COPPER MOBILITY IN SOILS AS AFFECTED BY SEWAGE SLUDGE AND LOW MOLECULAR WEIGHT ORGANIC ACIDS

摘要

Copper is an essential micronutrient, but at increased concentrations,it quickly becomes toxic to plants, and remediation is needed. Becausethe land disposal of copper containing sewage sludge is increasing eachyear, there is a need to evaluate the mobility of copper in soil as affectedby sewage sludge and low molecular weight organic acids (citric acid andoxalic acid). Copper mobility was studied in a Marvyn soil (fine-loamy,siliceous, subactive, thermic, Typic Kanhapludult) without or with 1 of 2sewage sludges from the Birmingham, Alabama area. A total of 5column experiments were performed. The columns were leached withsolutions containing potassium sulfate (10 M/L) to maintain properionic strength, in addition to different combinations of copper, oxalicacid, and citric acid. The Cu~(2+) concentration in all applied solutions was1000 mg Cu per kg of solution. In the column experiments containingsewage sludge, the effluent copper concentration did not reach theinfluent concentration. In the column experiments without sewagesludge, the influent copper concentrations were easily reached in theeffluent, independent of the addition of oxalic or citric acid. A batchequilibrium study showed that both sewage sludges could adsorb morethan 50,000 mg of copper per kilogram of sewage sludge, compared with1250 mg of copper per kilogram of Marvyn soil. This amount is so highthat sewage sludges could possibly be used for copper detoxification inmine tailings or farm lands where copper pollution is a potentialproblem for vegetation.