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Puget Sound

Emissions and Inventories

Transboundary Air Quality
Introduction Air QualityAir Pollutants EmissionsResearchCrossborder Collaboration Crossborder ActivitiesInternational Air ProgramsEPA Region 10

Air pollutants are emitted from both natural and anthropogenic 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.

EmissionsIn order to monitor increases or decreases in emissions of air pollutants in airsheds, researchers compile emissions inventories and update them regularly.

Emissions inventories use models and estimates when actual measurements are not available.

Generally, emissions are estimated using emission factors that are derived using information about the particular source being considered. An inventory is divided according to three distinct emissions sources: point, area and mobile.

Future projections of emission levels from different sources depend on a variety of actions. Some are affected by policy decisions, others are affected by population and economic growth, and others reflect the personal choices that Puget Sound Georgia Basin residents and communities make every day.

Emissions Trends in the Puget Sound Georgia Basin

Emission trends reveal the sources of pollutant emissions and their potential effects on communities and the environment may be surmised. In Southwest BC and Northwest Washington, air pollutant emission sources include area sources, transportation, industry, and agriculture. Past efforts, such as controls on stationary sources and on-road mobile sources, have substantially reduced concentrations of certain pollutants and concentrations of others are forecast to continue declining despite significant growth in the region (e.g. NOx, VOC). However, ambient concentrations of other pollutants are forecast to increase significantly (e.g. SO2, NH3).

The emissions of smog-forming pollutants for the entire Puget Sound airshed are forecast to decrease by 20 percent from 1996 to 2018, based on the inventories and forecast available at the present time. The most recent forecasts for the Lower Fraser Valley portion of the Georgia Basin show similar decreases after 1996, but the trend slows, with overall smog-forming emissions showing slight increases after 2015.

Oxides of Nitrogen (NOx) Emissions

Ship at sunsetEmissions of NOx come mainly from the mobile sector. Significant decreases recently identified in the Puget Sound airshed are the result of new vehicle standards that reduce tailpipe emissions.

The most recent emission inventory for the lower Fraser Valley (year 2000) documents the beginning of a change in important sources within the Georgia Basin airshed. Similar decreases are not observed in the Georgia Basin because of increases in NOx emissions from the marine sector.

Marine sector emissions account for 22 percent of the NOx, with light-duty vehicles responsible for 23 percent. It is projected that NOx emissions from the marine sector will surpass the combined emissions of the light and heavy transportation sectors by 2010.

Particulate Matter Emissions

Agriculture is the dominant source of PM10 (21 percent), with space heating (especially wood burning) emitting 20 percent of the PM2.5.

Sulfur Dioxide (SO2) Emissions

Large decreases in SO2 emissions in Puget Sound during the late 1990s have resulted from significant point source reductions. Increases of SO2 in the Georgia Basin are related to increases in the marine sector and are directly tied to fuel consumption and the amount of sulphur in the fuel. Marine sector sources emit 33 percent of the SO2, the largest single source sector in the airshed.

Volatile Organic Compounds (VOC) Emissions

Biogenics (natural emission sources) contribute 36,600 tonnes/year (33 percent) of the VOCs in the Georgia Basin and 189,000 tonnes/year (46 percent) of the VOCs in the Puget Sound airshed. These are significant portions of the VOC emissions within the Basin that cannot be controlled through regulation or technology.

Forecast and Backcast of the 2000 Emission Inventory for the Lower Fraser Valley Airshed (1985 – 2025)

Source: Greater Vancouver Regional District




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