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Monday, August 2, 2021

U.S. Geological Survey investigating presence of mercury in Cache Creek

Formal report projected to be concluded in 2017

Scientists of the U.S. Geological Survey (USGS) have been working on an ongoing project in the Cache Creek settling basin, near Woodland, to investigate the presence of sediment and mercury trapped in the basin. The Cache Creek settling basin is of particular interest to the USGS as it collects debris from the creek before it washes into the Yolo Bypass.

USGS scientists began measuring flows in Cache Creek in 2009 and started measuring mercury in 2010 according to Charles Alpers, a USGS research chemist. Alpers said that the study is designed to go through 2016, but the exact time it will end is not yet conclusive. The data, which is currently being gathered, is expected to be reported in a USGS report and journal articles are projected to be written sometime in 2017.

Alpers reported that the USGS is not a regulatory agency and the work he and his colleagues are conducting in Cache Creek is a way of providing scientific input to local, state or federal agencies to help solve societal problems. The USGS provides information and quantitative data to regulatory agencies in order to assist them in making decisions regarding policy and land use. They have also partnered with the California Department of Water Resources which has asked USGS to do research in the Cache Creek settling basin.

“The area was built by the U.S. Army Corps [of Engineers] in 1937 and expanded in 1993. [It] is an engineered area surrounded by levees,” Alpers said in regards to the ongoing project at Cache Creek.”

Alpers further explained that mercury mines such as the Reed Mine in California, “are sources of mercury that dissolve to the sediments of Cache Creek and cause it to carry a higher concentration of mercury than is typical for other watersheds in the area,” Alpers said.

According to Alpers, one-half to one-third of the mercury that comes into the Sacramento River and Sacramento-San Joaquin Delta can be traced back to Cache Creek. There there is much interest in controlling that mercury as it can cause a lot of problems for fish and those who consume that fish.

“There is an organic form of mercury called methylmercury. When this methylmercury gets into the fish or other animals that eat the fish it can cause them to be at risk for neurological damage. Mercury is known to be a neurotoxin to humans and animals and there are advisories regarding not to eat some of the fish because of the mercury,”  Alpers said.

David Osleger, professor of geology at UC Davis, conducted research in mercury contaminated Clear Lake located northwest of Davis. He said mercury can take two forms though in its more toxic form is methylmercury, which is created during metabolism by certain bacteria. According to Osleger, the neurotoxin bioaccumulates in fish thereby making its way up the food chain.

“Humans who eat contaminated fish are more likely to feel the effects, which damages the nervous system and immune system, among others.  Women who are pregnant are particularly vulnerable since embryonic development may be seriously impacted by methylmercury in the system,”Osleger said.

In regards to the majority of the American public, Osleger suspects people are under-informed about mercury hazards. Osleger believes students should be informed more about mercury.

“We discuss it in certain geology courses where relevant, but not in all. Whenever the opportunity arises in any course, perhaps in discussion sections, students should be informed of the sources of mercury hazards in California, how it accumulates in the environment, and potential dangers to humans,” Osleger said.

Raul Stebbins, a first-year chemistry major said he is surprised more people aren’t concerned about mercury poisoning.

“From what I understand, the problem of mercury contamination will only worsen in the coming years, I believe more people should become interested in the effects [it] causes so steps can be taken to educate the general public about the problem is poses,” Stebbins said.
In the March 3 article “U.S. Geological Survey investigating presence of mercury in Cache Creek,” it was reported that the U.S Army Corps of Engineers was expanded in 1939. The expansion was in 1993, not 1939. Also, mercury does not dissolve “into” sediments, but rather it dissolves “to” sediments in Cache Creek.

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