Abstract:
This research project investigated the level of organochlorine and organophosphorus pesticides residues in water and sediment of Owena River, Southwestern Nigeria. The organochlorine and organophosphorus pesticides extracted were analyzed with Shimadzu Gas chromatography with electron capture detector (ECD) and Flame Photometric Detector (FPD) respectively. Some physico-chemical properties of water and sediments were analysed during wet and dry season using standard methods. The sediment samples was majorly sandy with low organic matter content. The organochlorine pesticide found in water samples was endosulfan-sulfate (ND-0.015 mg/L), while alpha-BHC, beta-BHC, lindane, chlorothanonil, delta-lindane, heptachlor epoxide, dieldrin, endosulfan ii, p’-p-DDD and p-p DDT were all below instrument detection limit. The Organophosphorous pesticides residue (mg/L) found in water samples were carbaryl (ND-0.260) (dry), phosphamidon (0.331-5.592) (dry) and (ND-2.459) (wet), dichlofenthion (ND-0.101) (dry) and (ND-0.887) (wet), methyl parathion (ND-0.908) (dry) and (ND-1.493) (wet), pirimiphos-methyl (ND-1.117) (dry) and (0.332-1.205) (wet), parathion (0.137-0.460) (dry) and (ND-0.837) (wet), bromophos-ethyl (ND-1.955) (dry) and (ND-0.591) (wet), ethion (ND-4.456) (dry) and (ND-0.939) (wet) and carbofenthion (ND-1.162) (dry) and (ND-0.985) (wet), while dichlorvos, mevinfos, dimethoate, fenthion and malathion were below instrument detection limit. The organochlorine pesticides (mg/kg) detected in sediment were lindane (ND-0.268), chlorothalonil (ND-0.363), dieldrin (ND-0.158), endosulfan (ND-0.415) and p’p DDT (ND-0.318), however alpha-BHC, beta BHC, delta lindane, heptachloro epoxide and P’-p DDD were below instrument detection limit. The organophosphorus pesticides (mg/kg) detected in sediment were diazinon (ND-0.856) (wet), phosphamidon (ND-2.426) (wet), dichlofenthion (ND-0.249) (wet),methyl parathion (ND-0.100) (dry) and (ND-1.257) (wet), pirimiphos-methyl (ND-0.036) (dry) and (ND-1.099) (wet) and Parathion (ND-0.499) (wet), while dichlorvos, mevinfos, carbaryl, dimethoate, pirimicarb, fenthion, isofenphos, bromophos-ethyl, ethion, carbofenthion and malathion were below instrument detection limit. The concentration of each pesticide residue detected was higher than the European standard value of 0.0001 mg/L for individual residual limitand 0.0005 mg/L for total residual limit for both organochlorines and organophosphorus, thus posing a threat to both human using the water and as well as the aquatic life.
