scholarly journals The Influence of Water-rock Reactions and O Isotope Exchange with CO2 on Water Stable Isotope Composition of CO2 Springs in SE Australia

2017 ◽  
Vol 114 ◽  
pp. 3832-3839 ◽  
Author(s):  
Rūta Karolytė ◽  
Gareth Johnson ◽  
Sascha Serno ◽  
Stuart M.V. Gilfillan
Keyword(s):  
Stable Isotope ◽  
Isotope Exchange ◽  
Isotope Composition ◽  
Stable Isotope Composition ◽  
Influence Of Water ◽  
Water Stable Isotope ◽  
O Isotope

The dominant environmental driver of leaf water stable isotope enrichment differs for H-2 compared to O-18

2020 ◽  
Author(s):  
Matthias Cuntz ◽  
Lucas A Cernusak ◽  
Keyword(s):  
Stable Isotope ◽  
Relative Humidity ◽  
Air Temperature ◽  
Gordon Equation ◽  
Isotope Composition ◽  
Environmental Variable ◽  
Leaf Water ◽  
Source Water ◽  
Stable Isotope Composition ◽  
Water Stable Isotope

<p>Several important isotopic biomarkers derive at least part of their signal from the stable isotope composition of leaf water (e.g., leaf wax δ<sup>2</sup>H, cellulose δ<sup>2</sup>H and δ<sup>18</sup>O, lignin δ<sup>18</sup>O). In order to interpret these isotopic proxies, it is therefore helpful to know which environmental variable most strongly controls a given leaf water stable isotope signal. We collated observations of the stable isotope compositions of leaf water, xylem water, and atmospheric vapour, along with air temperature and relative humidity, to test whether the dominant driver of leaf water <sup>2</sup>H concentration could differ from that of <sup>18</sup>O concentration. Our dataset comprises 690 observations from 35 sites with broad geographical coverage. We limited our analysis to daytime observations, when the photosynthetic processes that incorporate the leaf water isotopic signal primarily take place. The Craig-Gordon equation was generally a good predictor for daytime bulk leaf water stable isotope composition for both δ<sup>2</sup>H (R<sup>2</sup>=0.86, p<0.001) and δ<sup>18</sup>O (R<sup>2</sup>=0.63, p<0.001). It showed about 10% admixture of source water was caused by unenriched water pools such as leaf veins or the Péclet effect. Solving the Craig-Gordon equation requires knowledge of relative humidity, air temperature, and the stable isotope compositions of source water and atmospheric vapour. However, it is not possible to invert the Craig-Gordon equation to solve for one of these parameters unless the others are known. Here we show that the two isotopic signals of δ<sup>2</sup>H and δ<sup>18</sup>O are predominantly driven by different environmental variables: leaf water δ<sup>2</sup>H correlated most strongly with the δ<sup>2</sup>H of source water (R<sup>2</sup>=0.68, p<0.001) and atmospheric vapour (R<sup>2</sup>=0.63, p<0.001), whereas leaf water δ<sup>18</sup>O correlated most strongly with air relative humidity (R<sup>2</sup>=0.46, p<0.001). We conclude that these two isotopic signals of leaf water are not simply mirror images of the same environmental information, but carry distinct signals of different climate factors, with crucial implications for the interpretation of downstream isotopic biomarkers.</p>

Spatiotemporal patterns of soil water stable isotope composition in forested headwater catchment

2020 ◽  
Author(s):  
Adnan Moussa ◽  
Ginevra Fabiani ◽  
Julian Klaus
Keyword(s):  
Stable Isotope ◽  
Soil Water ◽  
Vadose Zone ◽  
Isotope Composition ◽  
Critical Zone ◽  
Hydrological Processes ◽  
Hydrological Models ◽  
Stable Isotope Composition ◽  
Landscape Elements ◽  
Water Stable Isotope

