Correction of cryogenic vacuum extraction biases and potential effects on soil water isotopes application

Wen, Mingyi; Lu, Yanwei; Min, Li; Dong, Haiqing; Xiang, Wei; Zhao, Ying; Cui, Buli; Cheng, Bing

doi:10.1016/j.jhydrol.2021.127011

Cited by 15 publications

(20 citation statements)

References 49 publications

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“…This correlation has also been found for both 2 H and 18 O (i.e. δ 18 O CVD − δ 18 O source ) in soil samples (Wen et al, 2021). However, using cellulose in wood as an example, much of the O-bound H is engaged in H bonding that links cellulose fibrils together, i.e.…”

Section: Introductionmentioning

confidence: 53%

“…The samples in the sample tubes were heated in 80 • C water, and the extracted water was con-densed and trapped in the collection tubes by liquid nitrogen. The extraction was maintained for 2 h to achieve a complete extraction (West et al, 2006). After the extraction, the vacuum inside the system was released by adding dry nitrogen gas until atmospheric pressure conditions were reestablished.…”

Section: Water Extraction and Stable Isotope Analysismentioning

confidence: 99%

“…Hydrogen and oxygen isotope ratios (δ 2 H and δ 18 O) in plant water are powerful tools for tracing the water movement of ecosystems and providing information on the source water used by plants (Goldsmith et al, 2017;Flanagan and Ehleringer, 1991;Brinkmann et al, 2019;Nehemy et al, 2019). The most widely used approach for determining the δ 2 H and δ 18 O of plant water is by first extracting water from plants using cryogenic vacuum distillation (CVD) method (Ehleringer et al, 2000;West et al, 2006;Ingraham and Shadel, 1992;Orlowski et al, 2013). Since no isotopic fractionation generally occurs during plant water uptake (White et al, 1985;Zimmermann et al, 1967;Poca et al, 2019), it is generally believed that the isotope ratios in stem water (root crown water for grasses) derived from the CVD extraction (δ CVD ) are equal to that in the plant source water (δ source ).…”

Section: Introductionmentioning

confidence: 99%

“…During the CVD extraction, successive isotope fractionation processes occur at each phase change of the water (liquid-vapour-solid-liquid). When liquid sample water is distilled to water vapour, isotope fractionation is expected if incomplete extraction occurs (Orlowski et al, 2013;West et al, 2006). When the water vapour is trapped by liquid nitrogen and turns into solid ice, a sublimation isotope fractionation is also expected.…”

Section: Introductionmentioning

confidence: 99%

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Technical note: On uncertainties in plant water isotopic composition following extraction by cryogenic vacuum distillation

Diao

Schuler

Goldsmith

et al. 2022

Hydrol. Earth Syst. Sci.

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Abstract. Recent studies have challenged the interpretation of plant water isotopes obtained through cryogenic vacuum distillation (CVD) based on observations of a large 2H fractionation. These studies have hypothesized the existence of an H-atom exchange between water and organic tissue during CVD extraction with the magnitude of H exchange related to relative water content of the sample; however, clear evidence is lacking. Here, we systematically tested the uncertainties in the isotopic composition of CVD-extracted water by conducting a series of incubation and rehydration experiments using isotopically depleted water, water at natural isotope abundance, woody materials with exchangeable H, and organic materials without exchangeable H (cellulose triacetate and caffeine). We show that the offsets between hydrogen and oxygen isotope ratios and expected reference values (Δ2H and Δ18O) have inversely proportional relationships with the absolute amount of water being extracted, i.e. the lower the water amount, the higher the Δ2H and Δ18O. However, neither Δ2H nor Δ18O values, were related to sample relative water content. The Δ2H pattern was more pronounced for materials with exchangeable H atoms than with non-exchangeable H atoms. This is caused by the combined effect of H exchange during the incubation of materials in water and isotopic enrichments during evaporation and sublimation that depend on absolute water amount. The H exchange during CVD extraction itself was negligible. Despite these technical issues, we observed that the water amount-dependent patterns were much less pronounced for samples at natural isotope abundance and particularly low when sufficiently high amounts of water were extracted (>600 µL). Our study provides new insights into the mechanisms causing isotope fractionation during CVD extraction of water. The methodological uncertainties can be controlled if large samples of natural isotope abundance are used in ecohydrological studies.

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Section: Introductionmentioning

confidence: 53%

Section: Water Extraction and Stable Isotope Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Technical note: On uncertainties in plant water isotopic composition following extraction by cryogenic vacuum distillation

Diao

Schuler

Goldsmith

et al. 2022

Hydrol. Earth Syst. Sci.

