The Survey And Evaluation About Water Pollution In Town Of Xixi Nan And The Purification Effect Of The Environmental Conditions On The Nitrogen And Phosphorus Pollution

The main content of this study include:(1)to analyze the content of COD,TN,TP and NH4-N and study their regularities of distribution and extent of pollution in the water body of Leihe and Longhe,which was located in south town of Xixi in Huangshan;(2)to discuss the change rules of the pollution in different time and different space in Longhe and Leihe;(3)to make evaluations to contamination in the water of south town in Xixi by using the method of single factor pollution index and comprehensive pollution index;(4)to discuss what effect the environment conditions of Leihe on the natural water purification by analyzing the state of local soil、bottom mud and aquatic plant.The result shows that :(1)the water body in Leihe was contaminated more seriously,the concentrations of COD and TN are higher,the concentrations of COD and TN in Longhe are58.333-121.667mg/L and 6.794-15.857mg/L respectively,the concentrations of COD and TN in Leihe are 96.667-108.333mg/L and 4.413-8.427mg/L respectively.The concentrations of TP and NH4-N are less,(2)the change rules of the pollution in Longhe and Leihe are similar in different time,the content of contamination increases obviously in winter,on the contrary, the content of contamination decreases obviously in summer.The daily variation characteristic of pollution concentration in Longhe is that the highest is in the morning and the lowest is in the noon;however,the highest is in the afternoon and the lowest is in the noon;however,in Leihe the highest is in the afternoon and the lowest is in the noon.The content of pollution increased gradually from the beginning to the end in Longhe water body,however,the content of pollution in Leihe was higher in upstream and downstream.(3)according to the evaluation hierarchies, the content of TN in Longhe has reached the serious pollution levels,the content of COD reached the moderate pollution levels,the content of TP has even reached the pollution cordon,but the concentration of NH4-N is relatively low. The contents of NH4-N and TP in Leihe are relatively low,but COD and TN are still heavy pollution items,the conditions in Leihe are better than in Longhe ingeneral,the extent ranking of the pollution is TN>COD>TP≥NH4-N inturn.(4)the sediment in Leihe and the content of nitrigen and phosphorus in the water have high correlation in time and space,the contents of nitrogen and phosphorus in the water decrease obviously because of the adsorption effect of sediment.(5)a large number of nitrogen and phosphorus was fixed in the soil that surrounds Leihe, the value of which is beyond the value of its background 5-6 times,the rapid infiltration of the soil which was acted as a pre-processing has a significant effect on reducing nitrogen and phosphorus pollution that was directly discharges into the river.(6)the total nitrogen fixation amount of aquatic plant in Leihe is 9.9 kg;total phosphorus fixation amount is 0.243 kg;the TN is 471% beyond the background value and TP is 286%;the special distribution of TN in the black algae and TN in the water body also maintained a certain correlation.(7)the cooperation of the environmental conditions such as the soil, sediment and aquatic plants makes the water self-purification capacity in Leihe is much stronger than Longhe.