Effect of Biochar, Earthworm Manure and Calcium Carbide Slag on the Improvement of Acidic Soil of Copper Sulfide Mine

Objective To solve the problems of low pH value, poor organic matter level and high heavy metal content of acidic soil of copper sulfide mine, Method this study adopted the method of organic-inorganic combined improvement, took the polluted acidic soil in Chengmenshan copper mining area of Jiangxi Province as the research object, based on soil culture test and pot experiment, to explore the improvement effect of different addition amounts (3%, 5%, 10%) of biochar combined with organic fertilizer earthworm manure and calcium-containing solid waste carbide slag on acid soil and the effects on the growth of Pennisetum purpureum and the content of heavy metals in the grass. Result The results showed that the application of soil conditioner could significantly improve the physical and chemical properties of acidic soil of copper sulfide mine and reduce the total and available contents of Pb, Cu and Zn in soil, and the improvement effect of ECB3 (10% biochar +2% carbide slag +5% earthworm manure) was the most obvious. What is more, taking Cu²⁺ adsorption as an example, the adsorption of Cu²⁺ by biochar belongs to single-layer surface adsorption, mainly chemical adsorption. After the application of soil amendments, the plant height of grass increased by 55.96%～183.43%, the biomass increased by 26.7 times, the content of heavy metals in the above-ground part of sweet elephant grass decreased significantly, and the ability to enrich heavy metals in the root was enhanced. According to the correlation analysis between the total and available contents of heavy metals in soil and the physicochemical properties of soil, there is a significant negative correlation between the physicochemical properties of soil and the content of heavy metals in soil. Conclusion Redundancy analysis between plant and soil environmental factors showed that the absorption capacity of grass to heavy metals was not only affected by its physiological characteristics, but also affected by soil environmental factors and soil biological availability of heavy metals.