长江上游珍稀鱼类保护区代表性测站氨氮生态风险评估

Ecological Risk Assessment of Ammonia Nitrogen in Rare Fish Reserve in the Upper Reaches of the Yangtze River

基于2020年最新颁布的《淡水水生生物水质基准——氨氮》,采用风险商模型评估了长江上游珍稀鱼类保护区内三个河段六个代表性测站的氨氮生态风险状况。结果显示,金沙江的氨氮风险明显高于川江和赤水河,其中金沙江宜宾站的氨氮风险最高,其短期风险商(S_(SRQ))和长期风险商(L_(LRQ))的均值分别为0.131、0.630,均属于中等级别,表明宜宾站氨氮对水生生物的危害虽然未超出容许限值,但不可忽略;川江的氨氮风险明显低于金沙江和赤水河,其中川江朱沱站的氨氮风险最低,S_(SRQ)、L_(LRQ)的均值分别为0.052、0.283,且在整个调查期内,朱沱站的S_(SRQ)均低于0.1,表明朱沱站氨氮对水生生物的急性危害远低于容许限值,可忽略;向家坝站2014年7月的L_(LRQ)>1,属于高级别,同期金沙江向家坝坝段出现了鱼类大面积死亡现象,死因可能为氨氮超标。由此可见,风险商模型能够准确识别长江上游珍稀鱼类保护区的氨氮风险,且在长江上游珍稀鱼类保护区中,氨氮生态风险的主要影响因素是氨氮浓度。因此,为了长江上游珍稀鱼类保护区水生生态系统的健康稳定,需进一步加强污染源治理,削减氨氮负荷。

Based on the latest "Freshwater Aquatic Biological Water Quality Criteria-Ammonia Nitrogen" issued in 2020, the risk quotient model was used to assess the ecological risk status of NH_(3)-N at six representative stations in three river sections of the Rare Fish Reserve in the upper reaches of the Yangtze River. The results show that the NH_(3)-N risk of the Jinsha River is significantly higher than that of the Chuanjiang River and Chishui River. Among them, the Yibin station of the Jinsha River has the highest NH_(3)-N risk, the mean values of the short-term risk quotient(S_(SRQ)) and long-term risk quotient(L_(LRQ)) are 0.131 and 0.630, respectively, which belong to the medium level, indicating that although the harm of NH_(3)-N to aquatic organisms at Yibin Station does not exceed the allowable limit, it cannot be ignored;The NH_(3)-N risk of Chuanjiang River is significantly lower than that of Jinsha River and Chishui River. Among them, Zhutuo Station has the lowest NH_(3)-N risk, the mean values of S_(SRQ)and L_(LRQ)are 0.052 and 0.283, respectively, and the S_(SRQ)of Zhutuo Station is lower than 0.1 during the whole investigation period, indicating that the acute harm of NH_(3)-N to aquatic organisms at Zhutuo Station is far below the allowable limit and can be ignored;The L_(LRQ)of Xiangjiaba Station in July 2014 is greater 1, belonging to the high level. During the same period, large-scale fish deaths occurred in the Xiangjiaba section of the Jinsha River, and the cause of death may be excessive NH_(3)-N. It can be seen that the risk quotient model can accurately identify the NH_(3)-N risk in the rare fish reserve in the upper reaches of the Yangtze River, and in the rare fish reserve in the upper reaches of the Yangtze River, the main factor influencing the ecological risk of NH_(3)-N is the NH_(3)-N concentration. Therefore, in order to maintain the health and stability of the aquatic ecosystem in the Rare Fish Reserve in the upper reaches of the Yangtze River, it is necessary to further strengthen the treatment of pollution sources and reduce the load of NH_(3)-N.