Model Ecosystem Studies of Lead and Cadmium and of Urban Sewage Sludge Containing these Elements

Abstract

AbstractThe environmental fate and effects of cadmium and lead were studied in a laboratory model ecosystem with a terrestrial/aquatic interface, using silica sand, Bloomfield soil (sandy loam) and Drummer soil (silty clay loam) as substrates. Applications were made directly to the substrates as lead and cadmium chloride and as sewage sludge as a source of heavy metals. The mobilization and incorporation of cadmium and lead into food chain organisms were proportional to sorption capacity of the substrate and were highest in silica sand and lowest in Drummer soil. Following the application of sewage sludge there was clear cut mobilization and transfer of cadmium, copper, lead, and zinc into food chains, alga (Oedogonium cardiacum), daphnia (Daphnia magna), mosquito larva (Culex pipiens quinquefasciatus), snail (Physa), and fish (Gambusia affinis). Cadmium exerted a particularly adverse affect on the various organisms in the model ecosystem and its presence in relatively high levels in sewage sludge could become a limiting factor in its use on soils and for crop production.