Kelum Chamindu

University of Peradeniya | UOP · Department of Civil Engineering

Abstract Soil gas diffusivity (Dp/Do, gas diffusion coefficients in soil and in free air, respectively) and its relation to soil moisture is of great importance for describing and quantifying essential provisional and regulatory functions associated with terrestrial ecosystems such as soil aeration and greenhouse gas (GHG) emissions. Because gas mi...

Soil density plays an important role in regulating the migration of greenhouse gases from terrestrial soils to the atmosphere. Soil moisture is one of the main soil physical controls determining the fate and transport of gases in soils. This study investigated the transport of methane (CH4) originating from a simulated CH4 source within a variably...

The increased frequency of extreme weather variations worldwide has resulted in dramatic changes in the soil water content via pronounced drying and rewetting cycles (DWCs). A comprehensive exploration of carbon dioxide (CO2) and nitrous oxide (N2O) emissions in response to DWCs can help summarize the existing results and better estimate terrestria...

Soil-gas diffusivity and its variation with soil moisture plays a fundamental role in diffusion controlled migration of climate-impact gases from different terrestrial agroecosystems including cultivated soils and managed pasture systems. The wide contrast in soil texture and structure (e.g., density, soil aggregation) in agriculture topsoils (0-10...

Amendment application is one of the effective measures in removing coarse‐textured soil structural obstacles. However, the application of water‐based spent drilling mud (WBSM) as a potential amendment and its associated impacts on soil's basic physical and hydraulic properties is not well studied. This research is aimed to investigate the applicati...

Core ideas • Soil from highly CKDu affected area showed higher concentration of col-loids • Colloid deposition increases with the decreasing flow rate and with increasing ionic strength • Cd(II) attachment was pronounced at low flow rate and high ionic strength • Colloid attachment is the key mechanism on colloid retention in porous media Transport...

Clay content in soil potentially has strong influence on soil structure and thereby controls soil physical, hydraulic, and gas transport properties. Only few studies have investigated the effect of clay content on saturated hydraulic conductivity (Ks) and gas transport parameters such relative gas diffusivity (Dp/D0) and air permeability (Ka) under...

Field and laboratory scale observations conducted during last few decades provided ample evidences to prove colloid-facilitated transport of numerous contaminants in porous media including radionuclides, hydrophobic organic compounds (HOCs), heavy metals, pesticides, pathogens, etc. Therefore, it is vital to investigate colloid and colloid-facilita...

Groundwater pollution due to toxic contaminants can be identified as a major health risk worldwide as it is a main source of drinking water. Among different methods of contami-nant transport, an overlooked and often underestimated mechanism constitutes colloid-facilitated transport (CFT), whereby the strongly-sorptive contaminants can potentially m...

Colloids are typically defined as the particles with characteristic dimensions falling in the window of 1 nm-10 µm. Owing to the high charge and the large specific surface area, colloids can adsorb a wide range of charged contaminants and transport them through the subsurface to groundwater aquifers. This phenomenon is termed as 'colloid-facilitate...

Accurate prediction of soil-gas diffusivity (Dp/Do: where Dp and Do are gas diffusion coefficients in soil and free air, respectively) and its variation with soil physical conditions (e.g., soil type/texture, soil density, soil moisture status) are important prerequisites for simulating subsurface gas migration and emission of greenhouse gases acro...

Grazed pastures can be introduced as a dominant source of nitrous oxide (N2O), a high potent greenhouse gas. Although past studies have examined N2O emissions in relation to soil physical properties, linking emissions with soil gas diffusivity (Dp/Do) and its dependency on soil physical properties and soil moisture are lacking. This study to empiri...

Grazed pastures can be introduced as a dominant source of nitrous oxide (N2O), a high potent greenhouse gas. Although past studies have examined N2O emissions in relation to soil physical properties, linking emissions with soil gas diffusivity (Dp/Do) and its dependency on soil physical properties and soil moisture are lacking. This study to empiri...

Contaminant migration in subsurface may potentially lead to severe health and environmental problems. In classical contaminant migration studies, only two mobile phases (liquid and gas) are explored. The presence of a third and a hidden mobile phase, the so-called colloidal phase, has been largely overlooked and its potential to carry contaminants...

With the increased use of natural gas, safety and environmental concerns from underground leaking natural gas pipelines are becoming more widespread. What is not well understood in leakage incidents is how the soil conditions affect gas migration behavior, making it difficult to estimate the gas distribution. To shed light on these concerns, an inc...

Methane (CH4) transport in soil is primarily affected by soil physical conditions such as soil-texture and soil-structure, soil-moisture, soil-gas diffusivity, permeability and soil-temperature. Aggregated soils have distinct soil structure with two pore regions characteristics (i.e., inter-aggregate and intra-aggregate regions) and therefore show...

Landfills are one of the major sources of atmospheric methane (CH4), which causes global warming. The microbial oxidation of methane in engineered covers is considered a potent option for the mitigation of methane emissions from landfills or sites containing wastes of low methane generation rates. Studies have shown that microbial oxidation of CH4...

