scholarly journals Effects of climatic seasonality on the isotopic composition of evaporating soil waters

2018 ◽  
Author(s):  
Paolo Benettin ◽  
Till H. M. Volkmann ◽  
Jana von Freyberg ◽  
Jay Frentress ◽  
Daniele Penna ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Water Samples ◽  
Meteoric Water ◽  
Water Isotopes ◽  
Source Water ◽  
Stable Water Isotopes ◽  
Dual Isotope ◽  
Left Behind ◽  
Biased Estimates ◽  
By Products

Abstract. Stable water isotopes are widely used in ecohydrology as tracers of the transport, storage, and mixing of water on its journey through landscapes and ecosystems. Evaporation leaves a characteristic signature on the isotopic composition of the water that is left behind, such that in dual-isotope space, evaporated waters plot below the Local Meteoric Water Line (LMWL) that characterizes precipitation. Soil and xylem water samples can often plot below the LMWL as well, suggesting that they have also been influenced by evaporation. These soil and xylem water samples frequently plot along linear trends in dual-isotope space. These trendlines are sometimes termed evaporation lines and their intersection with the LMWL is sometimes interpreted as the isotopic composition of the precipitation source water. Here we use numerical experiments based on established isotope fractionation theory to show that these trendlines are often by-products of the seasonality in evaporative fractionation and in the isotopic composition of precipitation. Thus, they are often not true evaporation lines, and, if interpreted as such, can yield highly biased estimates of the isotopic composition of the source water.

scholarly journals Effects of climatic seasonality on the isotopic composition of evaporating soil waters

2018 ◽  
Vol 22 (5) ◽  
pp. 2881-2890 ◽  
Author(s):  
Paolo Benettin ◽  
Till H. M. Volkmann ◽  
Jana von Freyberg ◽  
Jay Frentress ◽  
Daniele Penna ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Water Samples ◽  
Meteoric Water ◽  
Water Isotopes ◽  
Source Water ◽  
Stable Water Isotopes ◽  
Dual Isotope ◽  
Left Behind ◽  
Biased Estimates ◽  
By Products

Abstract. Stable water isotopes are widely used in ecohydrology to trace the transport, storage, and mixing of water on its journey through landscapes and ecosystems. Evaporation leaves a characteristic signature on the isotopic composition of the water that is left behind, such that in dual-isotope space, evaporated waters plot below the local meteoric water line (LMWL) that characterizes precipitation. Soil and xylem water samples can often plot below the LMWL as well, suggesting that they have also been influenced by evaporation. These soil and xylem water samples frequently plot along linear trends in dual-isotope space. These trend lines are often termed “evaporation lines” and their intersection with the LMWL is often interpreted as the isotopic composition of the precipitation source water. Here we use numerical experiments based on established isotope fractionation theory to show that these trend lines are often by-products of the seasonality in evaporative fractionation and in the isotopic composition of precipitation. Thus, they are often not true evaporation lines, and, if interpreted as such, can yield highly biased estimates of the isotopic composition of the source water.

Use of stable water isotopes to identify hydrological processes of meteoric water in montane catchments

2015 ◽  
Vol 29 (23) ◽  
pp. 4957-4967 ◽  
Author(s):  
Tsung-Ren Peng ◽  
Kuan-Yu Chen ◽  
Wen-Jun Zhan ◽  
Wan-Chung Lu ◽  
Lun-Tao John Tong
Keyword(s):  
Meteoric Water ◽  
Hydrological Processes ◽  
Water Isotopes ◽  
Stable Water Isotopes

scholarly journals O, H and C isotopic systematics of Icelandic groundwater

2019 ◽  
Vol 98 ◽  
pp. 07031
Author(s):  
Arny E. Sveinbjörnsdóttir ◽  
Andri Stefánsson ◽  
Jan Heinemeier
Keyword(s):  
Isotopic Composition ◽  
Carbon Isotopes ◽  
Upper Mantle ◽  
Lower Crust ◽  
Natural Waters ◽  
Large Range ◽  
Carbon Sources ◽  
Water Isotopes ◽  
Stable Water Isotopes ◽  
Range Of Values

