洞庭湖区水环境现状调查与分析

为摸清洞庭湖区水体污染现状,揭示各区域水体营养化水平及营养盐的空间分布特征,利用长江水利委员会水文局在湖区的水文-水质综合站网,于2017年8月在全湖24个代表性断面开展了水文-水质同步监测,分析了洞庭湖各区域营养水平和水环境质量状况,计算了出入湖的污染物通量。结果表明,全湖除汨罗江和六门闸为中度富营养化外,其他区域为轻度富营养化,洞庭湖总体营养水平呈恶化趋势;藕池河北支(东洞庭湖入口之一)总氮含量显著高于其他区域,其次是东洞庭湖出口处;沅水总磷含量显著高于其他区域,其次是大通湖、东洞庭湖出口处和藕池河;六门闸(东洞庭入口之一)高锰酸盐指数含量显著高于其他区域,其次是大通湖、沅水;汨罗江叶绿素a含量显著高于其他区域,其次是东洞庭湖出口处和六门闸。根据地表水环境质量标准进行单因子数据分析及评价,总氮总磷两项营养指标的污染比较严重,使得全湖水质类别为Ⅳ类或者Ⅴ类,甚至为劣Ⅴ类。空间分布上,入湖污染负荷主要来源是沅水,其次是长江三口之一的松滋河;长江干流监利至螺山段污染负荷的主要来源为洞庭湖。经综合考虑,对洞庭湖实施水资源保护和综合治理已刻不容缓。

Water environment investigation and analysis for Dongting Lake

In order to reveal the present pollution situation and the spatial distribution characteristics of eutrophication and nutrient level in Dongting Lake, with the comprehensive monitoring network set by the Hydrology Bureau of Changjiang Water Resources Commission, synchronous lake-wide monitoring on hydrological elements and water quality was conducted in August 2017 and the nutrient level and water environment situation were analyzed as well as in-and-out pollutant flux calculated. The results showed that the lake was in light eutrophication except the middle eutrophication of the Miluo River and Liumenzha station(an entrance of the East Dongting Lake), in general, posing a worsening trend; The content of total nitrogen at the Oouchi River (one entrance of the East Dongting Lake) was highest than that in other regions, followed by the East Dongting Lake outlet; TP content of the Yuanshui River was significantly higher than other regions, followed by Datong sub-Lake, the East Dongting Lake outlet and the Ouchi River; Permanganate index at Liumenzha station were significantly higher than those in other areas, followed by Datong sub-Lake and the Yuanshui River; The content of chlorophyll in the Miluo River was significantly higher than that in other regions, followed by the East Dongting Lake outlet and Liumenzha station. According to single factor evaluation, TN and TP pollution were the most severe, resulting in a class IV or V for the whole lake, even in inferior class V; In view of the spatial distribution, the pollutant from the Yuanshui River into the lake was the primary source, followed by the Songzi River entering the lake from the Yangtze River; the Dongting Lake was the primary pollution source of Jianli-Luoshan section of the Yangtze River. On overall consideration, the water quality in Dongting Lake poses a deterioration trend, so it is urgent to protect water resources and adopt comprehensive control measures and the related departments should seriously pay attention to it.