of migratory high-pressure systems. Regional high SO₄^2- episodes can occur in all seasons and are positively correlated with temperature, except in winter, when low temperatures associated with near-surface inversions and poor ventilation can also result in high SO₄^2- pollution episodes. In eastern North America, regional SO₄^2- episodes typically last up to 5 days, but extended events may last up to 11 days. Monitoring studies in eastern Canada suggest that as much as 60-70% of the total annual wet SO₄^2- deposition may be deposited in a single deposition episode (Environment Canada, 1997c).

In contrast, the critical factors for dry deposition are the concentration of SO₂ in the air very near the surface and the ability of the surface to "capture" pollutants that come into contact with it (Hicks, 1992). Dry deposition rates are characterized by a strong diurnal cycle and are intrinsically linked to ambient air concentrations. Very little deposition occurs at night, while high rates of daytime deposition are dominated by the frequency and intensity of high air pollution episodes. Recent research on dry deposition suggests that, on average, dry deposition accounts for about 25% of total (dry plus wet) sulphur deposition, although considerable uncertainty remains in the estimates of dry deposition values (Environment Canada, 1997c). Furthermore, the relative magnitude of dry deposition contributions to total sulphur deposition varies seasonally, and the relative importance of wet versus dry deposition varies with location. Dry deposition is relatively more important than wet deposition in areas close to major source regions, while wet deposition dominates at greater distances, indicating the importance of long-range transport processes. Of the total sulphur emitted in eastern North America, it is estimated that about one-third of the annual average amount of anthropogenic sulphur emissions is wet-deposited in eastern North America, while two-thirds is either dry-deposited or transported out of this region.

2.3.1.1.2 Concentrations of sulphur dioxide in air

This section includes a brief description of the analytical and statistical methods used to estimate SO₂ concentrations in air at monitoring stations located close to copper smelters and refineries and zinc plants. The approach used for source attribution is also described. Resulting data on SO₂ concentrations in air at these sites are summarized in Tables 10, 11 and 12.

Monitoring methods: Monitoring of ambient SO₂ levels is conducted using instrumental methods such as fluorescence detectors. These instruments work on a continuous basis or with a high sampling frequency, such as one reading per minute. The detector signals are averaged over some period of time (typically 5-15 minutes), and these values are recorded. The recorded levels are averaged over longer time periods (usually 1 hour and 24 hours) to determine whether permit levels and provincial regulations are being met.

Data sources and analysis: Data were generally obtained from the facility operators as 1-hour averages. These were then used in the calculation of 24-hour and monthly average ambient SO₂ concentrations. Ambient concentrations averaged over the growing season were generally calculated from monthly averages. The growing season was defined to include the months April through October. One-hour and growing season averages were used in the assessment of risk to the environment. Twenty-four-hour averages were used in the assessment of risk to human health.

Environmental assessment: Handling of values below the detection limit ("non-detects") is a significant issue when dealing with ambient SO₂ data, for two reasons. First, up to 98% of the data may be non-detects. These values therefore exert a significant influence on temporal averages. Second, most monitoring is performed to ensure that relatively high, short-term thresholds are not exceeded. Therefore, monitoring is conducted or data are recorded to levels that are less sensitive than may be of significance when considering chronic exposure.

The normal method of correcting for non-detects is to set all values for non-detects to one-half the detection limit. This makes the assumption that non-detect values are equally distributed between zero and the detection limit. Detection limits for data used in this assessment ranged from 0.5 to 50 mg/m³. Setting non-detects to one-half the detection limit would have raised some estimates of seasonal average concentration by close to 25 mg/m³. This would have caused the chronic effects threshold values for environmental organisms to be exceeded owing to non-detected concentrations. To preclude this, only non-detects having associated detection limits of less than 3 mg/m³ were corrected to one-half the detection limit. One exception to this was a facility having several monitors with detection limits of 13 mg/m³. Non-detect values from these monitors were corrected to one-half the detection limit, as the percentage of non-detects was low, resulting in their having only a minor influence on seasonal averages.