Stable water isotopes of oxygen and hydrogen have been studied in Icelandic natural waters since 1960 for hydrological and geothermal research. All the waters are of meteoric and seawater origin. The measured range in δD and δ18O is large -131 to +3.3‰ and -20.8 to +2.3‰ respectively. Some of the waters are more depleted than any present-day precipitation suggesting a pre-Holocene component in the groundwater. Carbon isotopes of streams, rivers, soil and groundwater have been studied since 1990 in order to evaluate the carbon sources and reactions that possibly influence the carbon systematics of the water. Results show large range of values, for δ13CDIC -27.4 to +4.5‰ and for 14CDIC +0.6 to +118 pMC. Apart from atmospheric, organic and rock leaching, input of gas at depth with similar isotopic composition as the pre-erupted melt of the upper mantle and lower crust beneath Iceland have been identified as sources for carbon in the deeper groundwater.

scholarly journals Experimental observation of transient <i>δ</i><sup>18</sup>O interaction between snow and advective airflow under various temperature gradient conditions

2017 ◽  
Vol 11 (4) ◽  
pp. 1733-1743 ◽  
Author(s):  
Pirmin Philipp Ebner ◽  
Hans Christian Steen-Larsen ◽  
Barbara Stenni ◽  
Martin Schneebeli ◽  
Aldo Steinfeld
Keyword(s):  
Temperature Gradient ◽  
Isotopic Composition ◽  
Ice Cores ◽  
Transport Processes ◽  
Water Isotopes ◽  
Polar Regions ◽  
Stable Water Isotopes ◽  
Climate History ◽  
Stable Isotopes Of Water ◽  
Past Climate Variability

Abstract. Stable water isotopes (δ18O) obtained from snow and ice samples of polar regions are used to reconstruct past climate variability, but heat and mass transport processes can affect the isotopic composition. Here we present an experimental study on the effect of airflow on the snow isotopic composition through a snow pack in controlled laboratory conditions. The influence of isothermal and controlled temperature gradient conditions on the δ18O content in the snow and interstitial water vapour is elucidated. The observed disequilibrium between snow and vapour isotopes led to the exchange of isotopes between snow and vapour under non-equilibrium processes, significantly changing the δ18O content of the snow. The type of metamorphism of the snow had a significant influence on this process. These findings are pertinent to the interpretation of the records of stable isotopes of water from ice cores. These laboratory measurements suggest that a highly resolved climate history is relevant for the interpretation of the snow isotopic composition in the field.

scholarly journals Technical note: Evaluation of a low-cost evaporation protection method for portable water samplers

2020 ◽  
Vol 24 (12) ◽  
pp. 5821-5834
Author(s):  
Jana von Freyberg ◽  
Julia L. A. Knapp ◽  
Andrea Rücker ◽  
Bjørn Studer ◽  
James W. Kirchner
Keyword(s):  
Water Samples ◽  
Low Cost ◽  
Field Tests ◽  
Technical Note ◽  
Water Isotopes ◽  
Stable Water Isotopes ◽  
Sample Collection ◽  
Isotopic Signatures ◽  
Protection Method ◽  
Cost Efficient

Abstract. Automated field sampling of streamwater or precipitation for subsequent analysis of stable water isotopes (2H and 18O) is often conducted with off-the-shelf automated samplers. However, when water samples are stored in the field for days and weeks in open bottles inside autosamplers, their isotopic signatures can be altered by evaporative fractionation and vapor mixing. We therefore designed an evaporation protection method which modifies autosampler bottles using a syringe housing and silicone tube, and we tested whether this method reduces evaporative fractionation and vapor mixing in water samples stored for up to 24 d in 6712 full-size portable samplers (Teledyne ISCO, Lincoln, USA). Laboratory and field tests under different temperature and humidity conditions showed that water samples in bottles with evaporation protection were far less altered by evaporative fractionation and vapor mixing than samples in conventional open bottles. Our design is a cost-efficient approach to upgrade the 1 L sample bottles of the ISCO autosamplers, allowing secure water sample collection in warm and dry environments. Our design can be readily adapted (e.g., by using a different syringe size) to fit the bottles used by many other field autosamplers.

