| Since various pesticide (especially organic pesticide and herbicide) abusing and the industrial sewage discharge to farmland during the past a period, many farmland are contaminated gravely, the soil environmental quality worsen gradually, dealing with the environmental quality and restoring the contaminating soil will become the most priority task from many improve agriculture field. Since the soil types are various and the soil environment structure is complicated, which is unlikely to centralize treatment by the traditional treatment way to deal. Therefore, seeking the effect and economic way on manpower and material resources to restore contaminate soil, the method have already became the most concerned study by the workers.The paraquat is as a kind of synthesize organic herbicide, which has been put into use broadly, and belong to crop of amine compound, is a kind of strong base salt, easy to dissolve in water and completely ionize, colloid adsorption being away from mostly solving that the form being an organic positive ion, the negative ion be brought along the solution in soil. The Plug-to-plug adapter ion of the paraquat molecule can promptly, solid with soil interlinking, the adsorbing modulus (Kd) is general greater than it's 1000 L/kg. The paraquat have been restricted because it is difficult to act on living things activity by this strong key use in soil, and the microorganism acting on is very slow, therefore, it is important that the paraquat pollution source easy to be left in soil, to affect the environmental seriously.The sunlight as a kind of inexhaustible energy, and being endless to supply, it depend on solves an effect by the fact that the photosynthesis and brightness descend, the stabilizing and continuing renewalfor of which play an important role to keep the earth environment system. The thesis base on the sunlight degradation studying from abroad and home, which studies the sunlight degrades the paraquat herbicide studies in the soil. the study had considered so many factors about the sunlight degradation (such as: the sunlight intensity, illumination time, soil size, dry humidity of soil)under the artificial imitational polluted soil and the natural soil, and apply the sunlight to carry on the experiment of the light-chemistry degradation the paraquat in organic soil, adopt the UV1700 ultraviolet to check the paraquat residual in the soil, to discuss how the photocatalyst catalysis take effect on the sunlight degradation.The result indicates: The paraquat degradation in artificial preparation simulation contaminating still is to be nearly 0 under the dark condition. but the paraquat degradation is up to 0.45% in the field soil at the same dark condition; the paraquat's degradation rates from 28.3% to 40.3% under the sunlight direct irradiating in the soil, while the paraquat's degradation rates from 41.7% to 67.8% under the sunlight photocatalyst in the soil. The sunlight degradation of the paraquat accords with one-level dynamics equation under different condition , under direct irradiation of the sunlight half-life period of the paraquat is from 8.56 to 12.16 h, under the photocatalyst the half-life period is from5.10 to 8.35 h, under the dark condition the paraquat half-life period is 770.0 h in the field soil.The research is discovered, the sunlight degradation paraquat is effect on the soil type, moisture content, organic quality, pH value and the weather situation. At the same time, the photocatalyst is also affected by the sunlight degradation paraquat: H2O2, TiO2, NO3-ion, NH4+ ion, surface activity dose and with other organic or inorganic ion, which embody that the degradation rate accelerates under the photocatalyst effecting. These effects compose a positive and negative synthetical process, which is described by mathematic model that:The test results indicate that the sunlight degradation the paraquat in the supercrust soil may carry by the photochemical effect, which is feasible to use on technical economy on certain stage. |
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