Water isotopic ratios from a continuously melted ice core sample
Water isotopic ratios from a continuously melted ice core sample
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DOI：
10.5194/amt-4-2531-2011
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发表时间：
2011-01-01
影响因子：
3.8
通讯作者：
Johnsen, S. J.
中科院分区：
文献类型：
--
作者：
Gkinis, V.;Popp, T. J.;Johnsen, S. J.
介绍了一种适用于冰芯研究的液态水在线高分辨率同位素分析新技术。我们在购自Picarro Inc.的波长扫描腔衰荡光谱仪（WS-CRDS）与波长扫描腔衰荡光谱仪（WS-CRDS）之间建立了接口。和连续流分析（CFA）系统。该系统提供了对从连续融化的冰棒产生的连续液态水流进行δ O-18和δ D的异常水同位素分析的可能性。通过将样品泵送通过熔融石英毛细管并在自制烘箱中在170 ℃的温度下以100%的效率瞬时蒸发来实现亚微量液态水的注入。校准程序允许正确报告VSMOW-Sunday量表上的数据。我们应用必要的校正的基础上评估的性能的系统，仪器漂移和依赖于水的浓度在光学腔。监测熔化速率，以便将深度标度分配给所测量的同位素分布。光谱方法的应用产生的组合不确定度的系统在低于0.1%和0.5千分之一的三角洲O-18和三角洲D，分别。该性能与质谱法所实现的性能相当。样品在传输线中的分散限制了该技术的时间分辨率。在这项工作中，我们调查和评估这些分散效果。通过使用最佳的过滤方法，我们展示了如何测量的配置文件可以被校正的平滑效果所产生的样品分散。考虑到该技术提供的显着优势，即同时测量Delta O-18和Delta D，可能与传统上在CFA系统上测量的化学成分结合，显着减少分析时间和功耗，我们认为它是一种替代品传统同位素比质谱法有可能用于现场冰芯研究。我们目前的数据在2010年的季节在该领域获得的NEEM深冰芯钻探项目在格陵兰北部的一部分。
A new technique for on-line high resolution isotopic analysis of liquid water, tailored for ice core studies is presented. We built an interface between a Wavelength Scanned Cavity Ring Down Spectrometer (WS-CRDS) purchased from Picarro Inc. and a Continuous Flow Analysis (CFA) system. The system offers the possibility to perform simultaneuous water isotopic analysis of delta O-18 and delta D on a continuous stream of liquid water as generated from a continuously melted ice rod. Injection of sub mu l amounts of liquid water is achieved by pumping sample through a fused silica capillary and instantaneously vaporizing it with 100% efficiency in a home made oven at a temperature of 170 degrees C. A calibration procedure allows for proper reporting of the data on the VSMOW-SLAP scale. We apply the necessary corrections based on the assessed performance of the system regarding instrumental drifts and dependance on the water concentration in the optical cavity. The melt rates are monitored in order to assign a depth scale to the measured isotopic profiles. Application of spectral methods yields the combined uncertainty of the system at below 0.1% and 0.5 parts per thousand for delta O-18 and delta D, respectively. This performance is comparable to that achieved with mass spectrometry. Dispersion of the sample in the transfer lines limits the temporal resolution of the technique. In this work we investigate and assess these dispersion effects. By using an optimal filtering method we show how the measured profiles can be corrected for the smoothing effects resulting from the sample dispersion. Considering the significant advantages the technique offers, i.e. simultaneuous measurement of delta O-18 and delta D, potentially in combination with chemical components that are traditionally measured on CFA systems, notable reduction on analysis time and power consumption, we consider it as an alternative to traditional isotope ratio mass spectrometry with the possibility to be deployed for field ice core studies. We present data acquired in the field during the 2010 season as part of the NEEM deep ice core drilling project in North Greenland.