Influence of mining ground fissures on soil microorganism and enzyme activities in northern Shaanxi coal mining area

As an important type of mining damage in the middle reaches of the Yellow River Basin,the law and mechanism of affecting soil characteristics have become a current hot research subject.In order to investigate the effect of mining cracks on soil microbial characteristics,the soil samples around the cracks (within 60 cm of horizontal distance and 60 cm of vertical depth to shallow) were collected from the mining cracks with a width of 20-40 cm in Northern Shaanxi Coal Mine Area in this experiment,and the number of soil bacteria,actinomycetes,and fungi and the activities of sucrase,catalase,urease,and phosphatase were determined by absolute quantitative PCR and microplate reader,respectively,to analyze the spatial change characteristics of soil microorganisms and enzymes.On this basis,the effects of mining cracks on soil microorganisms and enzymes on a small spatial scale were interpreted in combination with the main physicochemical characteristics of the soil.The results showed that:① the negative effect of mining ground cracks on soil microbial and enzyme activities was mainly characterized by horizontal differences,and significantly weakened with the increase of horizontal distance.When the horizontal distance was more than 75,79,91,72,82,89,and 96 cm,the negative effects of mining ground cracks on soil bacteria,actinomycetes,fungi,phosphatases,sucrase,catalase,and urease basically disappeared,and the damage of soil microbial characteristics was mainly concentrated within 1 m of horizontal distance,which could be used as a targeted area for accurate remediation of soil microorganisms in the damaged area of coal mining in northern Shaanxi;② The average decreases of organic matter,ammonium nitrogen,available phosphorus,available potassium,clay,moisture content,pH and the average increase in porosity in the soil around mining ground cracks were 9.51%-28.46%,24.31%-29.31%,12.61%-19.86%,4.11%-6.51%,4.93%-6.46%,2.36%-4.26%,and 1.98%-3.14%,respectively.The correlation coefficients exceeded 0.8 and 0.6,respectively,and reached a highly significant positive correlation level (P