Tracing Anthropogenic Thallium in Soil Using Stable Isotope Compositions

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• 作者：Michael Kersten ; Tangfu Xiao ; Katharina Kreissig ; Alex Brett ; Barry J. Coles ; Mark Rehk盲mper
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：August 19, 2014
• 年：2014
• 卷：48
• 期：16
• 页码：9030-9036
• 全文大小：297K
• ISSN：1520-5851

文摘

Thallium stable isotope data are used in this study, for the first time, to apportion Tl contamination in soils. In the late 1970s, a cement plant near Lengerich, Germany, emitted cement kiln dust (CKD) with high Tl contents, due to cocombustion of Tl-enriched pyrite roasting waste. Locally contaminated soil profiles were obtained down to 1 m depth and the samples are in accord with a binary mixing relationship in a diagram of Tl isotope compositions (expressed as 蔚²⁰⁵Tl, the deviation of the ²⁰⁵Tl/²⁰³Tl ratio of a sample from the NIST SRM 997 Tl isotope standard in parts per 10⁴) versus 1/[Tl]. The inferred mixing endmembers are the geogenic background, as defined by isotopically light soils at depth (蔚²⁰⁵Tl 鈮?鈭?), and the Tl emissions, which produce Tl-enriched topsoils with 蔚²⁰⁵Tl as high as 卤0. The latter interpretation is supported by analyses of the CKD, which is also characterized by 蔚²⁰⁵Tl 鈮?卤 0, and the same 蔚²⁰⁵Tl value was found for a pyrite from the deposit that produced the cocombusted pyrite roasting waste. Additional measurements for samples from a locality in China, with outcrops of Tl sulfide mineralization and associated high natural Tl backgrounds, reveal significant isotope fractionation between soils (蔚²⁰⁵Tl 鈮?+0.4) and locally grown green cabbage (蔚²⁰⁵Tl between 鈭?.5 and 鈭?.4). This demonstrates that biological isotope fractionation cannot explain the isotopically heavy Tl in the Lengerich topsoils and the latter are therefore clearly due to anthropogenic Tl emissions from cement processing. Our results thus establish that isotopic data can reinforce receptor modeling for the toxic trace metal Tl.