<p>The vadose zone is a key component of the critical zone (CZ) and the interface of the atmosphere and the subsurface. A better understanding of critical zone hydrological processes is key for improving hydrological models and sustainable resource management. Isotopes of Hydrogen (<sup>2</sup>H) and Oxygen (<sup>18</sup>O) are a common tool to decipher hydrological processes in the CZ. However, there is still lack in understanding the spatiotemporal distribution of the soil water stable isotope composition (<sup>2</sup>H and <sup>18</sup>O) at catchment scale. Until today, only a few studies evaluated long-term variability and spatial patterns. Here we present results of bi-weekly measurements of the soil water stable isotope over nine months. SWI composition were measured using direct vapour equilibration and accounted for different landscape elements (eight locations per campaign) in the forested Weierbach (~0.42 km<sup>2</sup>) experimental catchment in Luxembourg.</p><p>Preliminary results show that a strong similarity of δ<sup>18</sup>O depth profiles between different landscape elements at the same sampling date. However, after a snowmelt event we observed a much higher variability throughout the catchment likely from different melt, fractionation, and infiltration processes. The δ<sup>18</sup>O profiles throughout the landscape change consistently with time driven by a combination of rainfall and evaporation. Lc-excess data showed that soil water was experiencing kinetic evaporative fractionation in the top 30 cm of the soil throughout the year. The presented high frequent data on isotopic composition of soil pore water are useful to analyse spatial difference in vadose zone processes for better understanding soil-atmosphere interaction and flow processes. Eventually such data can be used for constraining spatially distributed hydrological models.</p>

scholarly journals Storage Changes Stable Isotope Composition of Cucumbers

2021 ◽  
Vol 5 ◽  
Author(s):  
Micha Horacek ◽  
Wolfgang Papesch
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Isotope Composition ◽  
Isotopic Signature ◽  
Stable Isotope Composition ◽  
Vegetable Food ◽  
O Isotope ◽  
Linear Correlations ◽  
Special Relevance ◽  
Reference Samples

Vegetable food stuff produced under controlled and identical conditions from one farm of identical “age” (batch) has a similar isotopic composition. This fact can be used to control the origin of vegetables. This question is of special relevance when food-contaminations have to be traced back to the producer, or certain production claims have to be controlled. However, as vegetables are harvested, brought to whole-sale merchants and to retail shops, where they remain until being bought by the consumer, one has to consider possible changes in isotopic composition during this transfer period, when comparing vegetables of questioned origin with reference samples taken directly from the field/producer. We investigated changes in the isotope composition of vegetables during storage by studying as an example cucumbers from one batch. We stored the cucumbers in a vegetable storage under controlled conditions and removed one sample every day and analyzed its isotopic composition. We found changes in the δ15N and δ18O isotope values over the investigated period of 21 days, with both parameters showing positive linear correlations, and maximum enrichments with time of more than 1.5‰ for δ15N and more than 2‰ for δ18O. However, within the interval the samples remained in a saleable condition the isotope variations remained more or less within the variability of the sample batch. Our study demonstrates that changes in the isotopic signature in vegetables might occur after harvest during storage and have to be taken into account when (commercial) samples collected in a market are investigated.

scholarly journals Chemical and stable isotope composition of surface and groundwater in the surroundings of the Los Humeros Caldera, Puebla, Mexico

2019 ◽  
Vol 98 ◽  
pp. 07013
Author(s):  
Thomas Kretzschmar ◽  
Matteo Lelli ◽  
Ruth Alfaro ◽  
Juan Ignacio Sanchez ◽  
Yann Rene Ramos
Keyword(s):  
Stable Isotope ◽  
Isotope Composition ◽  
Regression Line ◽  
Sustainable Use ◽  
Geothermal Reservoir ◽  
Maximum Temperature ◽  
Stable Isotope Composition ◽  
Local Fracture ◽  
Hydrogeological Model ◽  
Fracture Systems

It is important to develop a regional hydrogeological model to identify possible recharge and discharge areas for a sustainable use of a geothermal reservoir. The Los Humeros geothermal area is situated within five surficial watersheds and coveres an area of more than 15.000 km2. A total of 208 well and spring samples were collected between June 2017 and November 2018. The stable isotope data for this region define a regression line of δDH2O = 8.032·δ18O + 12 and indicate that groundwater is recharged by regional precipitation. At least 39 groundwater wells, with a maximum temperature of 35 °C, show temperatures above the reported mean average surface temperature of 15 °C. Characteristic elements for geothermal reservoir fluids (B, Li, As) are also present in these groundwaters, indicating a possible connection between the reservoir fluid and the local groundwater through local fracture systems. Concentration of B in these hot wells is between 150 and 35000 ppb.

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