松桃河流域氨氮和锰污染特征及生态风险评价

以地处"锰三角"核心区的松桃河流域为研究对象,应用统计学方法对2011～2019年松桃河流域17个监测断面的18个水质指标进行统计分析,重点研究松桃河流域主要污染物氨氮和锰污染特征、时空变异及来源解析,利用商值法、安全阈值法对松桃河流域氨氮和锰的生态风险进行评价.结果表明:松桃河流域主要受到氨氮和锰污染,两者在P<0....

Pollution characteristics and ecological risk assessment of ammonia nitrogen and manganese in Songtao River Basin of Guizhou Province,China

This study researches the Songtao River basin, which is located in the core area of so called “Manganese Triangle Area in China. Statistical method was utilized to analyze the 18 water quality indexes of 17 monitoring sections in Songtao River obtained from year 2011 to 2019; emphases were made on contaminative features, spatio-temporal variations and source analysis of the major contaminants in Songtao River, e.g. NH₃-N and Mn; the ecological risks of characteristic pollutants in Songtao River were evaluated by quotient method and safety threshold method respectively. The results show that Songtao River basin is mainly polluted by NH₃-N and Mn, which are positively correlated at the level of P < 0.0001denoting a homology. Wastewater from the electrolytic manganese enterprises and leaching liquor from the landfill are the dominant sources of NH₃-N and Mn. The spatio-temporal variations of NH₃-N and Mn are basically the same, and their contaminative degree in major monitoring sections is closely related to the spatial distributions of electrolytic manganese enterprises and slag landfills. On the time dimension, the pollution in Songtao River basin has gradually declined yearly while the case for Muchi River, a branch of Songtao River, is on the opposite. Regarding aquatic organism exposure, two evaluative methods were applied to estimate the effects of the two major toxins on Songtao River water. The quotient method demonstrates the acute and chronic toxic effects as 10.37% and 44.93% for NH₃-N, 69.81% and 77.89% for Mn; While the safety threshold method denotes the acute and chronic toxic effects to be 5.6% and 24.33% for NH₃-N, 34% and 90% for Mn. A significant variation was noticed between the evaluations of the two methods. The quotient method was more conservative, which shows double risk levels of safety threshold method assessed for the NH₃-N chronic and acute toxicity and Mn chronic toxicity. The current water quality standard for Songtao River is higher than the safe concentrations of NH₃-N and Mn, which brings an “unprotecting” condition for the aquatic organisms in Songtao River. We suggest that the investigation on aquatic species in the Songtao River, the collection for toxicity data and the experiments on biological toxicology should be carried out, and the water quality standard of characteristic pollutants in Songtao River should be optimized as the scientific basis for formulating the regional water quality standards, which in turn to realize the differentiated risk management and ensure the ecological safety of water environment.