PORTLAND, Ore. – New techniques to measure Willamette River contaminants in the Portland Superfund site over a long period of time have revealed ongoing problems facing some areas of the river, the complexity of trying to clean them up and the continuing concern that the pollution presents.
The studies, done by researchers at Oregon State University, examined concentrations of polycyclic aromatic hydrocarbons (PAH) – carcinogenic and mutagenic compounds produced by industrial activities, automobiles, wood stoves and the combustion of almost any organic material.
They found that in some sites efforts to “cap” severely polluted areas and keep PAH contained have worked surprisingly well, while in other places efforts to remove them have nearly tripled dissolved PAH concentrations, at least for some period of time.
The work was done over five years in an 18.5-mile stretch of the lower Willamette River, and published in Environmental Science and Technology, a professional journal. Superfund is the federal government's program to clean up the nation's uncontrolled hazardous waste sites.
“Decades of heavy industrial use have made this area of the Willamette River a mega-Superfund site, the worst of the worst,” said Kim Anderson, a professor of environmental and molecular toxicology at OSU. “There are no simple answers to this type of pollution, but we’re trying to do a better job of perfecting our cleanup strategies and doing monitoring that more accurately reflects the real risks to humans, fish and wildlife.”
Historically, Anderson said, most sampling for contaminants was done at certain spots in a specific point in time – which may not have provided an accurate picture of river pollutants that move, flux higher and lower with fresh inputs from weather or human activity, and often experience low concentrations of toxic compounds over extended periods of time.
New techniques have been developed to put “passive” sampling devices in the river that can stay in place for longer periods and better capture episodic events of pollution that come and go.
“Our goal is to use monitoring that more realistically mimics natural biological systems, so we can see what fish, people and other life forms are being exposed to,” Anderson said. “That includes an understanding of bioavailability -- not just what’s there, but how it could affect you.”
Among the findings of the recent monitoring:
- Some of the higher and most toxic PAH depositions are downriver of the superfund site.
- Concentrations of these pollutants can be either higher or lower in different seasons, depending on the site and the nature of the pollution.
- A sand-and-clay sediment cap placed over 23 acres of creosote contamination in 2004 at the McCormick and Baxter Superfund site has dramatically reduced PAH pollution in the water, although there are questions about how long the cap will last.
- The dredging and removal of 11,500 cubic meters of coal tar at the GASCO site in 2005 nearly tripled freely dissolved PAH concentrations, in part because of a containment curtain that did not work as effectively as had been planned.
- The overall PAH level just above this giant “tar ball” is still as high as it previously was, suggesting there are still other sources of pollution, some of which are unknown.
“It’s pretty obvious that there are still river pollutant sources we don’t know about, possibly from some old buried barrels, some leaking drain or something,” Anderson said. “But we’re getting better at fingerprinting these contaminants and ultimately we would like to track more of them down to their source.”
Cleanup, containment and monitoring efforts in this section of the Willamette River will need to continue for some time, Anderson said.
Some of the most serious problems in the river date to industrial activities in the early 1900s when environmental laws were largely nonexistent, such as tar products that were left over from manufactured gas production. Current PAH inputs to the river are largely from storm water runoff, residential heating, street cleaning and other activities, the study suggested.
The EPA water quality criteria do not specify levels of PAH that would be a threat to aquatic life, the researchers noted in their report. Oregon has water quality guidance for three PAH – naphthalene, acenaphthene and fluoranthene – and none of the sampling done in this study exceeded those levels.
However, the human health water quality criteria for consumption of water and organisms was routinely exceeded in many of these samples, researchers said, most frequently at the Superfund site but also in upriver sites.