Dynamic temperature effects on diffusive transport behaviors of VOC vapors in unsaturated soils

2021 ◽  
Author(s):  
Asma Parlin ◽  
Noriaki Watanabe ◽  
Mizuki Yamada ◽  
Kengo Nakamura ◽  
Takeshi Komai
Keyword(s):  
Soil Temperature ◽  
Vapor Phase ◽  
Contaminated Soils ◽  
Unsaturated Soils ◽  
Soil Column ◽  
Diffusive Transport ◽  
Near Surface ◽  
Dynamic Temperature ◽  
Flux Change ◽  
Temperature Levels

<p>Investigation of the transport behaviors of volatile organic compounds (VOCs) in contaminated soils has previously been conducted in various environments. Accordingly, the present study focuses on specific phenomena in the near-surface soil environment where dynamic temperature affects the diffusive flux of VOC vapor phase as previous studies have suggested that temperature variations significantly influence such transport behaviors near-surface soils, but the nature of those influences and their mechanisms have remained unclear because of unexpected correlation of flux with the temperature that impacts on VOC vapor transport. More specifically, current practices report on a set of experiments into the vertical and upward vapor phase diffusive transport of benzene and trichloroethylene (TCE) in sandy soils that were conducted in soil column with water content conditions of up to 10 wt% and sinusoidal temperature conditions ranging from 20 to 30°C. This studies experimentally investigated that in all conditions tested, the top (outlet) flux change correlated positively with temperature change, while the bottom (inlet) flux change showed negative correlations. These results are consistent with previous observations showing that, at relatively deeper locations, there is little correlation between near-surface vertical VOC flux and soil temperature levels, and that VOC concentrations can be independent of the soil temperature at those locations. The present study's results highlighted for the first time that the negative correlation impact of temperature on VOC transport may occur frequently at deeper locations of subsurface soil. This occurs because the VOC concentration gradient is reduced by VOC desorption and the evaporation of water containing VOCs that accompany increasing temperature levels. However, our results also show that such mechanisms have a positive impact on VOC emissions from the upper part of subsurface soils to the atmosphere that can act as a low concertation boundary.</p>

scholarly journals Water-Induced Inverse Correlation between Temperature and Flux Changes in Vertical Vapor-Phase Diffusive Transport of Volatile Organic Compounds in Near-Surface Soil Environments

2021 ◽  
Vol 11 (8) ◽  
pp. 3489
Author(s):  
Asma Akter Parlin ◽  
Noriaki Watanabe ◽  
Kengo Nakamura ◽  
Mizuki Yamada ◽  
Jiajie Wang ◽  
...  
Keyword(s):  
Grain Size ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Vapor Phase ◽  
Contaminated Soils ◽  
Inverse Correlation ◽  
Diffusive Transport ◽  
Near Surface ◽  
Temperature Changes ◽  
Volatile Organic

Volatile organic compounds (VOCs) in contaminated soils have been investigated in near-surface environments to describe their transport behaviors and the resultant impacts of vapor intrusion into buildings. Prior studies have suggested that temperature changes significantly influence such transport behaviors in near-surface soils; however, the nature of these influences and their mechanisms have remained unclear. This is because an inverse correlation between the in situ temperature and VOC flux changes has been suggested but has not been experimentally investigated or demonstrated. Herein, we show the results of a set of experiments on the vertical and upward vapor-phase diffusive transport of benzene in sandy soils for different sand grain size and water content combinations under sinusoidal temperature changes between 20 and 30 °C. Under all experimental conditions, changes in the flux from the soil surface correlated with temperature changes, whereas changes in the flux into the overlying soil showed inverse correlations. Concurrent monitoring of the relative humidity revealed that an inverse correlation was exhibited in response to the condensation and volatilization of water. Moreover, the intensity of the inverse correlation was independent of grain size but was larger at higher water contents. Overall, water in soil may induce an inverse correlation.

scholarly journals Water-Enhanced Flux Changes under Dynamic Temperatures in the Vertical Vapor-Phase Diffusive Transport of Volatile Organic Compounds in Near-Surface Soil Environments

2021 ◽  
Vol 13 (12) ◽  
pp. 6570
Author(s):  
Asma Akter Parlin ◽  
Monami Kondo ◽  
Noriaki Watanabe ◽  
Kengo Nakamura ◽  
Mizuki Yamada ◽  
...  
Keyword(s):  
Air Quality ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Vapor Phase ◽  
Inverse Correlation ◽  
Diffusive Transport ◽  
Near Surface ◽  
Voc Emissions ◽  
Transport Behavior ◽  
Volatile Organic

