The Effect of Thermal Convection on Earth-Atmosphere CO2 Gas Exchange in Aggregated Soil

Y. Ganot, N. Weisbrod, M. I. Dragila

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Gas transport in soils and surface-atmosphere gas exchange are important processes that affect different aspects of soil science such as soil aeration, nutrient bio-availability, sorption kinetics, soil and groundwater pollution and soil remediation. Diffusion and convection are the two main mechanisms that affect gas transport, fate and emissions in the soils and in the upper vadose zone. In this work we studiedCO2 soil-atmosphere gas exchange under both day-time and night-time conditions, focusing on the impact of thermal convection(TCV) during the night. Experiments were performed in a climate-controlled laboratory. One meter long columns were packed with matrix of different grain size (sand, gravel and soil aggregates). Air with 2000 ppm CO2 was injected into the bottom of the columns and CO2 concentration within the columns was continuously monitored by an Infra Red Gas Analyzer. Two scenarios were compared for each soil: (1) isothermal conditions, representing day time conditions; and (2) thermal gradient conditions, i.e., atmosphere colder than the soil, representing night time conditions. Our results show that under isothermal conditions, diffusion is the major mechanism for surface-atmosphere gas exchange for all grain sizes; while under nighttime conditions the prevailing mechanism is dependent on the air permeability of the matrix: for sand and gravel it is diffusion, and for soil aggregates it is TCV. Calculated CO2 flux for the soil aggregates column shows that the TCV flux was three orders of magnitude higher than the diffusive flux.
Original languageAmerican English
Title of host publicationAmerican Geophysical Union, Fall Meeting 2011
StatePublished - 1 Dec 2011
EventAmerican Geophysical Union, Fall Meeting 2011 - San Francisco, United States
Duration: 5 Dec 20119 Dec 2011


ConferenceAmerican Geophysical Union, Fall Meeting 2011
Country/TerritoryUnited States
CitySan Francisco
Internet address


  • 0428 BIOGEOSCIENCES / Carbon cycling
  • 1843 HYDROLOGY / Land/atmosphere interactions
  • 1865 HYDROLOGY / Soils
  • 1875 HYDROLOGY / Vadose zone


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