Hydrogeochemical Characteristics and Impact of Arsenic Released from a Gold Deposit in Tibet
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TECHNICAL ARTICLE
Hydrogeochemical Characteristics and Impact of Arsenic Released from a Gold Deposit in Tibet Hongyu Gu1 · Huayong Ni1 · Yingchun Wang2,3 · Yujie Liu1 · Dan Li1 · Zhi Zhang1 Received: 16 December 2019 / Accepted: 8 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract High arsenic concentrations are common in the water and soils in Tibet. In this study, arsenic concentrations were found to be below detection limits in natural river water, although the high background concentrations of HCO3− and the pH all favor arsenic release. Lake water had the highest arsenic concentrations due to intense evaporation. The impact of mining on arsenic release was assessed using a mixing model composed of three end-members: KS02 (a post-mining sample), R07 (a river water sample), and S12 (spring water that contains arsenic). The results indicated that mining operations are likely responsible for a small proportion (2.0%) of direct release of arsenic from deep thermal water, and that most arsenic was released by desorption from Fe oxyhydroxides. The mixing model also revealed that so far, mining operations have accelerated carbonate dissolution, but have not led to arsenopyrite oxidation. Therefore, HCO3− concentrations increased during mining, which along with the pH (> 7.0), led to desorption of arsenic from Fe oxyhydroxide. Keywords Arsenic · Mining operation · Hydrogeochemistry · Mixing model
Introduction Arsenic is a metalloid that is harmful to humans and animals (Sako et al. 2016; Smith et al. 1999; Wei et al. 2017). Metal mines, such as Pb–Zn mines and gold mines, often contain arsenic-bearing minerals (Bidone et al. 2016; Devore et al. 2019; Roussel et al. 2000). The Tibetan Plateau is the source of all of Asia’s major rivers. Water in Tibet naturally has high pH values due to high HCO3− concentrations (Tian et al. 2015, 2016). Mining operations often increase the release of arsenic, which is a potential threat to water quality. Therefore, assessing the impact of mining on arsenic release is urgent because of the long-term, large-scale mining operations in Tibet.
* Hongyu Gu [email protected] 1
Chengdu Center, China Geological Survey, Chengdu 610081, China
2
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China
3
College of Energy Resources, Chengdu University of Technology, Chengdu 610059, China
Arsenic is a common component in soils and rock in Tibet. The main arsenic-bearing minerals are arsenopyrite (FeAsS), orpiment (AsS), and arsenic-bearing pyrite. Depending on the arsenic phases and their content, the arsenic can be mobilized after excavation, reflecting physicochemical changes such as increases in specific surface areas and exposures to water and air (Tamoto et al. 2015). Many studies have revealed the mechanisms of arsenic release, such as oxidation of arsenic-bearing minerals, competitive adsorption (Appelo et al. 2002; Mcarthur 1999), reduction of arsenic (V) (Islam et
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