scholarly journals Experimental observation of transient δ<sup>18</sup>O interaction between snow and advective airflow under various temperature gradient conditions

2017 ◽  
Author(s):  
Pirmin P. Ebner ◽  
Hans Christian Steen-Larsen ◽  
Barbara Stenni ◽  
Martin Schneebeli ◽  
Aldo Steinfeld
Keyword(s):  
Temperature Gradient ◽  
Isotopic Composition ◽  
Ice Cores ◽  
Transport Processes ◽  
Water Isotopes ◽  
Polar Regions ◽  
Stable Water Isotopes ◽  
Equilibrium Processes ◽  
Stable Isotopes Of Water ◽  
Past Climate Variability

Abstract. Stable water isotopes (δ18O) obtained from snow and ice samples of polar regions are used to reconstruct past climate variability, but heat and mass transport processes can affect the isotopic composition. Here we present an experimental study on the effect on the snow isotopic composition by airflow through a snow pack in controlled laboratory conditions. The influence of isothermal and controlled temperature gradient conditions on the δ18O content in the snow and interstitial water vapor is elucidated. The observed disequilibrium between snow and vapor isotopes led to exchange of isotopes between snow and vapor under non-equilibrium processes, significantly changing the δ18O content of the snow. The type of metamorphism of the snow had a significant influence on this process. These findings are pertinent to the interpretation of the records of stable isotopes of water from ice cores. These laboratory measurements suggest that a highly resolved history is relevant for the interpretation of the snow isotopic composition in the field.

scholarly journals Stable water isotopes in the MITgcm

2017 ◽  
Vol 10 (8) ◽  
pp. 3125-3144 ◽  
Author(s):  
Rike Völpel ◽  
André Paul ◽  
Annegret Krandick ◽  
Stefan Mulitza ◽  
Michael Schulz
Keyword(s):  
Isotopic Composition ◽  
Observational Data ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Sea Surface ◽  
Water Isotopes ◽  
Model Data ◽  
Stable Water Isotopes

Abstract. We present the first results of the implementation of stable water isotopes in the Massachusetts Institute of Technology general circulation model (MITgcm). The model is forced with the isotopic content of precipitation and water vapor from an atmospheric general circulation model (NCAR IsoCAM), while the fractionation during evaporation is treated explicitly in the MITgcm. Results of the equilibrium simulation under pre-industrial conditions are compared to observational data and measurements of plankton tow records (the oxygen isotopic composition of planktic foraminiferal calcite). The broad patterns and magnitude of the stable water isotopes in annual mean seawater are well captured in the model, both at the sea surface as well as in the deep ocean. However, the surface water in the Arctic Ocean is not depleted enough, due to the absence of highly depleted precipitation and snowfall. A model–data mismatch is also recognizable in the isotopic composition of the seawater–salinity relationship in midlatitudes that is mainly caused by the coarse grid resolution. Deep-ocean characteristics of the vertical water mass distribution in the Atlantic Ocean closely resemble observational data. The reconstructed δ18Oc at the sea surface shows a good agreement with measurements. However, the model–data fit is weaker when individual species are considered and deviations are most likely attributable to the habitat depth of the foraminifera. Overall, the newly developed stable water isotope package opens wide prospects for long-term simulations in a paleoclimatic context.

