Measurements and modelling of the ozone deposition velocity to concrete tiles, including the effect of diffusion

A range of models were fitted to the experimental time-dependent curves for the deposition velocity of O3 to concrete floor tile samples. The models included modified Langmuir isotherms assuming adsorption of O3 on the material surfaces and models assuming direct reaction on and diffusion of O3 into the material from the air. The best fit was obtained with a simple two-parameter model assuming direct reaction of O3 with adsorbed surface water and direct diffusion of O3 into the material from the air. However, models assuming an additional second-order reaction of O3 with an adsorbed surface species with a given start mass gave improved curve fit in the first 500 min. Applying the best model to experimental data obtained over the whole air humidity range resulted in markedly lower equilibrium deposition velocities than those measured after 48 h. The modelling gave a deposition velocity minimum in the 50–70% relative air humidity range in agreement with observations. The deposition velocity minimum could be explained with a reduced constant for the reaction of O3 with water or OH− ions on the surface.