Chemical segregation by heterogeneous emissions

Ozone pollution in the boundary layer results from photoactivated chemistry of primary pollutants released at the ground. As emissions are highly inhomogeneous in space and time and some chemical time-scales are of the order or larger than dynamical time-scales, it is admitted that turbulent transport and mixing is a key factor in ozone production. We study the interaction between chemistry and convective boundary layer turbulent with a large eddy simulation model coupled to CHIMERE, a detailed chemical model, over a 10×10km domain. Our results show that when emissions are concentrated over a limited area, strong values of segregation between chemical species are obtained over the first two active hours during the morning, leading to significant impact in terms of pollutants concentration. After 3 h, for each heterogeneous emission case considered, segregation drops to a few percents for most compounds pairs, due to the strong convective mixing of the boundary layer.