dc.description.abstract | Organochlorine pesticides (OCPs) are highly persistent in the environmental media including
soil, water, and air, and are also widely detected in food materials. High levels of OCPs are
associated with diverse ill health effects that include carcinogenicity, teratogenicity, endocrine
disruption, immune system suppression, and environmental degradation. There is inadequate
data on the extent of OCPs contamination in Igembe South sub county. Hence, the aim of this
study was to determine the organochlorine pesticide residues levels in water, sediments, soil
and khat from selected points in Igembe south in Meru County where khat has been cultivated
over the years. The study was guided by interviews using structured questionnaires to gain data
on the kind of pesticides applied in the area. Thereafter, field sample collection and testing of
khat, sediments, water, and soil samples to determine organochlorine pesticide residue levels was
carried out. Soil and khat were sampled from farms where khat is grown, while sediments and
water sampling done from the Ura river traversing the farms. Soxhlet method was applied
during extraction of pesticides from soil, sediments and khat samples while solvent-solvent
extraction method applied to extraction from the water samples. The extracts were cleaned by
eluting with HPLC grade n-hexane through preconditioned aluminum oxide chromatographic
column and concentrated using a rotary evaporator and further concentrated under a stream of
nitrogen to 500 μL. Samples were analyzed for presence of 17 OCPs using a gas chromatograph
equipped with an electron capture detector. The mean values of physicochemical parameters of
River Ura water ranged between 6.7±0.04 and 7.8±0.04 for pH, 48±0.58 to 167±1.15 μS/cm for
electrical conductivity and 25±1.15 to 88±1.00 mg/L TDS levels. The mean residue levels of
organochlorine pesticides in the soil samples collected ranged from <0.001± 0.00 -
197.07±36.47 μg per kg with the highest recorded in soil samples from Anchenge sampling site
in March 2016. In water, pesticide residue levels varied from <0.001± 0.00 to 5.64±0.99 μg/L
with the highest levels recorded in water samples collected from Kiiji site in March. The
sediment samples had pesticide residue levels varying from <0.001 to 134.96±24.36 μg/kg and
the highest concentration was in sediment samples from Ikandu site collected in March. In the
khat samples, concentrations ranged between <0.001 - 110.11±5.31 μg/kg. According to the
findings, environmental samples from the Igembe South sub-county still contain DDT and its
metabolites, heptachlor, aldrin, dieldrin, endrin, lindane, and other pesticides that have been
banned. Organochlorine pesticide concentrations varied widely in water, soil, sediment, and
khat. The variances were caused by differences in the site's locations, human activities, seasonal
variations and environmental factors. | en_US |