Man-made structures influence on ozone behavior revealed by LIDAR

The distribution of pollutants in the atmosphere is key to the validation of dispersion models. While dispersion models tend to assume that air masses are homogeneous, experimental measurements of pollutants using a LIDAR show a different picture. Air masses are very complex and the concentrations of pollutants are influenced by multiple factors. In this paper we present the influence of anthropogenic structures, i.e. a intersection with heavy traffic and a small village, on the ozone concentrations in the atmosphere in their areas of influence. The data were collected using a LIDAR DIAL in the UV region (λon= 280nm, λoff=286nm). The selected wavelengths correspond to the same absorption value on the SO2 curve to avoid interferences. Measurements were conducted in two dimensions in order to determine pollutant concentrations on certain planes in the atmosphere. The area under study was about 3,2 106 m2 in a circular sector, ranging from -70 to 70 degrees in vertical angle, in 10 degrees steps, and 1,500 meters of radio. The resulting plane is perpendicular to the ground. The results show that over the two man-made structures the concentration of ozone is lower than in the rest of the area under study. The heavy traffic intersection is located 750 meters east of the LIDAR location, and the village is 750 meters to the west. The LIDAR location was not established before hand with the purpose of exploring the influence of the two man-made structures on the distribution of pollutants in the atmosphere, and we only realized their significance upon analysis of the results. Different sets of data have been compared, focusing in particular on the measurements during the night and in rush hours to better discern the influence of human activity on the distribution of air pollutants.