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Problem: California's Gold Rush Legacy by Mika Pringle Tolson |
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| Mercury, a naturally occurring element in the earth’s crust, has become a major source of concern in recent years, and is likely to be on the top list of contaminants for the future. In its natural form, mercury is not significantly hazardous to humans, but when it is converted by bacteria to a form that is bioavailable - readily taken up into plant and animal tissue - it becomes a serious threat. Mercury is known to be a neurotoxin, and exposure in humans can lead to tremors, loss of memory, and even death. Understanding the major sources of mercury and its environmental fate are key to understanding the mercury problem. |
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| Mercury has been used for many applications, including thermometers, outdoor lighting, fungicides, and dental fillings, but most extensively in historic mining practices in California. Miners discovered that mercury creates an alloy with gold, and when heated, the mercury vaporizes leaving pure gold. Mercury mining boomed in California along with the gold rush in the late 19th century. Today there are over 300 abandoned mercury mines in the Coast Ranges. Runoff from these mines and mine tailings are the primary source of mercury contamination. But these problems are not limited to the areas surrounding the mines. |  |
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| Because most gold mines were located in the Sierra Nevada, the mercury was transported across the Central Valley to be used in placer gold mining in the mountains. Much of this mercury was spilled into Sierra streams and has accumulated throughout the sediments along many miles of river systems downstream from gold mining sites. We have only recently begun to understand the scope of the problem and its effects on humans and the environment. In the late 1980s, new techniques and equipment became available that have allowed for more accurate and reliable measurements of mercury in the environment. Since then, research on mercury has blossomed, but we are still in the early stages. The TSR&TP has been an active supporter of understanding and solving the problems of mercury in the environment and has funded many projects around the state. Over the last 10 years, researchers at UC Santa Cruz funded through our Coastal Toxicology Lead Campus Program have studied the sources, transport, and fate of mercury at the New Idria and New Almaden Quicksilver mine sites and their drainage into the San Francisco Bay system. Studies funded at UC Berkeley have included biological effects of environmental mercury exposure, engineering to stabilize mining waste, and methods to reduce acid rock drainage. UC San Diego researchers developed fluorescent chemosensors for monitoring heavy metals in water, and there are many ongoing studies at UCSD in bioremediation - using bacteria to clean up contaminated sites. At UC San Francisco, TSR&TP-funded researchers studied how heavy metals contribute to human cancer, and another group developed an assay to detect and identify hazardous metals in the skin. |
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Countless more studies have been funded at UC Davis, where the Ecotoxicology Lead Campus Program has focused efforts on the Clear Lake ecosystem, an EPA Superfund site contaminated from the adjacent Sulphur Bank Mercury Mine. Research supported by the Ecotoxicology program contributes to the overall understanding of how mercury gets into the food chain, from drainage pathways in the mines to the sediments, and into the biota. |
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| In addition, TSR&TP researchers will soon have a unique opportunity to study mine remediation on a long-term basis, assessing accumulation and transport of mercury at an active mine site. The University has recently acquired a new UC Natural Reserve at the McLaughlin Gold Mine located at the junction of Napa, Lake and Yolo counties. In addition to an active gold mine, the site contains abandoned mercury mines and a contaminated lake, Davis Creek Reservoir. An interdisciplinary team of geologists, ecologists, geochemists, and engineers will work on the problem. TSR&TP Associate Director Jim Hunt is spearheading the effort with seed funding from the program. Says Hunt, "The goal will be to develop new means of determining average contaminant levels and sources, in support of establishing Total Mean Daily Loads for watersheds with geothermal activity and historic mining." The following articles are short profiles of a sample of the mercury research that is currently being supported by the TSR&TP through the graduate fellowship program and through the Ecotoxicology Lead Campus Program. |
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