Environmental risk assessment method for dense tailings ponds areas – a case study of the Yellow River Basin of Henan Province, China

Tailings ponds are the final storage site for tailings associated with mine extraction and metal smelting. Even though they play an important supporting role in mineral excavation and utilization and related industrial development, they are also considered to be a major source of environmental risk, threatening regional ecological safety. However, the existing risk assessment methods refer to single ponds only, while there is no joint risk assessment method which can provide support for risk prevention and control in dense tailings pond areas. In this paper, the dense area of the tailings reservoir in the Yellow River basin was selected as the research object. By establishing the regional environmental risk evaluation indicator system of tailings reservoir composed of 5 system layers and 12 indicators, the weight of each index was determined by the combination of the hierarchical analysis method and entropy weight method. The environmental risk of the tailings reservoir was divided into 5 grades to study its environmental risk. In addition, the top three indicators with the highest individual environmental risk indicators were also considered the main environmental risk factors for regional tailings ponds. The results indicate that the mineral types of tailings ponds in the Yellow River Basin of Henan Province were mainly for Au, Mo, and other non-ferrous metals. Overall, the tailings ponds in the watershed exhibit a spatial distribution characteristic of declining from west to south, with a high risk of wet discharge and a high proportion of high-risk minerals. According to the results of the calculation of the regional environmental risk index, it is found that the risk level of the tailings reservoir in the Yellow River Basin gradually increases from north to south. The northern medium-low risk area centered on the Jiyuan and the southern medium-high risk area centered on Luanchuan and Ruyang have been observed. Finally, appropriate prevention and control suggestions are put forward for each risk level, which can provide decision support for risk prevention and control of tailings reservoirs in different types of areas.