Determination of organochlorine pesticides in the agricultural soil of Oke-Osun farm settlement, Osogbo, Nigeria

Abstract

This study was conducted to evaluate the levels and seasonal variations of some organochlorine pesticides (OCPs) in the cultivated land of Oke-Osun farm settlement, Osogbo, Nigeria. A field sampling programme was conducted in the rainy and dry seasons for 4 months each resulting in the analysis of a total of 40 samples. Soil samples collected at 20-m intervals were air-dried to a constant weight, sieved through a mesh of 2.0-mm pore size and selected by coning and quartering method. Solid-liquid extraction was used to extract OCPs from the soil. Qualitative identifications and quantitative evaluation of the OCPs were carried out with the aid of a Perkin Elmer gas chromatograph coupled with electron capture detector. Seasonal mean ranges of OCPs in soil (μg/kg) were 13.09 ± 21.66 β-BHC-42.01 ± 17.50 p, p(')-DDT in rainy season and 30.74 ± 17.38 α-BHC-82.88 ± 32.24 p, p(')-DDT in the dry season. The results obtained from this study revealed that agricultural soil samples of Oke-Osun farm settlement were contaminated with persistent organochlorine pesticides mainly as a result of their applications by farmers. Higher levels of OCPs were obtained for dry season than the rainy season. There were indications from this study that pesticides that have deleterious health effects on humans previously placed under legal restrictions by regulatory agencies were still being used by the farmers of Oke-Osun farm settlement and this gives cause for environmental concern.

Organochlorine Pesticide Residue Levels and Potential Human Health Risks in Kolanuts from Selected Markets in Osun State, Southwestern Nigeria

“…The reagents used in this study were Dichloromethane (GFS Chemicals, Columbus), n-Hexane (Ultrafine Limited, Marlborough House, London), Acetone (GFS Chemicals, Columbus), Silica gel 60-200 mesh (Labtech Chemicals), and anhydrous sodium sulphate (Merck, Germany). Extraction of pesticide residues in kolanuts was done following the method described by [36]. From each powdered sample, 20 g was weighed into a Whatman extraction thimble pre-extracted with nhexane and dichloromethane (DCM) to remove extraneous organic contaminants that might be adhering to the surface or pores of the thimble.…”

“…One part was spiked with 10 ppm standard mixture consisting of some of the available organochlorine insecticides of interest, and thoroughly mixed, while the other (control) group was left unspiked. The samples were taken through the extraction and clean-up protocols, following the procedures of [36]. Also, 10 mL of the standard 1000 mg/L mixture of the OCPs, in spectra grade n-hexane, was put into a clean, oven-dried sample bottle.…”

Dichloro-diphenyl-trichloro-ethane (DDT) and hexachlorohexane (HCH) pesticide residues in foodstuffs from markets in Ile-Ife, Nigeria

“…Accurately weighed 20 g portion of each powdered sample, selected by coning and quartering method, was weighed into a pre-extracted Whatman extraction thimble. The sample extraction was carried out as described elsewhere (Oyekunle et al, 2011) using a soxhlet extractor and dichloromethane (DCM) as the extracting solvent. The extract was concentrated by distilling-off the solvent (DCM) to about 3 mL.…”

Levels of Heavy Metals in the Soil: Effects of Season, Agronomic Practice and Soil Geology

“…A significant proportion of agricultural soil in developing countries like Nigeria, especially for those located in the rural areas, has not been adequately monitored or investigated to check the levels of heavy metals contained in the soil [5]. Worse still, there is little or no information about the level of heavy metals contained in the soil from season to season.…”