Canada’s Air Pollutant Emissions Inventory Report 2022: annex 2.9

A2.9 Estimation methodologies for Dust by sector

Coal Transportation

Description

Coal Transportation includes PM emissions resulting from the transportation of coal by open-top rail, truck or barge.

Most of the coal mined in Canada is carried to transshipment terminals (ports, for export) or to end use facilities by unit trains. Coal imported into Canada is predominantly shipped in lake and ocean vessels. Some imported coal is landed directly at the end-use facility; some is transported inland from import terminals by train or truck. Coal imported from central and western United States is generally transported by rail to end-use facilities. Trucks are typically only used for coal shipment over shorter distances, whether to rail load-out (where it is shipped by rail the rest of the journey), or directly to the end-user / transshipment (port) terminals (Cope and Bhattacharyya, 2001).

Load-in and load-out losses, including transportation within the mine site and to mine-mouth facilities, are estimated and reported by mine facilities to the NPRI as part of fugitive emissions. Emissions from fuel combustion during coal transport (diesel, gasoline or oil) are inventoried separately as part of the Transportation and Mobile Equipment source category.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5

Emissions are estimated for each source-destination rail, truck or barge transportation route and summed by province.

Emission factors for TPM for each rail or truck transportation route (source-destination) are derived from the distance travelled, the emission control/dust-mitigation effectiveness, and moisture (precipitation) along the route. For each province that a route crosses, the route emissions attributed to that province are determined from the proportion of the province-segment of the route to total route length. The PM₁₀ and PM_2.5 emissions are calculated from the TPM emissions using a scaling factor.

The mass of coal transported along each route is determined on the basis of either mine production of marketable coal (for mine to port or mine to end-user) or coal demand by end-user (for imported coal to end-users). Coal mine production sent to multiple destinations is proportioned on the basis of documented coal shipping volumes to each destination, reported coal demand for coal-users, or estimates from Cope and Bhattacharyya (2001). Where no information was available, coal production was proportioned to the various destinations on the basis of the distance between the mine and the destination.

Activity data

Coal mine production and coal-user demand: (Statistics Canada, n.d.[a], n.d.[b], n.d.[c]; Cope and Bhattacharyya, 2001) and company websites (accessed 2017).

Monthly climate summaries: ECCC (2017)

Rail Transportation Network: NRCan (n.d.[a]) (1:1 M scale used)

Mine Locations: BC MINEFILE (2017) and AER (2015), environmental assessment reports, and in-house remote-sensing.

Emission factors (EF)

Cope and Bhattacharyya (2001)

Construction Operations

Description

Construction Operations include PM emissions primarily resulting from soil disturbance on construction sites. The amount of soil disturbance depends on the surface area and duration of a construction project. The geographic region, type of construction (residential, industrial-commercial-institutional [ICI], engineering) and soil characteristics are all considered.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5

Residential construction

Emission factors (SNC-Lavalin Environment, 2005) are applied to the number of housing starts, the average lengths of construction (duration) and buildings-to-hectares conversion factors, by province and territory and dwelling type. The number of houses with basements and average basement area and depth (volume of earth moved) are also considered. Emission factors are corrected for soil texture using average provincial soil silt contents weighted by the areas of highest residential construction or average territorial level soil silt contents. The Thornthwaite precipitation-evaporation (PE) index by province and territory is used to correct the emission factors for soil moisture.

ICI and engineering construction

Methodology under review

The in-house estimates for ICI were last calculated for 2012 and were carried forward to 2018.

Activity data

Residential construction

Dwelling starts: Statistics Canada (n.d.[d]) and CMHC (2020)

Average lengths of construction: CMHC (2017)

Buildings to hectares conversion factors: SNC-Lavalin Environment (2005)

Average basement area and depth: SNC-Lavalin Environment (2005)

Number of homes with basements: SNC-Lavalin Environment (2005)

ICI and engineering construction

Methodology under review

Emission factors (EF)

Residential construction

TPM, PM₁₀, PM_2.5: SNC-Lavalin Environment (2005)

Correction factors:
% silt content^{Footnote 3}

Precipitation-Evaporation (PE) Index: SNC-Lavalin Environment (2005)

ICI and engineering construction

Methodology under review.

Mine Tailings

Description

Mine Tailings covers emissions of particulates resulting primarily from wind erosion of mine tailings located on active and inactive mine sites.

