METAL MOVEMENT IN SLUDGE-TREATED SOILS AFTER SIX YEARS OF SLUDGE ADDITION

Abstract

Sewage sludge was added annually for 6 years to a series of field plots at rates varying from 0 to 225 metric tons per hectare per year. The sludges were mixed into the surface 20 cm of soil. The data published here cover the last 4 years. The metals increased in the surface soil with sludge rate and with years of addition. Metal movement, within the profile, was limited to a depth of 5 cm below the zone of sludge incorporation for cadmium, copper, and lead. Zinc moved 5 to 10 cm deep. DTPA/HNO3 ratios for a given metal are nearly constant over the 4-year period and also at all depths. Relative availability of metals in the surface soil was Cd = Cu > Pb = Zn for Pacheco sludgetreated soils and Cd > Zn > Cu > Pb for the Oakland sludgetreated soils. Sewage sludge was added annually for 6 years to a series of field plots at rates varying from 0 to 225 metric tons per hectare per year. The sludges were mixed into the surface 20 cm of soil. The data published here cover the last 4 years. The metals increased in the surface soil with sludge rate and with years of addition. Metal movement, within the profile, was limited to a depth of 5 cm below the zone of sludge incorporation for cadmium, copper, and lead. Zinc moved 5 to 10 cm deep. DTPA/HNO3 ratios for a given metal are nearly constant over the 4-year period and also at all depths. Relative availability of metals in the surface soil was Cd = Cu > Pb = Zn for Pacheco sludgetreated soils and Cd > Zn > Cu > Pb for the Oakland sludgetreated soils. © Williams & Wilkins 1984. All Rights Reserved.