Content and chemical form of mercury and selenium in soil,sludge, and fertilizer materials

The content and chemical from of Hg and Se were determined for several samples of municipal sewage sludge and sludge ash, garden soil having a history of sludge and residential compost application, and selected fertilizer materials (peat moss, cow manure, residential compost, composted municipal refuse and sewage sludge, Miloganite). Municipal sewage sludge had the highest levels of total Hg (averaging 1240 ppb), while sludge ash had the lowest levels (averaging 5.6 ppb). Total Se levels were lowest in compost (averaging 255 ppb), while being highest in sludge ash (averaging 11550 ppb). The methylmercury percentage was fairly constant for all samples, averaging 6.0% of the total Hg content. Hexavalent Se averaged 24.3 of the total Se content, and was notably higher in sludge and fertilizer samples. Successive annual application of sludge and compost to garden soil resulted in a gradual increase of total Hg and Se in the soil, but had no significant influence on chemical form distribution for both elements.