The quantitative understanding of the transport behavior of volatile organic compounds (VOCs) in near-surface soils is highly important in light of the potential impacts of soil VOC emissions on the air quality and climate. Previous studies have suggested that temperature changes affect the transport behavior; however, the effects are not well understood. Indeed, much larger changes in the VOC flux under in situ dynamic temperatures than those expected from the temperature dependence of the diffusion coefficients of VOCs in the air have been suggested but rarely investigated experimentally. Here, we present the results of a set of experiments on the upward vertical vapor-phase diffusive transport of benzene and trichloroethylene (TCE) in sandy soils with water contents ranging from an air-dried value to 10 wt% during sinusoidal temperature variation between 20 and 30 °C. In all experiments, the flux from the soil surface was correlated with the temperature, as expected. However, the changes in flux under wet conditions were unexpectedly large and increased with increasing water content; they were also larger for TCE, the volatility of which depended more strongly on the temperature. Additionally, the larger flux changes were accompanied by a recently discovered water-induced inverse correlation between temperature and flux into the overlying soil. These results demonstrated that the flux changes of VOCs under dynamic temperatures could be increased by volatilization-dissolution interactions of VOCs with water. Future extensive studies on this newly discovered phenomenon would contribute to a better understanding of the impacts of soil VOC emissions on the air quality and climate.

scholarly journals The ERA5-Land soil temperature bias in permafrost regions

2020 ◽  
Vol 14 (8) ◽  
pp. 2581-2595 ◽  
Author(s):  
Bin Cao ◽  
Stephan Gruber ◽  
Donghai Zheng ◽  
Xin Li
Keyword(s):  
Soil Temperature ◽  
Land Surface ◽  
Soil Column ◽  
Land Surface Model ◽  
Surface Model ◽  
Active Layer Thickness ◽  
Near Surface ◽  
Warm Bias ◽  
Temperature Bias ◽  
Permafrost Regions

Abstract. ERA5-Land (ERA5L) is a reanalysis product derived by running the land component of ERA5 at increased resolution. This study evaluates ERA5L soil temperature in permafrost regions based on observations and published permafrost products. We find that ERA5L overestimates soil temperature in northern Canada and Alaska but underestimates it in mid–low latitudes, leading to an average bias of −0.08 ∘C. The warm bias of ERA5L soil is stronger in winter than in other seasons. As calculated from its soil temperature, ERA5L overestimates active-layer thickness and underestimates near-surface (<1.89 m) permafrost area. This is thought to be due in part to the shallow soil column and coarse vertical discretization of the land surface model and to warmer simulated soil. The soil temperature bias in permafrost regions correlates well with the bias in air temperature and with maximum snow height. A review of the ERA5L snow parameterization and a simulation example both point to a low bias in ERA5L snow density as a possible cause for the warm bias in soil temperature. The apparent disagreement of station-based and areal evaluation techniques highlights challenges in our ability to test permafrost simulation models. While global reanalyses are important drivers for permafrost simulation, we conclude that ERA5L soil data are not well suited for informing permafrost research and decision making directly. To address this, future soil temperature products in reanalyses will require permafrost-specific alterations to their land surface models.

Underestimated snow density in ERA5-Land as a cause for warm bias of soil temperature over permafrost regions

2021 ◽  
Author(s):  
Bin Cao ◽  
Stephan Gruber ◽  
Donghai Zheng ◽  
Xin Li
Keyword(s):  
Soil Temperature ◽  
Land Surface ◽  
Soil Column ◽  
Land Surface Model ◽  
Surface Model ◽  
Active Layer Thickness ◽  
Snow Density ◽  
Near Surface ◽  
Warm Bias ◽  
Permafrost Regions

&lt;div&gt; &lt;p&gt;ERA5 is the latest generation atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). ERA5-Land (ERA5L) is derived by running the land component of ERA5, Tiled ECMWF Scheme for Surface Exchanges over Land with a revised land surface hydrology (HTESSEL), at an increased resolution of 0.1&amp;#176;. This study evaluates ERA5L soil temperature in permafrost regions based on observations and published permafrost products. We find that ERA5L overestimates soil temperature in northern Canada and Alaska but underestimates it in mid&amp;#8211;low latitudes, leading to a near-zero overall bias (&amp;#8722;0.08 &amp;#730;C). The warm bias of ERA5L soil is more pronounced in winter than in other seasons. As calculated from its soil temperature, ERA5L overestimates active-layer thickness and underestimates near-surface (&lt; 1.89 m) permafrost area.This is thought to be due in part to the shallow soil column and coarse vertical discretization of the land surface model and to warmer simulated soil.&lt;/p&gt; &lt;p&gt;The soil temperature bias in permafrost regions correlates well with the bias in air temperature and with snow height. A review of the ERA5L snow parameterization in the code and a simulation example comparison with permafrost-specific processes rich model (GEOtop) both point to an error in snow metamorphism of HTESSEL leading to a low bias in ERA5L snow density as a possible cause for the warm bias in soil temperature. The apparent disagreement of station-based and areal evaluation techniques highlights challenges in our ability to test permafrost simulation models. While global reanalyses are important drivers for permafrost simulation, we conclude that ERA5L soil data are not well suited for informing permafrost research and decision making directly. To address this, future soil temperature products in reanalyses will require permafrost-specific alterations to their land surface models.&lt;/p&gt; &lt;p&gt;&lt;/p&gt;&lt;/div&gt;

