Mercury in water and sediment of Steamboat Creek, Nevada: Implications forstream restoration

The objective of this study was to characterize the sources, concentrations , and distribution of total and methylmercury in water, and channel and ban k sediments of Steamboat Creek, Nevada. This information was needed to begi n to assess the potential impacts of stream restoration on mercury pollutio n in this tributary to the Truckee River. The Truckee River flows into Pyra mid Lake, a terminal water body home to one endangered and one threatened f ish species, where stable pollutants will accumulate over time. Mercury in Steamboat Creek was originally derived from its headwaters, Washoe Lake, wh ere several gold and silver mills that utilized mercury were located. In th e 100 plus years since ore processing occurred, mercury-laden alluvium has been deposited in the stream channel and on streambanks where it is availab le for remobilization. Total mercury concentrations measured in unfiltered water from the creek ranged from 82 to 419 ng/L, with greater than 90 perce nt of this mercury being particle-bound (> 0.45 (m). Mercury in sediments r anged from 0.26 to 10.2 mug/g. Methylmercury concentrations in sediments of Steamboat Creek were highest in wetlands, lower in the stream channel, and still lower in streambank settings. Methylmercury concentrations in water were 0.63 to 1.4 ng/L. A streambank restoration plan, which includes altera tions to channel geometry and wetland creation or expansion, has been initi ated for the creek. Data developed indicate that streambank stabilization c ould reduce the mercury loading to the Creek and that wetland construction could exacerbate methylmercury production.