scholarly journals Technical note: Evaporating water is different from bulk soil water in <i>δ</i><sup>2</sup>H and <i>δ</i><sup>18</sup>O and has implications for evaporation calculation

2021 ◽  
Vol 25 (10) ◽  
pp. 5399-5413
Author(s):  
Hongxiu Wang ◽  
Jingjing Jin ◽  
Buli Cui ◽  
Bingcheng Si ◽  
Xiaojun Ma ◽  
...  
Keyword(s):  
Soil Water ◽  
Technical Note ◽  
Soil Evaporation ◽  
Bulk Soil ◽  
Precipitation Event ◽  
Water Evaporation ◽  
Evaporation Time ◽  
Water Losses ◽  
Evaporative Water ◽  
Pore Size Distributions

Abstract. Soil evaporation is a key process in the water cycle and can be conveniently quantified using δ2H and δ18O in bulk surface soil water (BW). However, recent research shows that soil water in larger pores evaporates first and differs from water in smaller pores in δ2H and δ18O, which disqualifies the quantification of evaporation from BW δ2H and δ18O. We hypothesized that BW had different isotopic compositions from evaporating water (EW). Therefore, our objectives were to test this hypothesis first and then evaluate whether the isotopic difference alters the calculated evaporative water loss. We measured the isotopic composition of soil water during two continuous evaporation periods in a summer maize field. Period I had a duration of 32 d, following a natural precipitation event, and period II lasted 24 d, following an irrigation event with a 2H-enriched water. BW was obtained by cryogenically extracting water from samples of 0–5 cm soil taken every 3 d; EW was derived from condensation water collected every 2 d on a plastic film placed on the soil surface. The results showed that when event water was heavier than pre-event BW, δ2H of BW in period II decreased, with an increase in evaporation time, indicating heavy water evaporation. When event water was lighter than the pre-event BW, δ2H and δ18O of BW in period I and δ18O of BW in period II increased with increasing evaporation time, suggesting light water evaporation. Moreover, relative to BW, EW had significantly smaller δ2H and δ18O in period I and significantly smaller δ18O in period II (p<0.05). These observations suggest that the evaporating water was close to the event water, both of which differed from the bulk soil water. Furthermore, the event water might be in larger pores from which evaporation takes precedence. The soil evaporative water losses derived from EW isotopes were compared with those from BW. With a small isotopic difference between EW and BW, the evaporative water losses in the soil did not differ significantly (p>0.05). Our results have important implications for quantifying evaporation processes using water stable isotopes. Future studies are needed to investigate how soil water isotopes partition differently between pores in soils with different pore size distributions and how this might affect soil evaporation estimation.

scholarly journals Technical note: Evaporating water is different from bulk soil water in δ<sup>2</sup>H and δ<sup>18</sup>O

2021 ◽  
Author(s):  
Hongxiu Wang ◽  
Jingjing Jin ◽  
Bingcheng Si ◽  
Xiaojun Ma ◽  
Mingyi Wen
Keyword(s):  
Soil Water ◽  
Pore Water ◽  
Water Cycle ◽  
Soil Surface ◽  
Technical Note ◽  
Precipitation Event ◽  
Evaporation Time ◽  
Evaporative Water ◽  
Small Pore ◽  
Added Water

Abstract. Soil evaporation is a key process in the water cycle and can be conveniently quantified with δ2H and δ18O in bulk surface soil water (BW). However, recent research shows that larger soil pore water evaporates first and differs from small pore water in δ2H and δ18O, which disqualifies quantification of evaporation from BW δ2H and δ18O. We hypothesize that BW has different isotopic compositions than evaporating water (EW). Therefore, our objectives are to test the hypothesis, and to evaluate if the difference alters the calculated evaporative water loss. We measured isotopic composition in soil water in two continuous evaporation periods in a summer maize field. Period Ⅰ had a duration of 32 days following a precipitation event and Period Ⅱ lasted 24 days following an irrigation event with a 2H-enriched water. BW was obtained by cryogenically extracting water from samples of 0–5 cm soil taken every three days; EW was derived from condensation water collected every two days on plastic film placed on soil surface. Results showed that when newly added water was heavier than pre-event BW, δ2H of BW in Period Ⅱ decreased with the increase of evaporation time, indicating evaporation of heavy water; when newly added water was lighter than pre-event BW, δ2H and δ18O of BW in Period Ⅰ and δ18O of BW in Period Ⅱ increased with increasing evaporation time, suggesting evaporation of light water. Moreover, relative to BW, EW had significantly smaller δ2H and δ18O in Period Ⅰ and significantly smaller δ18O in Period Ⅱ (p  0.05). Our results have important implication for quantifying evaporation process with water stable isotopes.

scholarly journals Characteristics of Soil Moisture and Evaporation under the Activities of Earthworms in Typical Anthrosols in China

