Soil ozone deposition: Dependence of soil resistance to soil texture

Soil deposition is an essential pathway for tropospheric ozone (O-3) removal, but its controlling factors remain unclear. Here, we explored the variability of soil O-3 resistance in response to soil texture. To this aim, data of O-3 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 (R-soll) 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 thy soil surface or RHsurf = 0%) and the increase of R-soll with RHsurf are both linked to soil clay content. These results can be explained by (i) the soil surface available for O-3 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 O-3 deposition. From these results, a new parameterization has been established to estimate R-soll as a function of RHsurf and soil clay fraction.