• Capillary Bundle Model for the Estimation of Air-water Interfacial Area and the Gas-filled Pore Size Distribution in Unsaturated Soil
  • Heonki Kim*

  • Dept. of Environmental Sciences and Biotechnology, Institute of Energy and Environment, Hallym University, Gangwon-Do, Chuncheon 24252, Korea

  • 모세관 모델을 이용한 불포화토양의 물-가스 접촉면적 및 가스공극 크기분포의 계산 및 검증
  • 김 헌 기*

  • 한림대학교 환경생명공학과, 한림대학교 에너지∙환경 연구소

  • This article is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.


Air-water interfacial area is of great importance for the analysis of contaminant mass transfer processes occurring in the soil systems. Capillary bundle model has been proposed to estimate the specific air-water interfacial areas in unsaturated soils. In this study, the measured air-water interfacial areas of a soil (loam) using the gaseous interfacial tracer technique were compared to those from capillary bundle model. The measured values converged to the specific solid surface area (7.6×104 cm2/cm3) of the soil. However, the simulated air-water interfacial areas based on the capillary bundle model deviated significantly from those measured. The simulated values were substantially over-estimated at low end of the water content range, whereas the model under-estimated the air-water interfacial area for the most of the water content range. This under-estimation is considered to be caused by the nature of the capillary bundle model that replaces the soil pores with a bundle of glass capillaries and thus no surface roughness at the inner surface of the capillaries is taken into account for the estimation of the air-water interfacial area with the capillary bundle model. Subsequently, appropriate correction is necessary for the capillary bundle model to estimate the air-water interfacial area in soils. Since the soil-moisture release curve data is the basis of the capillary bundle model, the model can be of use due to its simplicity, while the gaseous tracer technique requires complicated experimental equipment followed by moment analysis of the breakthrough curves. The size distribution profile of the pores filled with gas estimated by the water retention curve was found to be similar to that of particle size at different size range. The shifted distribution of gas-filled pores toward smaller size side compared to the particle size distribution was also found.

Keywords: Air water interfacial area, Unsaturated soil, Brooks and Corey model, Capillary bundle model, Interfacial tracer

This Article

  • 2021; 26(1): 1-7

    Published on Feb 28, 2021

  • 10.7857/JSGE.2021.26.1.001
  • Received on Oct 5, 2020
  • Revised on Oct 23, 2020
  • Accepted on Nov 5, 2020

Correspondence to

  • Heonki Kim
  • Dept. of Environmental Sciences and Biotechnology, Institute of Energy and Environment, Hallym University, Gangwon-Do, Chuncheon 24252, Korea

  • E-mail: heonki@hallym.ac.kr