Levels of Agricultural Pesticides in Sediments and Irrigation Water from Tono and Vea in the Upper East of Ghana

Abstract

Water and sediment samples were taken from selected irrigation dams located at Tono and Vea in the Upper East Region of Ghana and analyzed for organic pesticides using gas chromatography. Sixteen organic residues were identified of which thirteen had at least some trace concentrations ranging from 0.001 to 25.4 µg/L. It was found in the laboratory that the concentrations of DDT, BHC and heptachlor were above the upper limited recommended by WHO and the concentrations of DDT in both reservoirs were higher than 20 times the recommended limits. High concentrations of DDT were found in the water samples while the other two residues were identified in the sediments. The high DDT concentration in water was due to 1) the initial amount of DDT applied and the period in the reservoirs, 2) a half-life of 350 days suggested that much of the DDT originally used was not destroyed if applied less than this period, 3) its low solubility in water did not allow for dissolution and subsequent dispersal in water; 4) the indiscriminate uses of DDT for fishing as confirmed by the local people The high DDT level suggested that the water is not safe for many aquatic organisms and even humans. Generally the levels of these organic residues suggested that the dams have been polluted due to human activities such as farming and the unorthodox method of fishing. Therefore, steps should be taken to reduce the levels of DDT concentrations to preserve the aquatic life in the dams.