Groundwater contamination by ricefield pesticides: assessment of concentrations and some influencing factors
1995
Castaneda, A.R. | Bhuiyan, S.I. (International Rice Research Inst., Los Banos, Laguna (Philippines). Soil and Water Sciences Div.)
An analysis of 291 ground-water samples collected over 1989-1991 was made for determining ricefield pesticide residue concentrations. The samples were collected from 53 tubewells located within ricefield boundaries in irrigated and rainfed areas and used for domestic water supply. Mean concentrations of six commonly used pesticides ranged from 0.001 ppb for chlorpyrifos to 0.161 ppb for monocrotophos. The maximum concentration found in a single sample was 3.19 ppb for monocrotophos. Endosulfan was present in 86 percent and monocrotophos in 59 percent of all samples. Irrigated environment, lighter soil texture and dry season rice culture condition contributed to higher concentrations of pesticides in the groundwater. Increasing tubewell depths generally indicated a decreasing concentration trend. The study indicates that some concentrations of pesticide residues in groundwater exceeded the limit of 0.1 ppb for single pesticide and 0.5 ppb for multiple pesticides. As such, the main source of potable water in rural areas may be threatened by intensive and excessive use of ricefield pesticides. Development of management models capable of predicting residue behavior within the soil profile is necessary
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