DETERMINATION OF PESTICIDE RESIDUES IN SURFACE WATER OF A BEEL SYSTEM
A study was carried out in Jag chora sub-watershed of Hail haor at Sreemangal under the district of Moulvibazar in March 2003 to detect pesticide residue. Though uses of organochlorine group of pesticides are restricted for its persistent and high toxic effects but endosulfan (an organochlorine group of pesticide) is frequently applied especially in the tea gardens of this area to control tea mosquito bug. In rice fields organophophorus group of pesticide phenthoate are used to control pest. Therefore, a total of 12 water samples were collected from different locations of Jag chora and rice field just after a rainfall event. All samples were analyzed by packed column Gas Chromatographic (GC) and High Performance Liquid Chromatographic (HPLC) techniques in the laboratory of Atomic Energy Commission at Savar. Only one sample collected from stagnant water of rice fields, which was found with residue of alpha endosulfan (94.22 hg/l) and beta endosulfan (178.28 hg/l). But its residue value is below criteria for ambient water quality for aquatic organisms (0.22 μg/l) set by United States EPA. Generally, a large proportion of endosulfan and its principal degradation products, endosulfan sulphate, are associated with suspended sediments, which may not washed out just after a light rainfall. In case of phenthoate except one sample all other samples were observed its residue. Three samples of rice fields (where pesticide was applied one day before sampling) showed 82.56 to 91.00 mg/l phenthoate, residue, which is above the limits for paddy water discharge set by Japanese Environment Agency for paddy discharge water (70 mg/l). But other water samples of rice fields (where pesticide was applied two weeks before sampling) and Jag chora showed below the same limit.