望虞河西岸河流氮磷污染状况及其对调水水质的影响

Nitrogen and Phosphorus Pollution in the West Bank of Wangyu River and Its Impact on Water Quality of Water Diversion

为探讨望虞河西岸河流氮磷污染状况及其对调水引流入太湖水质的影响,分别于2017年11月以及2018年3和6月,选取望虞河西岸紧临入湖口的4条代表性河流,测定水体各形态氮、磷浓度,对各形态氮、磷时空分布规律及其对调水水质的影响进行研究。结果表明:(1)伯渎港、徐塘桥河、古市桥河和张塘河ρ(TN)平均值分别为4.93、5.20、2.27和3.78 mg·L^-1,ρ(TP)平均值分别为0.18、0.23、0.16和0.15 mg·L^-1,NO3^--N和PO43^--P分别为氮、磷的主要形态;(2)夏季伯渎港、徐塘桥河和古市桥河TN平均浓度最高,分别为各自最低季节的1.24、1.44和2.01倍;4条河流氮、磷浓度沿汇入望虞河方向呈下降趋势,但入河断面水质未达到区域水功能区划制定的Ⅲ类水质目标;(3)研究区91.3%的水体断面处于中度富营养化水平,56.5%的水体断面为磷限制状态;(4)电导率、CODMn和ρ(Chl-a)为各形态氮、磷分布的主要影响因素。研究区河流营养盐的汇入对望虞河入湖口水质有较大影响,尤其是磷素污染,需加强水体溶解性磷浓度的削减控制。夏季研究区氮素污染最为严重,且夏季为望虞河引水期,应加强该时段入河支流水体污染控制,保障调水水质。

In order to investigate the characteristics of nitrogen and phosphorus pollution in the west bank of the Wangyu River and its impact on the water quality of the Taihu Lake, the concentrations of nitrogen and phosphorus in various forms were measured at four representative tributaries in the west bank of the Wangyu River in November of 2017, and March and June of 2018. The form composition, seasonal and spatial distribution of nitrogen and phosphorus and their influence on the quality of water diversion were studied. The results are as follows:(1)The average concentrations of TN in Bodugang, Xutangqiaohe, Gushiqiaohe and Zhangtanghe were 4.93, 5.20, 2.27, 3.78 mg·L^-1, respectively, and the average TP concentrations were 0.18, 0.23, 0.16, 0.15 mg·L^-1, respectively;NO3^--N and PO43^--P were the main forms of nitrogen and phosphorus, respectively.(2)The average concentration of TN in Bodugang, Xutangqiaohe and Gushiqiaohe in summer were the highest, which were as 1.24, 1.44 and 2.01 times as that of the lowest season, respectively;Along the inflow direction to Wangyu River, the concentration of nitrogen and phosphorus in the four tributaries had a downward trend. However, the water quality of the river entry section of the tributaries does not meet the water quality target(Class Ⅲ) of the regional water function zoning.(3)91.3% of the water sections in the study area were at the moderate eutrophication level and 56.5% of the water sections were in phosphorus-limited state.(4)EC, CODMn and Chl-a were the main factors affecting the distribution of nitrogen and phosphorus forms. The influx of nutrients in the study area has a great impact on the water quality of the Wangyu River, especially phosphorus pollution. It is necessary to strengthen the reduction of dissolved phosphorus concentration in water bodies. Nitrogen pollution is the most serious in summer which is the diversion period of the Wangyu River. It is necessary to strengthen the pollution control of the tributaries entering the river to ensure the water quality during water diversion.