Performance of the Picarro CRDS water isotope analyzer for δ2H tracer studies

The Picarro water isotope analyzers (L2130-i/L2140-i) have become a standard technique to measure the natural abundance of δ¹⁸O, δ²H and ¹⁷O-excess of water isotopes in climate, environment, and hydrological studies. In addition, some applications require to measure highly enriched δ²H water isotope samples, e.g., when tracing water flows in hydrology. In this case, the ²H/¹H ratio is used as a tracer when fluorescent tracers are not an option, e.g., when tracing drinking water.

Measuring highly enriched water samples with optical spectroscopy comes along with two challenges: (i) the memory effect, the carryover from small fractions of water from one sample to another, and (ii) the spectroscopic limits of the analyzer. Here, we address both challenges by characterizing the memory effect for highly enriched δ²H samples considering the recently developed express mode that allows to reduce/remove the memory effect at a much faster rate compared to the standard mode [1, 2] and by reviewing the spectroscopic limits of the analyzer.

In this study, we tested the performance of the Picarro L2130-i water isotope analyzer for a set of samples with varying ²H/¹H ratios of 0.1 to 2.0% (corresponding to δ²H values of about 6,000 to 130,000‰). We found that (i) the analyzer shows an excellent linearity over a high δ²H enrichment range (up to 130,000‰); (ii) the analyzer shows a negligible concentration dependence at high enrichment levels; (iii) the spectroscopic limits of the analyzer can be extended by reducing the injection volume (<1.8uL); (iv) the memory effect can be reduced significantly when using the express mode compared to the standard mode.

Our results show that the Picarro L2130-i water isotope analyzer is an adequate tool for measuring highly enriched δ²H water samples, and we will discuss best practices when measuring these samples.  

 

References

[1] Hofmann, M. E. G., Lin, Z., Woźniak, J., and Drori, K.: Improved throughput for δ18O and δD measurements of water with Cavity Ring-Down Spectroscopy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14254, https://doi.org/10.5194/egusphere-egu21-14254, 2021.

[2] Landais, A., Minster, B., Zuhr, A., Hofmann, M., and Fourré, E.: Performances of express mode vs standard mode for δ18O, δD and 17O-excess with a Picarro analyzer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4278, https://doi.org/10.5194/egusphere-egu22-4278, 2022.