Study on the Improvement of Coal Gangue and Soil Composite Matrix by Organic Acid Erosion of Plant Roots

Abstract Coal gangue is a kind of solid waste produced in the process of coal mining and washing, which a large amount of stockpiling poses a serious threat to the environment in Guizhou karst area. Coal gangue contains a certain amount of organic matter, clay minerals and other soil components, which creates favorable conditions for coal gangue preparation. Organic acids secreted by simulated plant roots were used to treat coal gangue, and scanning electron microscope was used to analyze the surface microstructure after acid etching. The result showed that organic acid soak of simulated root system could effectively etch that surface of coal gangue and destroy its compact mineral structure. After acid etching, BET specific surface area increased by 37.81%, average pore size of adsorption and desorption increased by 60.94% and 49.11%, respectively, and pore volume increased greatly, indicating that organic acid could significantly promote the transformation of coal gangue into soil. The pot experiment was carried out with shallot, strawberry, garland chrysanthemum and ryegrass as plants. The results showed that the biomass of different plants was significantly different due to different optimum mixing ratio. Compared with the control group, the water content of strawberry was 81.36g, and the change was obvious. The results show that heavy metals in coal gangue distribute to different parts through plant roots, and the contents in different parts are different. The enrichment in roots of different plants is the highest, and the enrichment in stems and leaves (edible parts) varies with different plants. Ni, Hg and Zn have the strongest mobility among the four plants, while Pb and Cu have the weakest mobility. Through high-throughput sequencing analysis of soil microbial community composition, diversity and species difference analysis under the optimal coal gangue doping conditions for plant growth, coal gangue doping in soil can improve soil microbial community composition, diversity and species difference, promote soil micro-ecological virtuous cycle, and provide theoretical basis and experimental support for coal gangue agricultural resources and soil improvement.