Remediation of a Magnesium-Contaminated Soil by Chemical Amendments and Leaching

The deposition of magnesium (Mg)-rich dust from magnesite mining activities has resulted in serious land degradation. However, the main factors limiting plant growth in Mg-contaminated soils are unclear. Moreover, little information is available on the remediation of Mg-contaminated soils. In this study, remediation of soils contaminated with Mg-rich dust was investigated in a pot experiment using maize as the indicator plant. There were five treatments: (i) control; (ii) leaching; (iii) application of CaCl2; (iv) leaching+CaCl2 application; and (v) application of Ca(H2PO4)(2)H2O. Soil properties and growth of maize (Zea mays L.) seedlings were measured. Leaching alone significantly decreased soluble Mg concentration. Leaching+CaCl2 application greatly increased exchangeable Ca concentration and decreased soil pH by 03 units. Application of CaCl2 alone increased soluble Mg concentration sharply, which directly inhibited the germination of maize seeds. Application of Ca(H2PO4)(2)H2O significantly increased the concentrations of exchangeable Ca and available phosphorus and decreased soil pH by 17 units. The biomass of maize seedlings increased in the order of control=leaching)H2O. These results suggested that the plant growth in Mg-contaminated soils was limited primarily by Ca deficiency and secondarily by high soil pH when exchangeable Ca was sufficient. High soil pH suppressed plant growth probably mainly by inhibiting phosphate uptake from the soil. Applying acid Ca salt with low solubility is an attractive option for the remediation of Mg-contaminated soils. Copyright (c) 2015 John Wiley & Sons, Ltd.