Long-Term Leakage of DDT and Other Pesticides from a Tree Nursery Landfill

A landfill consisting mainly of organic waste from a tree nursery and containing an estimated 900 kg of DDT (1,1-(2,2,2-trichloroethylidene)bis(4-chlorobenzene) has been monitored since 1994. Downstream ground water was sampled from four wells. More than 10 years of monitoring of two of the wells is presented in the report, in addition to sampling of the waste. A total of seven pesticides were detected in the ground water. In addition to DDT, there were two other insecticides and four fungicides occurring in the ground water downstream of the landfill. The maximum concentration of pesticides was 3.76 μg/L of which 2.70 μg/L was permethrin in October 2000. The maximum concentration of DDT in the ground water was 0.52 μg/L, indicating that the leachate DDT concentrations probably exceed the water solubility of the compound. The investigation shows that the practice of establishing local landfills of waste from nurseries is environmentally unsafe. In 2002, the landfill was covered with clayey soil and vegetated. It seems that this has stabilized the pesticide concentrations in the ground water and removed the occurrence of extreme values. However, the vegetated soil layer has not been able to prevent the leakage of pesticides to the ground water, still present 5 years later.