Effects of Acid Mine Drainage on Calcareous Soil Characteristics and Lolium perenne L. Germination

Acid mine drainage (AMD) is a serious environmental problem resulting from extensive sulfide mining activities. There is a lack of more comprehensive and detailed studies on the effect of AMD on calcareous soil characteristics and seed germination. In this study, five calcareous soil samples, collected from Xiaoyi, Taigu, Xiangning, Hejin, and Xixian counties in Shanxi Province, China, were used to investigate the effects of acid AMD on soil characteristics and Lolium perenne L. germination through laboratory culture experiments. The results showed that the increase in the total soil calcium oxide and magnesium oxide (CaO + MgO) contents led to a rise in the amount of Fe2+ in AMD converted into Fe3+, and that major ions (H+, Fe, SO42-) in AMD were trapped in the soil. The total Cao + MgO contents in the soil collected from Hejin and Taigu counties were 14.23% and 6.42%, the pH of AMD-polluted soil decreased to 7.24 and 3.10, and 98.7% and 54.0% of the Fe2+, 99.9% and 58.6% of the total Fe, and 76.0% and 26.4% of the SO42-, respectively, were trapped in the soil when the AMD volume to soil mass ratio was 10 mL/g. The results for the soil from Taigu County showed that when the soil had an AMD volume to soil mass ratio of 10 mL/g, the organic matter, available phosphorus (available P), available potassium (available K), Cr, and Cd contents in soil decreased by 16.2%, 63.0%, 97.1%, 7.8%, and 73.2%, respectively; the total phosphorus (total P) and total potassium (total K) did not significantly change; whereas the available nitrogen (available N) and total nitrogen (total N) increased to 16.1 times and 1.76 times, respectively. Compared to the initial soil collected from Taigu County, the Lolium perenne L. germination rate decreased by 81.1%, and the cumulative amount of Cr in the Lolium perenne L. increased by 7.24 times in the AMD-polluted soil when the AMD volume to soil mass ratio was 6 mL/g. The soil conditions could not support Lolium perenne L. germination when the AMD volume to soil mass ratio was 10 mL/g. The outcomes of this study could have important implication in understanding the hydrological/geochemical-behaviour of major ions of AMD in calcareous soil. The findings also have great significance in predicting plant growth behavior in AMD-polluted calcareous soil.