Effects of Sewage Sludges Contaminated with Polychlorinated Dibenzo-p-dioxins, Dibenzofurans, and Biphenyls on Agricultural Soils

Abstract

The fate of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) in sewage sludges after agricultural application was analyzed. This study was based on the experiments designed for two soils with different agronomical characteristics after applying different rates of sewage sludge. The concentrations of PCDDs, PCDFs, and PCBs in soils were determined before and after the application of sewage sludges, and a general increase was observed with the applied rate, especially in the case of the PCDDs. The values of sludge-treated areas were 1.2-11.6 times higher than the respective values of the noncontaminated areas. Changes observed in the ratio between PCDD and PCDF levels and in the isomeric distribution also suggest the influence of the sewage sludge on the soil. The values of sludge-treated areas were compared with the limits proposed in Germany for agricultural and horticultural land uses. The results of the soil investigation showed that, in the case of an initial soil with low contamination, the final soil did not exceed the limit; but, in the case of an initial soil with considerable contamination, the final soil exceed the limit, which restricts the cultivation of certain vegetables.