Chemical and microbial properties in contaminated soils around a magnesite mine in northeast China

We measured soil chemical and microbial properties at a depth of 0–20 cm among mine tailings, abandoned mined land, contaminated cropland, and uncontaminated cropland around a magnesite mine near Haicheng City, Liaoning Province, China. The objective was to clarify the impact of Mg on the soils. We found that soluble Mg²⁺ concentration and pH were significantly higher in contaminated soils (266–345 mg kg⁻¹ and 9·9–10·3, respectively) than in uncontaminated soils (140 mg kg⁻¹ and 7·1, respectively). Soil nutrients (total N, total P, mineral N, available P and soluble Ca) and microbial biomass C and N decreased as pH and soluble Mg²⁺ concentration increased. In addition, an increase of microbial metabolic quotient and a decrease of N mineralization rate were found in contaminated soils. Soluble Mg²⁺/Ca²⁺ ratios in contaminated soils were 3·5–8·9‐times higher than in uncontaminated soils. Our results indicate that soil contamination in such magnesite mine regions is characterized by high pH, Mg²⁺ concentration and soluble Mg²⁺/Ca²⁺ ratio, and low microbial activity and N and P availability. Future soil amelioration in the magnesite regions should consider applying acid ameliorants to neutralize high pH and applying calcareous ameliorants to increase Ca²⁺ concentration. Copyright © 2011 John Wiley & Sons, Ltd.