(In the photo above, researchers are collecting water samples from Lake Killarney. From left: Dr. Alex Horner-Devine, professor of civil and environmental engineering at UW in Seattle; Samantha Fung, graduate student in hydro-biogeochemistry at UW in Seattle; Pamela Barrett, post-doctoral researcher at UW in Seattle; and Erin Hull, '16, UW Tacoma environmental science. Photo by Kenneth Burkart, used with permission.)
UW Tacoma Associate Professor Jim Gawel has been studying arsenic contamination in the freshwater lakes of South King and Pierce Counties since arriving on campus in 1999.
The arsenic came from the windblown smokestack emissions of the American Smelting and Refining Company (ASARCO) copper smelter that operated on the shores of Commencement Bay from 1890 until 1986. The widespread contamination of land and water by the operation of the smelter led the U.S. Environmental Protection Agency to launch one of the nation's first and largest Superfund clean-ups in 1983, encompassing Commencement Bay, Ruston and areas of North Tacoma.
The UW Superfund Research Program recently published a story about what Gawel and his students found in Lake Killarney, 7 miles northeast of the UW Tacoma campus. We are pleased to reprint the story in full, with permission.
Shallow Lakes Offer Deep Insights into Lake Chemistry
By Lisa Hayward Watts, UW Superfund Research Program, May 2018
Nothing about Lake Killarney’s idyllic appearance hints at the potential cancer risk lying just below the surface.
The shallow lake in South King County, Washington, is ringed with homes and the headquarters of the international relief organization World Vision. The lake is favored by waterfowl, rich with aquatic plants, and stocked with rainbow trout, largemouth bass, and other fish.
So it came as a surprise to Dr. James Gawel when he and his undergraduate students from the University of Washington Tacoma measured high levels of arsenic in water samples from Lake Killarney. Gawel is an associate professor in UW Tacoma’s School of Interdisciplinary Arts and Sciences. He studies arsenic in lakes as part of the UW Superfund Research Program. The project is headed by Dr. Rebecca Neumann, an assistant professor in the UW Department of Civil and Environmental Engineering.
A lake that breaks the rules
“It was pretty amazing to find this little lake that broke the rules about what we thought we knew about lake chemistry,” recalled Gawel.
“Normally, when oxygen is present, arsenic tends to stick to particles and fall out of the water column,” he explained, and then settle at the bottom in the sediments.
Lake Killarney turned out to have levels of arsenic more than six times the minimum level that the Washington Department of Ecology identifies as likely to have harmful effects on sediment-dwelling organisms. Gawel and Neumann recently co-authored a paper about arsenic in shallow lakes in Science of the Total Environment.
The lake is located downwind from the former ASARCO smelter in Ruston. Aerial transport of lead and arsenic from the former smelter led to widespread contamination in the area and its eventual designation as one of the first Superfund sites in the nation.
How arsenic enters the food chain
Even given that history and the high levels of arsenic in the sediment, finding it in Lake Killarney’s water column was a surprise.
Shallow lakes like Lake Killarney are less likely to show the type of stratification that larger lakes exhibit, Gawel explained. In summer, cold, heavier waters typically occupy lake bottoms in a layer that doesn’t mix with warmer surface waters because of their different densities. This stratification tends to keep arsenic trapped at the bottom of the lake.
In contrast, shallow lakes warm up more thoroughly and don’t form separate layers. That leaves more opportunity for arsenic in the sediment to mix into the water.
Second, arsenic resembles phosphorus in its chemical structure—enough so that phytoplankton mistakenly take it up instead of the phosphorus they need to make the phospholipids that are an important component of almost all cell membranes.
In oxygen-rich water, phytoplankton can take arsenic up so quickly that it doesn’t have a chance to bind to particles and settle into the sediment. Instead, arsenic enters the food chain as part of the phytoplankton that feed zooplankton, insects, fish, and other organisms.
What’s the health risk?
That finding led Gawel and Neumann to wonder: Does arsenic in shallow lakes pose a hazard to human health?
Exposure to arsenic is known to increase the risks of cancer. But because arsenic is water-soluble, it can be flushed from the body rather than accumulating in fat like fat-soluble mercury and polychlorinated biphenyls (PCBs), which tend to bioaccumulate as they move up the food chain. Instead, arsenic diminishes in concentration as it moves up the food chain.
One of the biggest concerns is the level of potential arsenic exposure associated with eating warm-water fish species like the sunfish, crappies, and bottom-dwelling crayfish--fish that tend to be eaten more often by immigrant and lower-income populations that fish for supplemental food for their families. Lakeside residents tend to primarily fish for sport fish like rainbow trout.
Gawel and Neumann are currently collaborating with Dr. Julian Olden of UW’s School of Aquatic and Fisheries Science to sample arsenic in lake fish and crayfish.
Olden will begin gill-netting this summer. Gawel and Neumann are also working with Dr. Alex Horner-Devine in UW’s Department of Civil and Environmental Engineering to better understand the chemical and physical transfer of arsenic from sediments to lake water in shallow lakes.
John Burkardt, UW Tacoma Communications, 253-692-4536 or firstname.lastname@example.org