Air quality overview: Olympic National Park

Cummings, Tonnie

Olympic National Park, located in Northwest Washington, is designated as a Class I air quality area and is afforded special protection under the federal Clean Air Act. The park is vulnerable to air pollution from nearby urban areas, as well as to pollution from regional and even global sources. To better understand and protect air quality the National Park Service has monitored air quality and air pollution-sensitive resources in the park since 1980. In 1994, the National Park Service Air Resources Division published a comprehensive review of the status of air quality and air pollution effects in five Class I parks in the Pacific Northwest. This report provides an update on air quality-related research and monitoring that has taken place at Olympic National Park. Park air quality is currently in compliance with all the National Ambient Air Quality Standards, but these standards do not provide adequate benchmarks for assessing ecosystem condition. The National Park Service Air Resources Division has, therefore, adopted the goal of natural conditions for assessing visibility impairment and uses ecological thresholds from the scientific literature to assess potential effects from ozone and deposition of nitrogen, sulfur and toxic air pollutants. Current average visibility at Olympic National Park is about 48 percent hazier than natural conditions. 2000-2009 data indicate a statistically significant improvement in visibility on the clearest and average days and a slight improvement on the haziest days. Currently, 36-47 percent of the visibility impairment at the park is due to sulfate particles in the atmosphere resulting from sulfur dioxide emissions from power plants and other sources. Under natural conditions, the contribution to visibility impairment from sulfate would be less than 19 percent. There were no trends in nitrate, ammonium or sulfur concentrations in precipitation from 2000-2009. 1989-2008 data indicated a significant decrease in wet ammonium concentrations. About 25 percent of the nitrogen, and about 20 percent of the sulfur, is in the form of dry deposition at Olympic National Park. Sensitive park ecosystems are considered at high risk for both acidification and nitrogen enrichment. Critical loads for sulfur have not been developed, but nitrogen deposition at Olympic National Park appears to be below critical levels shown to affect lichen communities. Efforts are underway to determine nitrogen critical loads for other ecosystem components. Monitoring indicates ozone concentrations vary throughout the park, with higher average and cumulative ozone values generally occurring at higher elevations. Ozone concentrations have not reached levels known to harm human health or vegetation. Elevated concentrations of toxic air pollutants have been detected in snowpack, vegetation, fish and sediment samples from the park. Concentrations of some pollutants, such as mercury in fish, exceeded wildlife and human health thresholds. Ongoing studies are investigating the extent of mercury contamination.

Air quality overview: Olympic National Park

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