| Jilin Province,seated in Songliao Plain, is the only one corn-plant belt of China. It is seated on the same latitude with America corn-plant belt and Ukraine corn-plant belt, those are called "Golden corn-plant belt" in the world. Jilin corn-plant belt owns advantaged natural advantage to develop corn planting which covers 31 million m2 through 13 counties. It is reported that corn area destoryed by grasses accounts for 90.1% in China. It reduced the yield by 0.12 billion kilograms every year. It destroys the corn quality and quantity seriously. It can reduce yield by 10-20% without weed control during postemergence 2 to 5 weeks. And more damages will happen after that. The grass is growing with corn, and scrabbles for light, space, CO 2 on the ground, which lead the corn belt to be close canopy, poor ventilation, and low photosynthetic efficiency. At the same time, the grass scrabbles for nutrient, moisture, which causes corn malnutrition and low quality. Chemical weed control is developing fast during last few years, using area expending, kinds increasing and using methods are becoming more rational. Excluding stem-leaves treatment herbicide and various complex herbicides, the kinds of pre-emergence single herbicides has developed more than 10 kinds by now. But the commonly used herbicides are still Alachlor, Acetochlor, Metolachlor, Atrazine, Metribuzin,2,4-D butylate, and the complexed. In recent years, Atrazine, Acetochlor and Atrazine-Acetochlor mix were developing very fast and became the most important products among pre-emergence herbicides. Atrazine and Acetochlor which are the most widely used selective herbicides in the world are widely used for controlling grass of main crops, such as corn. And the mixture of these two herbicides not only expand controlling spectrum,decrease Atrazine dosage, but also reduce its environment residue and groundwater pollution. Atrazine belongs to low toxicity herbicide and residue effect is long in soil. Animal test results shows it has carcinogenesis, teratogenesis and mutagenesis effect on animals and mankind. Acetochlor degradation period is long and harmful to mankind and plant. Ecological environment was destroyed and polluted in different degree after long term use of Atrazine and Acetochlor. It will damage to next crop if the residue quantity is high in soil or irrigation water and also will threaten people's health.This research intends to use GPS to make a precise coordinates in the corn planting distract in Jilin province, and uses the chromatography quantitatively to analyze the pesticide residue of Atrazine and Acetochlor in three different areas of soil plough layer, and the soil in different seasons(spring, summer, and autumn). Then, according to the residue data of Atrazine and Acetochlor in the soil of different levels and different seasons, it will draws out its relative back ground level in soils. By researching on the time and space distribution of pesticide residue of Atrazine and Acetochlor in the soil of different seasons, this research provides a scientific way to help farmers to use pesticides safely and rationally, and prevents environment from polluting one more time. It provides assessments on the risk level of ecological environment and human health, and generates corresponding adjustment strategies for agriculture management department. The most important is that the research provides scientific basis for improving and protecting ecological environment.
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