Levels of pesticide residues and metabolites in soil at Vikuge farm, Kibaha district, Tanzania – A classic case of soil contamination by obsolete pesticides

Abstract

The paper reports on the state of soil contamination by obsolete pesticides at Vikuge State Farm, Coast Region, Tanzania, where, in 1986, a 170 m3 “donation” of partially expired pesticides were stored in an open shed that eventually collapsed. Analyses of soil samples collected in 2000 from the old storage site at the farm for 80 different pesticide residues and metabolites have revealed alarmingly high concentrations of pesticide residues to qualify Vikuge as one of the most contaminated sites in the world. Most of the residues found in the soil at high concentrations were organochlorines, their concentrations being up to 282,000 mg/kg dry weight for total DDT (28.2% by mass). Commercial formulations contain only between 5 and 10 % DDT. The concentrations of HCH were up to 63,360 mg/kg (6.4 % by dry mass). A herbicide, pendimethalin [N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine], was also found at concentrations up to 40,900 mg/kg dry weight (4% by mass). As expected, higher concentrations of the residues were found in the surface soil samples and the concentrations of the residues were decreased with increasing depth and distance from the point source. Immediate decontamination of this site is highly recommended. Tanzania Journal of Science Vol. 30 (2) 2004: pp. 77-86