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Ben-Noah, I., Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, HaMaccabim Road 68, P.O. Box 15159, Rishon LeZion, 7505101, Israel, Department of Soil and Water Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 76100, Israel; 
Friedman, S.P., Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, HaMaccabim Road 68, P.O. Box 15159, Rishon LeZion, 7505101, Israel

The physical processes governing advective and diffusive gas movement and distribution in dry soils are, in general, well understood and quantified. In this study, we derived and applied analytical and numerical models to describe these processes under different conditions and scenarios and conducted gas flow experiments in 200-L barrels packed with dry quartz sand in a temperature-controlled laboratory. We used either pure N2 (0% O2) or atmospheric air (20.9% O2) injection or gas extraction from (or into) buried point sources (or sinks) to examine the effects of (a) source depth, (b) source discharge rate, and (c) injection cycle period on gas concentration and pressure distribution. We further quantified the contribution of diffusion from the atmospheric soil surface for the different scenarios, made possible by injecting N2 and tracking the complementary O2 concentration [i.e. the difference between atmospheric (20.9%) and the measured soil O2 concentration]. An analytical solution for steady air flow from a point source in a finite, cylindrical domain is presented. The main findings are that air injection, and air extraction, are efficient at aerating the soil volume above the buried gas source or sink. On the other hand, air injection increases the aeration's effectiveness, especially below the source. Shortening the cycle period of gas injection increases gas-use efficiency (i.e., increases the injected gas concentration) in most of the soil domain. The measurements were in good agreement with the results computed by the models’ analytical and numerical solutions.

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Forced and natural gas movement in dry sand – Barrel experiments and models

Ben-Noah, I., Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, HaMaccabim Road 68, P.O. Box 15159, Rishon LeZion, 7505101, Israel, Department of Soil and Water Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 76100, Israel; 
Friedman, S.P., Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, HaMaccabim Road 68, P.O. Box 15159, Rishon LeZion, 7505101, Israel

Forced and natural gas movement in dry sand – Barrel experiments and models

The physical processes governing advective and diffusive gas movement and distribution in dry soils are, in general, well understood and quantified. In this study, we derived and applied analytical and numerical models to describe these processes under different conditions and scenarios and conducted gas flow experiments in 200-L barrels packed with dry quartz sand in a temperature-controlled laboratory. We used either pure N2 (0% O2) or atmospheric air (20.9% O2) injection or gas extraction from (or into) buried point sources (or sinks) to examine the effects of (a) source depth, (b) source discharge rate, and (c) injection cycle period on gas concentration and pressure distribution. We further quantified the contribution of diffusion from the atmospheric soil surface for the different scenarios, made possible by injecting N2 and tracking the complementary O2 concentration [i.e. the difference between atmospheric (20.9%) and the measured soil O2 concentration]. An analytical solution for steady air flow from a point source in a finite, cylindrical domain is presented. The main findings are that air injection, and air extraction, are efficient at aerating the soil volume above the buried gas source or sink. On the other hand, air injection increases the aeration's effectiveness, especially below the source. Shortening the cycle period of gas injection increases gas-use efficiency (i.e., increases the injected gas concentration) in most of the soil domain. The measurements were in good agreement with the results computed by the models’ analytical and numerical solutions.

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