Lindane and propuxur residues in the top soils of some cocoa growing areas in five districts of the Central Region of Ghana

Abstract

Lindane and propoxur residues in some topsoil samples from five cocoa growing districts in the Central Region of Ghana have been determined. Ten soil samples were taken randomly at a depth of 0-10 cm from pre-selected farms in each district. Some physical and chemical properties of the soils were determined. The pesticide residues were extracted from 50 g of topsoil by continuous Soxhlet extraction using a (1:1 v/v) acetone-chloroform mixture for six hours. Clean up of the extract was done by liquid-liquid partitioning and column chromatography using alumina and silica gel adsorbents. The pesticide residues were finally analysed by gas- chromatography using ⁶³Ni electron capture detector (ECD) and flame ionization detector (FID) for lindane and propoxur, respectively. Lindane and propoxur pesticide residues were found to be present in all the soils to which these pesticides had already been applied. Generally, lindane residues occurred in greater amounts than propoxur. The concentrations of lindane ranged from 2.1 to 15.4 mg kg^-1 and propoxur from 1.71 to 7.95 mg kg^-1. Both the extracted lindane and propoxur residues correlated negatively with pH, cation exchange capacity, moisture content, and organic carbon. Propoxur correlated positively with the amount of clay but there was no significant correlation between the amount of clay and the extracted lindane concentration.

KEY WORDS: Lindane, Propoxur, Soil, Pesticide monitoring
Bull. Chem. Soc. Ethiop. 2006, 20(2), 193-199.