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Technical note: Conservative storage of water vapour - practical in situ sampling of stable isotopes in tree stems

Magh, Ruth and Magh, Ruth-Kristina and Gralher, Benjamin and Herbstritt, Barbara and Kubert, Angelika and Lim, Hyungwoo and Lundmark, Tomas and Marshall, John (2022). Technical note: Conservative storage of water vapour - practical in situ sampling of stable isotopes in tree stems. Hydrology and Earth System Sciences. 26 :13 , 3573-3587
[Research article]

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Abstract

Using water-stable isotopes to track plant water uptake or soil water processes has become an invaluable tool in ecohydrology and physiological ecology. Recent studies have shown that laser absorption spectroscopy can measure equilibrated water vapour well enough to support inference of liquid-stable isotope composition of plant or soil water, on-site and in real-time. However, current in situ systems require the presence of an instrument in the field. Here we tested, first in the lab and then in the field, a method for equilibrating, collecting, storing, and finally analysing water vapour for its isotopic composition that does not require an instrument in the field. We developed a vapour storage vial system (VSVS) that relies on in situ sampling into crimp neck vials with a double-coated cap using a pump and a flow metre powered through a small battery and measuring the samples in a laboratory. All components are inexpensive and commercially available. We tested the system's ability to store the isotopic composition of its contents by sampling a range of water vapour of known isotopic compositions (from -95 parts per thousand to +1700 parts per thousand for delta H-2) and measuring the isotopic composition after different storage periods. Samples for the field trial were taken in a boreal forest in northern Sweden. The isotopic composition was maintained to within 0.6 parts per thousand to 4.4 parts per thousand for delta H-2 and 0.6 parts per thousand to 0.8 parts per thousand for delta O-18 for natural-abundance samples. Although H-2-enriched samples showed greater uncertainty, they were sufficient to quantify label amounts. We detected a small change in the isotopic composition of the sample after a long storage period, but it was correctable by linear regression models. We observed the same trend for the samples obtained in the field trial for delta O-18 but observed higher variation in delta H-2 than in the lab trial. Our method combines the best of two worlds, sampling many trees in situ while measuring at high precision in the laboratory. This provides the ecohydrology community with a tool that is not only cost efficient but also easy to use.

Authors/Creators:Magh, Ruth and Magh, Ruth-Kristina and Gralher, Benjamin and Herbstritt, Barbara and Kubert, Angelika and Lim, Hyungwoo and Lundmark, Tomas and Marshall, John
Title:Technical note: Conservative storage of water vapour - practical in situ sampling of stable isotopes in tree stems
Series Name/Journal:Hydrology and Earth System Sciences
Year of publishing :2022
Volume:26
Number:13
Page range:3573-3587
Number of Pages:15
Publisher:COPERNICUS GESELLSCHAFT MBH
ISSN:1027-5606
Language:English
Publication Type:Research article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Oceanography, Hydrology, Water Resources
(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Geosciences, Multidisciplinary
URN:NBN:urn:nbn:se:slu:epsilon-p-118351
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-118351
Additional ID:
Type of IDID
DOI10.5194/hess-26-3573-2022
Web of Science (WoS)000821944900001
ID Code:28448
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:16 Aug 2022 08:26
Metadata Last Modified:16 Aug 2022 08:31

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