The Georgia Basin-Puget Sound Airshed Characterization Report 2014: chapter 1

1. Introduction

Rebecca Saari, Roxanne Vingarzan and Rita So (Environment Canada)

1.1 Report Objectives

The Georgia Basin - Puget Sound Airshed Characterization Report, 2014 was undertaken to characterize the air quality within the Georgia Basin/ Puget Sound airshed (the airshed), a vibrant, rapidly growing, urbanized area of the Pacific Northwest. Growth within this region continues to put stress on the environment, due to urban sprawl, increasing transportation demands, expansion of ports and developments in the energy sector, among the many challenges faced in managing air quality in the area.

This airshed includes jurisdictions in both Canada and the United States. Both countries routinely evaluate their air quality standards and objectives based on emerging science. This report is an update of the 2004 publication by the same name and represents new data, trends, regulations, studies, and policy implications pertaining to the Georgia Basin/ Puget Sound airshed. The work is intended to provide scientific information to assist in the management of air quality in this international airshed.

Its specific objectives are to:

  • Identify and describe the key factors, natural and anthropogenic, affecting air quality in the region;
  • Establish a current benchmark against which changes in air quality over the next 10 years can be measured;
  • Determine if significant transboundary transport of air pollution occurs within the Georgia Basin/Puget Sound airshed;
  • Describe the anticipated consequences on air quality of specific air quality management actions;
  • Describe the impacts of air quality on the ecosystem and on human health;
  • Describe the impacts of climate change on air quality; and
  • Provide a scientific basis for the development of public education and communication materials designed to enhance citizen understanding of air quality
    in the region.

It should be noted that this report synthesizes the results of many studies on air quality in the area. It is not meant to simply report the work of others, but to summarize and link their many important findings. References are provided to acknowledge these sources, and to furnish readers with an avenue for more thorough research.

1.2 Defining the Airshed

The term “airshed” is inspired from aquatic science, which employs the term “watershed” to describe the “land area from which water drains toward a common watercourse in a natural basin.” Unlike water, air is not typically bound to a specific region. However, stagnant periods do arise when the weather and topography combine to trap air pollutants within a well-defined geographic area. Under these conditions, this area or “airshed” comes very close to the definition of “watershed” given above. It is under these conditions that the term is used in this report.

This report explores the state of air quality in Georgia Basin/Puget Sound airshed (see Figure 1.1), which is actually comprised of two smaller sub-regions: the Georgia Basin and the Puget Sound. The Georgia Basin portion comprises the Canadian portion of the airshed, as well as the north-western tip of Whatcom County and San Juan County in Washington State and the southern coastline of the Strait of Juan de Fuca. It should be noted that the southern boundary of the Georgia Basin airshed extends to the higher terrain of the north Cascades. The Puget Sound portion encompasses the counties to the south of Whatcom County (Figure 1.1). An important international transport region for airborne pollutants exists in the Lower Fraser Valley, which is bisected by the Canada-U.S. border, and along the southern edge of Haro Strait, situated at the eastern end of the Strait of Juan de Fuca. This report emphasises the atmospheric properties of this region which are most important to air quality.


1.3 Defining the Issues

The report focuses on three air pollution issues: ground-level ozone (ozone), particulate matter (PM) and visibility. Ozone and PM are pollutants of concern for multiple reasons. They both cause deleterious effects and play key roles in poor regional air quality and climate change. Ozone and PM are pollutants that can form in the atmosphere from chemical or physical processes. To distinguish them from pollutants that are released directly into the air, pollutants that form in the atmosphere are referred to as “secondary pollutants”. Due to their complex formation pathways, secondary pollutants like ozone and PM often present unique challenges to developing sound ambient objectives and control policies.

Ozone and PM both have known harmful effects. Ozone is detrimental to human health and causes damage to vegetation and physical structures. Fine particulate matter is linked to respiratory and cardiac problems, increased mortality, and poor visibility. Poor visibility is a quality of life issue for many people in the airshed and has the potential to harm the economy by limiting tourism (McNeill and Roberge, 2000). Agencies are challenged when setting protective ambient objectives for particulates because their harmful health effects occur at very low concentrations; in other words, there is little evidence to suggest a threshold below which no adverse health effects would be anticipated (WHO, 2006).

