682 research outputs found
Effects of microplastics on evaporation dynamics in porous media
No full textMicroplastics (MPs) pollution is an emerging threat to soil ecosystems. The present study aims to investigate the impacts of MPs on soil water evaporation dynamics and patterns. Two series of laboratory experiments were conducted using sand particles and clay mixed with different MPs to investigate how evaporation dynamics and patterns are influenced by the presence of MPs. Quartz sand including 0, 0.75, 1.5, and 4.5% of Polyethylene (PE) and Polyvinylchloride (PVC) were used to evaluate MPs effects on evaporation rates while bentonite mixed with sand and 0, 0.75, 1.5, 4.5, 6, 8, and 10% of PE and PVC were used to investigate evaporation-induced cracking patterns. The experiments were conducted under controlled laboratory conditions in a climate chamber at constant ambient temperature. Our results suggest that the addition of MPs led to more water evaporation compared to the samples without MPs. Microscopic imaging and analysis enabled us to evaluate the possible MPs effects on the modification of soil characteristics and pore structure affecting the evaporation behavior. Moreover, although increasing MPs concentrations appeared to induce only minor effects on the crack morphology formed as a result of evaporation from the mixture of sand and bentonite, the type of MPs (PE vs PVC) had more notable effects on the drying-induced cracking patterns. The reported experimental data and analysis extend our physical understanding of the parameters influencing soil water evaporation in the presence of MPs
Characterization of wettability control on dynamics of two phase flow in natural porous media
No full textLeveraging high-fidelity lattice Boltzmann simulations (1,2) combined with analytical modeling, we investigate the interplay of surface wettability, small-scale heterogeneity of the pore geometry, and mobility conditions influencing the characteristics of immiscible two-phase fluid displacement in natural porous media (3). We present a detailed pore-scale analysis of flow regimes occurring during favorable (M>1) and unfavorable (M<1) displacement conditions in a rock sample of Tuscaloosa sandstone under a wide range of wettability (25^°<θ<175^°). As manifested by the saturation profile of invading fluid, we distinguished a transition of invasion morphology from fingering to compact (stable) displacement as the wetting condition varies from drainage to strong imbibition under both favorable and unfavorable mobility conditions. It becomes evident that the appearance of corner-flow plays a key role in the emergence of the transition zone in the displacement patterns. Furthermore, the corner-flow active zone is found to be mainly concentrated ahead of the primary invasion front and it is heterogeneously distributed in the pore space, preferentially hosted by small pores. It is found that the heterogeneous distribution of corner-flow events does not necessarily impose an adverse effect on the recovery of the defending fluid, as the maximum recovery efficiency is observed under the strong imbibition condition, where the corner flow is prevalent. In addition to numerical simulations, we derived an analytical model that can forecast the saturation profile of fluids as a function of wettability under different boundary conditions. The analytical model showed a reasonable agreement with the numerical results and can be a useful diagnostic tool for optimizing the displacement process in porous media (4).
Key words: Porous media, Heterogeneity, Two-phase flow, Wettability, Lattice Boltzmann modeling
References
[1] S. Bakhshian, H. S. Rabbani, S. A. Hosseini & N. Shokri, New insights into complex interactions between heterogeneity and wettability influencing two‐phase flow in porous media. Geophysical Research Letters, 47(14), e2020GL088187 (2020).
[2] S. Bakhshian, S. A. Hosseini, N. Shokri, Pore-scale characteristics of multiphase flow in heterogeneous porous media using the lattice Boltzmann method, Scientific Reports, 9 2045–2322 (2019).
[3] H. S. Rabbani, B. Zhao, R. Juanes, N. Shokri, Pore geometry control of apparent wetting in porous media, Scientific Reports, 8 Article number:448 15729 (2018).
