Fate of Mutagenic Chemicals in Soil Amended Petroleum and Wood Preserving Sludges

Abstract

A field study using monoliths (lysimeters) of a sandy clay loam soil was conducted to assess the fate of mutagenic chemicals after refinery and wood preserving bottom sediment sludges were land treated. The Ames Salmonelialmicrosome assay* was used to determine the direct (without metabolic activation, - S9) and indirect (with metabolic activation, + S9) mutagenicity of the wastes, unamended soil, waste amended soils, and leachate. Extracts having a mutagenic ratio (MR) (MR=No. colonies from sample extract/No, colonies from DMSO solvent control) of ≥ 2 were considered positively mutagenic. Extracts of the wood preserving waste sludge without activation were non-mutagenic (MR < 2) but extracts with activation (+ S9) produced very strong indirect mutagenicity (MR = 7.9). After soil incorporation, the waste amended soil produced very strong direct (MR =8.9) and indirect (MR = 11.9) mutagenicity by day 180 and remained mutagenic (MR = 5.7, - S9; MR = 3.95, + S9) through day 350. The amount of residue in leachate from the wood preserving waste amended lysimeters was significantly greater ( P<0.05) than the unamended soil during the first 90 days after waste application, but was not different after 90 days. The leachate residue from wood preserving waste amended lysimeters in the 90-180-day period produced mutagenic responses both with (MR = 2.24 and 2.51) and without (MR = 2.29) activation. Polynuclear aromatic hydrocarbons were the main constituents identified in the leachate residues that produced a mutagenic response. Soil treatment of the refinery sludge reduced its weak indirect mutagenicity before soil incorporation (MR = 2) to non-mutagenic (MR =1.4) immediately following soil treatment. The MR of the waste amended soil increased to L7 by day 180 but by day 350 decreased to a level equal to that observed at day 0 (MR = 1.4). Leachate from the refinery amended lysimeters had significantly greater (P<0.05) amounts of organic residue than unamended lysimeters 180 to 350 days after waste application. The leachate from one refinery waste amended Ivsimeter (90-180 days after waste application) produced a mutagenic response (MR =3.16). The refinery sludge was detoxified shortly after soil treatment, but the wood preserving sludge required > 350 days to detoxify in the soil environment. The possibility exists that mobile mutagenic chemicals may leach into underlying groundwater from the treatment zone of soils amended with refinery and wood preserving sludges.