Abstract

This study investigated the compositions and distributions of pesticides buried at five sites in Tanzania. Samples were collected from various depths up to 220 cm. The analytes in samples were extracted by pressurized fluid extraction. Labelled internal standards were used for identification and quantification. Clean-up of extracts was conducted by using column chromatographic techniques. Determination of the analytes was performed by using a high resolution GC–MS. The dominant compounds detected were 4,4'-DDT (dichlorodiphenyltrichloroethane), 2,4'-DDT, 4,4'-DDE, 2,4'-DDE, 4,4'-DDD, 2,4'-DDD, hexachlorocyclohexane (HCH)  isomers (α-, β-, γ-, δ- and ε-HCH), aldrin, dieldrin, endrin, pentachlorobenzene, hexachlorobenzene, pentachloroanisole, endosulfans, chlordanes, heptachlor and heptachloroepoxides. The highest concentrations of total DDT and total HCH ranged 5.2 to 5410 mg/kg dry weight (dw) and  1.4 to 42200 mg/kg dw, respectively, while the highest concentrations for other compounds varied from 1.1 to 7200 mg/kg dw. The results indicated aged contaminants but the rate of degradation was generally very slow. The concentrations of the compounds decreased with increase in distance from the burial points. There were variations in the distribution of the compounds among the sampling sites and depths; some showed even distribution or accumulation downwards indicating some risks for groundwater contamination.

Key words: Buried pesticides, soil, Tanzania.