Review on airflow in unsaturated zones induced by natural forcings

Abstract

[1] Subsurface airflow in unsaturated zones induced by natural forcings is of importance in many environmental and engineering fields, such as environmental remediation, water infiltration and groundwater recharge, coastal soil aeration, mine and tunnel ventilation, and gas exchange between soil and atmosphere. This review synthesizes the published literature on subsurface airflow driven by natural forcings such as atmospheric pressure fluctuations, topographic effect, water table fluctuations, and water infiltration. The present state of knowledge concerning the mechanisms, analytical and numerical models, and environmental and engineering applications related to the naturally occurring airflow is discussed. Airflow induced by atmospheric pressure fluctuations is studied the most because of the applications to environmental remediation and transport of trace gases from soil to atmosphere, which are very important in understanding biogeochemical cycling and global change. Airflow induced by infiltration is also an extensively investigated topic because of its implications in rainfall infiltration and groundwater recharge. Airflow induced by water table fluctuations is important in coastal areas because it plays an important role in coastal environmental remediation and ecological systems. Airflow induced by topographic effect is studied the least. However, it has important applications in unsaturated zone gas transport and natural ventilation of mines and tunnels. Finally, the similarities and differences in the characteristics of the air pressure and airflow are compared and future research efforts are recommended.Citation: Kuang, X., J. J. Jiao, and H. Li (2013), Review on airflow in unsaturated zones induced by natural forcings, Water Resour.

Effects of vadose zone on groundwater table fluctuations in unconfined aquifers

“…This dynamic behavior significantly affects water and nutrient exchange between the land and ocean. The fluctuating groundwater table also alters the eco-environmental condition of coastal aquifers, including the moisture content in the overlying vadose zone (Kuang et al, 2013;Xin et al, 2013b).…”

Influence of the air phase on water flow in dikes

“…Consequently, most of the available software for modeling unsaturated zone flow is based on the Richards equation, which does not account for the air flow. However, there is an increasing evidence that in some situations air flow must be taken into account: heterogeneous soils [1][2][3], rapid downward infiltration [4], water table fluctuations [5], seismic events [6] or overtopping of dikes [7][8][9][10]. In such cases the two phase flow model should be taken into account.…”

Temporal variations in air permeability and soil CO2 flux in volcanic ash soils (island of Vulcano, Italy)

“…The strong dependence of the soil CO 2 flux to atmospheric pressure is probably due to a sort of pumping effect: the fast decrease in atmospheric pressure produces an increase in the soil CO 2 pressure gradient, which results in an increase in CO 2 flux. This effect is known in the literature as barometric pumping [e.g., Auer et al ., ; Perrier and Richon , ; De Gregorio et al ., ; Kuang et al ., ]. Likewise, at the Camping site but also at the p3 site, the soil permeability has a slight influence on the soil CO 2 flux, despite the fact that it is moderately correlated with the VWC (Table ).…”