Characterization of the
Georgia Basin/Puget Sound Airshed

Executive Summary in Adobe Portable Document Format ( 297 kb)
Complete Report in Adobe Portable Document Format ( 2 897 kb)

Executive Summary

The Characterization of the Georgia Basin/Puget Sound Airshed study was undertaken to characterize the air quality within a rapidly growing, urbanized area of the Pacific Northwest, the Georgia Basin/Puget Sound air basin (the Basin). Growth within this region continues to put stress on the environment. Expansion of suburban development, increasing transportation demands and developments in the energy sector are just a few of the challenges faced in managing air quality in the area.

The Basin includes jurisdictions in both Canada and the United States, and both countries are currently implementing new air quality standards and guidelines. Thus, it was critical to characterize the nature of air pollution within the Georgia Basin/Puget Sound airshed at this time. The study will provide scientific information to assist in the development of an International Airshed Strategy and direction on specific policy issues related to particulate matter, ozone and visibility, the implementation of the Canada Wide Standards, the implementation of new US Environmental Protection Agency air quality standards for particulate matter and ozone, and the US Regional Haze Rule.

The goal of the study was to establish a common understanding of the current status of and trends in air quality in the Georgia Basin/Puget Sound airshed. Its specific objectives were to:

• Determine the significance of the transboundary transport of air pollution within the Georgia Basin/Puget Sound airshed;

• 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;

• Identify the key gaps in our scientific understanding of air quality as it relates to particulate matter, ozone and visibility in the Basin, including gaps, if any, in monitoring, inventory and modeling approaches and systems;

• Describe the anticipated consequences for air quality of specific air quality management actions; and

• Provide the basis for the development of public education and communications materials designed to enhance citizen understanding of air quality in the region.

Although the area described and studied in this report is commonly known as the Georgia Basin/Puget Sound airshed, it is really two smaller airsheds: Georgia Basin and Puget Sound. The Georgia Basin airshed comprises the Canadian portion of the Basin, Whatcom 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 air basin encompasses the counties to the south of Whatcom County.

The study focused on three air pollution issues: ground-level ozone (ozone), fine particulate matter (PM) and visibility. These issues are not only matters of public concern but are also significant factors in the development of international air quality standards and strategies.

The following sections outline the key areas of focus of the study, the major findings, and the implications for the development of strategies to improve air quality.

What Determines Air Quality?

In the Georgia Basin/Puget Sound, air quality is largely determined by the weather patterns that circulate air throughout the airshed, and these in turn are influenced by the topography of the region. The air moves and disperses airborne chemicals that are emitted from a variety of human and natural sources, both from within and outside the Basin.

Periods of stagnation occur primarily in the summer and winter. At these times, the windflow patterns do not allow air pollutants to flow between the two airsheds, effectively isolating them from one another and allowing air pollutants to build up within each airshed.

Not all pollutants that affect the Georgia Basin/Puget Sound air basin originate within the airshed. Airborne chemicals from Eurasia and California have been observed to add to the overall mixture of pollution within the Basin. Although these pollutants are usually well-dispersed by the time they arrive, they nevertheless add a small, but measurable, amount to the ozone and PM ambient concentrations. The most favourable time for air pollutants to enter the Basin from the Pacific Ocean is during the spring, particularly April and May. In addition, interactions between airborne pollutants can cause secondary air pollutants to form in the atmosphere.

Emissions

Emissions of air pollutants come from both natural and anthropogenic, or human-created, sources. These airborne pollutants may undergo chemical reactions in the atmosphere, creating new pollutants that can affect human and ecosystem health, and cause visibility problems. Emissions from anthropogenic sources can be controlled through regulation or the application of technology, but natural emissions are beyond human control.

Over the next decade, emissions of pollutants from the on-road vehicle sector are projected to decrease in both airsheds, but emissions from agricultural practices are projected to increase, as are emissions from the marine sector.