Growing season average SO₂ concentrations at monitoring stations located near copper and zinc production facilities

1. With the exception of the three monitoring stations indicated as being operated by Falconbridge-Sudbury, all data for the Sudbury region were provided by the OME (courtesy of D. Racette, Northern Region). All other data were provided by the individual companies. It should be noted, however, that some monitoring stations are not operated by the companies. These include the MEF-operated site at Gaspé and the Robson site near Cominco-Trail, which is operated by a local pulp mill.
2. Total number of measurements refers to the number of 1-hour average values used to calculate the growing season average.
3. Growing season average concentrations that exceed the Estimated No-Effects Value (ENEV) (10 µg/m³) are shown in bold. Those that exceed the Critical Toxicity Value (CTV) (21 µg/m³) are in bold and underlined. These effects thresholds are discussed in Section 2.4.1.1.1.
4. For data obtained from HBM&S, Cominco and the OME (Sudbury region), values below the detection limit were corrected to one-half the detection limit. Data for Noranda-Gaspé, Noranda-Horne and Falconbridge-Kidd Creek were corrected for detection limit errors using the statistical method described in the text. Data for two of the monitoring stations at Kidd Creek could not be evaluated in this way due to a shortage of detected readings. Also, insufficient data were available for Falconbridge-Sudbury to allow any detection limit correction. Therefore, ranges within which these averages are expected to fall are shown. Data for Noranda-CEZinc were not corrected, as the detection limit was quite low (0.5 µg/m³).

One-hour average SO₂ concentrations during the growing season at monitoring stations located near copper and zinc production facilities

1. With the exception of three monitoring stations operated by Falconbridge-Sudbury, all data for the Sudbury region were provided by the OME (courtesy of D. Racette, Northern Region). All other data were provided by the individual companies. It should be noted, however, that in some cases monitoring stations are operated by organizations other than the company. These include the MEF-operated site at Gaspé and the Robson site near Cominco-Trail, which is operated by a local pulp mill.
2. The number of 1-hour averages that exceed the ENEV (450 µg/m³) are shown in bold. Those that exceed the CTV (900 µg/m³) are in bold and underlined. These effects thresholds are discussed in Section 2.4.1.1.1.
3. For Falconbridge-Sudbury, only summary data that indicated the number of exceedences of 650 µg/m³ were available.

Annual summary of 24-hour ambient air concentrations of SO₂ near copper smelters and refineries and zinc plants in Canada

1. Site types: Rs=residential, Ru=rural, Co=commercial, In=industrial.
2. The arithmetic mean value was calculated by substituting one-half of the detection limit for those samples that did not contain detectable levels of SO₂. This assumption affects the calculated value markedly when detection limits are relatively greater and ambient concentrations relatively low. The effect of this assumption was minimal for most sites and affected the mean value by less than 30% for all sites except those marked with a "2" superscript.
3. The concentration ranges correspond to the WHO Air Quality Guideline for Europe 24-hour average concentration of SO₂ of 125 µg/m³ (WHO, 2000).
4. Although it includes both a copper smelter and a zinc plant, HBM&S has been included with copper smelters, since it was reported that there were no releases to air from the zinc plant.
5. Data from the OME (courtesy of D. Racette, Northern Region). For the Sudbury region, site locations are reported with respect to both the Falconbridge (F) and Inco (I) facilities.

Correction for non-detects when estimating chronic (i.e., growing season) exposures using data from monitors having higher detection limits was conducted as follows. This includes all monitors at the Falconbridge-Kidd Creek, Noranda-Horne and Noranda-Gaspé facilities, which had detection limits of 25-50 mg/m³. Seasonal averages for these sites were estimated using a statistical method (El-Shaarawi, 1989; El-Shaarawi and Esterby, 1992). This involved fitting detectable values to a suitable statistical distribution; using this distribution to estimate concentrations for sample values that were below the detection limit; and, finally, calculating the average using all detected and estimated values. The Weibull distribution was found to best describe the data (El-Shaarawi, 1999). It has the form:

F(x) = 1 - Exp{-[(x - x₀)/k]^m}

where x₀ is the regional background ⁷ concentration, which is taken to be 2.6 mg/m³ (Linzon, 1999), and "m" and "k" are fitting parameters for shape and scale, respectively. Further information on the methods used is provided in CED (2000).

Growing season average concentrations are shown in Table 10. The percentages of values that were above the detection limit ("% detects") are also indicated. Values shown in bold are above the chronic Estimated No-Effects Value (ENEV) (10 mg/m³), and those bolded and underlined are above the Critical Toxicity Value (CTV) (21 mg/m³) for sensitive vegetation. These effects thresholds are discussed in Section 2.4.1.1.1. One-hour average concentrations are shown in Table 11. In this table, the number of 1-hour averages measured over the period of the growing season that fall into defined concentration ranges is indicated. The concentration intervals shown correspond to the acute (1-hour) ENEV (450 mg/m³) and CTV (900 mg/m³) for sensitive vegetation (discussed in Section 2.4.1.1.1). A more detailed description of these data and their processing is contained in CED (2000).

