Preliminary risk assessment of pesticide on selected water pathways of Laguna [Philippines]
2004
Peralta, G.A. | Varca, L.M. | Bajet, C.M. | Fabro, L.E. | Navarro, M.F. | Quintana, B.B.,Philippines Univ. Los Banos, College, Laguna (Philippines). National Crop Protection Center
After site identification, available information, pesticide usage and other relevant data required for the risk assessment were gathered from local sources, through interviews and surveys and the use of map.Preliminary risk assessment using Pesticide Impact Ranking Index or PIRI follows, for the selected cases with best available data. PIRI's objective is to determine which among an array of pesticides has the greatest potential of contaminating the environment and the water pathways, and deserves a closer evaluation for ecolotoxicological studies. It takes into account the selected pesticides chemical properties, application rates and frequency, climatic seasons and soil variables. The project sites are in the towns of Pagsanjan, Lumban, Liliw and Calauan, Laguna [Philippines]. The land use area is basically planted to agricultural crops. The topography is generally from level to gently sloping to undulating. Amount of rainfall from Jan to Dec 2001 was around 1951.70 mm. For the same period, the minimum temperature is about 23.5 deg C while the maximum is around 31.8 deg C. Pesticide usage in the selected sites comprised largely of insecticides mostly pyrethroids, organophosphates and organochlorines. In paddy rice the frequency of spray application ranged from 1-2 per cropping season (4 months). In vegetables the number of application ranged from 2-10 per cropping season (4-5 months). And on pineapples, 15-16 times per cropping season that last for about a year is the normal practice of most growers. PIRI's results on paddy rice showed that the selected pesticides applied during the dry season cropping, have less impact on both ground and surface water, than the wet season planting. Mobility impact is greater than toxicity hazards furthermore, the surface water is more affected than ground water. 2,4-D herbicide gave the highest relative pollution potential, followed by Cypermethrin, lambda cyhalothrin and then deltamethrin in descending order. On low land vegetables, toxicity impact is greater than mobility impact on surface water. But on high land vegetables, mobility impact is greater than toxicity and the most affected catchment is the surface water. Fungicides top the mobility impact but for toxicity pyrethroids have greater impact on the surface water. For pineapple, toxicity impact is higher than mobility, and surface water is more affected than ground water.
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