The isotopic composition of phloem water and its relations to xylem water at daily and sub-daily resolutions

2021 ◽  
Author(s):  
Magali F. Nehemy ◽  
Benettin Paolo ◽  
Andrea Rinaldo ◽  
Jeffrey J. McDonnell
Keyword(s):  
Isotopic Composition ◽  
Water Transport ◽  
Isotope Composition ◽  
Water Status ◽  
Three Dimensional ◽  
Plant Water Status ◽  
Source Water ◽  
Plant Water ◽  
Xylem Water Potential ◽  
Dual Isotope

&lt;p&gt;Isotopic tracing is de rigueur&amp;#160;in ecohydrology and for quantifying tracing water sources that contribute to xylem water. But, tree transpiration is not a one dimensional process from roots to leaves. Three dimensional storages actively participate in water transport within the stem complicating in unknown ways, the otherwise straightforward tracing from source to xylem. Phloem is the largest elastic storage and works as a hydraulic capacitor, and as such is of great importance to tree water transport and functioning. Water stored in phloem moves into xylem vessels buffering changes in xylem water potential and sustaining tree hydraulic integrity. Although phloem water is of great importance to transpiration, we lack understanding about the relationship between xylem and phloem water isotopic composition. Assessing the isotopic composition of phloem is a needed next step to fully comprehend patterns of tree water use and improve understanding about isotopic offset between xylem and source water. Here we show daily and sub-daily dual-isotope measurements of phloem water in relation to xylem and leaf water in &lt;em&gt;Salix viminalis&lt;/em&gt; along with high-resolution measurements of plant water status and transpiration rates in a large lysimeter. We found that phloem was more depleted in heavier isotopes than xylem and leaves. On average &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H phloem water was 2.05 &amp;#8240; and &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O phloem water was 0.66 &amp;#8240; more negative than xylem water. The largest difference observed between phloem and xylem isotopic composition occurred at night during a period of tree water deficit. Although, there was variability in the observed difference between xylem and phloem throughout the experiment, xylem and phloem isotopic composition were highly correlated (&amp;#948;&lt;sup&gt;2&lt;/sup&gt;H r = 0.89; &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O r = 0.75). Our sub daily measurements showed that xylem and phloem differences decreased during predawn and morning compared to previous evening and midday measurements. We observed that the &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H difference between phloem and xylem increased with the increase in daily use of phloem water storages, while &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O difference between phloem and xylem increased with transpiration rate. Our results show that xylem and phloem isotope composition are in sync and that observed differences can be related to changes in plant water status and possible fractionation associated with transport within phloem-xylem. Further studies are necessary to understand how phloem affects source water interpretations across different tree species and larger trees, where phloem contribution to daily transpiration may be larger.&lt;/p&gt;

Origin of the waters sourced by trees in a pre-Alpine forested catchment

2020 ◽  
Author(s):  
Giulia Zuecco ◽  
Chiara Marchina ◽  
Amin Anam ◽  
Michael Engel ◽  
Jay Frentress ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Samples ◽  
Vacuum Distillation ◽  
Stream Water ◽  
Bulk Soil ◽  
Water Isotopes ◽  
Stable Water Isotopes ◽  
Forested Catchment ◽  
Cryogenic Vacuum ◽  
Suction Lysimeters

