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Effects of “soil‐like” particle size on gas transport and water retention properties in aged municipal solid waste from a Sri Lankan open dumpsite
Author(s) -
Shanujah M.,
Deepagoda T. K. K. Chamindu,
Karunarathna A. K.,
Nasvi M. C. M.,
Shreedharan V.,
Babu G. L. S.,
Smits Kathleen M.,
Oldenburg Curtis M.
Publication year - 2020
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.1002/saj2.20100
Subject(s) - methane , particle size , landfill gas , soil gas , soil water , environmental science , saturation (graph theory) , soil science , greenhouse gas , environmental engineering , chemistry , geology , oceanography , mathematics , organic chemistry , combinatorics
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 diffusivity ( D p / D 0 ), soil‐water characteristics (SWC), and particle size distribution in “soil‐like” fractions of aged solid waste retrieved at 2.5–5 m depth from an old open dumpsite situated at Kurunegala, Sri Lanka. The “soil‐like” fraction was proportioned into three groups based on particle size (0–4.75, 4.75–9.5, and 9.5–25 mm) to investigate the particle size effect on D p / D 0 and SWC. The simulated methane concentration profiles in different size groups were also examined using the transport simulator TOUGH2‐EOS7CA based on the multiphase flow of multicomponent gas mixture (methane, water vapour and air) under dry and half‐saturation conditions across a predefined temperature gradient. The results highlighted distinct two‐region characteristics (i.e., inter‐aggregate and intra‐aggregate pore regions) in all three size fractions which could be adequately parameterized with existing and modified bimodal functions. We proposed a useful practical tool for estimating D p / D 0 for known mean particle size and volumetric water content in the absence of direct measurements. The results further revealed that D p / D 0 is particle‐size dependent; however, D p / D 0 remained invariant across all size fractions at the volumetric water content of ∼0.22–0.25 cm 3 cm −3 . Numerical results further showed a pronounced effect of particle size and soil moisture on gas transport properties.