The table below summarizes predicted emission trends for several key air pollutants in the Georgia Basin and Puget Sound airsheds. Actual future emission levels will depend on population and economic growth as well as on policy decisions taken by Canada and the United States.

 

Table 4.2 Emission trends for the Puget Sound (Department of Ecology, 2001) and Georgia Basin (GVRD, 2003) airsheds

Pollutant	Emission Trend
	Puget Sound 1996-2018	Lower Fraser Valley 2000-2020
NOx	-43%	-25%
SO2	-61%	+23%
VOC	-11%	-13%
NH3	+20%	+31%
PM10 (Includes road dust)	+23%	+16%
PM2.5 (Includes road dust)	+19%	+ 10%

Ambient Air Quality

Airborne chemicals and the associated meteorology are measured at a number of sites to quantify air quality both in time and space. The ambient measurements indicate how successful various air quality management strategies are. With relation to the three key air quality issues, the research found:

Ozone

• The amount of ground-level ozone in the ambient air is primarily the result of photochemical reactions. Ozone and its precursors can be transported great distances. As a result, the highest ozone concentrations are often observed downwind of urban centres at high elevations in rural areas.

• Rural areas are “NO_x-limited” due to the relatively large amounts of naturally occurring VOC emissions and the small amounts of NO_x emissions. Reducing ozone in rural areas may require large reductions in anthropogenic NO_x emissions from urban areas.

• Ozone concentrations of 40 to 50 ppb are often recorded at rural coastal locations during the spring and identified as “background” concentrations. These concentrations are caused by emissions from both natural and anthropogenic sources, including transport from outside the Basin. Thus, a portion of background ozone is anthropogenic and, therefore, controllable.

Particulate Matter

• Fine particulate matter is dominated by carbonaceous material. In urban centres, nearly 50 per cent of the particle mass comes from combustion.

• Natural emissions of volatile organic compounds represent from one-third to one-half of the total VOC emissions in the Basin. The magnitude of natural emissions poses limits on achievable reductions in total VOC emission levels and on the effectiveness of nitrogen oxide emissions controls in reducing ambient PM and ozone concentrations.

Visibility

• SO₂, organic carbon and NO_x are the dominant pollutants responsible for degraded visibility in the Basin. SO₂ and NO_x are transformed in the atmosphere to sulphates and nitrates, which combine chemically with ammonia from agricultural sources and with sodium from natural marine emissions to form fine particulate matter.

Social and Economic Context

Air quality is integrally linked to all aspects of the sustainability of the Georgia Basin/Puget Sound region – a healthy environment, a vibrant economy and social well-being. However, air pollution is related to a number of social and economic trends in the region, including increases in population, transportation demands and energy consumption, and shifts in industry. This air pollution causes significant social, environmental and economic impacts. Examples include:

• Health impacts from airborne pollutants range from eye, nose and throat irritation to decreased lung function and cancer.

• Contaminants in the air can damage farm crops and vegetation, reducing yields of economically important crops. In the United States, agricultural losses due to ozone have been estimated to be between $1 billion and $3 billion annually.

• The reduction in visibility caused by the buildup of airborne particles in the air can have detrimental effects on tourism. For a single extreme visibility event, computer models estimate losses in future tourist revenue to be $7.45 million in the Greater Vancouver area and $1.32 million in the Fraser Valley.

• Increasing concentrations of heat-trapping gases are contributing to climate change, with far-reaching and unpredictable environmental, social and economic consequences.

State of Our Knowledge

Significant gaps still exist in our knowledge of how specific air pollutants react with each other and impact human and environmental health within the Basin. Methodologies used to compile emission inventories and to forecast emission trends rely on assumptions and computer modelling techniques that need further refinement. Air quality computer models applied to the Georgia Basin/Puget Sound airshed provide estimates of pollutant concentrations for days or weeks, but predictions of seasonal or annual concentrations are not available. The computer models being applied to the Basin need further evaluation, particularly for winter conditions. However, even with the gaps in knowledge and the shortcomings of different methodologies, the study confirmed that current levels of several air pollutants are reported to be causing impacts to human and environmental health, and must be addressed.

