三峡水库蓄水运行后入出库断面水质评价与预测

三峡工程运行后库区水质问题关系库区环境安全和当地社会经济发展,把握三峡库区水质变化趋势是水污染治理的基础。采用内梅罗污染指数法,基于2004—2016年三峡库区长江干流入库断面(重庆朱沱)和出库断面(湖北宜昌南津关)水体DO、高锰酸盐指数和氨氮的水质监测数据评价库区水质,并利用差分自回归移动平均模型(ARIMA模型)建立入出库断面水质变化趋势模型。结果表明:2004—2016年入库断面梅罗污染指数(Ip)为1.72～3.22,水质属轻污染—重污染,变化波动大;出库断面Ip为0.82～1.46,水质属清洁—轻污染,总体保持平稳;入库断面水质指标逐年偏向《地表水环境质量标准》(GB 3838—2002)中Ⅱ级标准,出库断面水质指标逐年偏向Ⅰ级标准,入出库断面首要污染物是氨氮,ARIMA模型预测显示未来入出库断面水质好转。

Water quality evaluation and prediction of the reservoir inflow and outflow after the Three Gorges Project operation

Water quality is essential to the environmental security and socioeconomic development in the Three Gorges Reservoir Area after the Three Gorges Project operation.To analyze the changes of water quality in the reservoir after Three Gorges Project operation,the water quality and changing trends in the reservoir inflow(Zhutuo section in Chongqing)and outflow(Nanjinguan section in Hubei Yichang)of Changjiang River mainstream were evaluated based on the water quality monitoring data(DO,permanganate index,ammonia nitrogen)from 2004 to 2016 by using Nemerow pollution index method and ARIMA model.According to the calculation results,the Nemerow pollution index(I p)of inflow section fluctuated largely from 1.72 to 3.22,the water pollution level was between light pollution and heavy pollution.The I p of outflow section ranged smoothly from 0.82 to 1.46,the water pollution level was between clear and light pollution.The pollution factors of inflow were closer to ClassⅡof“Environmental quality standard of surface water”(GB 3838-2002),the pollution factors of outflow were closer to ClassⅠ.Ammonia nitrogen was the major pollutant in the reservoir.According to the ARIMA prediction model,water quality would keep well in the future.