Concentrations and modes of occurrence of trace elements in the Late Permian coals from the Puan Coalfield, southwestern Guizhou, China

Abstract

The concentration, mode of occurrence, and origin of trace elements in the Late Permian coals from the Puan Coalfield, southwestern Guizhou, China, were examined using inductively coupled plasma-mass spectrometry (ICP-MS), X-ray fluorescence (XRF), cold-vapor atomic absorption spectrometry (CV-AAS), ion-selective electrode method (ISE), sequential chemical extraction procedure (SCEP), scanning electron microscopy equipped with energy-dispersive X-ray (SEM-EDX), and optical microscope. Results show that minerals in the No. 2 Coal from the Puan Coalfield were mainly made up of epigenetic pyrite of low-temperature hydrothermal fluid origin and kaolinite of detrital terrigenous origin. Elements including As (36.9 microg/g), Cd (10.2 microg/g), Cr (167.3 microg/g), Cu (365.4 microg/g), Hg (2.82 microg/g), Mo (92.6 microg/g), Ni (82.6 microg/g), Pb (184.6 microg/g), Se (6.23 microg/g), Zn (242.3 microg/g), and U (132.7 microg/g) are significantly enriched in the No. 2 Coal from the Puan Coalfield. However, concentrations of trace elements in the other four coals, the No. 1, No. 8, No. 11, and No. 18 Coals, were close to the usual ranges found for Guizhou of China, China, and USA. Results of SEM-EDX and SCEP showed that As, Cd, Hg, Mo, Ni, Pb, and Zn occur mainly in veined pyrite, while Cr, Cu, and U distribute mainly in kaolinite, indicating that the low-temperature hydrothermal fluid and detrital materials of terrigenous origin are the main contributors to the enrichment of these trace elements in the No. 2 Coal.

Abundance, Distribution, and Modes of Occurrence of Uranium in Chinese Coals

“…Significant uranium enrichment in coals only occurs in Shanxi, Yunnan, Guizhou, Guangxi, Xinjiang, Inner Mongolia, Sichuan, and Chongqing Provinces of China (Table 1), e.g., the Datong coal (averaging 38.2 mg/kg and 28.8 mg/kg uranium [31]), the Dazhai coal (52.5 mg/kg [32] and 56.0 mg/kg [33]), the Yanshan coal (167 mg/kg [34] and 153 mg/kg [35]), the Luquan coals (34.1 mg/kg [36]), the Guiding coal (229 mg/kg [34] and 200 mg/kg [30]), the Puan coal (32.4 mg/kg [37]), the Zhijin coal (49.6 mg/kg [38]), the Heshan coal (10.2 mg/kg to 326 mg/kg [39][40][41][42]), the Yishan coal (71.7 mg/kg [43]), the Sawabuqi coal (365 mg/kg [44]), the Yili coal (320 mg/kg [45] and 147 mg/kg [46]), the Shenli coal (25.9 mg/kg [47]), the Shiping coal (39.8 mg/kg [48]), and the Moxinpo coal (376 mg/kg [49]). …”

“…With respect to the Chinese coals, uranium is associated with: (1) organic matter [30,34,36,39,42,[77][78][79][80][81][82][83], (2) as physical adsorption by pores and pelitic components [46,84], (3) silicates [34,36,37,47,65,66,77,82,[85][86][87][88][89][90][91][92][93], (4) phosphate minerals [94][95][96], (5) uranium minerals [30,34,45], and (6) mixed affinity to both organic and inorganic matter [19,35,97]. Overall, the modes of occurrence of uranium in Chinese coals was deduced indirectly, i.e., correlation with ash yield and major element oxide, and sequential chemical extraction, with only a few from direct evidences of SEM-EDS (Scanning electron microscope combined with an X-ray energy dispersive spectrometer) identification.…”

Quantitative Assessment of Variability and Uncertainty of Hazardous Trace Element (Cd, Cr, and Pb) Contents in Chinese Coals by Using Bootstrap Simulation

“…Coals by Provinces The provinces with relatively more data for Cr are Xinjiang with 129 samples, 45,50,51 Guizhou with 124 samples, 12,16,36,37,52 and Anhui with 111 samples. 50,[53][54][55][56][57] The provinces with very few data samples include Guangdong, Gansu, and Zhejiang, with one or two averaged content original samples.…”

“…Coals by Provinces The provinces with relatively more data samples of Pb are Guizhou with 168 samples, 12,13,16,35,37,52 Shanxi with 83 samples, 17,39,40,59 and Xinjiang with 74 samples. 45,51 For provinces with very few data samples such as Fujian, Qinghai, Guangdong, Gansu, and Zhejiang, statistical analysis was only conducted on the original data because of the available data restriction for bootstrap simulation.…”

Fluorine in Chinese Coal: A Review of Distribution, Abundance, Modes of Occurrence, Genetic Factors and Environmental Effects

“…In 2012, a geochemical review of trace elements [13] reported the F value to be 130.0 mg/kg in Chinese coal, which was higher than the average worldwide (88 mg/kg) [14], the report was based on more data and included wider areas than previous studies, we prefer accept this value (130.00 mg/kg) as the mean F value in Chinese coals. According to reports in recent years, the F content is higher than 130.0 mg/kg in many coal-deposits of China (Table 1), especially in SW and North China [15][16][17][18]. …”