scholarly journals Simulation of Daily Mean Soil Temperatures for Agricultural Land Use Considering Limited Input Data

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 441
Author(s):  
Philipp Grabenweger ◽  
Branislava Lalic ◽  
Miroslav Trnka ◽  
Jan Balek ◽  
Erwin Murer ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Input Data ◽  
Agricultural Land ◽  
Soil Column ◽  
Soil Conditions ◽  
Snow Layer ◽  
Time Step ◽  
Soil Temperatures ◽  
Dimensional Simulation ◽  
Limited Input Data

A one-dimensional simulation model that simulates daily mean soil temperature on a daily time-step basis, named AGRISOTES (AGRIcultural SOil TEmperature Simulation), is described. It considers ground coverage by biomass or a snow layer and accounts for the freeze/thaw effect of soil water. The model is designed for use on agricultural land with limited (and mostly easily available) input data, for estimating soil temperature spatial patterns, for single sites (as a stand-alone version), or in context with agrometeorological and agronomic models. The calibration and validation of the model are carried out on measured soil temperatures in experimental fields and other measurement sites with various climates, agricultural land uses and soil conditions in Europe. The model validation shows good results, but they are determined strongly by the quality and representativeness of the measured or estimated input parameters to which the model is most sensitive, particularly soil cover dynamics (biomass and snow cover), soil pore volume, soil texture and water content over the soil column.

Measurement of Soil Suction and Soil-Water Characteristics of Bentonite-Sand Mixtures

2010 ◽  
Author(s):  
Pan Hu ◽  
Qing Yang ◽  
Maotian Luan
Keyword(s):  
Soil Water ◽  
Vapor Phase ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Phase Method ◽  
Soil Suction ◽  
Compacted Bentonite ◽  
Water Characteristics ◽  
Wide Range ◽  
High Level

The soil-water characteristic curve (SWCC) is a widely used experimental means for assessing fundamental properties of unsaturated soils for a wide range of soil suction values. The study of SWCC is helpful because some properties of unsaturated soils can be predicted from it. Nowadays, much attention has been paid to the behaviours of highly compacted bentonite-sand mixtures used in engineering barriers for high level radioactive nuclear waste disposal. It is very important to study the various performances of bentonite-sand mixtures in order to insure the safety of high-level radioactive waste (HLW) repository. After an introduction to vapor phase method and osmotic technique, a laboratory study has been carried out on compacted bentonite-sand mixtures. The SWCC of bentonite-sand mixtures has been obtained and analyzed. The results show that the vapor phase method and osmotic technique is suitable to the unsaturated soils with high and low suction.

Cover crop effects on soil temperature in a clay loam soil in southwestern Ontario

2021 ◽  
pp. 1-10
Author(s):  
X.M. Yang ◽  
W.D. Reynolds ◽  
C.F. Drury ◽  
M.D. Reeb
Keyword(s):  
Soil Temperature ◽  
Cover Crops ◽  
Environmental Performance ◽  
Cover Crop ◽  
Crop Production ◽  
Surface Soil ◽  
Clay Loam ◽  
Near Surface ◽  
Soil Temperatures ◽  
Surface Soil Temperature

Although it is well established that soil temperature has substantial effects on the agri-environmental performance of crop production, little is known of soil temperatures under living cover crops. Consequently, soil temperatures under a crimson clover and white clover mix, hairy vetch, and red clover were measured for a cool, humid Brookston clay loam under a corn–soybean–winter wheat/cover crop rotation. Measurements were collected from August (after cover crop seeding) to the following May (before cover crop termination) at 15, 30, 45, and 60 cm depths during 2018–2019 and 2019–2020. Average soil temperatures (August–May) were not affected by cover crop species at any depth, or by air temperature at 60 cm depth. During winter, soil temperatures at 15, 30, and 45 cm depths were greater under cover crops than under a no cover crop control (CK), with maximum increase occurring at 15 cm on 31 January 2019 (2.5–5.7 °C) and on 23 January 2020 (0.8–1.9 °C). In spring, soil temperatures under standing cover crops were cooler than the CK by 0.1–3.0 °C at 15 cm depth, by 0–2.4 °C at the 30 and 45 cm depths, and by 0–1.8 °C at 60 cm depth. In addition, springtime soil temperature at 15 cm depth decreased by about 0.24 °C for every 1 Mg·ha−1 increase in live cover crop biomass. Relative to bare soil, cover crops increased near-surface soil temperature during winter but decreased near-surface soil temperature during spring. These temperature changes may have both positive and negative effects on the agri-environmental performance of crop production.

