| Three Gorges Project is the critical backbone of the project with powering generation,blocking flood,shipping and others to govem and the develop of the Yangtze River.It be maintained the water level at 145m in Late May to early June of each year,blocked major floods to ensure the safety of Downstream in July to September,and remained this level after the flood peak;gradually increased to 175m in October,may be deferred to finish in November in the case of the dry season;maintained the water level in order to power generation in December to April of the following year.Therefore, the construction of the Three Gorges Reservoir will bring a series of changes,for example,slowing down the river flow,adding the sedimentation,showing signs of cyclical fluctuations in the opposite normal seasonal changes.It must be carried out more than a million immigrants in order to protect the sustainable development and the ecological environment in the reservoir areas.Immigrants involved in most of which are in the southern border of the Dabashan Mountain in Sichuan and Hubei and in the western mountains in Hubei.The part of the staff was placed in non-reservoir areas,and the other part was placed in the nearest areas,the latter may farm and fertilize the Drawdown Areas and the non-flooded areas in the face of the reality which is lack of land,it is bound directly or indirectly to affect the environment of the reservoir areas.Firstly,the paper studied the basic physical and chemical properties and inorganic phosphorus forms and some impacted factors of 6 profiles of dry landand paddy fields in Wanzhou Typical Drawdown Areas;and then,analyzed separately the characteristics of adsorption and desorption, adsorption kinetics and adsorption thermodynamic parameters;Finally,analyzed the morphology of inorganic phosphorus and which form or forms to impact available phosphorus in the indoor simulation of soil column experiment on the base of different treatments.1.By studying the basic physical and chemical properties,the content of inorganic phosphorus forms of dry land and paddy fields of purple soil of the Three Gorges reservoir areas,the results showed that:①the content of organic matter and phosphorus was higher,and the content of nitrogen and kalium were lower relatively,because of the soil quality,farming systems,and fertilization,pH was essentially neutral to alkaline,and there was no significant differences of dry land and paddy fields;the content of the organic matter,nitrogen and phosphorus gradually decreased along with the increasing depth in the soil profiles,but the pH and kalium didn't show a certain degree of regularity.②the inorganic phosphorus in the soil profiles of dry land and paddy fields was the main body of phosphorus,and paddy field was greater than the proportion of dry land,because the rate of dry land was at 60%～85%and at 75%～95%of paddy fields;Ca-P is the main of inorganic phosphorus in the soil profiles of dry land and paddy fields,and Ca10-P was the highest,followed by Ca2-P,Ca2-P is the least,the rest of the forms were O-P＞Fe-P＞Al-P;on the whole,the content of organic phosphorus of the dry land was generally higher than paddy field,the content of organic phosphorus of dry land and paddy fields decreased with increasing depth,but the differences of organic phosphorus of the dry land in the B layer and C layer was greater than paddy fields.③through correlation analysis and regression analysis,showed that Ca2-P,Al-P were the main sources of available phosphorus in dry land and paddy fields,Ca8-P was an important source,while the Fe-P, Ca10-P and O-P were smaller contribution to the available phosphorus.And organic matter,pH and the redox environments,increased or decreased the effectiveness of phosphorus by influencing the content and forms of inorganic phosphorus.2.Through the analysis of the characteristics of P adsorption,desorption rate,adsorption dynamics,the dynamic equations and thermodynamic parameters of dry land and paddy fields, derived:①absorption characteristics of dry land,MBC,SPR,RDP,Qm were no significant difference from paddy field,although the temperature little effected to the MBC,SPR and RDP, significantly impacted on Qm.②the desorption rate of dry land and paddy fields lowered with increasing temperature,the one of the former was bigger than the latter in the same temperature,that is,the risk of eutrophication of paddy field because phosphorus was released was smaller than the dry land in a short period.③in the study,phosphorus adsorption of purple soil mainly occurred in the 0～7h,adsorption capacity of dry land and paddy field were accounted for about 90%in this period of time,soil absorption of phosphorus was from the quick reaction into the slow response.④in this study,simulated the best for kinetics of phosphorus adsorption was Elovich equation, followed by the first-order kinetic equation,parabolic diffusion equation and two-constant equation were the worst.⑤in the study,the standard adsorption heat of dry land was 5.96 kJ·mol-1,the paddy fields was 9.32 kJ·mol-1;take 298K and 1×105Pa as an example,the free energy changes of dry land was -1.56 kJ·mol-1,and paddy fields was -0.61 kJ·mol-1,indicated that dry land and paddy fields can be carried out absorption spontaneous reaction,and paddy fields was more prone to adsorption reaction and the effect of temperature was relatively small on the adsorption reaction.3.The content of available phosphorus,organic phosphorus and the forms of inorganic phosphorus changed in the indoor simulation of soil column experiment on the base of different treatments, results showed that:①the content of available phosphorus and organic phosphorus and Ca2-P,Ca8-P, Al-P and Fe-P of dry land and paddy field increased to varying degrees,and the content of the treatments of adding organic matter in the same water was much more than the treatments that did not adding organic matter,and the content of submerged treatments was greater than the wet treatments in same organic matter;the content of Ca10-P and O-P of submerged treatments in the same organic matter was prone to the higher effective forms of inorganic phosphorus,but the content of treatments of adding organic matters increased.②the content of Ca2-P,Ca8-P,Al-P transferred to the bottom and had the accumulated phenomenon in the profiles,and the content of Fe-P,Ca10-P and O-P gradually decreased from A layer to C layer and didn't obviously transferred to the bottom.③through analysis,partial correlation analysis,path analysis and regression analysis,found that Ca2-P was the main source of available phosphorus,the content of Fe-P significantly increased after flooding and wetting,and had also become a very rich source of potential P.In this paper,I put forward my views and suggestions on the basis of the above,and look forward to having some reference to prevent and control the eutrophication and resolve the environment of agricultural production of the drawdown areas in Three Gorges reservoir areas. |
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