Evaluating the distribution and potential ecological risks of heavy metal in coal gangue
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RECENT ENVIRONMENTAL GEOCHEMICAL TRENDS
Evaluating the distribution and potential ecological risks of heavy metal in coal gangue Ya-qiao Sun 1 & Kang Xiao 1 & Xiao-dong Wang 1 & Zi-hao Lv 1 & Ming Mao 1 Received: 1 June 2020 / Accepted: 28 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The heavy metals, which derived from accumulated coal gangue, are important source of environmental pollution. In this study, coal gangue dumps, collected in Shaanxi Province, China, were used to evaluate the potential ecological risks and release characteristics of heavy metals, including the chemical forms, release characteristics, and potential ecological risks by using the methods of Tessier’s sequential extractions, leaching experiments, gray GM (1, 1) forecasting mode, and potential ecological risk index. The results indicated that gangue samples contained high levels of metals, especially of Pb, which was the 20–31 times of the background value, whereas the sum of exchangeable and carbonate fractions in Co and Cu was a large proportion (4–11%) of the total. Potential ecological risks were at strong level regardless of the type of the coal gangue because of Mo and Pb and the comprehensive ecological risk index of 351.51–412.27. Weathering promotes the release of heavy metals in the gangue. Furthermore, the contents of Cu and Pb in leaching solution and their release times in weathered gangue were significantly higher than those of the fresh one. This research provides a scientific basis for the prevention and control of heavy metal pollution in coal-containing areas. Keywords Heavy metal . Coal gangue . Weathering . Grey model . Potential ecological risk
Introduction Coal plays a dominant role (70%) in energy consumption of China (Huang et al. 2017). A large amount of solid waste-coal gangue would be produced in processing and accounts for 10– 15% of the raw coal, approximately (Li and Wang 2019). Currently, the cumulative amount of coal gangue is estimated to be more than 5.0 billion tons given the large production of coal that covers an area of about 15,000 km2 (Zhou et al. 2014). Exposed to weathering and leaching, heavy metals are easily emitted into soil, resulting in a decreased buffering and purification capacity of soil and threatening the ecological environment (Hua et al. 2018; Zhou et al. 2019), and the Responsible editor: Philippe Garrigues * Kang Xiao [email protected] 1
School of Water and Environment, Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang’an University, No. 126 Yanta Road, Xi’an 710000, China
heavy metal elements released by coal gangue accumulate on the surface of soil (Zhang et al. 2019). Since most of the plant roots grow in the surface of soil, the absorption of heavy metals by plant roots will increase the enrichment of heavy metals and the subsequent risk in food chain, which would be detrimental to human health (Antunes et al. 2008; Hanson and Solomon 2002). Although the content of trace metal
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