Explanation of heavy metal pollution in coal mines of china from the perspective of coal gangue geochemical characteristics

In the process of coal gangue surface accumulation and underground filling disposal, the heavy metals contained in coal gangue will inevitably precipitate out and migrate, which will cause serious environmental pollution. Seventy-five gangue samples of different geological ages are obtained from 25 coal mines in China. The contents of Hg, Pb, Cd, Cr, As, Cu, Zn, Mn, Se, and Be in gangue samples are determined. The enrichment coefficients of heavy metal elements in coal gangue are analyzed. The formation of heavy metal elements in gangue is studied by cluster analysis and principal component analysis. The results showed that the contents of Pb, Se, and As in gangue samples formed in Late Carboniferous and Early Permian are highest; the contents of Cr, Cd, Be, Cu, and Zn in gangue samples formed in Late Permian are highest. The later the formation age of coal gangue, the lower the overall enrichment of heavy metal elements. The contents of Cu, Be, Cd, Zn, and Cr in coal gangue are mainly controlled by sedimentation. The contents of Pb and Se are mainly affected by the affinity between heavy metal elements in coal gangue. The affinity between Mn and other heavy metal elements is weak, and sulfur had a certain influence on the content of Mn.