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High-Resolution, Continuous Method for Measurement of Acidity in Ice Cores

机译：冰芯酸度的高分辨率连续测量方法

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摘要

The acid content of ice core samples provides information regarding the history of volcanism, biogenic activity, windblown dust, forest fires, and pollution-induced acid rain. A continuous ice core analysis allows for collection of high-resolution data in a very efficient manner, but this technique has not been readily applied to the measurement of pH and acidity in ice cores. The difficulty arises because the sample is highly undersaturated with respect to carbon dioxide (CO_2) immediately after melting, making it difficult to maintain stable concentrations of dissolved carbon dioxide and carbonic acid (H_2CO_3). Here, we present a solution to this problem in the form of a small flow-through bubbling chamber that is supplied with a known concentration of CO_2. The bubbling action allows for quick equilibration while the small size of the chamber limits sample mixing in order to maintain high resolution. Thorough error analysis provides a measurement uncertainty of ±0.20 μM or ±5% of the acidity value, whichever is greater, and the T95 signal response time is determined to be 1.25 min. The performance of the technique is further evaluated with data from a 63-year ice core from northwest Greenland for which all major ion species were also measured. The measured acidity closely matches the acidity derived from a charge balance calculation, indicating that all of the analytes were measured accurately. The performance specifications that we provide are applicable to ice cores with low concentrations of alkaline dust (<500 ppb), which includes the vast majority of ice cores that are collected. To date, the method has not been evaluated with samples containing high alkaline dust concentrations, such as Greenland cores from the last glacial period, where measurement could be made difficult by memory effects as particles coat the internal surfaces of the sample stream.
机译：冰芯样品中的酸含量可提供有关火山历史，生物活动，飞尘，森林大火以及污染引起的酸雨的信息。连续的冰芯分析允许以非常有效的方式收集高分辨率数据，但是该技术尚未很容易应用于冰芯中pH和酸度的测量。出现困难的原因是样品在熔化后立即就二氧化碳（CO_2）高度不饱和，从而难以维持稳定浓度的溶解二氧化碳和碳酸（H_2CO_3）。在这里，我们以一个小型流通鼓泡腔室的形式提出了这个问题的解决方案，该腔室装有已知浓度的CO_2。鼓泡作用可实现快速平衡，而小体积的样品室则限制了样品的混合，以保持高分辨率。彻底的误差分析可提供±0.20μM或酸度值的±5％（以较大者为准）的测量不确定度，并且T95信号响应时间确定为1.25分钟。利用格陵兰西北部63年冰芯的数据进一步评估了该技术的性能，还对所有主要离子种类进行了测量。测得的酸度与电荷平衡计算得出的酸度非常匹配，表明所有分析物均已精确测量。我们提供的性能规格适用于碱性粉尘浓度低（<500 ppb）的冰芯，其中包括收集的绝大多数冰芯。迄今为止，该方法尚未用含高碱性尘埃浓度的样品（例如上一个冰期的格陵兰岩心）进行评估，由于颗粒覆盖了样品流的内表面，记忆效应可能使测量变得困难。

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  • 来源
    《Environmental Science & Technology》 |2012年第3期|p.1659-1666|共8页
  • 作者

    Daniel R. Pasteris; Joseph R. McConnell; Ross Edwards;

  • 作者单位

    Division of Hydrologic Sciences, Desert Research Institute, Reno, Nevada 89512, United States;

    Division of Hydrologic Sciences, Desert Research Institute, Reno, Nevada 89512, United States;

    Division of Hydrologic Sciences, Desert Research Institute, Reno, Nevada 89512, United States,Department of Imaging and Applied Physics, Curtin University, Perth, WA 6845, Australia;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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