We investigate the influence of near‐surface wind conditions on subsurface gas transport and on soil‐atmosphere gas exchange for gases of different density. Results of a sand tank experiment are supported by a numerical investigation with a fully coupled porous medium‐free flow model, which accounts for wind turbulence. The experiment consists of a two‐dimensional bench‐scale soil tank containing homogeneous sand and an overlying wind tunnel. A point source was installed at the bottom of the tank. Gas concentrations were measured at multiple horizontal and vertical locations. Tested conditions include four wind velocities (0.2/1.0/2.0/2.7 m/s), three different gases (helium: light, nitrogen: neutral, and carbon dioxide: heavy), and two transport cases (1: steady‐state gas supply from the point source; 2: transport under decreasing concentration gradient, subsequent to termination of gas supply). The model was used to assess flow patterns and gas fluxes across the soil surface. Results demonstrate that flow and transport in the vicinity of the surface are strongly coupled to the overlying wind field. An increase in wind velocity accelerates soil‐atmosphere gas exchange. This is due to the effect of the wind profile on soil surface concentrations and due to wind‐induced advection, which causes subsurface horizontal transport. The presence of gases with pronounced density difference to air adds additional complexity to the transport through the wind‐affected soil layers. Wind impact differs between tested gases. Observed transport is multidimensional and shows that heavy as well as light gases cannot be treated as inert tracers, which applies to many gases in environmental studies.

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气体穿过土壤-大气界面传输不同密度的气体：实验和建模

我们研究了近地表风条件对地下气体传输以及不同密度气体对土壤-大气气体交换的影响。沙箱实验的结果得到了数值研究的支持，该研究采用了完全耦合的无介质多孔流模型，该模型考虑了风的湍流。该实验由一个二维的台式土壤罐组成，该罐中装有均匀的沙子和一个覆盖的风洞。点源安装在水箱底部。在多个水平和垂直位置测量气体浓度。测试条件包括四种风速（0.2 / 1.0 / 2.0 / 2.7 m / s），三种不同的气体（氦气：轻，氮：中性，二氧化碳：重）和两种运输情况（1：稳态供气）从点源； 2：终止供气后，在浓度梯度减小的情况下进行运输）。该模型用于评估土壤表面的流动模式和气体通量。结果表明，地表附近的流动和输运与上覆风场密切相关。风速的增加加速了土壤与大气之间的气体交换。这是由于风廓线对土壤表面浓度的影响以及由于风引起的对流，这导致地下水平运输。气体与空气之间存在明显的密度差，这会增加通过风影响的土壤层的运输的复杂性。测试气体之间的风影响有所不同。观察到的运输是多维的，表明重气体和轻气体均不能视为惰性示踪剂，