Abstract
The presence of pesticide residues in surface water bodies is one of the most important environmental concerns. Pesticides include Fenitrothion (O,O-Dimethyl O-(3-methyl-4-nitrophenyl phosphorothioate), Diuron (3-[3,4-dichlorophenyl]-1,1-dimethylurea) and Irgarol (2-[tert-butylamino]-4-[cyclopropylamino]-6-[methylthio]-1,3,5-triazine). Diuron, Irgarol and Fenitrothion are toxic to reef building (hermatypic) corals, non-target algae and wide variety of aquatic organisms respectively hence the need for their continuous monitoring. In this study, water samples were collected from Kurose River in Higashi-Hiroshima at monthly intervals. Pesticide extraction was by Solid Phase Extraction (SPE) and analysis by an HPLC system equipped with a UV-Vis detector (SPD-10A, Shimadzu). Sampling points from upstream to downstream were Namitakiji, Tokumasakami, Izumi, Ochiya, Hinotsume and Kurosebunka Centre. The pesticide ranges were; Diuron (not detected (n.d) - 4620ng/L), Irgarol (n.d - 50ng/L) and Fenitrothion (n.d - 310ng/L). Diuron levels were highest in May (Time rice fields are prepared for planting). Fenitrothion levels were highest in April (Attributed to use in rice nursery beds). Irgarol levels (Only detected at Izumi - Midstream of Kurose River) were highest in May but lower than Diuron (Attributed to the fact that Irgarol sources are protective paints for structures and not rice fields). Results compare well with study by Sakugawa et al., (2010), who found highest levels of Diuron at Misonou (An area very close to Izumi). Fenitrothion and Irgarol results also compared well with other studies done in same area.
