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Nitrogen is one of the significant pollutants emitted from coal combustion, and the study of its distribution and occurrence is very important for the efficient and clean utilization of coal resources. Four kinds of coal with different metamorphic ranks from major coal-producing provinces of China were studied. A gravity float-and-sink experiment was applied to obtain coal samples with different densities from Shanxi Province. The microscope optical method, Kjeldahl method, and X-ray photoelectron spectroscopy (XPS) were used to assess the occurrence, form, and distribution of nitrogen in the coal. The results show that the nitrogen content was about 0.47%–1.85%, and the maximum nitrogen content was positively correlated with the rank of coal, but the difference was not obvious. In the low-rank coal, the nitrogen content was mainly related to vitrinite and inertinite, while in the middle–high-rank coal, the nitrogen content was mainly related to inertinite and minerals. Pyrrolic (N-5) and pyridinic (N-6) were the main forms of nitrogen in the low-rank coal. The contents of N-6 and N-5 decreased with increases in the coal density, but the contents of quaternary N-Q1 and quaternary N-Q2 increased. N-Q2 mainly comes from fixed ammonia nitrogen in minerals, and vitrinite and liptinite contain more N-6 and less N-Q1 than inertinite. This research provides valuable evaluation guidance for the efficient utilization of coal. [ABSTRACT FROM AUTHOR]

To investigate the influence mechanism of weathering in the biogas production from coal, the characteristics of three coal samples with different weathering degrees obtained from the Wuhai mining area in Inner Mongolia and from the Xishan and Jincheng mining areas in Shanxi province were analyzed using the following methods: humic acid (HA) extraction, three-dimensional fluorescence spectroscopy, X-ray photoelectron spectroscopy and X-ray diffractometry. The results showed that the HA content in weathered coal increased with an increase in weathering degree. The content of dissolved organic matter in moderately and intensively weathered coals was clearly higher than that in slightly weathered coals. Meanwhile, the C–C and C–H in the aromatic ring was broken under the action of weathering, thus decreasing the aromaticity. Additionally, the weathering process also intensified the disordering of the directional arrangement of the macromolecular structure, causing the crystallinity of the coal to decrease. These conditions facilitated the degradation and utilization of coal by microorganisms and can be helpful to produce more biogas from coal. [ABSTRACT FROM AUTHOR]

To determine the fates of the persistent pollutants cadmium (Cd) and micro-plastics in agricultural soils, an in-depth understanding of the interactions between Cd and mulching film is required. In the present work, pot experiments are conducted under natural conditions to study the influence of various Cd concentrations on the aging process of polyethylene mulching film in soil collected from Changzhi, Shanxi Province. The results indicate that during 150 days, the aging degree of the mulch film increases gradually as the increased Cd concentration in the soil. Further, the results of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometry and X-ray photoelectron spectroscopy (XPS) demonstrate that the average vinyl index (VI) of the aging mulch film increases from 1.29 to 1.82, while the oxygen-to-carbon (O/C) ratio of the mulch film decreases significantly from 0.344 to 0.045, as the Cd concentration is increased from 0 to 10 mg kg–1. When the aging time exceeds 90 days, the oxygen-containing functional groups (C–O and C O) generated consumed by the adsorbed Cd. In addition, electron paramagnetic resonance (EPR) measurements indicate that Cd both enhances the formation of hydroxyl radical (· OH) on the surface of the mulch film and prevents the combination of · OH and electrons, thereby accelerating the aging of the mulch. Hence, the present study indicates that the presence of Cd will hasten the decomposition of mulch, which will inevitably result in the faster release of micro-plastics from the mulch into the soil environment. [Display omitted] • Cd accelerates the aging of polyethylene mulch films. • Cd consumes the available C-O/C O groups. • DMPO-OH signal intensity increases with the Cd concentration. [ABSTRACT FROM AUTHOR]