Soil ozone deposition: Dependence of soil resistance to soil texture

Soil deposition is an essential pathway for tropospheric ozone (O3) removal, but its controlling factors remain unclear. Here, we explored the variability of soil O3 resistance in response to soil texture. To this aim, data of O3 deposition over bare soil obtained from micrometeorological measurements under contrasted meteorological conditions for five sites were used. The results obtained are twofold: (i) soil resistance (Rsoil) increased with soil surface relative humidity (RHsurf), but (ii) this relationship exhibited large site-by-site variability. Further analysis showed that the minimum soil resistance (corresponding to completely dry soil surface or RHsurf = 0%) and the increase of Rsoil with RHsurf are both linked to soil clay content. These results can be explained by (i) the soil surface available for O3 deposition at a microscopic scale which is a function of the soil specific surface area, and (ii) the capacity of a soil to adsorb water according to its clay content and therefore to reduce the surface active for O3 deposition. From these results, a new parameterization has been established to estimate Rsoil as a function of RHsurf and soil clay fraction.