Car Exhaust, Runoff Increasingly Polluting Puget Sound
A Washington state Department of Ecology study has found that while industrial contamination of the Puget Sound is declining, mud and sand in the Sound are increasingly being polluted with toxins from vehicle exhaust and urban runoff.
In the study, called Temporal Monitoring of Puget Sound Sediments: Results of the Puget Sound Ambient Monitoring Program, 1989-2000, Ecology scientists collected and tested sediments at 10 sites in Puget Sound for 12 years.
The sites range from the Strait of Georgia at the north end down to a location in Budd Inlet near Olympia. They were selected to represent background conditions that are not directly influenced by industrial or municipal wastewater discharges.
The study, announced on Aug. 15, found that toxic metals are declining in Puget Sound sediments while chemicals known as polycyclic aromatic hydrocarbons (PAHs) are increasing in some locations.
The decline in metals may be due to federal clean-water and air regulations imposed in the early 1970s that have limited pollution discharges by industries and cities, according to Margaret Dutch, who led the study for Ecology. In turn, the rise in PAHs may be due to increasing urbanization and vehicle use near Puget Sound. Other marine-sediment experts agree with the theory, Dutch said.
"The findings support what we're seeing in other studies, that pollution from industries is decreasing while pollution from individual citizens and urban runoff is growing," said Ecology Director Jay Manning. "While individuals are affecting the environment more than ever before, it also means that each of us has more power to make things better."
Toxic metals enter the environment as wastes from industrial manufacturing, mining operations, combustion products and agricultural pesticides, while PAHs are formed by the incomplete burning of organic matter, including fossil fuels. They also are found in coal tar, crude oil, creosote and roofing tar.
PAHs can enter the environment from vehicles that discharge them into the atmosphere through exhaust emissions and onto roads and parking lots through oil and gasoline leaks. As the PAHs fall to the ground, stormwater runoff carries them into Puget Sound. Parking-lot sealants also may be a major source of PAHs in Puget Sound.
Peter Van Metre, a U.S. Geological Survey scientist, said his agency measured large amounts of PAHs in runoff from parking lots that are coated with coal-tar-based and asphalt-based sealants.
"We have measured increases in PAHs in sediment cores in lakes and reservoirs in response to increasing urbanization and vehicle use. In line with Ecology's findings, our studies across the nation show similar trends in sediments. Metals are declining while PAHs are rising," said Metre.
Dutch said PAHs tend to bind to sediments and sink to the bottom. They can be toxic and cause cancer in marine life, including producing liver lesions and tumors in fish that live on or near the sediments. PAHs also can change the growth rates and behavior of sediment-dwelling invertebrates.
As a part of the study, Ecology scientists studied the size of sediment grains, the content of organic carbons, the concentrations of more than 180 metals and organic contaminants, and the abundance of sediment-dwelling invertebrates.
"When we examine changes over time in sediment chemistry and changes in the communities of small animals that live in the sediments, we get a better understanding of both the natural and human-driven changes in Puget Sound's marine environment," Dutch said. "These changes may serve as red flags to highlight important trends or issues of concern for the Sound."
As an example of a natural change, the study found an increase in fine-grained sediments and changes in the types and numbers of sediment-dwelling organisms at the Strait of Georgia site. The changes may be due to heavy rains in 1996 and 1997, which increased flow in the Fraser River and resulted in greater amounts of fine sediments being deposited in northern Puget Sound locations, Dutch said.
Coincidentally, these changes occurred during the same time that eelgrass populations were declining in the San Juan Islands. Eelgrass is important because it provides habitat for fish survival.
Dutch said that, based on the findings from the Strait of Georgia station, both the University of Washington and the U.S. Geological Survey have initiated sediment surveys in the San Juan Islands to see if there is a connection between fine-grained sediments and the decrease in eelgrass.
"We've made progress controlling toxic discharges that accumulate in sediments, yet each time we fix one problem in Puget Sound, we discover another," said Brad Ack, director of the Puget Sound Action Team, the state agency responsible for developing the cleanup and protection plan for Puget Sound. "PAHs and stormwater runoff are difficult new problems, directly tied to increasing population in the basin. Saving Puget Sound is ultimately about smarter land use and management of wastes in the basin. There are no easy solutions."
Washington state Department of Ecology: http://www.ecy.wa.gov
This article originally appeared in the 08/01/2005 issue of Environmental Protection.