Air Quality
This indicator examines trends in air quality related to the concentrations of fine particulate matter in the Puget Sound Georgia Basin. Fine particulate matter is one component of air quality, chosen because of its effect on human health and visibility.

Why is it happening?

The main sources of PM_2.5 in the region are mobile emissions (e.g. cars, trucks, marine vessels); industrial emissions (e.g. oil refineries, bulk shipping terminals); and "area sources" (e.g. agriculture, construction, wood stoves/fireplaces and outdoor burning).

Progress may be outpaced by growth

Government action has led to new vehicles and fuels that are much cleaner than those of the past. Unfortunately, these efforts may be overwhelmed by the significant population growth that is forecast for the region, as well as an expansion in marine traffic.

Formation of PM2.5 from Precursor Gases
PM2.5 can be formed in the atmosphere from "precursor gases," which include sulfur oxides (SOx) and nitrogen oxides (NOx). Sulfur oxides convert into sulfates and nitrogen dioxide into nitrates, both of which contribute to the formation of PM2.5.27

Air Pollution Sources

Diesel Particulates

Diesel fuel is heavier and oilier than gasoline, has a higher density and is ignited by compression rather than spark. Diesel fuel is used in diesel vehicles, such as Recreational Vehicles and trucks, school and city buses, marine vessels, trains and agricultural equipment.

The exhaust from diesel combustion results in the formation of tiny particles, fine particulate matter (PM_2.5). This contains carbon particles and other gases that become visible as they cool, thereby adding to haze.⁴

Of particular concern is the forecasted increase in marine diesel emissions, as well as agricultural emissions. Both Puget Sound and the Georgia Basin have considerable commercial and recreational marine traffic, including a four-fold increase in cruise traffic between Seattle and Alaska between 1998 and 2004.⁵

Vehicles and Trucks

In 2000, vehicles and trucks in the Greater Vancouver Regional District (GVRD) and more populated portion of the Fraser Valley Regional District contributed 32 percent of all smog forming gases.²⁸ Smog-forming gases include NOx, VOC, SOx, PM_2.5 and NH₃. In the Puget Sound, about 57 percent of human caused emissions are attributable to motor vehicles.²⁹

Indoor Burning

Wood stoves and fireplaces are a significant contributor to PM_2.5. As much as 60 percent of fine particulates in some Seattle residential neighborhoods can come from wood burning, and 85 percent of tribal reservation homes in the Puget Sound area use wood heating appliances.

Outdoor Burning

Burning wood, brush and other plant matter is a source of PM_2.5.

Dust

Wind disperses dust into the air, particularly in areas cleared of plant matter and left bare. Construction and driving on unpaved roads are also significant sources of dust.

Improvements in air quality are due to past and ongoing programs to reduce emissions in the Puget Sound Georgia Basin. However, seasonal and geographic variation occurs due to factors such as weather and topography.

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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