Synthetic Pyrethroids Pesticide Residues in Soils and Drinking Water Sources from Cocoa Farms in Ghana

Abstract

The contamination of pesticides in 32 soils and 64 drinking water samples was investigated from cocoa farms in the Dormaa West District of Ghana to assess pollution status. A total of nine synthetic pyrethroids pesticides were measured with a high resolution Varian CP-3800 Gas Chromatograph equipped with 63 Ni electron capture detector (ECD). Eight synthetic pyrethroid residues namely fenvalerate, deltamethrin, cypermethrin, bifenthrin, permethrin, lambda-cyhalothrin, allethrin and cyfluthrin were detected with lambda-cyhalothrin and allethrin occurring most frequently in soil and water respectively. The concentrations of synthetic pyrethroids residues in the soil samples were in the ranges of; 0.02-0.03 mg/kg for lambda-cyhalothrin, 0.010-0.02 mg/kg for allethrin, 0.010-0.04 mg/kg for cyfluthrin, <0.01-0.04 mg/kg for cypermethrin, 0.02-0.06 mg/kg for deltamethrin, and <0.01-0.03 mg/kg for bifenthrin. Similarly, the synthetic pyrethroids residues in the water samples were in the ranges of; 0.01-0.05 µg/L for allethrin, 0.01-0.04 µg/L for fenvalerate, 0.01-0.04 µg/L for cypermethrin and 0.01-0.05 µg/L for deltamethrin. The concentrations of synthetic pyrethroids pesticide residues recorded in the soil samples analysed were generally below and within their respective US MRLs for agricultural soils, except the mean concentration values recorded for pesticides such as lambda-cyhalothrin at Diabaa (S2) and Krakrom (S3), allethrin at Diabaa (S2) and deltamethrin at Kwakuanya (S4), which were above their respective US MRLs for agricultural soils. The trends of synthetic pyrethroids pesticide residues in the water samples analysed from the various distances to cocoa farms decreased with an increase of water source to cocoa farm (ranking; 0-15m>16-30m>above 30m). All synthetic pyrethroids pesticide residues recorded in the water samples were below and within their respective WHO MRLs for drinking water except for deltamethrin, which exceeded the WHO MRL at Kwakuanya (S4) at distance 0-15m from a cocoa farm. The presence of synthetic pyrethroids residues in the soil and water samples analysed is an indication of the use of the pesticide by cocoa farmers in the study area. The routine monitoring of pesticide residues in the study area is necessary for the control and reduction of environmental pollution.