How much mercury and methylmercury are in streams?
Stream water typically carries trace levels of mercury and methylmercury. Median concentrations of mercury in filtered water at our eight study sites ranged from about 0.4 to 4.9 nanograms per liter (parts per trillion). Median concentrations of methylmercury ranged from less than 0.04 to 0.32 nanograms per liter. Top-predator game fish in our study streams had median methylmercury concentrations ranging from about 0.02 to 1.2 micrograms per gram (parts per million), expressed on a wet weight basis. On an equal mass basis, the concentration of methylmercury in fish is approximately one million times greater than in stream water.
