Sources, transport, and fate of mercury in San Francisco estuary and tributaries (California)

This dissertation describes the sources, transport, and fate of mercury in San Francisco Bay, which in addition to being one of the largest and most populated estuaries in the world, is also downstream of two of the largest mercury mines in the world. The work quantifies the input of New Almaden mercury mines to the southern reach of San Francisco Bay and demonstrates the importance of flow based mercury flux measurements. The depositional history of mercury downstream of the mine, shows that transport of contaminant mercury was predominantly controlled by both the style of mining and changes in the hydrology of the watershed. The depositional history also shows that elevated mercury concentrations in south San Francisco Bay are the result of erosion from mercury mine wastes from mercury mines in the watershed, and the contribution of natural weathering in this system is of little importance. Although inputs from historic mercury overwhelm contemporary inputs of natural and industrial mercury to San Francisco Bay estuary, the concentrations of mercury in this system are similar to other large, heavily industrialized estuaries. Because of the strong association of water column mercury with suspended material and dissolved organic carbon, and in view of the non-conservative behavior of mercury, the estuary is a natural sink for much of the mercury contamination in this system, although there is some loss the atmosphere via evasion. In addition, despite potentially elevated mercury concentrations in California crude oil deposits, typical concentrations in California gasoline are similar to other reported values. Mercury from gasoline and diesel consumption is a relatively small source of mercury to the local atmosphere. In total, the dissertation provides a picture of the physical and chemical distribution of mercury in the estuary, which is an important foundation for studies to link concentrations of mercury in air, water, and soil to concentrations in biota.