Isotope‐ratio infrared spectroscopy: a reliable tool for the investigation of plant‐water sources?

Martín‐Gómez, Paula; Barbeta, Adrià; Voltas, Jordi; Peñuelas, Josep; Dennis, Kate J.; Palacio, Sara; Dawson, Todd E.; Ferrio, Juan Pedro

doi:10.1111/nph.13376

Cited by 122 publications

(179 citation statements)

References 28 publications

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“…Measurements were repeated until values became stable around a mean. Mean analytical uncertainties quantified as SD of different replicate measurements for each sample were ±0.06 ‰ for δ 18/16 O and ±0.27 ‰ for δ 2/1 H. Post-processing correction was made by running the ChemCorrect ™ v1.2.0 (Picarro Inc.) to exclude the influence of volatiles according to Martín-Gómez et al (2015).…”

Section: Set-up Of the Equilibration Proceduresmentioning

confidence: 99%

“…More materials like filter paper, cotton, protein powder and wheat flour were included to identify whether the chemical identity causes or influences the effect. Finally we had to exclude that the effect resulted from artefacts like old water or volatiles and solutes interfering with the isotope measurements (Martín-Gómez et al, 2015;Schmidt et al, 2012;Schultz et al, 2011;West et al, 2011). Silage, which is likely a source of volatiles and solutes in rather large amounts (e.g.…”

Section: Introductionmentioning

confidence: 99%

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2H and 18O depletion of water close to organic surfaces

Chen¹,

Auerswald²,

Schnyder³

2016

Biogeosciences

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Abstract. Hydrophilic surfaces influence the structure of water close to them and may thus affect the isotope composition of water. Such an effect should be relevant and detectable for materials with large surface areas and low water contents. The relationship between the volumetric solid : water ratio and the isotopic fractionation between adsorbed water and unconfined water was investigated for the materials silage, hay, organic soil (litter), filter paper, cotton, casein and flour. Each of these materials was equilibrated via the gas phase with unconfined water of known isotopic composition to quantify the isotopic difference between adsorbed water and unconfined water. Across all materials, isotopic fractionation was significant (p<0.05) and negative (on average −0.91 ± 0.22 ‰ for 18/16 O and −20.6 ± 2.4 ‰ for 2/1 H at an average solid : water ratio of 0.9). The observed isotopic fractionation was not caused by solutes, volatiles or old water because the fractionation did not disappear for washed or oven-dried silage, the isotopic fractionation was also found in filter paper and cotton, and the fractionation was independent of the isotopic composition of the unconfined water. Isotopic fractionation became linearly more negative with increasing volumetric solid : water ratio and even exceeded −4 ‰ for 18/16 O and −44 ‰ for 2/1 H. This fractionation behaviour could be modelled by assuming two water layers: a thin layer that is in direct contact and influenced by the surface of the solid and a second layer of varying thickness depending on the total moisture content that is in equilibrium with the surrounding vapour. When we applied the model to soil water under grassland, the soil water extracted from 7 and 20 cm depth was significantly closer to local meteoric water than without correction for the surface effect. This study has major implications for the interpretation of the isotopic composition of water extracted from organic matter, especially when the volumetric solid : water ratio is larger than 0.5 or for processes occurring at the solid-water interface.

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Section: Set-up Of the Equilibration Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

2H and 18O depletion of water close to organic surfaces

Chen¹,

Auerswald²,

Schnyder³

2016

Biogeosciences

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“…In order to assess whether soluble organic compounds present in some soil water samples did not impact the laser analyzer isotope measurements (Martín-Gómez et al, 2015), a representative set of colored samples were analyzed with and without the Picarro micro combustion module (MCM) set up between the high-precision vaporizer and the analyzer inlet. This system was designed to partly remove organic volatile compounds using a catalytic process.…”

