Arsenic distribution and speciation in deposited coal mine dust

This study investigates arsenic (As) species, sources, and transformation patterns in deposited coal mine dust (DCMD) from three coal mines—QSY, MHJ, and SCC—in the Ningdong Coalfield, China. While the parent coals have low As levels, the DCMD shows significant enrichment, with concentrations 137 to 345 times higher. The mineral composition of the DCMD reflects that of the parent coals but includes secondary minerals such as gypsum and various trace elements, including As. This enrichment results from multiple factors: polluted waters used for dust control in the working front (WF), gangue dust introduced during mining operations, wear from mining machinery affecting Fe levels, and precipitation of As-salts from alkaline mine drainage. In the parent coals, As(V) comprises 60-65% of the As, while As(III) accounts for 14-35%. In contrast, the DCMD samples reveal As(V) as the dominant species (22-58%), with As(III) making up 18-44%. Arsenic leachability is influenced by Fe content, enhancing As adsorption and limiting mobility in QSY mine, while mixed As complexes in MHJ and SCC under alkaline conditions affect As mobility. The presence of more toxic As(III) in DCMD highlights environmental and health risks, emphasizing the need to avoid high-As polluted waters for dust control.