2020 ◽  
Vol 12 (16) ◽  
pp. 6603
Author(s):  
Li Ma ◽  
Ming’an Shao ◽  
Tongchuan Li
Keyword(s):  
Soil Temperature ◽  
Soil Water ◽  
Agricultural Development ◽  
Soil Layer ◽  
Soil Surface ◽  
Soil Evaporation ◽  
Water Evaporation ◽  
Soil Columns ◽  
Soil Surface Temperature ◽  
Water Holding

Earthworms have an important influence on the terrestrial ecological environment. This study assesses the effect of different earthworm densities on soil water content (SWC) and evaporation in a laboratory experiment. Four earthworm densities (0 no-earthworm, control [C]; 207 earthworms m−2, low density [LDE]; 345 earthworms m−2, medium density [MDE]; and 690 earthworms m−2, high density [HDE]) are tested in soil columns. Results show that cumulative evaporation occurs in the decreasing order of densities: C (98.6 mm) > LDE (115.8 mm) > MDE (118.4 mm) > HDE (124.6 mm). Compared with the control, earthworm activity decreases cumulative soil evaporation by 5.0–20.9%, increases soil temperature to 0.46 °C–0.63 °C at 8:00, and decreases soil temperature to 0.21 °C–0.52 °C at 14:00 on the soil surface. Temperature fluctuations reduce with increasing earthworm densities. A negative correlation is found between cumulative soil evaporation and earthworm density (R2 = 0.969, p < 0.001). Earthworms significantly (p < 0.05) decrease the surface SWC loss (0–20 cm) soil layer but increase the subsoil SWC loss (60–100 cm) by adjusting the soil temperature and reducing soil water evaporation. Earthworm activities (burrows, casts…) improve the soil water holding ability by adjusting soil temperature and reducing soil water evaporation. Thus, the population quantity of earthworms may provide valuable ecosystem services in soil water and heat cycles to save water resources and realize sustainable agricultural development.

Quantifying genetic effects of ground cover on soil water evaporation using digital imaging

2010 ◽  
Vol 37 (8) ◽  
pp. 703 ◽  
Author(s):  
Daniel J. Mullan ◽  
Matthew P. Reynolds
Keyword(s):  
Soil Water ◽  
Leaf Area ◽  
Rapid Development ◽  
Ground Cover ◽  
Genetic Differences ◽  
Soil Evaporation ◽  
Water Evaporation ◽  
Analysis Tool ◽  
Area Index ◽  
Normalised Difference Vegetation Index

Rapid development of leaf area and/or aboveground biomass has the potential to improve water harvest of rain fed wheat in Mediterranean-type environments through reduced soil evaporation. However, quantitative relationships between genetic differences in early ground cover and soil water evaporation have not been established. Furthermore, accurate phenotyping of ground cover and early vigour have typically been achieved via destructive sampling methods, which are too time-consuming to undertake within breeding programs. Digital image analysis has previously been identified as an alternative indirect method of analysis, whereby computer analysis is ued to determine percentage ground cover. This study uses a digital ground cover (DGC) analysis tool for high throughput screening of four large wheat populations. The DGC methodology was validated via comparisons with alternative measures of canopy cover, such as normalised difference vegetation index (NDVI) (r2 = 0.69), biomass (r2 = 0.63), leaf area index (r2 = 0.80) and light penetration through the canopy (r2 = 0.70). The wheat populations were utilised to estimate the potential variation in soil evaporation associated with genetic differences in early ground cover, which was validated using established models. Estimates of genetic differences in soil evaporation within the four populations (6.90–24.8 mm) suggest that there is sufficient genetic variation to increase water harvest through targeting faster ground cover. Implications for improved wheat yields and breeding are discussed.

Diurnal Soil-Water Evaporation: Time-Depth-Flux Patterns

1973 ◽  
Vol 37 (4) ◽  
pp. 505-509 ◽  
Author(s):  
R. D. Jackson ◽  
B. A. Kimball ◽  
R. J. Reginato ◽  
F. S. Nakayama
Keyword(s):  
Soil Water ◽  
Water Evaporation ◽  
Evaporation Time

scholarly journals Mass Transport Limitations of Water Evaporation in Polymer Electrolyte Fuel Cell Gas Diffusion Layers

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2967
Author(s):  
Adrian Mularczyk ◽  
Andreas Michalski ◽  
Michael Striednig ◽  
Robert Herrendörfer ◽  
Thomas J. Schmidt ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Liquid Water ◽  
Evaporative Cooling ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Ex Situ ◽  
Water Evaporation ◽  
Evaporative Water ◽  
Gas Diffusion Layers ◽  
Diffusion Layers

Facilitating the proper handling of water is one of the main challenges to overcome when trying to improve fuel cell performance. Specifically, enhanced removal of liquid water from the porous gas diffusion layers (GDLs) holds a lot of potential, but has proven to be non-trivial. A main contributor to this removal process is the gaseous transport of water following evaporation inside the GDL or catalyst layer domain. Vapor transport is desired over liquid removal, as the liquid water takes up pore space otherwise available for reactant gas supply to the catalytically active sites and opens up the possibility to remove the waste heat of the cell by evaporative cooling concepts. To better understand evaporative water removal from fuel cells and facilitate the evaporative cooling concept developed at the Paul Scherrer Institute, the effect of gas speed (0.5–10 m/s), temperature (30–60 °C), and evaporation domain (0.8–10 mm) on the evaporation rate of water from a GDL (TGP-H-120, 10 wt% PTFE) has been investigated using an ex situ approach, combined with X-ray tomographic microscopy. An along-the-channel model showed good agreement with the measured values and was used to extrapolate the differential approach to larger domains and to investigate parameter variations that were not covered experimentally.

