| Based on the soil and water samples collected from Beijing North canal wetlands and Mencheng Lake, Yong-ting River, the various physical and chemical indicators were measured in the paper. It also investigated the nature of the two different soil adsorption characteristics and its influencing factors through the conventional adsorption desorption experiment and the method of establishing the freeze-thaw cycle simulation system. In addition, the paper explored the soil phosphorus migration path under the action of freezing and thawing using phosphate oxygen isotope tracer method of preliminary.Using crossing Langmuir adsorption isotherm equations of the soil from north canal wetland and the shore of Yong-ting river, phosphorus adsorption process for the fitting, the effect of temperature and pH on the adsorption characteristics were investigated. The adsorption process of North canal wetland soil with three kinds of adsorption kinetics of empirical equation were analyzed, and the results show that it is the most accurate to describe the process of the North canal wetland soil phosphorus adsorption using secondary dynamic equation. The fitting curve of the R2 value reached more than 0.99,12 hours after the adsorption process reached equilibrium, and the process for the exothermic reaction, temperature, decrease of the adsorption of phosphorus. In the pH range of 6.0-9.0, EPCo value with the increase of pH basically presents the rising trend, in the pH= 7.0, EPCo lowest value. Compared with North canal Yong-ting river soil, the adsorption characteristics of the soil under the same conditions, the former on the equilibrium adsorption of phosphorus is greater than the latter, and the former EPCo value is greater than the latter. It shows phosphorus content in soil initial was not the only factors affecting soil EPCo value size.It is also related to the nature of the soil and its internal structure.The paper also investigated the physical and chemical indicators of water change trend, and analyzed the stages of freezing and thawing soil characteristics of the adsorption of phosphorus using the soil of Yong-ting river shore as the main body to simulate the amphibious acetone, under the condition of freezing and thawing alternate environment and tracking the migration process of phosphorus by the phosphate oxygen isotope under the action of freezing and thawing. The results show that with the increase of freeze-thaw cycles, the water pH value decrease first and then again, but in general are still characterized by smaller and dissolved oxygen value keep on rising, then basically remain unchanged. The overlying water DIP value significantly decreased after a cycle, and after cycling three times, it is basically zero, then in a stable state in the absence of phosphorus. On the contrary, the content of NO3-N increased significantly at the early stage of the freeze-thaw cycle, slightly reduced, mid to late to maintain the background value of state before the above freezing and thawing. It showed the freeze-thaw action contributed to the soil to phosphorus adsorption capacity, and enhance the desorption of nitrogen. The content of the effective phosphorus in the lower soil significantly reduced, and the upper increased, which shows freezing and thawing of soil phosphorus migration has obvious lifting effect. For the measure of phosphorus content in soil-water system, according to the overall content decreased significantly, we suspect that this part of the lack of phosphorus is likely to be transformed into other forms of difficult soluble phosphorus.The migration process of δ18O under the action of freezing and thawing is more intense,it not only affects the migration of phosphorus in the horizonral direction, but also in the vertical direction. |
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