Human health assessment: The health assessment was based on data for the entire year, rather than being restricted to the growing season. Summary statistics for the 24-hour averages over the most recent year for which data were provided are summarized in Table 12 for all of the facilities except for Noranda-CCR, for which data were not obtained. For each site, the table includes the arithmetic mean and maximum concentration of SO₂ for the most recent year for which data were provided, as well as the identity, location and type of site (e.g., residential) and the number of samples. The frequency of samples with concentrations in various ranges, corresponding to the 24-hour WHO Air Quality Guideline for Europe for SO₂ of 125 m g/m³ (WHO, 1987, 2000), is also presented for each site.

The arithmetic mean values in Table 12 were calculated by assuming a value of one-half of the detection limit for those samples that did not contain detectable levels of SO₂. This assumption can affect the mean markedly when detection limits are relatively great (as for Falconbridge-Kidd Creek, Noranda-Gaspé and Noranda-Horne) and ambient concentrations relatively low. Those instances when the mean value is affected by more than 30% by this assumption are indicated in the table.

Near those facilities with multiple monitoring sites, the arithmetic mean 24-hour concentration of SO₂ is generally increased in relation to the proximity to the facility. In addition, the mean level of SO₂ at virtually all of the sites is elevated compared to background levels at remote or rural locations, which are reported to be 5 mg/m³ or less (FPACAQ, 1987; Linzon, 1999; WHO, 2000). As noted in the table, these increased levels are also reflected in exceedences of the 24-hour WHO Air Quality Guideline for Europe for SO₂ of 125 m g/m³.

Source attribution: Both Table 10 and Table 11 include a column labelled "Emission-based source attribution." These attributions are based on the percentage contribution of separate operations to total emissions from a facility. In relating these source attributions to monitored concentrations, it is assumed that the amount that each source is contributing to measured ambient SO₂ concentrations is proportional to its emissions. For facilities comprising only a copper smelter or copper refinery or zinc plant, 100% of SO₂ emissions from the facility may be attributed to those sources. However, for combined facilities, such as those at Sudbury, Kidd Creek or Trail, several different operations may be contributing to total SO₂ emissions.

For these combined sources, the percentage contribution of each operation of concern to total SO₂ emissions from the facility has been estimated based on the following:

• The Sudbury region includes the Inco facility as well as the Falconbridge facility. As they share an airshed, results for ambient SO₂ monitoring in this region are influenced by the presence of the two. The Inco facility includes a nickel/copper smelter, a copper refinery and a nickel refinery, while the Falconbridge-Sudbury facility includes only a nickel/copper smelter. Source attribution was determined using a combination of emission data for 1995 contained in MacLatchy (1996) and from personal communication with Inco facility operators. Due to a lack of data on emissions from the Inco nickel refinery, it was assumed that SO₂ emissions were - like those from the Inco copper refinery -negligible. No major process changes at either of these facilities are believed to have occurred since 1995.
• The Falconbridge-Kidd Creek facility includes a copper smelter, copper refinery, zinc plant and concentrator. Source attribution was determined from 1995 emission data provided by Falconbridge. No major process changes are believed to have occurred at this facility since 1995.
• The Cominco-Trail facility includes a lead smelter and a zinc plant. The fraction of emissions attributable to the zinc plant was determined based on 1998 emission data provided by Cominco (personal communication with facility operators). These data reflect the significant process changes that took place at the facility in 1996.
• The HBM&S facility in Flin Flon includes a zinc plant and a copper smelter. Due to the process used, the zinc plant does not emit SO₂. Therefore, all of the SO₂ detected is attributed to the copper smelter, and the facility is listed in Tables 10 and 11 as a copper smelter.

It should be noted that these attributions ignore background (natural, regional, local -defined in footnote ⁷ on page 37) contributions to measured concentrations. This omission may be significant at some facilities that include major SO₂ emission sources that are not the subject of these assessments (e.g., the lead plant at Cominco-Trail). Details of the source attribution calculations are provided in CED (2000).