[4] S. Bakhshian, S. A. Hosseini, Pore-scale analysis of supercritical CO2-brine immiscible displacement under fractional-wettability conditions, Advances in Water Resources 126 96–107 (2019)
Modes of interaction and varying feedback between groundwater and climate depending on soil characteristics
No full textClimate, climate variability, and climate change could influence groundwater. Shifts in precipitation patterns, recharge, or snowmelt are among the several climate-related variables with important impacts on groundwater. However, the climate-groundwater relationship is not one-way. Groundwater can also impact the climate itself via its influence on different processes and variables such as evaporation, soil moisture, and vegetation. Understanding the interactions and the feedback relationship between groundwater and climate is crucial for sustainable water resource management and resilient adaptation to climate change. Current understanding of how climate influences groundwater and the resulting feedback from groundwater and its impacts on climate is limited. This is of particular importance in the face of projected climatic changes. Here, we aim to develop a simple analytical framework to extend the projection capabilities required to characterize the climate-groundwater interactions depending on the soil characteristics serving as an intermediate domain between the groundwater and climate systems. Our proposed analytical framework can be used to identify potential regions with significant two-way (bidirectional) interactions between climate and groundwater using soil characteristics and soil water retention curves following the theoretical lines discussed in Shokri and Salvucci (2011) and Or and Lehmann (2019). Using this framework, we identify regions of expected hydraulic connections between groundwater and soil surface, depending on the competition between capillary forces and the limiting gravity and viscous forces, and the groundwater depth (GWD) in the city of Hamburg. We argue that in regions with bidirectional interactions, groundwater is potentially more vulnerable to climate change and variability. Moreover, our initial results suggest that regions with finer textured soils are more sensitive to changes in evaporation and air temperature in terms of hydraulic connections between groundwater and the soil surface, which can influence the groundwater-climate interactions. Our analysis provides the basis for further investigation of the feedback impacts of groundwater on several variables, such as soil moisture, ground cooling capacity, and vegetation patterns under different climate change scenarios. ReferencesOr, D., & Lehmann, P. (2019). Surface evaporative capacitance: How soil typeand rainfall characteristics affect global-scale surface evaporation. Water Resources Research, 55, 519-539.https://doi.org/10.1029/2018WR024050.Shokri, N., Salvucci, G. (2011). Evaporation from porous media in the presence of a water table. Vadose Zone J., 10, 1309-1318
Author Correction: The fusion–fission optimization (FuFiO) algorithm (Scientific Reports, (2022), 12, 1, (12396), 10.1038/s41598-022-16498-4)
No full textThe original version of this Article contained an error in the spelling of the author Nima Darabi which was incorrectly given as Nima Darabai. The Article also contained an error in the Equation in the Analyses based on competitions on evolutionary computation (CEC) section, under the subheading ‘Computational time and complexity analyses’ where “ O(FuFiO) ” was incorrectly given as “ O(FFO)”
Pore-scale dynamics of salt transport and distribution in drying porous media
No full textUnderstanding the physics ofwater evaporation from saline porous media is important in many natural and engineering applications such as durability of building materials and preservation of monuments, water quality, and mineral-fluid interactions. We applied synchrotron x-ray micro-tomography to investigate the pore-scale dynamics of dissolved salt distribution in a three dimensional drying saline porous media using a cylindrical plastic column (15 mm in height and 8 mm in diameter) packed with sand particles saturated with CaI2 solution (5% concentration by mass) with a spatial and temporal resolution of 12 μm and 30 min, respectively. Every time the drying sand column was set to be imaged, two different images were recorded using distinct synchrotron x-rays energies immediately above and below the K-edge value of Iodine. Taking the difference between pixel gray values enabled us to delineate the spatial and temporal distribution of CaI2 concentration at pore scale. Results indicate that during early stages of evaporation, air preferentially invades large pores at the surface while finer pores remain saturated and connected to the wet zone at bottom via capillary-induced liquid flow acting as evaporating spots. Consequently, the salt concentration increases preferentially in finer pores where evaporation occurs. Higher salt concentration was observed close to the evaporating surface indicating a convection-driven process. The obtained salt profiles were used to evaluate the numerical solution of the convection-diffusion equation (CDE). Results show that the macro-scale CDE could capture the overall trend of the measured salt profiles but fail to produce the exact slope of the profiles. Our results shed new insight on the physics of salt transport and its complex dynamics in drying porous media and establish synchrotron x-ray tomography as an effective tool to investigate the dynamics of salt transport in porous media at high spatial and temporal resolution. © 2014 AIP Publishing LLC
Comment on "Analytical estimation show low depth-independent water loss due to 1 vapor flux from deep aquifers by John S. Selker [2017]”
