Isoprothiolane Degradation in Water Column of Paddy Field from Penaga Village, Seberang Perai Utara, Pulau Pinang, Malaysia

Rice field is one of the agriculture areas in Malaysia that is exposed to the usage of pesticide before the paddy planting phase, during vegetative phase and the post- harvesting phase. The study was to determine the water quality and also degradation of isoprothiolane in paddy field water samples. Isoprothiolane is one of the fungicides that is used during the vegetative phase to kill the fungi on the paddies. This study of isoprothiolane degradation in water samples was conducted in four different conditions, namely autoclaved water sample exposed to sunlight, autoclaved water sample kept in dark, non-autoclave water sample exposed to sunlight and non-autoclaved water sample kept in dark via laboratory batch experiment in a course of 30 days. The extraction and determination of the isoprothiolane in the water samples were done by solid phase extraction method (SPE) and analyzed by Gas Chromatography–Mass Spectrometry (GC-MS). The study revealed that isoprothiolane degraded very slowly in all four conditions within 30 days of observation, and the degradation rates ranged from 0.0003 to 0.0037 day-1. The study also proved that the residue of isoprothiolane remained at least a month after its application.