Open dumps are complex ecosystems with respect to Greenhouse Gas (GHG) emission which occurs as a consequence of anaerobic decomposition of organic substances typically available in Municipal Solid Waste (MSW). Subsurface soil conditions (e.g. soil texture, structure) and atmospheric boundary conditions (e.g. wind, temperature) are the major key fa...

Grazed pastures rich in nitrogen (N) from ruminant urine and fertilizer inputs are significant sources of nitrous oxide (N2O), a highly potent greenhouse gas. Diffusion-controlled emission of N2O from pasture systems can be described by soil-gas diffusivity (Dp/Do), and its dependency on soil physical properties and soil moisture dynamics. But stud...

Open dumps constitute a major source of greenhouse gases (GHGs), predominantly methane and carbon dioxide, in developing countries. In an aged dump, typical waste composition is dominated by the “soil-like” fraction of which physical, hydraulic and gas transport characteristics markedly affect GHG emissions. This study characterized soil-gas diffus...

Grazed pasture constitutes a major source of agriculturally derived nitrous oxide (N2O), which is a potent greenhouse gas. Soil texture and structure, soil moisture, and soil‐gas diffusivity are considered to be major soil physical drivers controlling pastoral N2O emissions. Research gaps exist regarding their combined roles on N2O emissions dynami...

Grazed pastures and cultivated fields are significant sources of greenhouse gas (GHG) emissions, in particular N2O emissions derived from fertilizer deposition and animal excreta. Net surface emissions rely on subsurface gas transfer controlled mainly by diffusion, expressed as the soil-gas diffusivity (Dp/Do). The value of Dp/Do is a function of s...

Soil density plays a crucial role in controlling migration of greenhouse gases (GHG) from terrestrial soils to the atmosphere. Soil moisture is the fundamental soil physical control of gas migration and emission in subsurface soil. This study explored migration of methane gas developed from a simulated methane source buried in a differently – compa...

Aggregated porous media are widely used as plant growth substrates due to its inherent structural properties and their distinctive mass transport characteristics. Soil-gas diffusivity (Dp/Do; where Dp and Do are gas diffusion coefficients for a given gas in porous medium and free air, respectively) characterizes the ability of the media to facilita...

Aggregated porous media are widely used as plant growth substrates due to its inherent structural properties and their distinctive mass transport characteristics. Soil-gas diffusivity (Dp/Do; where Dp and Do are gas diffusion coefficients for a given gas in porous medium and free air, respectively) characterizes the ability of the media to facilita...

Grazed pasture constitutes a major source of agriculturally derived nitrous oxide (N2O), a potent greenhouse gas. Soil texture and structure, soil moisture, and soil-gas diffusivity are considered to be major soil physical drivers controlling pastoral N2O emissions. Research gaps, however, still exist with regard to their combined roles on N2O emis...

Grazed pasture has long been recognized as a dominant source of global nitrous oxide (N2O), a highly potent greenhouse gas. Among the main soil physical controls on N2O emissions, soil structure, moisture status, and soil-gas diffusivity play important and combined roles in controlling N2O emissions. A wide range of research has been conducted to i...

Density-induced soil structural changes may potentially alter both soil total porosity and soil pore size distribution, and thus change the soil’s water retention characteristics, gas diffusion and transport properties, and subsequent greenhouse emissions. In this study, we characterized and parameterized water retention, pore size distribution, ga...

Characterization of differently-textured porous materials, as well as different volumetric porous media mixtures, in relation to mass and heat transport is vital for many engineering and research applications. Functional relations describing physical properties (e.g., grain-size distribution, total porosity), thermal and gas diffusion properties of...

Mitigation of atmospheric emission of methane from leaky underground infrastructure is important for controlling the global anthropogenic greenhouse gas burden. Overexposure to methane may also cause occupational health problems in indoor/outdoor environments at the local scale. Subsurface soil conditions (e.g., soil heterogeneity) affect methane m...

Aims Poorly drained arctic ecosystems are potential large emitters of methane (CH4) due to their high soil organic carbon content and low oxygen availability. In wetlands, aerenchymatous plants transport CH4 from the soil to the atmosphere, but concurrently transport O2 to the rhizosphere, which may lead to oxidation of CH4. The importance of the l...

A major concern resulting from the increased use and production of natural gas has been how to mitigate fugitive greenhouse gas emissions (predominantly methane) from natural gas infrastructure (e.g., leaky shallow pipelines). Subsurface migration and atmospheric loading of methane from pipeline leakage is controlled by source configurations and su...

A soil's grain-size distribution affects its physical and hydraulic properties; however, little is known about its effect on soil thermal properties. To better understand how grain-size distribution affects soil thermal properties, specifically the effective thermal conductivity, a set of laboratory experiments was performed using binary mixtures o...

Detailed characterization of partially saturated porous media is important for understanding and predicting vadose zone transport processes. While basic properties (e.g., particle- and pore-size distributions and soil-water retention) are, in general, essential prerequisites for characterizing most porous media transport properties, key transport p...

