Effects of zero-valent iron (Fe0) and temperature on the transformation of DDT and its metabolites in lake sediment

Zero-valent iron improves the transformation of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] and its metabolites in aged and highly contaminated lake sediment under biotic conditions. The addition of Fe0 has a strong effect on transformation rates at 22 °C and 9 °C, the most enhanced degradation being obtained for DDT and DDOH [2,2-bis(p-chlorophenyl)ethanol]. At 22 °C and 10 weeks’ incubation, the DDT concentration is reduced from 2.75 μmol g−1 (974 mg kg−1) to 0.98 μmol g−1 (346 mg kg−1) and 1.98 μmol g−1 (702 mg kg−1) in samples with and without the addition of iron, respectively. After 40 weeks’ incubation these concentrations have further decreased to 0.19 μmol g−1 (66 mg kg−1) and 0.74 μmol g−1 (264 mg kg−1).There is no significant transformation of any of the compounds at 9 °C without the addition of Fe0. In the presence of iron, however, DDT is reduced to 1.25 μmol g−1 (442 mg kg−1) within 40 weeks’ incubation. This study demonstrates the ability of adapted microorganisms to transform DDT under elevated temperatures in original, aged sediments, and also the stimulating effect of zero-valent iron, which is significant even at low temperatures.