基于CCME-WQI方法的鄱阳湖流域乐安河水质分析

Analysis of Water Quality of Le'an River in Poyang Lake Basin Based on CCME-WQI Method

鄱阳湖作为我国第一大淡水湖泊具有重要的水生态意义,其典型入湖河流的水质状况影响着湖泊水质.选择鄱阳湖典型入湖河乐安河为研究对象,基于乐安河干流上中下游共6个点位2012~2020年的水质监测数据,在系统分析了河流干流污染物浓度的时空变化趋势后,利用水质指数法评估河流水质状况,最后根据PCA法提取并分析河流水质的主要影响因子.结果表明:①研究时间段前期河流上游与下游水体污染较为严重,其原因为河流上游存在着德兴铜矿,下游存在着中小型矿山与农田.②2017年前乐安河下游水体水质最差,总磷与氨氮超标率分别为43.3%与85.0%,WQI平均值最低且为86.2.2017年后由于流域内污染物排放得到了有效治理,河流下游水质显著改善并持续处于优秀状态,WQI均值达到100.0.③乐安河干流水质影响因素可划分为人类活动、季节因素、污染物大气沉降与水体自身理化性质这4类,大坞河口与石镇街处人类活动为水质变化的主导因素,而余下点位处季节因子影响最大.④乐安河上、下游水体有机物污染明显,上游大坞河口处水质主要受附近采矿活动的影响,而下游石镇街处水质主要受农业面源影响.乐安河流域2017年前下游水体有机物污染严重,流域内采矿活动与农业活动对水质影响程度高,应提升流域内选矿废水的处理水平,规范流域下游农田面源污染物的排放.

As the largest freshwater lake in China,Poyang Lake plays a key role in supporting the balance of aquatic ecosystems,and the water quality of its inlet rivers affects the lake's water quality.Le'an River,a typical inlet river of Poyang Lake,was selected as the research object.Based on the water quality data of six monitoring points in the upper,middle,and lower reaches of the mainstream of Le'an River from 2012 to 2020,the CCME-WQI method was used to evaluate the water quality of the river after systematically analyzing the spatiotemporal variation of the concentration of pollutants in the mainstream of the river.Finally,the main influencing factors of the water quality of the river were extracted and analyzed according to the PCA method.The results showed that:①The water volume upstream and downstream of the river was more seriously polluted in the pre-study time period,which was due to the presence of Dexing Copper Mine in the upstream and small and medium-sized mines and farmland downstream.②Before 2017,the water volume downstream of Le'an River had the worst water quality,with TP and NH4+-N exceeding the standard rate of 43.3%and 85.0%,respectively,and the lowest WQI mean value of 86.2.After 2017,due to the effective management of pollutant discharges in the watershed,the water volume downstream of the river improved significantly and continued to be in an excellent state,and the mean value of the WQI reached 100.0.③The factors influencing the water quality of the mainstem of the Le'an River could be divided into four categories:human activities,seasonal factors,atmospheric deposition of pollutants,and the physical and chemical properties of the water volume itself,with human activities being the dominant factor for water quality changes at Dawuhekou and Shizhenjie,whereas the seasonal factors had the greatest influence at the remaining locations.④Organic matter pollution was obvious in the upper and lower Le'an River water volume,and the water volume at Dawuhekou was mainly affected by nearby mining activities,whereas the water volume at Shizhenjie was mainly affected by agriculture.Le'an River had serious organic matter pollution downstream before 2017,and mining and agricultural activities in the watershed had a high degree of impact on water quality.The treatment of mineral processing wastewater should be upgraded,and the discharge of pollutants from agriculture in the downstream of the watershed should be regulated.