The Research Of Nutrient Fluxes For The Main Inflow Rivers Of Nansi Lake

Nansi Lake is the largest freshwater lake in north China, and nutrients flow into the lake with the rivers carrying, which could have influence on the degree of eutrophication in Nansi Lake. In this paper, according to the nutrient concentration and river runoff of CODMn, TN, TP,NO2--N, NH3-N and NO3--N from 2008 to 2013, five inflow rivers of Upper Nansi Lake were selected to make an analysis of nutrition fluxes, water quality status, the main trend of rivers pollution and distribution characteristics of nutrient discharged quantity. The main results in this paper were showed as follows:(1) According to monitoring data of nutrient concentration in different hydrological period in 2013, improved Nemerow index method was used to evaluate the water quality of inflow rivers. The results were showed that water quality was in serious pollution in high water period in Si River, Guangfu River, Zhuzhaoxin River and Xinwanfu River, and water quality of Dongyu Rive was improved in each hydrological period.(2) By analyzing the nutrition fluxes of five inflow rivers, we can see that there were obvious differences between each nutrition flux. nutrition fluxes of TN, NH3-Nand CODMn were increased firstly and then decreased in Dongyu River, Xinwanfu River and Zhuzhaoxin River. The nutrition fluxes of NO3--N, TN, NH3-N and CODMn in Si River and all nutrition fluxes of Guangfu River were decreased year by year. According to analyzing the correlation between the nutrition fluxes and water quality and runoff, high correlation was showed between each nutrition flux and runoff in Dongyu River and Zhuzhaoxin River. Water quality and runoff were the important factors to affect nutrition fluxes in Si River, Guangfu River and Xinwanfu River.(3) Spearman rank correlation coefficient was used to analyze the nutrient pollution trend of five inflow rivers in Nansi Lake. The results were showed that the content of CODMn presented a significant decline trend from 2008 to 2013. The content of NH3-N and TN were increased in Dongyu River. The content of TN, NH3-N and CODMn were changed significantly in Guangfu River. The content of NH3-N, CODMn, NO2--N, NO3--N and TP were decreased in Xinwanfu River and Zhuzhaoxin River.(4) According to analyze the distribution characteristics of nutrition fluxes in Nansi Lake,we found that there were seasonal changes of nutrition fluxes in all rivers. The rate of nutrition fluxes were 70.56%, 61.75%, 60.30%, 62.37% and 71.53% in Guangfu River,Xinwanfu River, Zhuzhaoxin River from June to August. And, the pollutants mainly came from non-point source pollution. By analyzing the spatial distribution of five inflow rivers, it showed us that nutrient was mainly from Si River, Zhuzhaoxin River and Dongyu River.