New online method for water isotope analysis of speleothem fluid inclusions using laser absorption spectroscopy (WS-CRDS)

Abstract

Abstract.A new online method to analyse water isotopes of speleothem fluid inclusions using a wavelength scanned cavity ring down spectroscopy (WS-CRDS) instrument is presented. This novel technique allows us simultaneously to measure hydrogen and oxygen isotopes for a released aliquot of water. To do so, we designed a new simple line that allows the online water extraction and isotope analysis of speleothem samples. The specificity of the method lies in the fact that fluid inclusions release is made on a standard water background, which mainly improves the δD robustness.To saturate the line, a peristaltic pump continuously injects standard water into the line that is permanently heated to 140 • C and flushed with dry nitrogen gas. This permits instantaneous and complete vaporisation of the standard water, resulting in an artificial water background with well-known δD and δ 18 O values. The speleothem sample is placed in a copper tube, attached to the line, and after system stabilisation it is crushed using a simple hydraulic device to liberate speleothem fluid inclusions water. The released water is carried by the nitrogen/standard water gas stream directly to a Picarro L1102-i for isotope determination. To test the accuracy and reproducibility of the line and to measure standard water during speleothem measurements, a syringe injection unit was added to the line.Peak evaluation is done similarly as in gas chromatography to obtain δD and δ 18 O isotopic compositions of measured water aliquots. Precision is better than 1.5 ‰ for δD and 0.4 ‰ for δ 18 O for water measurements for an extended range (−210 to 0 ‰ for δD and −27 to 0 ‰ for δ 18 O) primarily dependent on the amount of water released from speleothem fluid inclusions and secondarily on the isotopic composition of the sample. The results show that WS-CRDS technology is suitable for speleothem fluid inclusion measurements and gives results that are comparable to the isotope ratio mass spectrometry (IRMS) technique.

Glacial–interglacial temperature change in the tropical West Pacific: A comparison of stalagmite-based paleo-thermometers

“…These novel methods are based on: i) the density of the water determined from liquidevapor homogenization (Krüger et al, 2011), ii) the concentrations of noble gases dissolved in the water (e.g., Kluge et al, 2008;Scheidegger et al, 2011), and iii) the fractionation of oxygen isotopes between fluid inclusion water and the surrounding calcite host (e.g., van Breukelen et al, 2008;Wainer et al, 2011). Fluid inclusion water isotopes can be measured using different analytical approaches (Affolter et al, 2014;Arienzo et al, 2013;Dublyansky and Sp€ otl, 2009;Vonhof et al, 2006). To date, most of these methods have been applied independently.…”

“…The d 18 O w as well as the hydrogen isotopic composition of the fluid inclusion water (dD w ) can be measured directly in the water released by crushing the calcite. Two different analytical approaches have been used and compared in this study: i) thermal combustion/elemental analysis (TC/EA) IRMS (Dublyansky and Sp€ otl, 2009), and ii) cavity ring-down spectroscopy (CRDS; Affolter et al, 2014).…”

“…The CRDS method recently developed at the University of Bern allows simultaneous determination of both dD w and d 18 O w of the released water vapor by measuring its isotope-specific optical absorbance and does not require any treatment of the water prior to analysis (Affolter et al, 2014). The setup is as follows: A speleothem sample is placed into a copper tube and attached to the measuring line.…”

Stable isotope compositions of speleothems from the last interglacial – Spatial patterns of climate fluctuations in Europe

“…These records have been dated by the U-Th series dating method providing numerical ages, making them valuable for paleoclimate studies on the LIG, although their geochemical compositions have not been evaluated in detail as yet (Govin et al, 2015). Besides conventional carbonate C and O isotope analyses, H and O isotope values of water trapped in the fluid inclusions of stalagmites have gained increasing importance in recent years as technical developments improved sampling resolution, analytical precision and throughput (Vonhof et al, 2006;van Breukelen et al, 2008;Dublyansky and Spötl, 2009;Griffiths et al, 2010;Wainer et al, 2011;Rowe et al, 2012;Arienzo et al, 2013;Ayalon et al, 2013;Affolter et al, 2014). The main advantage of fluid inclusion analyses is that -in contrast to C and O isotope ratios of the precipitating carbonate that depend on a large number of factors (see Fairchild and Baker, 2012) -H and O isotope compositions of the water are not fractionated during entrapment, and hence can directly reflect the composition of dripwater (Harmon and Schwarz, 1981;Yonge, 1982).…”

Water isotope systematics: Improving our palaeoclimate interpretations

“…For liquid water isotope analyses, off-axis and cavity ringdown spectroscopy now permit an order of magnitude greater throughput of water isotope samples compared to conventional isotope ratio mass spectroscopy (IRMS). Continued method development will lead to routine coupling of laser isotope systems to appropriate preparation lines for Quaternary applications such as the analysis of paleo groundwater (David et al, 2015), ice cores (Emanuelsson et al, 2015) and speleothem fluid inclusions (Affolter et al, 2014). This will further increase sample throughput and the size of datasets available to the research community.…”