2.3.1.1.3 Deposition of sulphate from air

The deposition of sulphate in acid-sensitive regions of eastern Canada and its connection to release of SO₂ from Canadian copper and zinc facilities is discussed briefly here, and in more detail in SENES Consultants (1999a).

Due to the relatively high SO₂ emission rates associated with the Inco copper smelter in Sudbury, a number of studies have been directed at evaluating mesoscale impacts of these emissions. Chan et al. (1984) analysed concentrations of sulphur and selected trace metals in ambient air and precipitation within a radius of 40 km from the Sudbury area during the period mid-1978 to mid-1980. The downwind concentrations of sulphate in precipitation and SO₂ in ambient air were noted to be significantly higher than upwind concentrations, by as much as an order of magnitude in the case of SO₂. However, the Inco smelter SO₂ emissions were estimated to contribute less than 20% of the total wet sulphur deposition during precipitation events within the 40-km distance from Sudbury. Furthermore, the ratio of wet-to-dry deposition was estimated to be 0.39, indicating that the magnitude of dry deposition was similar to that of wet deposition during precipitation events. Keller and Carbone (1997) examined changes in sulphate concentrations in lake waters over a 20-year period from the mid-1970s to the mid-1990s in relation to reductions in sulphur emission rates from smelters in the Sudbury area. The study noted that, although overall sulphate concentrations in Sudbury area lakes have been greatly reduced as a result of reductions in sulphur emissions from levels in the 1970s to the present, a strong relationship remains between current sulphate concentrations and distance from the smelters. Keller and Carbone (1997) concluded that the current estimate of the "Sudbury" contribution, ranging from 54% at 10 km to less than 30% at 100 km from Sudbury, probably includes a substantial residual component from historically deposited sulphur stored in the catchment areas. This residual effect may represent an important factor in the rate of recovery in lake ecosystems from future reductions of SO₂ emissions. Although significant positive responses in lake water sulphate levels are evident from past SO₂ emission reduction programs, the influence of residual sulphur levels from historical deposition may complicate the rate of recovery with respect to future reduction programs.

Since emitted SO₂ can be transported over long distances from its sources, the assessment of regional-scale acidic deposition is largely based on computer modelling. The available long-range transport models can be subdivided into essentially two types of models: 1) comprehensive, dynamic models that incorporate physical and chemical processes, which are best suited for use in short-term, episodic studies; and 2) semi-empirical models that are computationally more efficient and less costly to run and which are better suited to evaluating long-term deposition effects.

Comprehensive modelling attempts to incorporate all the available knowledge about component processes into the model. Due to the extensive data and computational and human resources needed to develop and run such models, comprehensive models are often run on an episodic basis. This is appropriate because regional sulphate concentrations exhibit episodic behaviour that is linked to stagnant high-pressure systems. However, episodic deposition simulations do not necessarily satisfy all of the requirements for assessments of effects of emissions, because the latter are typically concerned with average annual deposition rates. Various aggregation schemes must then be used to determine the total annual deposition rate for the cumulative effect of acid deposition events during the year.

An alternative approach to the use of comprehensive models is to apply semi-empirical techniques to characterize oxidation, transport and deposition processes. Semi-empirical methods essentially assume that only the net effect of the individual processes needs to be considered in modelling the overall process. These models consist of simplified equations that describe the interactions between simplified processes.

An example of a semi-empirical technique for acid deposition in North America is the use of source-receptor relationships.

Source-receptor modelling is a simplified method of relating changes in ambient concentrations or deposition of pollutants to changes in emissions. Such models rely on "transfer matrices," which assume that the total concentration or deposition of a pollutant at a receptor location is the sum of partial contributions, each of which is proportional to the emissions from a source or group of sources in a region. Thus, the transfer matrix is a mathematical expression of the atmospheric link between the long-range atmospheric transport and chemical transformation model, the observed ambient concentration or deposition rate, and the emissions from a specified group of sources or source regions. Although the transfer matrices may be developed using comprehensive modelling techniques to establish the source-receptor relationships, subsequent application of the transfer matrices assumes that the relationships remain stable, such that there is no need to use comprehensive models for every analysis.

