Abstract
Arsenic is one of the toxic trace elements in coals, which is harmful to both the ecological environment and human health. Based on published literature and the data obtained by our research group, a total of 5314 As concentrations of Chinese coals were analyzed. The arithmetic mean of arsenic content in Chinese coals is 6.97 mg/kg. Choosing the percentage of provincial coal resources in national coal resources as the weighting factor, the weighted average of arsenic content in Chinese coals is 5.33 mg/kg. The content of arsenic in Chinese coals increases from the north to the south. High arsenic content in coal primarily occurs in southwestern Yunnan and certain coalfields in the Guizhou Province. Additionally, arsenic is enriched in the coals from some regions, i.e., the western Yunnan, Guangxi, Tibet, southwestern Liaoning, Jilin, and Henan. The arsenic content in coals of different coal-forming periods shows an overall regularity: Paleogene and Neogene > Late Triassic > Late Permian > Late Jurassic and Early Cretaceous > Early and Middle Jurassic > Late Carboniferous and Early Permian. The modes of occurrence of arsenic in coals include sulfide-association, organic-association, arsenate-association, silicate-association, and soluble- and exchangeable-association. Generally, arsenic in Chinese coals exists predominantly in arsenic-bearing pyrite. Meanwhile, the organic arsenic content is relatively high in coal samples with a lower (<5.5 mg/kg) arsenic content and a low or medium ash yield (<30%).
Highlights
In 2016, China’s coal production was 3.41 billion tons, which was 7.9% lower than 2015, accounting for 46.1% of the total world coal production
As one of the most toxic trace elements in coals, arsenic could be released into the atmosphere during coal combustion and preferentially enriched in fly ash [4]
Ren et al [56] gave an arsenic content of 132 coal samples with 0.21–32,000 mg/kg, which was ascribed to the introduction of some high arsenic coal samples from the southwestern China
Summary
In 2016, China’s coal production was 3.41 billion tons, which was 7.9% lower than 2015, accounting for 46.1% of the total world coal production. As one of the most toxic trace elements in coals, arsenic could be released into the atmosphere during coal combustion and preferentially enriched in fly ash [4]. The atmospheric arsenic emissions from coal combustion reached 1564 tons in China in 2005 [8]. Absorption Fine Structure (EXAFS) have recently contributed to the modes of occurrence of arsenic in coals [24]. The average arsenic concentration of Chinese coals, spatial distribution, and modes of occurrence will be reviewed. In this paper, based on the published literature and the data of our research group, the arsenic in Chinese coals are completely reviewed, including arithmetic and weighted average of arsenic contents, distribution, abnormal enrichment, and modes of occurrence
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