Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, United States of America.
Department of Biology, University of Utah, Salt Lake City, UT, United States of America.
PLoS One. 2020 May 29;15(5):e0233712. doi: 10.1371/journal.pone.0233712. eCollection 2020.
Trace elements in hair originate from intake (e.g., diet, inhalation, skin absorption), are transported in the bloodstream, and then incorporated during hair formation. However, the trace element abundance and isotopic compositions may be altered by post-eruption environmental processes. Such alterations must be addressed to obtain a meaningful interpretation of hair analysis for biomonitoring. In this study, we used strontium (Sr) isotopic analysis together with sorption kinetics of ionic Sr to quantify the rate and extent of replacement of endogenous Sr in hair by exogenous Sr from ambient water. We found that with only 10 minutes of exposure at room temperature (22°C), more than 30% of original endogenous Sr in hair was replaced with exogenous Sr from the solution. After 16 days of exposure to the solution, more than 90% of endogenous Sr was replaced, with a warmer temperature (60°C) accelerating the exchange substantially. We also found that acid leaching of exposed hair did not remove or isolate the exogenous Sr; therefore, neither the original endogenous nor the exogenous 87Sr/86Sr signal could be separated. Nonetheless, these findings illustrated that the quantitative correlation between the fraction of exogenous Sr and the soaking time, if established, could be used to estimate the length of water contact time for hair in forensic studies. Even if such time since initial contact cannot be established, the combination of acid leaching and 87Sr/86Sr analysis of hair samples may still be valuable in provenance studies to identify recent changes in the exogenous Sr pool, including movements or changes in water source.
头发中的微量元素来源于摄入（例如饮食、吸入、皮肤吸收），在血液中运输，然后在头发形成过程中被整合。然而，微量元素的丰度和同位素组成可能会因喷发后的环境过程而改变。为了对头发分析进行生物监测获得有意义的解释，必须解决这些变化。在这项研究中，我们使用锶同位素分析和离子锶的吸附动力学来量化环境水中的外源锶替代头发中内源性锶的速率和程度。我们发现，在室温（22°C）下仅暴露 10 分钟，头发中超过 30%的原始内源性锶就被溶液中的外源锶所取代。经过 16 天的暴露，超过 90%的内源性锶被取代，较高的温度（60°C）大大加速了交换。我们还发现，暴露的头发经酸浸提后不能去除或分离外源锶；因此，原始的内源性锶和外源锶 87Sr/86Sr 信号都无法分离。尽管如此，这些发现表明，如果建立了外源锶分数与浸泡时间之间的定量相关性，那么在法医研究中可以用于估计头发与水接触的时间长度。即使无法确定初始接触的时间，酸浸提和头发样本 87Sr/86Sr 分析的组合在源研究中仍然有价值，可以识别外源锶库中最近的变化，包括水源的移动或变化。