Two such source-receptor models were considered in the evaluation of SO₂ emissions from copper and zinc facilities in Canada described in this report. The first was the Integrated Assessment Model (IAM), developed to support the assessment of ecological impacts at selected receptor sites in eastern North America due to changes in SO₂ emissions across the continent (Environment Canada, 1997c). The IAM is a framework of models that were designed to consider the entire acid deposition system as a whole - from emissions of acidifying pollutants through to aquatic, forest, agricultural, visibility, wildlife, materials and health effects. At present, the model can be used to perform quick calculations of the impact of regional SO₂ emission changes on wet sulphate deposition at a limited number of selected receptor sites. Specifically, SO₂ emissions have been grouped into a total of 40 source regions: 15 in Canada and 25 in the United States. The transfer matrix in the IAM source-receptor module is used to estimate the average annual total wet sulphate deposition at 15 receptor sites in eastern North America.

The second model considered involved the source-receptor matrices developed in 1996 by SENES Consultants Limited based on the MESOPUFF II model. The MESOPUFF II model was used to develop a source-receptor unit transfer matrix for 375 point sources of SO₂ emissions in eastern North America and 248 receptor points in Ontario, Quebec and the Maritime provinces (SENES Consultants, 1996a). The transfer matrix was developed in support of the Environment Canada project "SO₂ Emission Abatement Strategies and Economic Instruments."

The source-receptor relationships in the IAM are based on more detailed long-range transport modelling analyses using the Atmospheric Environment Service Long-Range Transport (AES-LRT) model (Olson et al., 1983). Consequently, for the purposes of this analysis, it is reasonable to assume that IAM is based on more reliable transformation and transport modelling, and that the IAM results provide a more accurate prediction of wet sulphate deposition rates for comparison with critical load values than the results derived from the MESOPUFF II model. For this reason, the remainder of the discussion will be based on the IAM results. A comparison of the results obtained using the IAM and MESOPUFF II models and discussion of their relative merits are contained in SENES Consultants (1999a).

The contribution of SO₂ emissions from Canadian copper smelters and refineries and zinc plants to wet sulphate deposition in eastern Canada was calculated based on the SO₂ emission rates listed in Table 3. The analysis was conducted on selected lake cluster groups (Algoma, Ontario; Sudbury, Ontario; Montmorency, Quebec; and Kejimkujik, Nova Scotia), consistent with other recently completed evaluations of the impact of SO₂ controls on sulphate deposition (Environment Canada, 1997c,d; Lam et al., 1998; Jeffries et al., 1999). The incremental contributions of individual facility emissions⁸ to wet sulphate deposition within the four lake cluster groups were estimated using the IAM source-receptor matrix. However, because IAM does not have a receptor at Sudbury, the nearest IAM receptor site to Sudbury (i.e., at Muskoka, Ontario) was added to the analysis.

It is estimated that copper smelters contributed from 95-97.5% of the wet sulphate deposition originating from copper and zinc facilities in Canada at these receptor locations, in line with their dominant share of the total SO₂ emissions from copper and zinc facilities as a source group. From the perspective of individual facility contributions, this industry's wet sulphate deposition is largely dominated by SO₂ emissions from three copper smelters: Inco's Copper Cliff smelter in Sudbury, the HBM&S copper smelter at Flin Flon, and the Noranda-Horne copper smelter. Collectively, these three smelters are estimated to account for the following fractions of wet sulphate deposition (relative to SO₂ emissions from all Canadian copper and zinc facilities):

• 85% at Algoma, Ontario;
• 87% at Montmorency, Quebec; and
• 76% at Kejimkujik, Nova Scotia.

Moving eastward, the significance of the emissions from the smelter at Flin Flon diminishes and is replaced by wet sulphate deposition from SO₂ emissions at the copper smelters operated by Falconbridge near Sudbury and Noranda-Gaspé. The latter contributes about 14% of the industry sector wet sulphate deposition at Kejimkujik, while the Falconbridge smelter contributes about 7-8% of the total wet sulphate deposition from copper and zinc facilities. Deposition rates at Sudbury were not calculated due to a lack of a suitable receptor point for IAM.

