Mercury warnings: upper Delta and Sacramento River

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yzer

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These are the new mercury warnings for fish caught in the Upper Delta and Sacramento River. New warning for the lower Delta came out last fall. This warning takes into account an 8 oz. serving size and includes fish species that are consumed by asian-american fishermen.

http://www.sacbee.com/101/story/871953.html

Here is the full flier for Sacramento River and Upper Delta fish:
http://www.oehha.org/fish/so_cal/pdf_zip/SRNDfactsheet041108.pdf

Here is the full flier for South Delta and San Joaquin fish:
http://www.oehha.org/fish/pdf/SJRSDfacts030907.pdf
 
I doubt that more mercury is getting into the delta/river system. But less water makes the mercury percentages higher, thereby increasing the mercury pollution. Robbing water from the rivers and the delta MUST be stopped!
 
The new mercury warnings do not mean that there is more mercury present in these streams than when the old warnings were issued. I remember reading mercury warnings that came in the California fishing regs pamphlets 40 years ago. It means that we have a lot more science on the health effects of mercury compounds today and how they enter the food chain than we used to. We also have more accurate ways to measure the mercury concentrations.

I don't think water exports have anything to do with the mercury problem. For the most part, this mercury has been present in these streams for 150 years: ever since mercury was used to separate gold in placer mining.

Mercury still enters the rivers every time a big storm washes out a mountain stream bed that holds old mercury deposits. Rain or snow melt leaches mercury out of hundreds of abandoned mercury mines or the tailings from placer or hard rock mines and releases it into the streams. Natural mercury is so plentiful (especially along the Coastal Range) that claims were never filed for the old mercury mines, so most of those locations are still unknown.

Mercury compounds are so light that they move freely about in the water. Water volume has nothing to do with concentration. The main culprit in forming mercury compounds is water temperature. The warmer the water, the faster the compounds form. In fact, you could say that pumping water out of the Delta faster would do a better job of cooling Delta water and making less mercury compounds.

As much as I'd like to blame mercury problems on water exports, I don't think that's the case.
 
Thanks for the education yzer! Your posts are always very informative and well presented.
 
I read recently that mercury is a naturally occuring substance in the South Bay, from the effluent of small streams dumping in to the South Bay.

Forgot the details, but it wasn't man's fault in this particular case (I remember that part, because I was very surprised).
 
There is mercury in the ground in California, and some of it leaches out naturally. Most of the problem, however, is related to human activity in one form or another. There is an abandoned mercury mine in West Marin that is a major toxic waste site.

BTG
 
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