Mechanism of uranium release from uranium mill tailings under long-term exposure to simulated acid rain: Geochemical evidence and environmental implication

Meiling Yin; Jing Sun; Yongheng Chen; Jin Wang; Jianying Shang; Nick Belshaw; ChuanChou Shen; Juan Liu; Huosheng Li; Wensheng Linghu; Tangfu Xiao; Xinjiao Dong; Gang Song; Enzong Xiao; Diyun Chen

doi:10.1016/j.envpol.2018.10.018

Mechanism of uranium release from uranium mill tailings under long-term exposure to simulated acid rain: Geochemical evidence and environmental implication

Environ Pollut. 2019 Jan:244:174-181. doi: 10.1016/j.envpol.2018.10.018. Epub 2018 Oct 9.

Authors

Meiling Yin¹, Jing Sun², Yongheng Chen¹, Jin Wang³, Jianying Shang⁴, Nick Belshaw⁵, ChuanChou Shen⁶, Juan Liu⁷, Huosheng Li¹, Wensheng Linghu⁸, Tangfu Xiao¹, Xinjiao Dong⁹, Gang Song¹⁰, Enzong Xiao¹, Diyun Chen¹⁰

Affiliations

¹ School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China.
² School of Earth Sciences, University of Western Australia, Perth, WA, 6009, Australia.
³ School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, Guangzhou, 510006, China; Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK. Electronic address: wangjin@gzhu.edu.cn.
⁴ College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
⁵ Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK.
⁶ Department of Geosciences, National Taiwan University, Taipei, 10617, Taiwan; Research Center for Future Earth, National Taiwan University, Taipei, 10617, Taiwan.
⁷ School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China; Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK. Electronic address: juan.liu@earth.ox.ac.uk.
⁸ College of Chemistry and Chemical Engineering, Shaoxing University, Shaoxing, 312000, China.
⁹ School of Life & Environmental Science, Wenzhou University, Wenzhou, 325027, China.
¹⁰ School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, Guangzhou, 510006, China.

PMID: 30336376
DOI: 10.1016/j.envpol.2018.10.018

Abstract

To date, there is not sufficient knowledge to fully understand the occurrence, transport and fate of residual uranium (U) from uranium mill tailings (UMT). Herein this study investigated different U release behaviors from natural UMT (without grinding) under four simulated acid rain (pH = 2.0-5.0) compared with controlled scenario (pH = 6.0) for 25 weeks. The results showed that the most notable U release was observed from UMT_pH2.0, followed by UMT_pH3.0 whereas a nonlinear relationship between pH and U release was observed from UMT_pH4.0-6.0. The divergence of U release behaviors was attributed to the presence of minerals such as calcite and clinochlore. Autunite, a secondary mineral formed after leaching, might regulate U release in UMT_pH3.0-6.0. Fick theory model revealed the shift of U release mechanism from surface dissolution to diffusion transport for UMT_pH2.0, UMT_pH3.0 and UMT_pH5.0 at varied stage, whereas UMT_pH4.0 and UMT_pH6.0 displayed univocal dissolution and diffusion mechanism, respectively. This study highlights the necessity of performing long-term leaching tests to detect the "shift event" of leaching kinetics and to better understand the mechanism of U release influenced by mineralogy of the natural UMT under simulated acid rain conditions, which is conducive to developing UMT management strategies to minimize the risk of U release and exposure.

Keywords: Acid rain; Leaching test; Uranium; Uranium mill tailings.

MeSH terms

Acid Rain*
Diffusion
Hydrogen-Ion Concentration
Kinetics
Minerals / adverse effects
Mining
Models, Chemical
Soil Pollutants, Radioactive / analysis*
Uranium / analysis*
Water Pollutants, Radioactive / analysis*

Substances

Acid Rain
Minerals
Soil Pollutants, Radioactive
Water Pollutants, Radioactive
Uranium