Plant Uptake of PCBs and Other Organic Contaminants from Sludge-Treated Coal Refuse

A field study of industrial organic contaminant uptake, in particular PCB uptake, by growing crops was conducted during 1990 at the St. David Coal Refuse Pile Reclamation Site, Fulton County, Illinois. The site had received one-time applications in 1987 of 785, 1570 and 3360 Mg ha^-1 dry wt. of Chicago municipal sewage sludge. Corn (Zea mays L.), cabbage (Brassica oleracea capitata L.), and carrot (Daucus carota L.) were grown on the sludge treatments and soil (i.e., sludge treated coal refuse) and plant samples were analyzed. Mean PCB concentratious in the soils were ≤4 mg kg^-1 dry wt. and there was no consistent effect on them of sludge application rate. Measurements on the 3360 Mg ha^-1 dry wt. of sludge treatment soil indicated that several organochlorine pesticides occurred at concentrations ≤217 μg kg^-1 dry wt. and several polynuclear aromatic hydrocarbons occurred at <1 to 3 mg kg^-1 dry wt. Mean PCB concentrations in the plant materials were <300 μg kg^-1 dry wt., however, there were differences among and within crops. Concentrations decreased in the order: carrot peels > carrot tops > cabbage wrapper and inner leaves > carrot core > corn ear leaf and stover > corn grain. There was insignificant PCB in corn grain. Except for cabbage wrapper leaves, the PCB concentrations in plant materials were not related to those in soil. Soil PCB concentrations accounted for 24% of the variance in cabbage wrapper leaf PCB concentrations and the bioconcentration factor (mg PCB kg^-1 dry wt. of leaf/kg PCB ha^-1 dry wt. of soil) was 0.0042. There was no detection of organochlorine pesticides in plant materials grown on the 3360 Mg ha^-1 dry wt. of sludge treatment soil and, except for indole and isophorone, only trace amounts of a very few other organic contaminants were observed in the plant materials. Indole ranging from no detection to 52 mg kg^-1 dry wt. may have been a natural constituent of cabbage. Isophorone ranging from 14 to 79 mg kg^-1 dry wt. was observed in three samples of cabbage wrapper leaves and its source is unknown. Despite the very large rates of Chicago sludge employed in this study, findings indicated that they did not (i) result in high levels of organic contamination in the treated coal refuse, and (ii) represent a significant organic contaminant hazard to the quality for food and feedstuffs of crops grown on the treated coal refuse.