Interaction of Metal and Other Contaminants Present in Sludge and Soil

Abstract

Laboratory experiments were conducted to evaluate the interaction of metals (As, Cd, Cr, Cu, Pb, and Ni) and nitrate-N present in municipal sludge with a soil sample. The soil selected for this experiment was Menfro silt loam, a common soil in central Missouri. A constant proportion of sludge was mixed with different amounts of soil, and the recovery of nitrate and heavy metals in the soluble fraction was analyzed and compared with the recovery from sludge samples without soil. The relative recovery of nitrate-N was ∼16–66% of the reference sample in Menfro silt loam, and the percent of relative recovery was related to the percent of added soil. The low recovery of the nitrate-N in these soils was unexpected since negatively charged nitrate ions are thought to react little with soils. The recovery of heavy metals varied from a high of 57% for Cr to a low of 7% for Cu in this soil. These interactions would cause a retardation of the heavy metal migration in the soil environment.