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“…A prerequisite for this is sampling the right water. Although CVE is the most widely used method (Amin et al, 2020;de la Casa et al, 2021;Wen et al, 2021), many other methods have also been used to extract plant water, such as high-pressure squeezing, high-speed centrifugation, and direct vapor equilibration (Yang et al, 2010). Different extraction methods, as compared by Millar et al (2018), yielded considerably distinct-isotopic signatures.…”

Section: Implications Of This Studymentioning

confidence: 99%

Causes and Factors of Cryogenic Extraction Biases on Isotopes of Xylem Water

Wen

Dong

et al. 2022

Water Resources Research

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Plant transpiration is the largest contributor to continental water flux (Jasechko, 2018;Jasechko et al., 2013). Understanding the sources of transpiration water is important for predicting the effects of global change on water security and ecosystem services. Stable isotope tracing is one of the most useful tools for the aforementioned purpose (Evaristo et al., 2015;Sprenger et al., 2016). A central assumption in the use of stable isotopes to investigate plant water sources is that, excluding leaf-evaporative effects, the stable isotopes 2 H and 18 O act as conservative tracers. Therefore, the isotopic composition of xylem water effectively reflects that of source water (Ehleringer & Dawson, 1992). This requires that there is no occurrence of significant isotopic fractionation during root water uptake and the subsequent water transport in plant organs (Ehleringer & Dawson, 1992;Washburn & Smith, 1934;Zimmermann et al., 1968); and sampling and isotopic analysis of plant water do not introduce errors (Brunel et al., 1995).However, recent studies have shown that isotopic signatures of the extracted xylem water do not always match those of the water source(s), thus creating isotopic offsets between stem water and the water source. Isotopic offsets, usually depleted in 2 H, of stem water relative to the water source, have now been reported in ecologically diverse plant species (de la Casa et al., 2021). Lin and Sternberg (1993) and Ellsworth and Williams (2007) first reported that fractionation, associated with transmembrane water transport at the root-soil interface, results in the depletion of stem water for drought-tolerant and salinity-tolerant plants. Zhao et al. (2016) did not find evidence for deuterium fractionation during water uptake; they attributed the observed soil-stem water isotopic offsets as a putative discrimination during water transport and redistribution within the plant. Other alternative explanations for the isotopic offsets of stem water have also been hypothesized, such as soil pore-scale isotopic heterogeneity (Lin & Horita, 2016;Oerter & Bowen, 2019;Oerter et al., 2014), vapor transport and condensation on the root tips (Vargas et al., 2017), and a mixture of sap and tissue water (Barbeta et al., 2022). However, a recent study by Chen et al. (2020) proved that little isotopic fractionation occurs during water uptake and transport among diverse habitats/species, and the offsets in δ 2 H are artifacts of cryogenic vacuum extraction (CVE).

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A process‐based water stable isotope mixing model for plant water sourcing

Neil,

Fu,

2024

Ecohydrology

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Stable isotopes of hydrogen and oxygen in water are common tools for investigating water uptake apportionment, but many of the existing methods rely on simple linear mixing approaches that do not mechanistically incorporate additional information about site physical properties and conditions. Here, we develop a ‘physically based root water uptake isotope mixing estimation’ model (PRIME) that combines a continuous and parametric probability density function for root water uptake with site physical data in a process‐based linear mixing framework. To demonstrate the application of PRIME, water uptake patterns of boreal forest Pinus banksiana trees were estimated on four dates in 2019. To aid in validation, estimates were compared with that of the Bayesian linear mixing model framework, MixSIAR. The two approaches provided similar results, but due to its continuous and parametric nature, PRIME provided estimates of superior resolution, certainty, and model parsimony. Although both models incorporate additional physical information into their mixing frameworks, PRIME does so in a mechanistic manner, thereby reflecting the relevant hydrological processes more effectively than the purely empirical approach taken by MixSIAR. Furthermore, because PRIME uses a continuous function to describe the predicted uptake pattern, it allows users to quantify water uptake with essentially infinite resolution, through integration over the desired depth ranges. These findings demonstrate the advantages of utilizing a continuous, parametric, and process‐based mixing model to estimate root water uptake apportionment, thus providing a relatively simple yet powerful tool with which to approach plant water sourcing.

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Correction of cryogenic vacuum extraction biases and potential effects on soil water isotopes application

Cited by 15 publications

References 49 publications

Technical note: On uncertainties in plant water isotopic composition following extraction by cryogenic vacuum distillation

Technical note: On uncertainties in plant water isotopic composition following extraction by cryogenic vacuum distillation

Causes and Factors of Cryogenic Extraction Biases on Isotopes of Xylem Water

A process‐based water stable isotope mixing model for plant water sourcing

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