Assessment of Organophosphorus and Pyrethroid Pesticide Residues in Watermelon (Citrulus lanatus) and Soil Samples from Gashua, Bade Local Government Area Yobe State, Nigeria

Abstract

Watermelon (Citrulus lanatus) samples were freshly harvested from the Mashangwari, Katakam and Krigasawa agricultural locations in Gashua, Bade Local Government Area, Yobe State Nigeria. The watermelon samples were divided into peel, pulp, seed, leaf, root and stem for the determination of some organophosphate pesticide residues (dichlorvos, diazinon, chlorpyrifos, fenthion, malathion and fenitrothion) and pyrethroid pesticide residues (cypermethrin, bifenthrin, permethrin and deltamethrin). Soil samples were also collected at different depths for the determination of the above pesticides. Sample collection and preparation was conducted using standard procedures. The concentrations of all the pesticides in the soil and watermelon samples were determined using GC/MS SHIMADZU (GC-17A) equipped with electron capture detector (ECD). The highest concentrations of organophosphorous and pyrethroid pesticides from the three agricultural locations were observed in the peel, while the lowest concentrations were detected in the root. The concentrations of all the pesticides detected in the soil samples were observed to be higher at a depth of 21-30 cm, while the lowest concentrations were observed at a depth of 0-10 cm. The concentrations of dichlorvos, diazinon, chlorpyrifos, fenthion, malathion, fenitrothion, bifenthrin, permethrin and deltamethrin in the watermelon and soil samples were much higher than the maximum residue limits (MRLs) set for vegetables and soil. The results also showed that there is an existence of a variety of organophosphorus and pyrethroid pesticides in the watermelon and soil from the three agricultural locations. The observed concentrations of the studied pesticides from the agricultural locations could explain either their persistence in the environment or continued use in the study area. Hence, routine monitoring of pesticide residues in these study locations is necessary for the prevention, control and reduction of environmental pollution, so as to minimize health risks.