Industrial organic compounds in selected Canadian soils

Studies were conducted to determine the concentrations of a large number of industrial organic compounds in selected Canadian agricultural soils and to assess the potential for land application of municipal sludges to cause significant polynuclear aromatic hydrocarbon (PAH), organochlorine pesticide (OC) and polychlorinated biphenyl (PCB) contamination of agricultural land. Twenty-four Agriculture and Agri-Food Canada, Soil Quality Evaluation Program (SQEP) benchmark soils and six intensively cropped southern Ontario soils exhibited similar small concentrations of a few base-neutral and acid (BN&A) extractable industrial organic compounds (seldom >1 mg kg−1 dry wt), PCBs (<200 μg kg−1 dry wt) and organophosphorus pesticides (OPs). Fonofos, the only OP detected, was observed at concentrations <100 μg kg−1 dry wt. Neutral and phenoxy acid herbicide analyses for 13 soils (seven SQEP and six intensively cropped) indicated infrequent detection of these compounds. There was no detection of carbamate herbicides. In most soils, only trace amounts (<10 μg kg−1 dry wt) of OCs were observed but in one intensively cropped soil, DDT exceeded 70 mg kg−1 dw. A greater incidence of compounds such as alpha chlordane, dieldrin, aldrin and DDT in intensively cropped than in other soils is assumed to reflect increased use of these compounds for intensive crop production. Soils treated with sludge according to recommended practice exhibited minor increases in PAH, OC and PCB concentrations. There is no risk to human health or the environment from industrial organic conpounds, except possibly DDT, in Canadian agricultural soils that have received no sludge or from PAHs, OCs and PCBs in soils that have received southern Ontario sludges according to recommended practice. Key words: Municipal sludge, industrial organic compounds, organic contaminants, agricultural sustainability, soil