TY - GEN

T1 - Effects of Soil Moisture on Simulated Methane Flow Under Varying Levels of Soil Compaction

AU - Lakshani, M. M.T.

AU - Deepagoda, T. K.K.C.

AU - Clough, T. J.

AU - Jayarathne, J. R.R.N.

AU - Thomas, S.

AU - Balaine, N.

AU - Elberling, B.

AU - Smits, K.

N1 - Publisher Copyright: © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

PY - 2023

Y1 - 2023

N2 - 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 compacted pasture soil. Simulations were carried out for dry and variably saturated soils. Steady-state methane flow was simulated as a density-dependent, multiphase flow considering a multicomponent mixture of CH4, water vapor and air, under different soil moisture conditions. We used measured soil–water characteristic (SWC) and gas diffusivity data at five density levels (1.1, 1.2, 1.3, 1.4, and 1.5 Mg m−3) to parameterize predictive models. Permeability was estimated using an existing SWC-based saturated hydraulic conductivity function. Results show a distinct effect of soil density on CH4 concentration profiles within the soil. Clear effects of soil moisture on CH4 transport could also be seen in differentially compacted soils. Relatively smaller CH4 concentrations were observed in dry soils where permeability, gas diffusivity, and air-filled porosity were higher. With increasing density, the profile-accumulated concentrations >0.3% increased up to 200 times under the dry condition. In moist soils, on the other hand, smaller air-filled porosity and higher moisture-controlled tortuosity resulted in reduced permeability and gas diffusivity, yielding high CH4 concentrations in the soil profile with only a maximum fivefold increase in the accumulated concentration with increasing density.

AB - 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 compacted pasture soil. Simulations were carried out for dry and variably saturated soils. Steady-state methane flow was simulated as a density-dependent, multiphase flow considering a multicomponent mixture of CH4, water vapor and air, under different soil moisture conditions. We used measured soil–water characteristic (SWC) and gas diffusivity data at five density levels (1.1, 1.2, 1.3, 1.4, and 1.5 Mg m−3) to parameterize predictive models. Permeability was estimated using an existing SWC-based saturated hydraulic conductivity function. Results show a distinct effect of soil density on CH4 concentration profiles within the soil. Clear effects of soil moisture on CH4 transport could also be seen in differentially compacted soils. Relatively smaller CH4 concentrations were observed in dry soils where permeability, gas diffusivity, and air-filled porosity were higher. With increasing density, the profile-accumulated concentrations >0.3% increased up to 200 times under the dry condition. In moist soils, on the other hand, smaller air-filled porosity and higher moisture-controlled tortuosity resulted in reduced permeability and gas diffusivity, yielding high CH4 concentrations in the soil profile with only a maximum fivefold increase in the accumulated concentration with increasing density.

KW - Methane transport

KW - Numerical modeling

KW - Soil compaction

KW - Soil moisture

KW - Soil–Gas diffusivity

U2 - 10.1007/978-981-19-2886-4_20

DO - 10.1007/978-981-19-2886-4_20

M3 - Article in proceedings

AN - SCOPUS:85140487099

SN - 9789811928857

T3 - Lecture Notes in Civil Engineering

SP - 271

EP - 282

BT - 12th International Conference on Structural Engineering and Construction Management - Proceedings of the ICSECM 2021

A2 - Dissanayake, Ranjith

A2 - Mendis, Priyan

A2 - Weerasekera, Kolita

A2 - De Silva, Sudhira

A2 - Fernando, Shiromal

A2 - Konthesingha, Chaminda

PB - Springer Nature Singapore

T2 - 12th International Conference on Structural Engineering and Construction Management, ICSECM 2021

Y2 - 18 December 2021 through 19 December 2021

ER -