Assessment of cypermethrin and profenofos residues in surface water and water sediments of Nyabarongo river

Abstract

The study was carried out to assess both Cypermethrin and Profenofos residues in Nyabarongo surface water and water sediments. Surface water and water sediments samples were collected at two different sampling sites on two sides of the river which are located at the nearest the junction of Nyabarongo and Nyabugogo. Both pesticides were analyzed using coupled Gas Chromatography Mass Spectrometer. The obtained results indicated that Cyprmethrin and Profenofos residues were absent in all surface water samples. However, these chemicals were detected in most water sediments samples. For 28 samples (14 on Kamonyi side and 14 on Nyarugenge side) analyzed for Cypermethrin all samples (equivalent to 100%) were contaminated and results were above the detection limits while for 27 samples (12 on Kamonyi side and 15 on Nyarugenge side) analysed for Profenofos only 6 samples (equivalent to 22%) were below the Limit of detection and 21 (equivalent to 78%) were above the limit of detection. Agricultural application of pesticides is the main source of pesticides in the river and may have reached it through spray drift, surface runoff or overland flow, leaching, drain flow and through flow. The results of analysis were ranged from 0.1663 mg/kg to 1.8353 mg/kg and 0.2021 to 1.0373 mg/kg in water sediments for Cypermethrin and Profenofos respectively. Data have shown that the water sediments of Nyabarongo river are most polluted. These pesticides have the potential to accumulate in water sediment because of their low water solubility or high octanol-water partition coefficient (Kow) greater and higher soil half-life at least greater than 30 days [1]. Though the persistence of both pesticides is not so high but their presence in water sediments may affect heath of biota as well as consumers of fish from Nyabarongo river