Section: Irrigation and Soil Watersmentioning

confidence: 99%

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

et al. 2018

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Abstract. Continental atmospheric relative humidity (RH) is a key climate parameter. Combined with atmospheric temperature, it allows us to estimate the concentration of atmospheric water vapor, which is one of the main components of the global water cycle and the most important gas contributing to the natural greenhouse effect. However, there is a lack of proxies suitable for reconstructing, in a quantitative way, past changes of continental atmospheric humidity. This reduces the possibility of making model-data comparisons necessary for the implementation of climate models. Over the past 10 years, analytical developments have enabled a few laboratories to reach sufficient precision for measuring the triple oxygen isotopes, expressed by the 17 O-excess ( 17 O-excess = ln (δ 17 O + 1) -0.528 × ln (δ 18 O + 1)), in water, water vapor and minerals. The 17 O-excess represents an alternative to deuterium-excess for investigating relative humidity conditions that prevail during water evaporation. Phytoliths are micrometric amorphous silica particles that form continuously in living plants. Phytolith morphological assemblages from soils and sediments are commonly used as past vegetation and hydrous stress indicators. In the present study, we examine whether changes in atmospheric RH imprint the 17 O-excess of phytoliths in a measurable way and whether this imprint offers a potential for reconstructing past RH. For that purpose, we first monitored the 17 O-excess evolution of soil water, grass leaf water and grass phytoliths in response to changes in RH (from 40 to 100 %) in a growth chamber experiment where transpiration reached a steady state. Decreasing RH from 80 to 40 % decreases the 17 Oexcess of phytoliths by 4.1 per meg/% as a result of kinetic fractionation of the leaf water subject to evaporation. In order to model with accuracy the triple oxygen isotope fractionation in play in plant water and in phytoliths we recommend direct and continuous measurements of the triple isotope composition of water vapor. Then, we measured the 17 O-excess of 57 phytolith assemblages collected from top soils along a RH and vegetation transect in inter-tropical West and Central Africa. Although scattered, the 17 O-excess of phytoliths decreases with RH by 3.4 per meg/%. The similarity of the trends observed in the growth chamber and nature supports that RH is an important control of 17 O-excess of phytoliths in the natural environment. However, other parameters such as changes in the triple isotope composition of the soil water or phytolith origin in the plant may come into play. Assessment of these parameters through additional growth chambers experiments and field campaigns will bring us closer to an accurate proxy of changes in relative humidity.

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“…First, a number of other types of interference have been studied in the L2120-i. Previous work has characterized interference from self-broadening (Schmidt et al, 2010) and from organic contaminants (Brand et al, 2009;West et al, 2010), tested algorithms for correcting for organic interference during or after analysis (Hendry et al, 2011;Schultz et al, 2011;West et al, 2011;Schmidt et al, 2012;Martín-Gómez et al, 2015;, and tested peripherals for pyrolyzing or oxidizing organic contaminants prior to analysis (Berkelhammer et al, 2013;Martín-Gómez et al, 2015;Lazarus et al, 2016). Second, the L2120-i has been widely used to measure δ 18 O-H 2 O and δ 2 H-H 2 O values in situations where background variation could be relevant to the calibration procedures and/or the fundamental measurements.…”

Section: Introductionmentioning

confidence: 99%

Effects of variation in background mixing ratios of N2, O2, and Ar on the measurement of δ18O–H2O and δ2H–H2O values by cavity ring-down spectroscopy

Johnson

Rella

2017

Atmos. Meas. Tech.

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Abstract. Cavity ring-down spectrometers have generally been designed to operate under conditions in which the background gas has a constant composition. However, there are a number of observational and experimental situations of interest in which the background gas has a variable composition. In this study, we examine the effect of background gas composition on a cavity ring-down spectrometer that measures δ 18 O-H 2 O and δ 2 H-H 2 O values based on the amplitude of water isotopologue absorption features around 7184 cm −1 (L2120-i, Picarro, Inc.). For background mixtures balanced with N 2 , the apparent δ 18 O values deviate from true values by −0.50 ± 0.001 ‰ O 2 % −1 and −0.57 ± 0.001 ‰ Ar % −1 , and apparent δ 2 H values deviate from true values by 0.26 ± 0.004 ‰ O 2 % −1 and 0.42 ± 0.004 ‰ Ar % −1 . The artifacts are the result of broadening, narrowing, and shifting of both the target absorption lines and strong neighboring lines. While the background-induced isotopic artifacts can largely be corrected with simple empirical or semimechanistic models, neither type of model is capable of completely correcting the isotopic artifacts to within the inherent instrument precision. The development of strategies for dynamically detecting and accommodating background variation in N 2 , O 2 , and/or Ar would facilitate the application of cavity ring-down spectrometers to a new class of observations and experiments.

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Isotope‐ratio infrared spectroscopy: a reliable tool for the investigation of plant‐water sources?

Cited by 122 publications

References 28 publications

<sup>2</sup>H and <sup>18</sup>O depletion of water close to organic surfaces

<sup>2</sup>H and <sup>18</sup>O depletion of water close to organic surfaces

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

Effects of variation in background mixing ratios of N<sub>2</sub>, O<sub>2</sub>, and Ar on the measurement of <i>δ</i><sup>18</sup>O–H<sub>2</sub>O and <i>δ</i><sup>2</sup>H–H<sub>2</sub>O values by cavity ring-down spectroscopy

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Isotope‐ratio infrared spectroscopy: a reliable tool for the investigation of plant‐water sources?

Cited by 122 publications

References 28 publications

&lt;sup&gt;2&lt;/sup&gt;H and &lt;sup&gt;18&lt;/sup&gt;O depletion of water close to organic surfaces

&lt;sup&gt;2&lt;/sup&gt;H and &lt;sup&gt;18&lt;/sup&gt;O depletion of water close to organic surfaces

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

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<sup>2</sup>H and <sup>18</sup>O depletion of water close to organic surfaces

<sup>2</sup>H and <sup>18</sup>O depletion of water close to organic surfaces