Environmental And Ecological Evaluation Of Application Of Chlorpyrifos In Paddy

Chlorpyrifos is one of the most commonly used pesticide of rice currently, which has important applicational value to the safety of farm produce and the evaluation of agricultural and ecological environment. In this thesis, environmental and ecological safety of using chlorpyrifos in paddy was evaluated by indoor determination and conditional test.1. Laboratory toxicity and application effect of barrel mixture in paddy of chlorpyrifos to two pestsLaboratory toxicity and field efficacy of chlorpyrifos, monosultap, imidacloprid, pymetrozine, chlorantraniliprole, and four kinds of pesticide mixture of chlorpyrifos to Chilo suppressalis and Nilaparvata lugens were studied. Results of virulence test in laboratory showed that chlorpyrifos and other four pesticides tested all had high activity to C. suppressalis. Pesticide mixture of chlorpyrifos and imidacloprid, pymetrozine, chlorantraniliprole in accordance with the proportion of 3:2, 3:1 and 5:1 had a higher virulence than pesticides used alone. There was obvious additive or synergistic effect, and the co-toxicity coefficient were 117.05, 178.25, 125.63 respectively. Toxicity of five kinds of pesticides to N. lugens was chlorpyrifos> pymetrozine> chlorantraniliprole> imidacloprid> monosultap, while pesticide mixture of chlorpyrifos and monosultap, imidacloprid, pymetrozine, chlorantraniliprole in accordance with the proportion of 2:3, 3:2, 3:1 and 5:1 had additive effect to some extent. Field efficacy results showed that chlorpyrifos with pymetrozine or chlorantraniliprole was better than any other pesticide mixture or individual.2. Residue analysis of chlorpyrifos in important products and environmental objects of paddy Residual dynamics of chlorpyrifos in rice plants and in field water was studied, as well as final residue in rice plants, rice husk and rice. The results showed that when chlorpyrifos was used at double maximum amount of the recommended dose, first-order kinetics equation of residues in rice plants was Ct = 8.1836e-0.1939x, half-life was 3.57d, while that of residues in field water was Ct = 0.7891e-0.1267x and 5.47d. 1d pre harvest, at low dose, chlorpyrifos final residues in plants, rice husk and rice were 0.522 mg/kg, 0.584 mg/kg, 0.385 mg/kg respectively, at high dose were 0.804 mg/kg, 0.711 mg/kg, 0.488 mg/kg respectively. At any dose, the residual amounts of chlorpyrifos in rice were both greater than the maximum residual limits of China.3. Evaluation of ecological security of chlorpyrifos to representative organisms in environment of rice regionToxic effect and bio-concentration of chlorpyrifos in Carassius auratus and Eriocheir sinensis was studied for providing a theoretical basis for environmental and ecological risk assessment. According to"environmental safety evaluation test guidelines of chemical pesticides"of China, chlorpyrifos was highly toxic to Carassius auratus and Eriocheir sinensis. After chronic exposure to chlorpyrifos, the activity of AChE and CarE in different tissues and organs was significantly inhibited. And the activity of AChE and CarE both recovered at different levels after exposing in water. In addition, chlorpyrifos was detected in different tissues or organs of Carassius auratus and Eriocheir sinensis, in which chlorpyrifos enriched easily in liver and gill.Based on the above findings, it is recommended that chlorpyrifos could be mixed with pymetrozine or chlorantraniliprole to use in paddy and the safety interval of chlorpyrifos in rice could be appropriatly prolonged. And it should be careful and rational to use chlorpyrifos in farmland near the water or rice-fish farming system, for avoiding non-target aquatic harm.