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An Isotopic Dilution Approach for Quantifying Mercury Lability in Soils
Environmental Science & Technology Letters ( IF 8.9 ) Pub Date : 2017-12-04 00:00:00 , DOI: 10.1021/acs.estlett.7b00510
Waleed H. Shetaya 1, 2 , Stefan Osterwalder 1 , Moritz Bigalke 3 , Adrien Mestrot 3 , Jen-How Huang 1 , Christine Alewell 1
Affiliation  

The accurate estimation of soil mercury lability is crucial for risk assessment. In comparison to chemical fractionation and speciation, isotopic dilution (ID) offers precise definition of labile mercury fractions while maintaining the natural equilibrium. We developed and applied an ID protocol with 199Hg to estimate the soil mercury (Hg) isotopically exchangeable (labile) pool or HgE using a range of industrially contaminated soils in Switzerland. The measured HgE values were consistent for the same soil against different spike levels (50, 100, and 200% of native 199Hg), indicating that the spiked and soil isotopes achieved required dynamic equilibrium at the soil–water interface. Total soil Hg (THg; mg kg–1) was the best predictor of HgE (mg kg–1) and %HgE and accounted for 96 and 63% of the variance, respectively. Nonetheless, despite the wide range of THg values (0.37–310 mg kg–1) in the studied soils, Hg lability spanned a narrow range (∼12–25% of THg), highlighting the large capacity of soils to sequester Hg in a very stable form. The “exchangeable pool” of Hg extracted by CH3COONH4 and MgCl2 (<0.25 and <0.32% of THg, respectively) largely underestimated Hg lability in comparison to ID, suggesting the potential usefulness of the ID approach.

中文翻译:

同位素稀释法定量土壤中的汞

准确估算土壤中汞的脆弱性对于风险评估至关重要。与化学分馏和形态形成相比,同位素稀释(ID)提供了不稳定汞含量的精确定义,同时保持了自然平衡。我们开发并应用了199 Hg的ID协议,以估算瑞士使用一系列工业污染土壤的同位素汞(同位素)可交换(不稳定)池或HgE的含量。对于相同的土壤,在不同的峰值水平(天然199 Hg的50%,100%和200%)下,测得的HgE值是一致的,这表明加标的土壤同位素在土壤-水界面处达到了所需的动态平衡。土壤总汞(THg; mg kg –1)是HgE(mg kg–1)和%HgE分别占方差的96%和63%。尽管如此,尽管研究土壤中的THg值范围很广(0.37–310 mg kg –1),但汞的易变性却在狭窄的范围内(约为THg的12–25%),突显了土壤在土壤中螯合Hg的能力很强。非常稳定的形式。与ID相比,CH 3 COONH 4和MgCl 2提取的Hg的“可交换库” (分别占THg的<0.25和<0.32%)大大低估了Hg的不稳定性,表明ID方法的潜在用途。
更新日期:2017-12-04
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