**5. Conclusion**

A data mining workflow, composed of principal component analysis and the Gaussian mixture model, was applied to find the trace elements' occurrence and leaching mechanism from coal and rock to surface and groundwater bodies. It is found that Se, Cd, Hg, and As were associated with sulfide minerals; Be and V occurred in carbonate minerals; Cr and Pb occurred mainly in clay minerals in the rock samples. While As and Hg were mainly occurred in sulfide minerals, Se, Cr, and Pb were embedded in clay minerals.