Advances in Heat-Pulse Methods: Measuring Soil Water Evaporation with Sensible Heat Balance

2017 ◽  
Vol 2 (1) ◽  
pp. 0 ◽  
Author(s):  
J.L. Heitman ◽  
X. Zhang ◽  
X. Xiao ◽  
T. Ren ◽  
R. Horton
Keyword(s):  
Soil Water ◽  
Heat Balance ◽  
Heat Pulse ◽  
Water Evaporation ◽  
Sensible Heat

Analytical solution for soil water redistribution during evaporation process

2013 ◽  
Vol 68 (12) ◽  
pp. 2545-2551 ◽  
Author(s):  
Jidong Teng ◽  
Noriyuki Yasufuku ◽  
Qiang Liu ◽  
Shiyu Liu
Keyword(s):  
Analytical Solution ◽  
Water Content ◽  
Soil Water ◽  
Exponential Function ◽  
Experimental Result ◽  
Water Evaporation ◽  
Evaporation Process ◽  
Climate Control ◽  
Water Redistribution ◽  
Control Apparatus

Simulating the dynamics of soil water content and modeling soil water evaporation are critical for many environmental and agricultural strategies. The present study aims to develop an analytical solution to simulate soil water redistribution during the evaporation process. This analytical solution was derived utilizing an exponential function to describe the relation of hydraulic conductivity and water content on pressure head. The solution was obtained based on the initial condition of saturation and an exponential function to model the change of surface water content. Also, the evaporation experiments were conducted under a climate control apparatus to validate the theoretical development. Comparisons between the proposed analytical solution and experimental result are presented from the aspects of soil water redistribution, evaporative rate and cumulative evaporation. Their good agreement indicates that this analytical solution provides a reliable way to investigate the interaction of evaporation and soil water profile.

A global meta-analysis reveals a significant offset in δ2H between plant water and its sources

2021 ◽  
Author(s):  
Javier de la Casa ◽  
Adrià Barbeta ◽  
Asun Rodriguez-Uña ◽  
Lisa Wingate ◽  
Jérôme Ogeé ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Soil Water ◽  
Meta Analysis ◽  
Water Evaporation ◽  
Source Water ◽  
Plant Water ◽  
Water Line ◽  
Plant Source ◽  
Sampling Campaign ◽  
The Mean

&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Long-standing ecological theory establishes that the isotopic composition of the plant water reflects that of the root-accessed sources, at least in non-saline or non-xeric environments. However, a growing number of studies challenge this assumption by reporting plant-source offsets in water isotopic composition, for a wide range of ecosystems. We conducted a global meta-analysis to systematically quantify the magnitude of this plant-source offset in water isotopic composition and its potential explanatory factors. We compiled 108 studies reporting dual water isotopic composition (&amp;#948;&lt;sup&gt;2&lt;/sup&gt;H and &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O) of plant and source water. From these studies, we extracted the &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H and &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O of both plant and source waters for 223 plant species from artic to tropical biomes. For each species and sampling campaign, within each study, we calculated the mean line conditioned excess (LC-excess), with the slope and intercept of the local meteoric water line, and the mean soil water line conditioned excess (SWL-excess), from the slope and intercept of the soil water evaporation line. For each study site and sampling campaign, we obtained land surface temperature and volumetric soil water from the ERA5 database. For each study species, we recorded the functional type, leaf habit and for those available wood density. We found, on average, a significantly negative SWL-excess: plant water was systematically more depleted in &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H than soil water. In &gt; 90% of the cases with significantly negative SWL-excess, we also found negative LC-excess values, meaning that access to sources alternative to soil water was unlikely to explain negative SWL-excess values.&amp;#160;&lt;/p&gt;&lt;p&gt;Calculated SWL-excess was affected by temperature and humidity: there were larger mismatches between plant and source water in isotopic composition in colder and wetter sites. Angiosperms, broadleaved and deciduous species exhibited more negative SWL-excess values than gymnosperms, narrow-leaved and evergreen species. Our results suggest that when using the dual isotopic approach, potential biases in the adscription of plant water sources are more likely in broadleaved forests in humid, and cold regions. Potential underlying mechanism for these isotopic mismatches will be discussed.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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