Study On Residue Of Pesticide Imidacloprid In Water And Soil

The extensive use of pesticides makes a contribution to increasing food production and eliminating pests and diseases, but at the same time, it also brings a lot of negative effects. After applying pesticides, a part of them remain in the plant, a part of them remain in the soil, and go into the groundwater under the leaching action of water, another part of them evaporate and dissipate into the air or flow into rivers and lakes with the rain and farmland drainage thus polluting surface water and aquatic organisms. At present, the world’s surface waters, more or less, is contaminated by pesticides. In addition to surface water, soil and groundwater sources are generally contaminated by pesticides.As a neonicotinoid insecticide, imidacloprid has covered almost all of the world’s countries and is used for more than 160 kinds of crops. It is also widely used in the domestic market. Therefore, imidacloprid is selected as the research object in this paper. In order to find out the residue of the application of imidacloprid in water and soil, simulation experiment was carried out and an analytical method of imidacloprid residue was built. This paper researches on the residue of imidacloprid in surface water, shallow groundwater and soil in two cases. One is different application conditions of imidacloprid with the same rainfall condition and another one is the same application conditions of imidacloprid with different rainfall conditions. Based on the experimental results, this paper gives some suggestions to the rational application of imidacloprid, to provide a scientific basis for the correct use of imidacloprid. And also provide some data to support for the corresponding study on non-point source pollution in rural areas. The research results are as follows:1.This paper uses HPLC-UV to carry out the determination of sample residue which is accurate and reliable. In the range of 0.02-0.50μg/mL, the linear relationship of the standard curve is good, the correlation coefficient r= 0.9988. The results of the standard recovery test of water samples and soil samples are able to meet the relevant requirements of pesticide residue analysis methods in our country.2.Under the moderate rain and heavy rain conditions, with the same application of imidacloprid and in the same water, the concentration of imidacloprid. moderate rain> heavy rain. In addition, the concentration of imidacloprid in surface water is higher than that in the shallow groundwater. Also, there is a large part of imidacloprid remains in soil. The effect of adsorption and interception to imidacloprid in soil is the main reason of imidacloprid concentration in soil and groundwater decreasing with depth.3.Under the light rain condition, imidacloprid has not been detected in surface water and shallow groundwater. The reason is that the surface runoff is not obvious under the condition of light rain. The scouring action of light rain to soil is also very weak. Besides, because of the effect of adsorption and interception to imidacloprid in soil, imidacloprid has little effect on water under light rain condition. However, under light rain condition, residue of imidacloprid in soil is obviously greater than those under moderate and heavy rain conditions.4.The residual effect of standard dosage of imidacloprid to water and soil is small. While the residual effects of imidacloprid are obviously increased when using higher dosage or high dosage and high dosage> higher dosage. Imidacloprid has a longer residual effect to surface water, shallow groundwater and soil when using high dosage. Therefore, it is recommended that farmers should use imidacloprid according to standard dosage. Do not arbitrarily increase the dosage.5.The maximum amount of imidacloprid residue in water appears under the moderate rain condition with high dosage and the residual influence lasts longer than other conditions. The maximum amount of imidacloprid residue in soil appears under the light rain condition with high dosage and the residual influence lasts longer than other conditions. Under the heavy rain condition, the rain can take away more imidacloprid and also dilute the concentration of imidacloprid in water. As a result, relatively speaking, its residual influence of water and soil is smaller than light rain and moderate rain conditions.