Soil fertility and heavy metal risk assessment in Jvhugeng mining area, Muli Coalfield, Qinghai Province

The mining of coal resources at the Jvhugeng mining area, Muli Coalfield, has damaged the ecological environment of the mining area. Through the determination of soil fertility indexes and heavy metal indexes in the study area, soil fertility and heavy metal ecological risks are evaluated by the principal component analysis method and the potential ecological hazard index method. The results show that the soil in the mining area is alkaline as a whole, rich in organic matters, total nitrogen, and available potassium, but lacking in available phosphorus. It has the characteristics of being rich in nitrogen potassium and poor in phosphorus. The soil fertility indicators in the No.3 minefield are the best. The comprehensive scores of soil fertility respectively are Duosuo Gongma minefield(−0.113), No.9 minefield(0.081), No.8 minefield(−0.369), No.5 minefield(−0.034), No.4 minefield(−0.145), and No.3 minefield(0.692). The soil fertility of the No.3 minefield is the best. The order of the ecological hazard intensity of the six heavy metals in the soil of the mining area from weak to strong is Cr, Pb, Cu, Hg, As and Cd, and the results of the risk evaluation of those heavy metals in the soil of each minefield show a slight ecological hazard. In conclusion, the overall fertility quality of the slag hill soil in the mine area is poor, and the heavy metals are of low risk. The slag hill soil could be used as the soil substrate in soil reconstruction, but it needs to be mixed with livestock manure and organic fertilizer to improve the fertility quality of the reconstructed soil. The results of the study provide a basis for soil restructuring and vegetation restoration in the Jvhugeng mining area of the Muli Coalfield.