AEROBIC BIODEGRADATION OF BIPHENYL AND POLYCHLORINATED-BIPHENYLS BY ARCTIC SOIL-MICROORGANISMS

We examined the degradation of biphenyl an the commercial polychlorina ted biphenyl (PCB) mixture Aroclor 1221 by indigenous Arctic soil micr oorganisms to assess both the response of the soil microflora to PCB p ollution and the potential of the microflora for bioremediation. In so il slurries, Arctic soil microflora and temperature-soil microflora ha d similar potentials to mineralize [C-14]biphenyl. Mineralization bega n sooner and was more extensive in slurries of PCB-contaminated Arctic soils than in slurries of uncontaminated Arctic soils. The maximum mi neralization rates at 30 and 7 degrees C were typically 1.2 to 1.4 and 0.52 to 1.0 mg of biphenyl g of dry soil(-1) day(-1), respectively. S lurries of PCB-contaminated Arctic soils degraded Aroclor 1221 more ex tensively at 30 degrees C (71 to 76% removal) than at 7 degrees C (14 to 40% removal). We isolated from Arctic soils organisms that were cap able of psychrotolerant (growing at 7 to 30 degrees C) or psychrophili c (growing at 7 to 15 degrees C) growth on biphenyl. Two psychrotolera nt isolates extensively degraded Aroclor 1221 at 7 degrees C (54 to 60 % removal). The soil microflora and psychrotolerant isolates degraded all mono-, most di-, and some trichlorobiphenyl congeners. The results suggest that PCB pollution selected for biphenyl-mineralizing microor ganisms in Arctic soils. While low temperatures severely limited Arocl or 1221 removal in slurries of Arctic soils, results with pure culture s suggest that more effective PCB biodegradation is possible under app ropriate conditions.