Chemical Composition Variations of Altered and Unaffected Coals from the Huaibei Coalfield, China: Implications for Maturity

The composition characteristics of altered coals in the Huaibei Coalfield, China, was investigated through a comparative analysis between altered and unaffected coals from the Wolonghu, Taoyuan and Renlou coal mines. Results indicated that the altered coals in Wolonghu coal mine are mostly anthracite coals, with a maximum vitrinite reflectance of 1.6–3.9% (average of 2.9%). Coals from Wolonghu coal mine were mainly consisted of vitrinite (66.2–97.0%), followed by inertinite (2.0–4.0%) and exinite (0.4–6.9%). Differences in volatile matter content were observed between the altered coals in Wolonghu coal mine and unaffected coals from neighboring coal mines, implying that the chemical composition and maturity of coals were changed after magmatic alteration. In addition, differences in hydrogen element were noted among the coals from Wolonghu, Renlou and Taoyuan coal mines, and the phenomenon of “deficient in hydrogen element” was observed in Wolonghu coals. The aliphatic hydrocarbon structure parameters suggested that the aliphatic chain lengths of Wolonghu coals are shorter than those of coal samples from the Renlou and Taoyuan coal mines. In addition, maturity is positively correlated with hydrogen enrichment degree, but negatively related with aliphatic hydrocarbon structure. Coals from Renlou and Taoyuan coal mines showed great weight loss with various heating rates at temperatures of 0–1000 °C, whereas those from Wolonghu coal mine had less weight loss.

Hydrochemical characteristics and water quality evaluation of shallow groundwater in Suxian mining area, Huaibei coalfield, China

The aim of this study is to evaluate the hydrogeochemical characteristics and water environmental quality of shallow groundwater in the Suxian mining area of Huaibei coalfield, China. The natural formation process of shallow groundwater in Suxian is explored using Piper trilinear charts and Gibbs diagrams, and by examining the ratios between the major ions. United States Salinity Laboratory (USSL) charts, Wilcox diagrams, and the water quality index (WQI) are further employed to quantify the differences in water quality. The results reveal that the main hydrochemical facies of groundwater are HCO3–Ca, and that silicate dissolution is the main factor controlling the ion content in shallow groundwater. The USSL charts and Wilcox diagrams show that most of the water samples would be acceptable for use in irrigation systems. The WQI results for each water sample are compared and analyzed, and the quality of groundwater samples around collapse ponds is found to be relatively poor.