&lt;p&gt;Stable water isotopes have proven to be useful tracers to determine the origin of water taken up by plants, quantify the relative contributions of water sources to stream runoff and investigate water flow paths. However, the presence of different water pools in a catchment and soil water allocation complicates our understanding of water cycling, and calls for research on processes governing soil water movement and storage, as well as interactions between soil and plants.&lt;/p&gt;&lt;p&gt;In this study, we used isotopic data from a forested catchment in the Italian pre-Alps to i) investigate the spatial and temporal variability of the isotopic signature of various water sources, and ii) determine which waters are used by beech and chestnut trees in the study area.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Ecohydrological and hydrometeorological monitoring took place in the 2.4-ha Ressi catchment (Northern Italy). Elevations range from 598 to 721 m a.s.l., while average slope is 31&amp;#176;. Average annual precipitation is about 1695 mm, while average annual temperature is 9.7 &amp;#176;C. The entire catchment is covered by deciduous forest, with beech, chestnut, hazel and maple as the main tree species.&lt;/p&gt;&lt;p&gt;Water samples for isotopic analysis were taken monthly from bulk precipitation, approximately bi-weekly from stream water, groundwater and soil water by two suction lysimeter cups in the riparian zone. Bulk soil water samples and twigs for xylem water extraction by cryogenic vacuum distillation were collected starting in June, 2017. All water samples were analysed by laser spectroscopy, except xylem water that was analysed by mass spectrometry.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Stream water, groundwater and soil water extracted by suction lysimeters were isotopically similar to precipitation and aligned to the local meteoric water line. Bulk soil water obtained by cryogenic vacuum distillation showed an evaporation signature, especially on the hillslope where soil moisture was lower and soil water had been extracted by suction lysimeters only during or just after a large rainfall event. This indicates that soil water sampled by suction lysimeters and extracted by cryogenic vacuum distillation is stored differently in the soil layers due to the different soil tension, and hillslopes tend to store less mobile soil water compared to the riparian zone. At greater depths, bulk soil water extracted by cryogenic vacuum distillation was slightly less evaporated and less enriched in heavy isotopes compared to soil water extracted from shallower layers. The isotopic composition of xylem water had a large temporal and tree-species variability, with chestnut xylem water samples more enriched in heavy isotopes than samples obtained from beech trees. Xylem water was more similar to soil water obtained by cryogenic vacuum distillation, suggesting that in the study area trees likely use more bulk soil water than the mobile soil water, groundwater and stream water.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Keywords: stable water isotopes; soil water; xylem water; forested catchment.&lt;/p&gt;

Identification of source-sink relationships in southern Africa by stable water isotopes analysis and Lagrangian moisture source diagnostics

2020 ◽  
Author(s):  
Marielle Geppert ◽  
Stephan Pfahl ◽  
Ulrich Struck ◽  
Ingo Kirchner ◽  
Elisha Shemang ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Southern Africa ◽  
Specific Humidity ◽  
Water Isotopes ◽  
Stable Water Isotopes ◽  
Moisture Source ◽  
Moisture Sources ◽  
Transport Patterns ◽  
Isotope Measurements ◽  
Water Isotope

&lt;p&gt;Many palaeoclimate reconstructions are based on the fact that stable water isotopes are conserved in different highly resolved paleo-archives such as ice cores or calcium carbonates. Stable water isotopes are tracers of moisture in the atmosphere because they record information about evaporation and condensation processes during the transport of air parcels. These processes cause isotopic fractionation that leads to isotopic enrichment or depletion. The isotopic composition of precipitation is strongly correlated with altitude above sea level, distance to the coast and local surface air temperature. Knowledge on the source and transport of moisture is thus crucial for the interpretation of stable isotopes in precipitation and in palaeo-archives.&lt;br&gt;Studies analysing the linkage between stable water isotope measurements and moisture sources in southern Africa are scarce. Yet, as changes in the transport pattern can influence precipitation patterns and amounts, in a semi-arid region like southern Africa that is threatened by droughts, this knowledge is of particular interest. Thus, the aims of this study are (1) to reveal the principal moisture source areas and transport routes of specific target areas in southern Africa, (2) to assess the influence of different transport patterns on the isotopic composition of precipitation and by this (3) to create a modern analogue for palaeoclimate studies in this region.&lt;br&gt;About 200 water samples, mainly from headwaters of rivers, but also from precipitation events, springs and lakes, were collected throughout southern Africa and the stable water isotope composition (&amp;#948;&lt;sup&gt;2&lt;/sup&gt;H and &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O) was analysed. To detect moisture sources for this set of isotope measurements, backward air parcel trajectories were calculated from the sample location, using the LAGRANTO tool based on ERA5 reanalysis data. Variations in specific humidity along the trajectories were then used to detect moisture uptake.&lt;br&gt;The analysis reveals main transport patterns related to the Intertropical Convergence Zone and easterly winds as well as the effects of topographical forcing, which is, for example, very pronounced above Lesotho. The results provide detailed insights into the relationships between atmospheric circulation and &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H and &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O values of precipitation over southern Africa, which is a prerequisite for the interpretation of isotopic records that are used for palaeoclimatic reconstructions.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document