Mercury and selenium content and chemical form in vegetable crops grown on sludge-amended soil

The content and chemical form of mercury and selenium were assessed for several vegetable crops grown on sludge-amended and untreated soil. Total edible tissue mercury and selenium content of sludge-grown crops averaged four and two times higher, respectively, than that of crops grown on untreated soil. In terms of plant/soil concentration factors, selenium was more readily assimilated by crops than mercury. Crops from sludged and untreated soil had methylmercury levels averaging 14.0 and 4.4%, respectively, of the total tissue mercury content. An average of 24% of the total tissue selenium content was present as hexavalent selenium.