Relative to other sources of SO₂ emissions in Canada, the analysis indicates that the SO₂ emissions from the copper and zinc facilities (particularly the copper smelters) in 1995 represented a significant source of wet sulphate. Results are summarized in Table 13. At Algoma and Montmorency, the industry sector contributions of 0.572 kg/ha/a and 1.611 kg/ha/a, respectively, at 1995 emission rates, represented about 30% of the average wet sulphate deposition from all anthropogenic Canadian sources for the 1990-1993 period. At Kejimkujik, the industry sector's contribution was smaller, representing about 14% of anthropogenic Canadian source contributions between 1990 and 1993. However, with respect to all sources of SO₂ emissions in North America, the relative magnitude of the wet sulphate deposition from Canadian copper and zinc facilities is substantially lower. At 1995 emission levels, these facilities as a source group were estimated to contribute approximately 3% of the 1990-1993 average anthropogenically derived wet sulphate deposition at Algoma, 9% at Montmorency and 2% at Kejimkujik. Despite the fact that sources in eastern Canada account for only 14% of the total SO₂ emissions in eastern North America, eastern Canada receives approximately 41% of the total wet sulphate deposition (Environment Canada, 1997c). Long-range transport modelling and monitoring data suggest that U.S. sources contribute up to 90-95% of the sulphate deposition in the very southwestern parts of Ontario, with the proportion attributable to U.S. sources declining with distance from the border (Acidifying Emissions Task Group, 1997). Therefore, whereas the copper and zinc facilities represent a significant source group for sulphate deposition from Canadian sources, their contribution to acid deposition from all sources in North America is considerably smaller. Moreover, although the contribution of large copper smelters, such as those located at Sudbury, to total sulphate deposition may be significantly higher within a radius of about 100 km of the facility (Keller and Carbone, 1997), the relative percent contribution of these facilities, both individually and collectively as an industry group, is much smaller at the regional scale of eastern Canada.

It is worthwhile to compare deposition values estimated using IAM (Table 13) with empirical deposition results. Wet deposition rates based on sulphate measured in samples collected by the Ontario Ministry of the Environment (OME) are shown in Table 14. The wet sulphate deposition rate of 22.9 kg/ha/a modelled for Muskoka using IAM is in good agreement with empirical sulphate deposition data for the years 1990-1993 at the three stations located near Muskoka (range of station averages -16.4-19.5 kg/ha/a). The IAM rate of 17.5 kg/ha/a for Algoma is also in good agreement with the average value of 24.1 kg/ha/a measured at the Turkey Lake station, located in the Algoma region. It should be recognized that monitored results represent deposition at a single location, while IAM estimates average deposition over relatively large areas, within which there may be considerable local variability. Table 14 also shows sulphate deposition rates for 1995, the year on which the incremental sulphate deposition rates are based.

1. Percentages in the section on North American SO₂ sources indicate the fractional contribution of source types to wet sulphate deposition from all North American sources. Due to rounding, values may not total 100%.
2. Percentages in the section on Assessed Canadian SO₂ sources indicate the fractional contribution of facility types to wet sulphate deposition from all North American sources.

1 Values are based on the unfiltered reactive sulphate content of wet-only deposition samples collected by the OME.

2.3.1.2 Metals

2.3.1.2.1 Fate of metals in air

Metals released to air from copper smelters and refineries and zinc plants are typically in particulate form. Releases may be divided into those from fugitive and low-level sources, and those released from high-level stacks.

Relative to stack emissions, fugitive particles are relatively coarse and are generally deposited close to the point of release. Because of the short transport times, chemical forms of the deposited particles are expected to be very similar to those of the source materials.

The fate of substances in stack emissions depends upon the physical and chemical nature of the substance and on a variety of site-specific factors, including stack height, velocity of release, surface topography and local meteorological conditions, such as wind speed and direction and precipitation frequency. Metals associated with fine suspended particles may be transported relatively long distances before deposition.

Although recent stack testing data from the Inco operation (Burnett, 1998) showed that about 80% of its emissions (by mass) were fine PM (<3 mm), results of older in-plume studies for the Falconbridge and Inco-Copper Cliff plumes reported by Chan and Lusis (1986) and Chan et al. (1983) suggested that metals such as Cu and Ni may be primarily associated with coarse particle sizes (equal to or greater than 2.5 mm), with mass median diameters greater than 9 mm. On the other hand, these authors reported that other trace metals such as Pb, Zn and As occurred most frequently (but not always) with fine particles (less than 2.5 mm) and typically with particles with mass median diameters closer to 1 mm. Results for Cd (and Cr) tended to fluctuate from one sampling run to another, but Cd was more likely to be associated with the fine particle fraction. Cumulative plots for coarse particle distributions of Cu indicated that approximately 60-95% or more of the Cu was associated with particles greater than 2.5 mm. Cumulative plots for the other trace metals were not reported. The extent to which results of this older study are representative of current conditions is unknown.