Figure 1.1 The Georgia Basin/Puget Sound airshed, delineating the Puget Sound and Georgia Basin airsheds.

Figure 1.1 The Georgia Basin/Puget Sound airshed, delineating the Puget Sound and Georgia Basin airsheds.

Description of Figure 1.1

Figure 1.1 is a relief map showing the area contained in the combined Georgia Basin/Puget Sound airshed, and delineating the areas encompassed by each airshed individually. The Georgia Basin covers all of the Strait of Georgia up to Quadra and Cortes Islands in the north and extending up Toba Inlet and into the Coast Mountains to approximately 50 km north of Whistler village. In the east it encompasses the Fraser Canyon west of Merritt as well as the town of Hope. In the west it encompasses the towns of Campbell River and Courtney and the area of Vancouver Island east of the Alberni Inlet as well as the entire southern tip of Vancouver Island below Nitinat Lake. It also encompasses the Strait of Juan de Fuca.

The southern boundary of the Georgia Basin airshed and the northern boundary of the Puget Sound airshed is a line extending from the southern shore of the Strait of Juan de Fuca to Port Angeles, then north along the western shore of Whidbey Island and up the southern edge of the Fraser Valley. The Puget Sound airshed is defined in the east by a line running north-south through the Cascade Mountain Range and including Glacier Peak in the east and Mt Ranier in the south. The south of the Puget Sound airshed includes all the reaches of Puget Sound as well as the town of Olympia. In the west it is defined by a line running north-south through the Olympic Mountains and extending out to the mouth of the Strait of Juan de Fuca. The combined Georgia Basin/Puget Sound airshed encompasses all of the areas described above.


Ambient concentrations of ozone and PM in the Georgia Basin/ Puget Sound airshed are in general below air quality guidelines and objectives, however exceedences do occur in hot spot areas. Unlike other common pollutants, ozone and fine particulate matter are difficult to control, because they can form spontaneously in the atmosphere; this formation occurs under the appropriate meteorological conditions when the chemical precursors are present.

These issues are not only matters of public concern but also relate to specific policy needs, such as compliance with Canada Wide Standards, the U.S. Environmental Protection Agency air quality standards and the U.S. Regional Haze Rule.

1.4 Guide to the Report

The report is divided into a number of sections, each of which deals with an aspect of air quality in the airshed. Chapter 2, “Fundamental Concepts of Air Quality”, presents basic concepts that define and influence air quality, including ambient air quality and standards, pollutant sources and atmospheric processes. The importance of meteorology is explained in Chapter 3, “Air Quality and Weather”. The effects of social and economic trends on air quality are discussed in Chapter 4, “Air Quality and Social and Economic Trends”.

Emissions inventories and forecasts are discussed in Chapter 5. Chapter 6, “Air Quality Monitoring”, discusses the established air quality monitoring networks in the Airshed. Ozone and secondary fine particulate matter are discussed in Chapter 7 and 8, respectively. The characterization of visibility is discussed in Chapter 9, “Visibility”.

Chapter 10, “Regional Air Quality Modelling”, presents the results of a number of studies providing scientific support for specific management actions and emissions controls to address ozone, particulate matter and volatile organic compounds in the airshed. Transboundary transport of pollutants is discussed in Chapter 11.

Effects of air quality on receptors are addressed in Chapter 12, “Atmospheric Deposition and Ecological Effects”, Chapter 13, “Air Quality and Climate Change” and Chapter 14, “Health and Economic Impacts of Poor Air Quality”.
The report concludes with Chapter 15, “Summary of Key Findings, Implications and Recommendations”.

1.5 References

McNeill, R. and Roberge, A., 2000. The Impact of Visual Air Quality on Tourism Revenues in Greater Vancouver and the Lower Fraser Valley. Environment Canada, Georgia Basin Ecosystem Initiative, Vancouver, BC.

WHO (World Health Organization), 2006. WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide - Global update 2005 - Summary of risk assessment. (Accessed: February 25, 2010)

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