Significance of Transboundary Transport

The study found that there is sufficient transboundary airflow to transport airborne pollutants across the international boundary. In fact, windflow patterns move pollutants across the international border in both directions through all seasons of the year in the Georgia Basin airshed. Furthermore, the results of computer-modeled simulations confirm that there is a significant transboundary transport of air pollution in the southern portions of the Georgia Basin airshed. The main exchange of air and pollution between the Georgia Basin and Puget Sound airsheds is through the “portal” situated to the south of Haro Strait, extending from south of Bellingham westward to Port Angeles. Flow through the portal is strongest in the fall.

Implications

The study identified the following key implications for developing strategies to improve air quality in the Georgia Basin/Puget Sound air basin:

• Because wind flow patterns move pollutants across the international border in both directions through all seasons of the year, the management of air pollution in the Georgia Basin/Puget Sound airshed will require coordinated attention by both Canada and the United States.

• The stagnant weather associated with episodes of poor air quality usually impacts the Georgia Basin and Puget Sound airsheds simultaneously. During these episodic events, the movement of air pollutants between airsheds is extremely limited. However, strategies taken to address episodes of poor air quality will continue to require coordinated international action in the Georgia Basin airshed.

• Interactions between airborne pollutants can cause secondary air pollutants to form in the atmosphere. Emission reduction strategies will be most effective when the synergistic effects of emission changes on air chemistry and subsequent air pollutants are considered.

• The concentration of ambient air pollution is linked to social and economic trends including increasing population, transportation demands, energy consumption and shifts in industry. Although emissions of pollutants from the on-road vehicle sector are projected to decrease over the next decade in both airsheds, emissions from the marine sector are increasing, as are emissions from agricultural practices. Some of the programs and strategies to reduce emissions and improve air quality will also assist with strategies to reduce greenhouse gas emissions, and vice versa.

• Ambient concentrations of air pollution, at present levels, have a negative impact on human health and the environment. These results support the need for continuous improvement of air quality while maintaining publicly acceptable concentrations in areas where air pollution levels are low.

• Fine particulate matter is dominated by carbonaceous material. In urban centres, nearly 50 per cent of the particle mass is from combustion. The management of emissions from combustion sources should be a continuing priority to reduce fine particulate concentrations and related human health problems.

• SO₂, organic carbon and NO_x are the dominant pollutants responsible for degraded visibility. SO₂ and NO_x emissions are transformed in the atmosphere to sulphates and nitrates, which combine chemically with ammonia from agricultural sources and with sodium from natural marine emissions to form fine particulate matter. Improving visibility will require attention to SO₂, organic carbon, NO_x and ammonia sources.

• The amount of ground-level ozone in the ambient air is primarily the result of photochemical reactions. Ozone and its precursors can be transported great distances. As a result, the highest ambient ozone concentrations are often observed downwind of urban centers and at high elevations in rural areas. The effectiveness of ozone control strategies needs to be evaluated by taking ambient measurements of ozone at appropriate locations, often downwind of urban centres and at high elevations in rural areas.

• Natural emissions of volatile organic compounds represent from one-third to one-half of the total VOC emissions in the Basin. The magnitude of natural emissions poses limits on achievable reductions in total VOC emissions in the Basin. Natural VOC emission levels also limit the effectiveness of NO_x emission controls in reducing ambient PM and ozone concentrations.

• Ozone concentrations of 40 to 50 ppb are often recorded at rural coastal locations in the spring and identified as “background” concentrations. These concentrations are caused by emissions from both natural and anthropogenic sources, including transport from outside the Basin. Thus, a portion of background ozone is anthropogenic and, therefore, controllable.

• The impact of the long-range transport of pollutants from the Pacific is more often noted in the spring. Air pollutants from sources outside the Basin are usually well dispersed, although the impact on ambient air quality in the Basin is measurable. Ambient air quality strategies within the Basin need to consider the addition of pollutant concentrations from distant sources.