Occurrence and mobility of toxic elements in coals from endemic fluorosis areas in the Three Gorges Region, SW China

Yan Xiong; Tangfu Xiao; Yizhang Liu; Jianming Zhu; Zengping Ning; Qingxiang Xiao

doi:10.1016/j.ecoenv.2017.05.045

Occurrence and mobility of toxic elements in coals from endemic fluorosis areas in the Three Gorges Region, SW China

Ecotoxicol Environ Saf. 2017 Oct:144:1-10. doi: 10.1016/j.ecoenv.2017.05.045. Epub 2017 Jun 6.

Authors

Yan Xiong¹, Tangfu Xiao², Yizhang Liu³, Jianming Zhu⁴, Zengping Ning³, Qingxiang Xiao¹

Affiliations

¹ State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; The Key Laboratory of Water Safety and Protection of the Pearl River Delta, Ministry of Education, School of Environmental Science and Engineering, Guangzhou University, Guangzhou 510006, China. Electronic address: xiaotangfu@vip.gyig.ac.cn.
³ State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
⁴ State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China.

PMID: 28595096
DOI: 10.1016/j.ecoenv.2017.05.045

Abstract

Fluorine (F) is a topic of great interest in coal-combustion related endemic fluorosis areas. However, little extent research exists regarding the environmental geochemistry of toxic elements that are enriched in coals and coal wastes in traditional endemic fluorosis areas, particularly focusing on their occurrences and mobilities during the weathering-leaching processes of coals and coal wastes in the surface environment. This paper addressed the issue of toxic elements in coals and coal wastes in the Three Gorges Region, Southwest (SW) China, where endemic fluorosis has historically prevailed, and investigated the distribution, occurrence, mobility features, and associated potential health risks. For this purpose, a modified experiment combined with long-term humidity cell test and column leaching trial was applied to elucidate the mobility of toxic elements in coals and coal wastes. In addition, sequential chemical extraction (SCE) was used to ascertain the modes of occurrence of toxic elements. The results demonstrated that the contents of toxic elements in the study area followed the order: stone coals > gangues > coal balls > coals. Furthermore, modes of occurrence of toxic elements were obviously different in coals and coal wastes. For example, cadmium (Cd) was mainly associated with monosulfide fraction in coals, molybdenum (Mo) and arsenic (As) were mainly associated with carbonate and silicate in coal gangues and stone coals, chromium (Cr) mainly existed in silicate and insoluble matter in coal gangues and coal balls, thallium (Tl) mainly occurred in organic matter in stone coals and sulfide in coals, and the occurrence of antimony (Sb) varied with different kinds of samples. Moreover, a large amount of toxic elements released to the leachates during the weathering and leaching process, which might pollute the environment and threaten human health. Based on the geo-accumulation index (I_geo), single factor index (P_i) and Nemerow index (P_N), soils _in the study area were mainly polluted by Cd, which constituted a potential risk to locally planted crops.

Keywords: Coal; Mobility; Mode of occurrence; Potential health risk; Three Gorges Region; Toxic element.

MeSH terms

Cadmium* / analysis
Cadmium* / toxicity
China
Coal / analysis*
Endemic Diseases*
Environmental Pollutants* / analysis
Environmental Pollutants* / toxicity
Fluorides* / analysis
Fluorides* / toxicity
Fluorosis, Dental / epidemiology*
Humans
Incineration
Soil / chemistry

Substances

Coal
Environmental Pollutants
Soil
Cadmium
Fluorides