Integrated Monitoring of Atmospheric Pollutants using Laser Photoacoustic Spectroscopy and Numerical Modeling

Pollution in cities is a critical problem generated by heavy traffic and industrial emissions. The primary pollutants from the environment, such as Volatile Organic Compounds (VOCs) in the presence of nitrogen oxides (NOx) and sunlight, contribute significantly to tropospheric ozone formation as a secondary pollutant. In this study, the concentrations of VOCs, such as ethylene, benzene, and toluene as primary polutants and ozone as a secondary pollutant, were measured using laser photoacoustic spectroscopy in an urban area in Southern Romania. Thus, the concentration values for ethylene were between 3.85 ppb and 195 ppb, from 0.227 ppb and 1.555 ppb for benzene, from 1.21 ppb and 12.46 ppb for toluene, and from 10.5 ppb to 108 ppb for ozone. The temporal variations of these pollutants, including their diurnal cycles, and wind speed and direction on pollutant concentration, were analysed. At the same time, a numerical model developed in COMSOL Multiphysics was used to simulate the dispersion and transport of pollutants within the urban geometry, using experimental data for validation. Through the results presented in this study, the photoacoustic spectroscopy system once again shows that it has high sensitivity with pollutant concentrations in the ppb range, and the numerical simulation offers valuable spatial distribution information of the factors influencing pollutant accumulation in the urban canyons.