Concentrators used for mining produce both a finely-milled concentrate rich in the desired metal(s) and a solids-laden mine tailings stream. This slurry is sent to a tailings pond where the solids settle out of suspension and the supernatant solution is either recycled back into the process or discharged as effluent. It is a common, though not universal, practice to keep the solids in the tailings pond submerged, even when the mine is inactive or closed. If the solids are no longer submerged, fugitive particulate emissions occur through wind dispersion. Wind may disperse dust from silt fractions within exposed substrate and coarse waste materials.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5

Particulate matter dust emissions are estimated by applying an emission factor to the area of exposed mine tailings. The emission factor, taken from Evans and Cooper (1980), is loosely based on wind soil-loss equations. A term to account for snow cover was added to the original equation.

EF_TPM = 1.33C x A x S

where C is a weather correction factor,

A is the area of mine tailings in acres, and

S is (365 – n_days_with_snow_cover) / 365

The emission factor is for TPM, with the smaller PM size fractions determined as ratios of TPM:

PM₁₀ = 0.8 x TPM, PM_2.5 = 0.2 x TPM

The weather correction factor C is calculated from the equation:

C = 0.345(V₃₀)³ / PE²

where V₃₀ is the average annual wind speed at 30 ft elevation (miles per hour), and

PE is the Thornthwaite precipitation-evaporation index, calculated as

PE = 115 ∑ [ P / (T-10) ]^(10/9) (sum of monthly)

where P is precipitation in inches and T is the temperature in Fahrenheit or 28.4 °F, whichever is greater.

The weather correction factor, C, is determined for each province, by year using monthly surface wind speed (CCMP, n.d), precipitation (CRU 4.03, 2019) and temperature (CRU 4.03, 2019). All data sources ranged from spatial resolution of 0.25 × 0.25 to 1 × 1 degree latitude/longitude resolution.

The snow cover correction is applied as a single provincial value (full time-series data were not available). Days with snow cover taken as the mean number of days with snow cover greater than 5 cm. Snow cover data were obtained from the Canadian Meteorological Centre (CMC, 2019) daily snow depth analysis, using 2000 to 2018 data, except years with missing data (2003 to 2005, and 2008).

The mine tailings areas were measured via a remote sensing classification of mine disturbance areas throughout the country. Mine disturbance areas were classified from Landsat-5 and Sentinel 1, and Sentinel 2 imagery for the years 1990, 2000, 2010, and 2018, using supervised random forest classification, processed using Google Earth Engine (Fuentes et al., 2020). Tailings areas are taken as one third of total mine disturbance areas, with further “within-mine” classification and mapping planned as a future improvement.

The classification of mine disturbance areas was restricted to a search area consisting of a 3 km buffer around known mine sites (existing or abandoned) identified in various ancillary data sources at any time between 1977 and 2016. Ancillary data sources used were Murray (1977), Natural Resources Canada, Map 900A, Producing Mines, 48th ed. (1996) to 66th ed. (2016), Parsons et al. (2012), Natural Resources Canada (NRCan), CanVec ManMade vector data (NRcan, n.d.[b]), filtered for “Industrial Waste,” which includes tailings.

The mine disturbance areas were manually refined and corrected in “challenging” regions for the automated classification, such as mountainous areas, badlands and high-arctic regions.

Activity data

Fuentes et al. (2020)

Emission factors (EF)

Evans and Cooper (1980) with addition of term to account for snow cover.

Paved and Unpaved Roads

Description

Emissions from Paved Roads originate from primary (road abrasion) and secondary (resuspended) PM emissions. Emissions from unpaved roads originate from suspended or resuspended silt from the road surface.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5

Road abrasion, or primary paved road emissions, are produced by multiplying the total vehicle kilometres travelled for each province and territory by pollutant-specific emission factors.

The methodology for secondary (resuspended) emissions is based on the U.S. EPA AP-42 methods. Paved road emissions follow the AP-42 Section 13.2.1, 2011 update (U.S. EPA, 2011). Unpaved roads estimation methods follow the AP-42 Section 13.2.2, 2006 update methods for publicly accessible roads (U.S. EPA, 2006). In both cases, a Canadian-specific traffic distribution model was used to determine traffic volume by road class and regional distribution of traffic for application of weather correction parameters. Unpaved roads also include facility-reported emissions occurring on private roads and parking lots.

