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 020?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 9.910.3, 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 3.58.9-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 (C) 2011 John Wiley & Sons, Ltd.