DEGRADATION OF DDT IN AN EVERGLADES MUCK AS AFFECTED BY LIME, FERROUS IRON, AND ANAEROBIOSIS

Abstract

DDT degraded slowly (<5 percent recovered as DDD) in an Everglades muck amended with alfalfa meal and incubated for 4 weeks under moist aerobic, moist anaerobic, and flooded anaerobic (unstirred) conditions. Degradation was more extensive in a flooded anaerobic environment subjected to continuous stirring where about 14 percent of the DDT was recovered as DDD. Liming the muck from pH 5.3 to 6.8 caused a greater conversion of DDT to DDD in the moist anaerobic environment than did the application of ferrous iron, while the opposite was true for the flooded anaerobic environment. DDT degradation was greatest where muck was amended with alfalfa meal, lime, and Fe2+ and followed the order of flooded anaerobic (stirred) > flooded anaerobic (unstirred) > moist anaerobic. Recovery of DDD from these environments was approximately 56, 32, and 10 percent, respectively. Lime caused a marked increase in bacterial populations in the anaerobic environments and was correlated with greater respiratory activity and increased DDT degradation. The application of Fe2+ particularly to flooded anaerobic muck samples appeared to substantiate a chemical mechanism for conversion of DDT to DDD. The extent of DDT degradation increased as the redox potential (Eh) decreased.