Astudy On Adsorption And Migration Behavior Of Profenofos

Profenofos is a kind of excellent insecticide due to its easy decomposition, low residue, insecticidal efficiency, relatively low toxicity, low dosage and relatively safe for the environment and plants. As a group of highly organophosphorus pesticide such as methamidophos, monocrotophos and so on are the restricted and banned of use in the world, Profenofos has been widely used. Migration of pesticide have a great influence on the environment and human health, the adsorption of pesticides on soil is the main way to inhibit migration of pesticides. In this paper the adsorption behavior of profenofos in soil as the research target for a series of experiments, get the following results:1. Profenofos adsorption was measured in soil using a batch equilibrium method. The results showed that the adsorption were well-described by the freundlich equation, which showed the adsorption isotherms was nonlinear with l/nf-ads less than1.0, resembled the L-type curve. Profenofos adsorption ability was relatively high. Free energy change of adsorptions indieated that physical adsorption was dominant in soil during the process.Solution pH, temperature, background electrolyte, soil/water ratio, and part removal of OM could affect profenofos adsorption in soil. Profenofos adsorption decreased when the p H increased from 4 to 8. Profenofos adsorption capacity increased this may be due to the more alkaline, the more decomposition of profenofos which leads to the less adsorption of profenofos. Profenofos adsorption capacity increased when the temperature increased from 15 to 35 ℃, the adsorption quantity of soil for profenofos in a certain stage is increased with temperature increase soil for profenofos adsorption activity and soil / solution ratio increased from l:10 to l:25 in soil. Profenofos adsorption decreased when the CaCl2 concentration increased from 0.002 mol/L to 0.05 mol/L, this is due to the ionic strength increases, and the competition of soil adsorption activity point of profenofos cation number also increased, leading to soil adsorption of profenofos diminish, whereas its adsorption decreased significantly when soil organic matter was removed partially, this is because the organic matter in soil of nonpolar groups to have larger adsorption of profenofos.2. Organic montmorillonite can be prepared for Ca-montmorillonite and profenofos adsorption was studied by Organic montmorillonite.The results show that Ca- montmorillonite can be made of the Na- montmorillonite. The Namontmorillonite as substrate, the organic surfactant as the intercalating agent, organic montmorillonite was prepared. The results of SEM, IR, showed that the organic intercalation agent has been inserted into the montmorillonite layers.Profenofos adsorption is greater in organic montmorillonite than in soil and different types of surfactant modified into different organic montmorillonite on profenofos adsorption effect is not the same, this is due to insert the longer the chain of organic matter, the greater the spacing of modified montmorillonite layer, the more the adsorption quantity of profenofos. In a certain stage, with the increase of the concentration profenofos, twelve alkyl three menthyl bromide of montmorillonite and the sixteen alkyl three methyl bromide of montmorillonite on profenofos adsorption capacity is increased, and the sixteen alkyl three methyl bromide of montmorillonite on profenofos adsorption capacity was more than twelve alkyl three menthyl bromide of montmorillonite three methyl bromide of montmorillonite greater than twelve alkyl three menthyl bromide of montmorillonite, may be the space of the sixteen alkyl three methyl bromide of montmorillonite greater than twelve alkyl three menthyl bromide of montmorillonite.3. The transferability of profenofos in different layers of red paddy soil and its main influence factors in topsoil were studied by thin layer chromatography(TLC). With paddy irrigation water as spread solution, the Rf values of profenofos in topsoil, middle soil and subsoil thin layer plate were 0.375, 0.301 and 0.092, respectively, which indicated the profenofos was moderate movement in topsoil, not easy to move in middle soil and difficult to move in subsoil; it also suggested profenofos was less likely to pollute groundwater, but may pollute surface water. To investigate the influence factors of mobile behavior of profenofos in red paddy soil, the amount of soil organic matter and clay changed, the pH and CEC(cation exchange capacity) of paddy irrigation water were adjusted. The results of soil thin layer chromatography showed that soil organic matter could inhibit the movement of profenofos in topsoil, but the soil organic matter oxidized easily have smaller inhabitation than the soil organic matter which are difficult to oxidize; there was a significant negative correlation between the content of clay minerals and the mobility of profenofos in soil, which correlation coefficient was-0.967(n=5, p?0.05). The transferability of profenofos in top red paddy soil rise with the increase of p H in paddy irrigation water when it is larger than 5; with the increase of CEC in paddy irrigation water, this transferability rise greatly. Generally, CEC in irrigation water and clay content of red paddy soil are the main influence factors of transferability of profenofos in different layers of this soil.4. Using pot experiment was studied residues of 40% Profenofos in soil and vegetable. Sample by acetone extraction,silica column chromatography purification, determining residues of profenofos in vegetable and soil by spectrophotometric method. The results show that residues of profenofos in soil can be absorption by the root of the small green vegetable, with the increase of the concentration of profenofos in the soil, the residues of profenofos in the small green stems and leaves also will increase, and the residue of profenofos in the stem is greater than the leaves. At 0.05 significant level, the content of profenofo in the stem and leaves of vegetable have significant differences with the soil processing concentration of profenofos in 1.000 and 10.00 mg/kg with 50.00, 100.0, and 200.0 mg/kg, vegetable plants absorb profenofo by root system, then transshipment to the stems and leaves through plant transpiration, stem migration ability is greater than the leaves in vegetable plant of profenofo. When soil and water contain high concentration profenofo, small greens stems were more vulnerable to poison than leaves.When the concentration of profenofo is greater than 10.00 mg/kg in soil original, containa certain amount profenofo, and the higher concentration of profenofo, the more residual of profenofo in the upper and lower soil; but the residues of profenofo in the soil and the profenofo concentration in the original soil were not said. When the concentration of profenofo in soil is 10.00 mg/kg, the residual concentration of profenofo in upper soil was 1.359 mg/kg and the residual concentration of profenofo in lower soil was 0.527 mg/kg; and when the original concentration of profenofo in soil increases to 200.0 mg/kg, the residual concentrations of profenofo in upper soil was 4.011 mg/kg and the residual concentrations of profenofo in lower soil was 1.462 mg/kg. Indicates that the residues of profenofo is small in soil, the pollution of profenofo in soil to the groundwater is less, most likely profenofo migrate to the surface runoff or in the air, to a certain degree of pollution in surface water.