NOx depolluting performance of photocatalytic materials in an urban area - Part II: Assessment through Computational Fluid Dynamics simulations

Abstract

Photocatalytic materials are proposed as a mitigation strategy of urban air pollution because of its deposition

feature. This study aims at evaluating their effect on NO2 concentrations in an urban environment under real

atmospheric conditions through Computational Fluid Dynamics (CFD) simulations. A comprehensive study is

performed to determine the potential of photocatalytic materials to remove NO2 at pedestrian level taking into

account the variability of wind speed, traffic emissions and the photoactive area in an urban environment. The

deposition velocity used to model the sink effect of a photoactive surface is derived from laboratory data and its

applicability to outdoor conditions is proved through microscale simulations. The CFD simulation performed to

assess the impact of a photocatalytic material on ambient pollutants in a real urban scenario is evaluated against

the measurements presented in Part I (Fernandez-Pampill ´ on ´ et al., 2020). Results show that the application of

photocatalytic materials in an urban environment yield a minimal reduction in NO2 concentrations below 1%

under the studied atmospheric conditions. In a hypothetical scenario, in which the photoactive area is extended

to an entire neighbourhood, small decrease of NO2 concentrations below 2% is obtained under the daytime

prevailing atmospheric conditions of the area of interest. Finally, the reduction of NO2 under several atmospheric

conditions results to be mainly dominated by wind flow and NOx emissions in the study street.