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Keywords:

  • bioremediation;
  • contaminated soil;
  • DDT;
  • dissolved organic carbon;
  • microorganisms;
  • sodium;
  • seaweed

Abstract

DDT [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] is a major environmental pollutant and economical methods to remove DDT from the environment are required. In this work we used seaweed (dried and ground) to enhance DDT transformation in waterlogged soils. Initial daily rates of DDT biodegradation increased in the following order relating to the percentage by weight of added seaweed to soil 0.5 > 1 > 0 > 3 > 5 > 13 (w/w). The actual percentages of DDT biodegradation occurring within 6 weeks were 80, 64, 60, 50, 40 and 34 respectively. During soil incubation DDD [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] was the major metabolite found with small amounts of DDE [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] produced. The maximum amount of 4,4′-dichlorobenzophenone (DBP) (2.5%) produced was found in soil amended with 0.5% (w/w) seaweed, indicating that further degradation of DDD occurred. High levels of dissolved organic carbon (DOC), between 309 and 509 mg kg−1 soil, were present in soil amended with 3–13% (w/w) seaweed immediately after seaweed addition. It is possible that the high levels of DOC in soils amended with larger amounts of seaweed significantly retarded DDT biodegradation, possibly due to binding of DDT to DOC and subsequently decreasing the bioavailability of DDT to soil microbes. Copyright © 2004 Society of Chemical Industry