Study On The Degradation Of Four Pesticides In Environmental Water

Pesticide contamination is considered one of the most contaminated sources of environmental water. Atrazine, Chlorpyrifos, Malathion and Butachlor were applied intensively and more frequently detected in environmental water in China. The objective of this research is to develop a multi-residue analytical method for determination of the above four pesticides and study on the degradation of these pesticides in environmental water.An analytical method for determination of atrazine, chlorpyrifos, malathion and butachlor in environmental water by solid-phase extraction (SPE) and gas-chromatography (GC) with nitrogen-phosphorus detector (NPD) was developed. The detection limits (3a) were 0.1 ug L-1 for atrazine, 0.1 ug L-1 for chlorpyrifos, 0.2 u.g L-1 for malathion and 0.05 ug L-1 for butachlor respectively. Linear range was 0.10 -10 mg L-1 for all four pesticides. The recoveries of four pesticides were between 70%-112% for river water, ground water and deionized water . The proposed method was applied to detect pesticides residue in environmental water. Butachlor was detected in surface water near agriculture field and atrazine was found in riverwater.Effects of pH, source of water and temperature on degradation of four pesticides were examined using orthogonal experimental design. The results showed that: (1) pH was the most important environmental factor of malathion degradation, the influence of water quality and temperature were slighter than pH and inorganic salts may catalyse the degradation of malathion; (2) Temperature was the most important environmental factor of butachlor degradation, H+ and OH- are also known to catalyse the degradation of butachlor, inorganic salts in water has little influence on butachlor degradation; (3) Temperature was the most important factor for chlorpyrifos degradation in water , the influence of pH was lesser than temperature ,and so water quality. Inorganic ions did not influence the degradation of chlorpyrifos, microorganism, irradiation and aerobic condition could promote the degradation of chlorpyrifos in environmental water, and (4) pH was the most important environmental factor of atrazine degradation. Acidic and Alkaline may enhance atrazine degradation. Temperature, water quality and irradiation had been not shown to affect atrazine degradation rates.Rotational regression design was employed to modeling the degradation of malathion and butachlor in water. Analysis and verification of model were conducted partly. The results showed that the established models may be used to predict the pollution of malathion and butachlor in environmental water. Models of malahtion and butachlor in different water are as follows:Malathion:Groundwater y = 39.22 - 2.81x1 - 2.26x2 + 0.62x3 + 0.06x,.x:2 - 0.04x1 x3 + 0.06x12 + 0.03x22River water y = 33.22 -1.55x1 - 2.90x2 + 0.14x3 + 0.04x1x2 + 0.04x12 - 0.02x1, x3 + 0.08x22Pond water y = 0.48 - 0.66x, - 0.97x2 + I.95x3 + 0.03x1x2 - 0.03x1x3 - 0.02x22 - 0.03x32Butachlr:Pond water y = 15.73 - 1.57xx - 0.96x2 + 1.92x3 + 0.02x12 + 0.04x22 - 0.02x2x3 - 0.02x32y, concentration of pesticide residue(ng L-1); x temperature(癈); x2 time(day);x3, concentration of pesticide (ug L-1)...