The road dust emissions are nominally the application of an emission factor to the vehicle kilometers travelled (VKT). The emission factor calculation differs for paved and unpaved roads. For paved roads, the emission factor is a function of the silt load—which in turn is a function of annual average daily traffic volume (AADT), average vehicle fleet weight, and weather corrections for wet-days, winter silt load adjustments (to account for grit application) and snow cover. For unpaved roads, the emission factor is a function of road surface silt content, mean vehicle speeds, and surface material moisture content, a correction to remove 1980s vehicle tailpipe, tire-wear and break wear emissions (which were included in the original model parameterization), and weather corrections for snow and frozen road surfaces.

Speeds on unpaved roads were estimated to be 70 km/hr for highways, 60 km/hr for collectors, 50 km/hr for arterial roads and resource and recreation roads, and 40 km/hr for local roads. The average fleet weight for Canada was estimated to be 2.676 t. The silt content of unpaved roads was taken as 3.9% (AP-42 section 13.2.2, 2006 update default value).

Silt loads were taken from the AP-42 Table 13.2.1-2. Silt load (sL) is a function of average annual daily traffic volume (AADT), with adjustments for winter grit application (winter baseline multiplier).

In order to determine the number of roads having traffic volumes (AADT) within the various silt load ranges and to apply regional weather correction parameters, the regional distribution of VKT is also required. The Natural Resources Canada road network was used, with roads reclassified into a subset of classes (paved/unpaved resources and recreation, local, collectors, arterial, highways, freeways, and winter roads). Winter roads are considered neither paved nor unpaved and are assumed to be not a source of dust. Freeways are only paved. Traffic counts from provinces and municipalities across Canada were collected by ECCC and spatially matched to the road network (approximately 500,000 data-points). Roads and census population (1991 to 2016 census years) were summarized by census subdivision using census geography vintages/versions from the 1996, 2006, and 2016 censuses (Statistics Canada 1996a, 1996b, 2006a, 2006b, 2016a, 2016b). The ratios of mean traffic volume by road class modelled against regional population density to a baseline of paved local roads was used to distribute the estimated total VKT in Canada to each road class in each census subdivision, by year (geography and population varying by census year). See section A2.4: Estimation methodologies for Transportation and Mobile Equipment for VKT estimation methods).

Weather parameters (soil moisture) and corrections (precipitation, winter multipliers) were applied on a monthly time-scale at the census subdivision level. The frost days and wet days were obtained from Climate Research Unit (CRU 4.03, 2019), 0.5 × 0.5 degree spatial resolution, monthly. Soil moisture was from the NOAA Climate Prediction Center (NOAA, n.d.), 0.5 × 0.5 degree spatial resolution, monthly. Winter silt load multipliers were applied, by census subdivision, for any month that the subdivision had more than 15 days with a mean temperature below zero.

It is assumed that no dust is (re)suspended from paved or unpaved roads on days with precipitation. The emission factor was adjusted using the factor:

Precip_Cor = (n_Days_per_Month – Precipitation_Days) / n_Days_per_Month

For unpaved roads, soil moisture was taken as the mean surface soil moisture content of the census subdivision, or 6.515% (the AP-42 2006 update, section 13.2.2 default value), if weather data were not available.

Activity data

See General inventory method. The method used to calculate VKT for Transportation and Mobile Equipment sources was used to estimate VKT for primary and secondary emissions.

Emission factors (EF)

Primary—EEA (2013)

Secondary—Methodology under review

References, Annex 2.9, Estimation methodologies for Dust by sector

[AER] Alberta Energy Regulator. 2015. Coal mine atlas, online interactive map application. Serial Publication: ST45. [last updated 2015 May 15; accessed 2017 Sept].

BC MINEFILE. 2017. Coal producer database search results, MINFILE digital data [last updated 2017 Sept; accessed 2017 Sept].

[CCMP] Cross-Calibrated Multi-Platform. No date. Gridded surface vector winds, level 3.5 – Monthly mean. Accessed via Remote Sensing Systems (REMSS.com). Spatial resolution: 0.25 × 0.25 degree. [accessed Jul 2019].

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[CMHC] Canadian Mortgage and Housing Corporation. 2017. Housing market information portal (database). [accessed 2017 Sept 20].

Cope DL, Bhattacharyya KK. 2001. A study of fugitive coal dust emissions in Canada. Unpublished report. Prepared for the Canadian Council of Ministers of the Environment.

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[ECCC] Environment and Climate Change Canada. 2017. Monthly climate summaries (database) [accessed 2017 Sept].

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