No data were identified on the speciation or bioavailability of metals in Canadian air contaminated by smelter or refinery emissions. Limited data from both copper and zinc smelting and refining operations in other countries indicate that most metals are released as particulate oxides, sulphides and/or sulphates (Eatough et al., 1979; Harrison and Williams, 1983; Whyte et al., 1984). In the atmosphere, oxides may react with sulphuric acid to form more soluble sulphates (Franzin et al., 1979; Zwozdziak and Zwozdziak, 1986). Because of their solubility, sulphate forms are expected to be relatively bioavailable.

As discussed in more detail below, metals may be deposited from the atmosphere by both wet and dry deposition processes. As a result, they can accumulate in a variety of media, including surface soils, lakewaters and sediments. Concentrations of deposited metals in such media typically decrease exponentially with distance from a source. The radius of local enrichment resulting from past releases from Canadian smelters and refineries - relative to background values - has been reported to vary from several tens of kilometres up to over 100 km, depending upon the site, the media and metal of interest (John et al., 1976; Glooschenko et al., 1986; Zoltai, 1988; Dumontet et al., 1990).

2.3.1.2.2 Deposition of metals from air -empirical

The following is a brief description of the types of monitoring data used to estimate annual soluble metal deposition. Also included are descriptions of the methods used for estimation of source attributions, water-soluble fractions of deposited metals and levels of regional background metal deposition. Notes providing greater detail on the handling of data have been compiled in CED (2000).

Dustfall: Dustfall monitoring involves exposing an open-topped canister containing a collection medium to the ambient air for some period of time. The collection medium is typically water but may include other liquids (e.g., alcohol/water mixtures) during winter months. Exposure time is typically 28-30 days. The collected material is then analysed for total metal content.

Dustfall samplers measure total deposition, as they collect both material deposited during precipitation events (wet deposition) and particles settling under the force of gravity (dry deposition). Collection efficiency for micron- and submicron-sized particles is limited, however, and the results from dustfall monitoring may slightly underestimate total deposition. These monitors are generally used close to facilities, where the majority of deposition is due to gravitational settling of larger particulates.

All dustfall monitoring data were obtained in the form of total deposition rates (mass/area/time). As monitoring is usually continuous, results for individual dustfall samples from the same station can be summed for all samples collected over the period of a year. Total soluble annual deposition rates were then calculated using the appropriate fractions for metal solubility.

Results for dustfall monitoring are provided in Table 15. It is generally noted that annual deposition rates decrease with increasing distance from the facilities. In particular, elevated deposition rates of Cu, Zn, Pb and Cd may be seen. Monitoring of Ni in dustfall samples was not conducted near any of the facilities. Values shown in bold are above the 25th percentile critical loads (CLs), and those bolded and underlined are above the 50th percentile critical loads. These effects thresholds are discussed in Section 2.4.1.1.3.

Dry deposition from total suspended particulate (TSP): TSP monitoring involves collection of PM by passing ambient air through a filter. This is usually done using high-volume air samplers, where air is passed through the filters at rates of typically 1000-1500 L/min. Sampling usually takes place over a 24-hour period and is normally conducted one to two times per week. The collection filters are then analysed for total metal content, allowing determination of the concentration of metals in air. The OME uses continuous monitoring with low-volume air sampling. Air is continuously passed at a rate of about 2 L/min, and filters are changed every 28 days.

Particulate material that settles through gravity onto the ground or surface waters is referred to as "dry deposition." Calculation of dry deposition rates from measurements of TSP concentrations in air requires the application of a deposition velocity, which describes the rate of descent of a "typically" sized particle. A velocity of 0.2 cm/s was used in this work. This value has been used by the Integrated Atmospheric Deposition Network (IADN) in determination of rates of dry deposition to the Great Lakes and is discussed in Hoff et al. (1996). Hoff et al. (1996) point out that deposition velocity is a function of particle size, hygroscopic growth of the aerosol, wind speed and humidity. In particular, the effective deposition velocity of 0.2 cm/s is derived based on a small particle to large particle mass ratio of 1.5:1, for "small" and "large" particles having diameters of about 0.5 mm and 5 mm, respectively.

