| As the control of point source pollution has been done,the main soure of N&P that feed into lake was non-point source pollution.Due to the excessive use and low utilization of synthetic fertilizer,crop-plantation has been proved to be the main source of non-point source pollution.According to the research that has been done,this papaer combined the characteristics of non-point source pollution of crop-plantation and the land use of Taihu Basin,proposing that the N&P discharged from the crop-plantation could be controlled and utilized if it was introduced to paddy fields,thus N&P that inflowed into Tai could be reduced.This paper aimed to simulate and study the utilization of tail water in different growth periods of rice in paddy fields.Thus two kinds of tail water diacharged from vegetable plantation(marked as S)and tea plantation(marked as C)were selected and simulated,different treatments of fertilization and irrigation were designed,and the N&P concentration during the certain period of rice were determined.Then considering the time difference between tail water generation and rice irrigation,three kinds of buffer systems were designed and their feasibility was verified.Furthermore,to facilitate the management of the measure,a neural network model was constructed to forecast the N&P concentration in paddy field surface water.The main conclusions of the paper were as follows:1.TN removal rate of C and S in jointing satge was 54.51-83.95%,71.39-93.69%,respectively,TN removal load 95.97-147.79mgN·m-2·d-1,293.46-385.13mgN· m2·d-1.TP removal rate of C and S in jointing satge was-67.30-85.92%,78.79-98.70%,respectively,TP removal load-4.82-6.1 5mgP·m-2·d-1,87.80-109.99mgP·m-2·d-1.2.TN removal rate of C and S in heading and flowering satge was 44.90-87.79%,63.44-87.43%,respectively,and TN removal load 131.74-257.60mgN·m-2·d-1,434.04-599.02mgN·m-2·d-1.TP removal rate of C and S in heading and flowering satge was-109.20-81.69%,85.34-98.16%,respectively,and TP removal load-13.03-9.75 mgP·m-2·d-1,158.50-182.31mgP·m-2·d-1.3.The treatment with reduced fertilization and tail water irrigation had the characteristics of shorter risk period,higher remove rate and remove load of N&P and good rice yield and quality.4.Total nitrogen of paddy field topsoil decreased after plantation,but there were no difference among treatments.Total phosphorus and avaliable phosphorus were not the same with total nitrogen.The growth rate of available phosphorus in topsoil ranged from 25.10%to 507.02%.5.Natural soil pond and hard surface pond with shading treatment were suitable to be used as buffer system,while the simulated hard surface pond without shading treatment was not.The avaliable phosphrous of simulated natural soil pond still should be concerened that it mustn't excess the threshold.6.Natural soil pond could remove the N&P that exist in tail water in some degree.TN removal rate of C and S in natural soil pond was 46.32%-69.31%,64.21%-81.16%,respectively,remove load 0.83-40.67mgN·m-2·d-1,36.32-111.20mgN·m-2·d-1.TP removal rate of C and S was 95.17-99.68%,93.59-98.91%,respectively,remove load 1.01-2.32mgP·m-2·d-1,12.18-37.03mgP·m-2·d-1.7.A BP neural network whose topological structure was "5-6-2" was constructed in this paper.It could welll predict the concentration of TN,but the accuracy of TP prediction should be strengthened. |
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