Selenium Speciation in Kerogen from Two Chinese Selenium Deposits: Environmental Implications

详细信息    查看全文

• 作者：Hanjie Wen ; Jean Carignan ; Yuzhuo Qiu ; and Shirong Liu
• 刊名：Environmental Science & Technology
• 出版年：2006
• 出版时间：February 15, 2006
• 年：2006
• 卷：40
• 期：4
• 页码：1126 - 1132
• 全文大小：296K
• 年卷期：v.40,no.4(February 15, 2006)
• ISSN：1520-5851

文摘

Selenium is an essential trace element for humans,animals, and vegetation. Its occurrence in the environmentis characterized by specific chemical and biochemicalproperties that control its elemental solubility, toxicity, andenvironmental behavior. The Laerma Se-Au deposit andYutangba Se deposit are two important Se-bearing depositsfound recently in China. In one of these areas (Yutangba),a serious environmental impact happened involving Sepoisoning. Previous studies have shown that Se in bothdeposits is closely related to organic matter, especiallykerogen fractions, but detailed relationships between Seand kerogen and Se chemical forms were not reported. Inthis study, the different speciation of Se is identified bytransmission electron microscopy (TEM) and othergeochemical techniques (infrared spectra (IS) and X-raydiffraction (XRD)) from kerogen samples extracted from orerocks of both deposits. The occurrence of organicallybound Se in the Laerma deposit and elemental Se nanograinsin the Yutangba deposit is observed, indicating thediversity of formation mechanisms and possible chemicalforms of Se in Se-rich rocks. The formation of elementalSe associated with organic matter is likely related to redoxconditions, whereas organic species are related to thehigher sulfur content of kerogen and possibly result fromS-Se substitutions. This discovery provides new evidencewith which to assess potential Se mobility duringweathering of ore-bearing rocks. In an altered rock, theelemental Se in kerogen is more steadily mobilized and ispotentially accumulated by vegetation, which mayexplain the sudden prevalence of Se poisoning in theYutangba area. In contrast, organically bound Se seemsmore resistant to chemical alteration compared to other Sespecies so that its bioavailability may be very restricted.