In-stack particle size data obtained for the main stack at Inco-Copper Cliff (Burnett, 1998) indicated that about 15% (by mass) of the PM was below 1 mm, with another 65% falling in the range 1-3 mm, and the remaining 20% larger than 3 mm. This is in reasonable agreement with the mass ratios assumed in derivation of the deposition velocity used in this work. This does not, however, consider particulates from fugitive sources, which tend to be of larger size and settle more rapidly. It should be recognized that the value of 0.2 cm/s was derived for use over large areas (the Great Lakes) located some distance from emission sources, and its application could significantly underestimate the extent of dry deposition close to emission sources, particularly fugitive sources.

Once dry deposition rates have been estimated, they may be summed with independent measurements of wet deposition to obtain total deposition rates. Often, however, no data on wet deposition are available. In this circumstance, total deposition may be estimated by applying a factor to a dry deposition value that is representative of "typical" total:dry deposition ratios. Two approaches were considered in estimating what this factor should be.

The first approach used data from OME monitoring stations that had both wet-only deposition monitors (described later on) and TSP monitors. Based on these data, the percentages of total deposition (sum of wet plus dry) that are due to dry deposition have been calculated and are indicated in Table 16 for each metal. Results shown are based on annual average deposition values calculated from several years of data for seven stations located within 100 km of the zinc or copper processing facilities. It is seen from these results that dry deposition typically represents 20-25% of total deposition at sites located within 100 km of the sources. Most of these monitoring stations are located at least a few kilometres from facilities. Therefore, the proportion of coarse particles released from fugitive sources is likely to be small. These percentages are therefore expected to be reasonably accurate for deposition occurring some distance from the emission sources.

1 Associated error values are sample standard deviations. Values in parenthesis are the number of values (monitoring station-years) averaged.

The second approach used data from company-operated stations that had both TSP and dustfall monitors. For these stations, the percentage of dry deposition was calculated by dividing the TSP-derived dry deposition by the dustfall-based total deposition. These results are also shown in Table 16 for the seven stations conducting both types of monitoring (five Cominco sites, one Noranda-CEZinc site, one Noranda-Gaspé site). These monitors are mostly located close to emission sources. Six of the seven stations considered are located between 0.8 and 4.3 km of the smelting facilities, with the seventh station located 10.5 km from the source. In general, the percentages obtained using this approach are somewhat less than those estimated from the OME data (see Table 16), the average dry deposition value (across the different metals) being 14%.

It is likely that both approaches underestimate the contribution of dry deposition to total deposition closer to emission sources. The first approach has been based on deposition further from sources, where larger particles represent only a small fraction of TSP. In the second approach, the deposition velocity of 0.2 cm/s is too low to account for larger particles, which represent a significant fraction of TSP close to sources.

Following consideration of this information, a factor (total:dry ratio) of 4 has been applied to estimate total deposition from dry deposition, corresponding to a dry deposition fraction of 25%. This is based on the first approach. Estimates of the proportion of dry deposition based on the second approach ranged from 6-27%, which would result in factors ranging from 4-17. These values were not used, as they are based on a limited number of samples and show significant variability. It must be recognized, therefore, that the total:dry ratio of 4 selected is the lowest factor that could be applied to dry deposition values in order to estimate total deposition, and that there is a high probability that this will underestimate total deposition especially closer to emission sources.

Deposition rates derived from TSP monitoring data are shown in Table 17. With the exception of the OME sites (Inco-Copper Cliff), all TSP monitoring was periodic. For each metal, the average of all values of metal concentration in air measured over one year was converted to a deposition rate using the deposition velocity of 0.2 cm/s. The dry soluble deposition rate was then calculated using the appropriate fraction for metal solubility. The factor of 4 was then applied to provide an estimate of total soluble deposition, shown as "est. of total" in Table 17.

As was seen in Table 15 for dustfall results, trends of decreasing deposition rates as a function of distance from the facility are also observed for the TSP-derived deposition rates (Table 17), and elevated deposition rates can be seen, especially for Cu, Zn, Pb and Cd. It should be noted, by comparing values in the two tables for monitoring at similar distances from the sources, that annual deposition rates estimated from TSP data are in nearly all cases somewhat lower than those measured in dustfall samples.

Wet plus dry deposition: In addition to monitoring TSP, from which dry deposition can be estimated, the OME and the IADN program monitor "wet-only" deposition. Wet-only monitors collect deposition in canisters that have covers. The apparatus have sensors that monitor moisture and activate a mechanism to open the lid when it is raining or snowing. The sensors are heated, which prevents the lid from remaining open after the precipitation event stops.

Deposition of soluble metals in the vicinity of copper and zinc production facilities ¹ - based on total suspended particulate sampling