scholarly journals Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands

2013 ◽  
Vol 10 (7) ◽  
pp. 4465-4479 ◽  
Author(s):  
K. L. Hanis ◽  
M. Tenuta ◽  
B. D. Amiro ◽  
T. N. Papakyriakou
Keyword(s):  
Soil Temperature ◽  
Air Temperature ◽  
Growing Season ◽  
Near Surface ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Soil Temperatures ◽  
Surface Soil Temperature ◽  
Filling Method ◽  
Highly Correlated

Abstract. Ecosystem-scale methane (CH4) flux (FCH4) over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. FCH4 was measured using eddy covariance with a closed-path analyser in four years (2008–2011). Cumulative measured annual FCH4 (shoulder plus growing seasons) ranged from 3.0 to 9.6 g CH4 m−2 yr−1 among the four study years, with a mean of 6.5 to 7.1 g CH4 m−2 yr−1 depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with FCH4, with near-surface soil temperature at 5 cm most correlated across spring, fall, and the shoulder and growing seasons. The response of FCH4 to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but the water table also exerted influence, with FCH4 highest when water was 2–13 cm below and lowest when it was at or above the mean peat surface.

Simulating transient infiltration in unsaturated soils

1998 ◽  
Vol 35 (6) ◽  
pp. 1093-1100 ◽  
Author(s):  
J R McDougall ◽  
I C Pyrah
Keyword(s):  
Hydraulic Conductivity ◽  
Unsaturated Soils ◽  
Flow Model ◽  
Unsaturated Flow ◽  
Surface Region ◽  
Infiltration Rate ◽  
Soil Suction ◽  
Wetting Front ◽  
Near Surface ◽  
Unsaturated Hydraulic Conductivity

Transient responses to various infiltration events have been examined using an unsaturated flow model. Numerical simulations reveal a range of infiltration patterns which can be related to the ratio of infiltration rate to unsaturated hydraulic conductivity. A high value of this ratio reflects a prevailing hydraulic conductivity which cannot readily redistribute the newly infiltrated moisture. Moisture accumulates in the near-surface region before advancing down through the soil as a distinct wetting front. In contrast, low values of the ratio of rainfall to unsaturated hydraulic conductivity show minimal moisture accumulation, as the relatively small volumes of infiltrating moisture are readily redistributed through the soil profile.Key words: numerical modelling, infiltration, unsaturated soil, soil suction, groundwater.

scholarly journals Evaluation of soil moisture in CMIP5 simulations over contiguous United States using in situ and satellite observations

2016 ◽  
Author(s):  
Shanshui Yuan ◽  
Steven M. Quiring
Keyword(s):  
United States ◽  
Soil Moisture ◽  
Soil Column ◽  
Regional Analysis ◽  
Soil Layer ◽  
Model Performance ◽  
Coupled Model ◽  
Cmip5 Models ◽  
Near Surface

Abstract. This study provides a comprehensive evaluation of soil moisture simulations in the Coupled Model Intercomparison Project Phase 5 (CMIP5) extended historical experiment (2003 to 2012). Soil moisture from in situ and satellite sources are used to evaluate CMIP5 simulations in the contiguous United States (CONUS). Both near-surface (0–10 cm) and soil column (0–100 cm) simulations from more than 14 CMIP5 models are evaluated during the warm season (April–September). Multi-model ensemble means and the performance of individual models are assessed at a monthly time scale. Our results indicate that CMIP5 models can reproduce the seasonal variability in soil moisture over CONUS. However, the models tend to overestimate the magnitude of both near-surface and soil-column soil moisture in the western U.S. and underestimate it in the eastern U.S. There are large variations in model performance, especially in the near-surface. There are significant regional and inter-model variations in performance. Results of a regional analysis show that in deeper soil layer, the CMIP5 soil moisture simulations tend to be most skillful in the southern U.S. Based on both the satellite-derived and in situ soil moisture, CESM1, CCSM4 and GFDL-ESM2M perform best in the 0–10 cm soil layer and CESM1, CCSM4, GFDL-ESM2M and HadGEM2-ES perform best in the 0–100 cm soil layer.

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