No full textSelker [2017] recently presented an analytical estimation of evaporative fluxes from deep aquifers. Regardless of the type of soil, ambient temperature and relative humidity, Selker [2017] assumed the thickness of liquid region above the water table equals to zero. Here, we illustrate the limitation of this assumption and its impact on the estimation of the evaporative fluxes from deep aquifers
AI-driven spatiotemporal quantification and prediction of soil salinity at European scale using the LUCAS database
No full textSoil salinization, referring to the excessive accumulation of soluble salt in soils, adversely influences nutrient cycling, microbial activity, biodiversity, plant growth and crop production thus affecting soil health and ecosystem functioning. Soil salinity quantification is a major step toward mitigation of its effects. Therefore, developing quantitative tools to predict soil salinity at regional and continental levels under different boundary conditions and scenarios is crucial for sustainable soil management and security of natural resources (1-3). This study proposes an AI-driven soil salinity quantification and projection approach focused on EU soils using a set of environmental covariates which consist of soil properties, terrain attributes, climate, and remotely sensed variables. The soil salinity point data which was used for model training and validation, expressed as electrical conductivity, was obtained from the LUCAS survey for the years 2015 and 2018. The novelty of this work lies in the careful integration of LUCAS data point with AI-driven models aiming to produce soil salinity maps for EU soils. Different AI algorithms including Random Forest, LightGBM, and XGBoost were used in this study enabling us to evaluate the performance of each algorithm in predicting soil salinity across EU with the XGBoost algorithm producing the most accurate results. Feature engineering technique was applied to reduce the models' collinearity; thus 17 covariates were selected as the most important model variables influencing soil salinity from the initial 34 covariates investigated in our analysis. The output of the predictive model will be a gridded dataset illustrating the spatial and temporal (yearly) distribution of soil salinity across the EU, accompanied by the corresponding uncertainty maps with the spatial resolution of 1-km. This information is crucial for identifying regions with elevated salinity levels and formulating necessary action plans to mitigate the situation.ReferencesHassani, A., Azapagic, A., Shokri, N. (2020). Predicting Long-term Dynamics of Soil Salinity and Sodicity on a Global Scale, Proc. Nat. Acad. Sci., 117(52), 33017-33027, https://doi.org/10.1073/pnas.2013771117 Hassani, A., Azapagic, A., Shokri, N. (2021). Global Predictions of Primary Soil Salinization Under Changing Climate in the 21st Century, Nat. Commun., 12, 6663. https://doi.org/10.1038/s41467-021-26907-3 Shokri-Kuehni, S.M.S., Raaijmakers, B., Kurz, T., Or, D., Helmig, R., Shokri, N. (2020). Water Table Depth and Soil Salinization: From Pore-Scale Processes to Field-Scale Responses. Water Resour. Res., 56, e2019WR026707, https://doi.org/10.1029/2019WR02670
Application of dynamic Bayesian network to performance assessment of fire protection systems during domino effects
No full textThe propagation of fire in chemical plants â also known as fire domino effects - largely depends on the performance of add-on passive and active protection systems such as sprinkler systems, water deluge systems, emergency shut down and emergency blow down systems, fireproofing, and emergency response. Although such safety barriers are widely employed to prevent or delay the initiation or escalation of fire domino effects, their inclusion in the modeling and risk assessment of fire domino effects has hardly been taken into account. In the present study, the dynamic evolution of fire protection systems has been investigated qualitatively using event tree analysis. To quantify the temporal changes and their impact on the escalation of fire domino effects, a dynamic Bayesian network methodology has been developed. The application of the methodology has been demonstrated using an illustrative case study, considering a variety of fire scenarios, target installations, and firefighting systems
THE STRUCTURE OF AUTHORING IN NIMA YUSHIJ'S POETRY: A BAKHTINIAN READING
No full textThis thesis employs Mikhail Bakhtin’s notion of architectonics to examine the poetry of Nima Yushij, the father of “New Persian Poetry.” The architectonic structure of Nima’s poems presupposes an authorial position situated outside the whole of the work. Outsideness provides the author with the distance that is necessary for consummating the hero and all other elements inside the work’s environment in determinate spatial and temporal boundaries. As Bakhtin puts it, only in this way can the author acquire a surplus of seeing that is required for adopting a valuational stance in relation the hero and the work as a whole. To Bakhtin, the author’s valuational stance toward the hero is the essence of the aesthetic product. This valuational position vis-à-vis the other, which generates what Michael Holquist calls the “structure of authoring,” is enacted on multiple levels in Nima’s poems as the hero, and sometimes the narrator, also perform the authorial function vis-à-vis other characters inside the poem, i.e., fixing them in determinate spatial and temporal boundaries. Of course, from the author’s perspective, the hero and the narrator are also situated inside the poem and occupy specific horizons in its environment. In this sense, their authoring activity is not a precisely aesthetic activity. Nevertheless, Nima utilizes the hero and the narrator’ activity to foreground the structure of authoring inside the poem, to make its dynamics “viewable.” This is a point that I will try to elucidate fully in the course of this study.Doctor of Philosophy (PhD
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