The gas diffusion coefficient, air permeability, and their interrelations with air-filled porosity are essential for characterization of diffusive and convective transport of gases in soils. Variations in soil bulk density can affect water retention, air-filled pore space, and pore-network connectivity and tortuosity and, thereby, control gas diffu...

Characterization of soil functional pore structure is an essential prerequisite to understand key gas transport processes in variably-saturated soils in relation to soil ecosystems, climate, and environmental services. In this study, the Water-induced Linear Reduction (WLR) soil-gas diffusivity model (Soil Sci. Soc. Am. J. 64:1588–1594) originally...

Arctic terrestrial ecosystems are characterized by large deposits of near-surface soil organic carbon in poorly drained areas. Recent changes in Arctic regions such as warming and changes in water balance have adverse effects on the dynamics of near-surface oxygen, leading to a potential increase in oxidation of near-surface carbon and emission of...

Growing plants to facilitate life in outer space, for example on the International Space Station (ISS) or at planned deep-space human outposts on the Moon or Mars, has received much attention with regard to NASA‘s advanced life support system research. With the objective of in situ resource utilization to conserve energy and to limit transport cost...

An inspirational 75-yr anniversary paper in SSSAJ (Jury et al., 2012) looked at the future of soil physics platformed on the soil-water phase. The soil-air phase parameters and processes in combination with ongoing advances in porous media measurement and visualization technologies offer us additional keys to understand and quantify soil functional...

Soil structure is essential to all soil ecosystem functions and services. Activities that impact on structure has significant effects on soil functions. This study examines the mechanisms involved in restoration of structure in 2-mm sieved soils of varying clay mineralogy. Totally seven soils, six similarly-textured (5 illites and 1 kaolinite sandy...

Over the last decade there has been a significant shift in global agricultural practice. Because the rapid increase of human population poses unprecedented challenges to production of an adequate and economically feasible food supply for undernourished populations, soilless greenhouse production systems are regaining increased worldwide attention....

Growing plants in containerized substrates has long been common practice in horticulture. Containerized plants (e.g., greenhouse tomatoes) have restricted access to essential growth resources such as oxygen, water, and nutrients. Since a wide range of inorganic and organic materials, and different combinations thereof, are commonly used as growth m...

The soil-gas diffusion is a primary driver of transport, reactions, emissions, and uptake of vadose zone gases, including oxygen, greenhouse gases, fumigants, and spilled volatile organics. The soil-gas diffusion coefficient, D-p, depends not only on soil moisture content, texture, and compaction but also on the local-scale variability of these. Di...

Understanding soil–gas phase properties and processes is important for finding solutions to critical environmental problems such as greenhouse gas emissions and transport of gaseous-phase contaminants in soils. Soil–air permeability, ka (μm2), is the key parameter governing advective gas movement in soil and is controlled by soil physical character...

Growing plants in extraterrestrial environments, for example on a space station or in a future lunar or Martian outpost, is a challenge that has attracted increasing interest over the last few decades. Most of the essential plant needs for optimal growth (air, water, and nutrient supply, and mechanical support) are closely linked with the basic phy...

Soil-gas diff usivity (Dp/Do) and its dependency on soil matric potential (ψ) is important when taking regulati ve measures (based on accurate predictions) for climate gas emissions and also risk-mitigating measures (based on upper-limit predictions) of gaseous- phase contaminant emissions. Useful information on soil functional pore structure, e.g....

Accurate predictions of the soil-gas diffusivity (D-p/D-o' where D-p is the soil-gas diffusion coefficient and D-o is the diffusion coefficient in free air) from easily measureable parameters like air-filled porosity (epsilon) and soil total porosity (phi) are valuable when predicting soil aeration and the emission of greenhouse gases and gaseous-p...

Accurate prediction of gas diffusivity (D(p)/D(O)) and air permeability (k(a)) and their variations with air-filled porosity (epsilon) in soil is critical for simulating subsurface migration and emission of climate gases and organic vapors. Gas diffusivity and air permeability measurements from Danish soil profile data (total of 150 undisturbed soi...

Colloid-facilitated transport enhances migration of strongly sorbing compounds (e.g., radionuclides, phosphorus, heavy metals) in soil and groundwater. Mobilization, transport and deposition of soil colloids are the underlying processes governing colloid-facilitated contaminant transport. Although significant progress has been made in simulating mo...

The presence of fractured vadose zones (e.g., limestone or clay tills) may potentially pose significant environmental concerns due to the rapid, preferential migration of gaseous plumes through interconnected pore networks. However, recent modelling studies related to fractured vadose zone processes are mostly limited to hydrogeological (water and...

The fact that colloids facilitate transport of contaminants such as heavy metals, pesticides, radionuclides etc. through porous media has gained widespread acceptance in the last few decades. Colloid attachment and straining have been identified as key mechanisms on colloid retention/filtration in porous media. Much research attention was focused o...

Mobilization, transport and deposition of soil colloids are the fundamental processes governing colloid-facilitated transport of contaminants. Although significant progress has been made in understanding the processes involving mobilization and transport of colloids in porous media, the leaching of natural colloids from soil parent material is not...