Entropy weight-TOPSIS model in soil quality evaluation of Beijing-Hebei limestone mining area

Ecological restoration of the limestone mining areas in Beijing-Hebei is crucial for alleviating regional ecological stress, safeguarding ecological security, and promoting sustainable development. Soil quality is the key to ecological restoration in limestone mining areas. However, current understanding of soil conditions and the dominant influencing factors in these areas remains limited. This study investigated soil quality in four representative limestone mining sites: Mancheng in Hebei Province, Xiazhuang in Beijing, Wenshuyu in Beijing, and Yutian in Hebei Province. Soil samples from the platform sites of the mining areas, both un-rehabilitated and rehabilitated, were collected. Eleven indicators, including pH, electrical conductivity (EC), soil nutrients, soil enzyme activities, and cation exchange capacity, were detected. The entropy weight-TOPSIS model was adopted to evaluate the soil quality (Ci) of the limestone mining areas around Beijing-Hebei. The results show that in the un-rehabilitated mining area, alkaline phosphatase has the largest weight, followed by CEC, urease, hydrolysable nitrogen, available phosphorus, available potassium, organic matter, EC, sucrase, catalase, and pH. In the rehabilitated mining area, alkaline phosphatase has the greatest impact, followed by urease and sucrase. The range of Ci in the un-rehabilitated platform site of the limestone mining area is from 0.123 to 0.644, and the overall level is relatively low. The Ci of the rehabilitated platform site was within the range of 0.145～0.873. Compared with the un-rehabilitated soil, the soil quality was improved. The enzyme activity, available phosphorus, and available potassium contents were abundant, while the overall levels of organic matter and hydrolysable nitrogen were relatively low, with large variation. Xiazhuang demonstrates the best restoration outcomes, whereas Mancheng, Wenshuyu, and Yutian exhibited relatively weak recovery. For the future restoration of the platform site in the limestone mining area, more attention should be paid to the relevant indicators of soil enzyme activity and the proportion of fertilization, etc. This study can provide guidance for the ecological restoration practice of limestone mining areas.