Spatial distribution characteristics of heavy metals in the soil of coal chemical industrial areas

Heavy metal soil pollution in the coal chemical industrial area has attracted increasing attention with the rapid development of the coal chemical industry. The spatial distribution and the source of heavy metals in the soil in coal chemical industrial areas should be investigated to help prevent further heavy metal pollution in industrial areas, and reduce heavy metal exposure to factory workers. A coal chemical factory in northwest China was studied. A chessboard sampling method was used to collect 153 soil samples. An inductively coupled plasma mass spectrometer (ICP-MS) and a mercury vapor analyzer were used to quantify five heavy metals (Pb, Hg, Cd, Cr, and As). The spatial distributions of these five heavy metals were simulated using several statistical methods and the spatial maps of the five heavy metal concentrations were obtained. The mean concentrations of the heavy metals excluding Pb were higher than their respective soil background values in Ningxia Hui Autonomous Region (Ningxia). The concentrations of Hg, Cd, Cr, and As were 4.00, 4.00, 1.50, and 1.08 times of their background concentrations, respectively. In contrast to the production flow chart, the soil on both sides of the trunk road and the coal transport corridor at the factory had relatively high Pb and Cd concentrations. The slag dump of the gasification residues had the highest Cr concentration because of the local prevailing winds. Concentrations of Hg, Cd, and As in the downwind direction of the prevailing winds from the coal combustion unit chimney were significantly high. In this study, the spatial distributions of five heavy metals (Pb, Hg, Cd, Cr, and As) in the soil at a coal chemical factory were obtained. The respective sources of heavy metals in the soil were determined. The present study provides a theoretical basis for the prevention and treatment of heavy metal pollution in coal chemical factories.