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Mercury
Mercury is present in the environment as a result of both natural processes and human activities. Natural sources of mercury include volcanoes, hot springs, and natural mercury deposits. Sources related to human activities include coal combustion, waste incineration, certain industrial activities and some mining activities. California environmental mercury issues relate to historical mining operations in two ways. The first is to mercury mining activity that occurred between 1846 and 1981, during which time about 100 million kilograms of mercury were produced within the state. The second is to historic gold mining activities that took place between 1848 and the first part of the 20th century, which depended upon gold recovery processes using mercury. Significant quantities of mercury were lost to the environment during both of these activities.
Mercury is a human neurotoxin with developing fetuses and small children being at greatest risk. The principal route of human exposure is through consumption of mercury contaminated fish. Mercury occurs in various forms and compounds in the environment, some of which are not bioavailable. When mercury enters an aquatic environment, by erosion, atmospheric deposition or as the result of human activity, it may encounter conditions that cause its conversion methyl mercury. Methyl mercury is readily taken up by aquatic organisms and tends to concentrate as it moves up the food chain. This process is referred to as biomagnification and can result in high mercury concentrations in predatory fish such as striped bass and sharks, and in fish eating birds and mammals.
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Cinnabar - New Almaden district, Santa Clara County, California. Cinnabar is a mercury sulfide with the chemical formula HgS. It was the main ore of mercury at many California mercury mines. It is characterized by its bright red color. Mercury was recovered by heating the cinnabar and collecting and cooling the mercury vapors that were produced. Click on image for larger view. |
The California Geological Survey (CGS) is currently a participant along with other state and federal government agency and university research groups in the three year CALFED research project titled “An Assessment of Ecological and Human Health Impacts of Mercury in the Bay Delta Watershed”.
For Additional Mercury Information See These Related Links:
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