Key Laboratory of High-temperature and High-pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100039, China.
Key Laboratory of High-temperature and High-pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
Sci Total Environ. 2021 Feb 10;755(Pt 2):142708. doi: 10.1016/j.scitotenv.2020.142708. Epub 2020 Oct 2.
Alkaline soils are widely distributed around the world. During the mining and transportation processes galena may be exposed to the alkaline soils. Weathering of galena may lead to the formation of different lead phases having higher bio-accessibility than galena, and thereby increasing the mobility and toxicity of lead. In this study, electrochemical techniques and Raman spectroscopic measurements were used for the evaluation of the interfacial processes that are involved in the galena weathering under the conditions of simulated saline soil and meadow soil solutions. The results showed that the release of Pb and S took place during initial stage of the oxidation. Thereafter, further transformation to anglesite would take place, even leading to the transformation to β-PbO and α-PbO at higher temperatures. Galena weathering prone to saline soil than that in meadow soil, and has a faster weathering rate in the saline soil at same ambient temperature. Higher temperatures was found to promote the weathering of galena, and the rate constant for the release of Pb (II) was approximate 10 to 10 mol∙m∙s, while surface reaction was found to control the weathering kinetics. Based on the surface characterization and evaluation of the thermodynamic and kinetic parameters, the weathering mechanism of galena in the alkaline soil and its environmental implications was suggested.
碱性土壤在全球范围内广泛分布。在开采和运输过程中，方铅矿可能会暴露在碱性土壤中。方铅矿的风化可能导致形成比方铅矿具有更高生物可利用性的不同铅相，从而增加铅的迁移性和毒性。在这项研究中，电化学技术和拉曼光谱测量被用于评估在模拟盐渍土和草地土壤溶液条件下方铅矿风化涉及的界面过程。结果表明，在氧化的初始阶段发生了 Pb 和 S 的释放。此后，即使在较高温度下，也会进一步转化为硫酸铅，甚至转化为β-PbO 和 α-PbO。方铅矿在盐渍土中的风化倾向比在草地土中更严重，并且在相同环境温度下，盐渍土中方铅矿的风化速率更快。发现较高的温度会促进方铅矿的风化，Pb(II)释放的速率常数约为 10 到 10^-10 mol∙m∙s，而表面反应被发现控制着风化动力学。基于表面特征描述和热力学及动力学参数的评估，提出了碱性土壤中方铅矿的风化机制及其环境意义。
