A study on the atmospheric concentrations of primary and secondary air pollutants in the Athens basin performed by DOAS and DIAL measuring techniques

摘要

In this work an analysis of continuous Differential Optical Absorption Spectroscopy (DOAS) measurements of primary and secondary air pollutants (SO_2, NO_2 and O_3) in the Athens basin is performed combined with Dif ferential Absorption Lidar (DIAL) vertical ozone measurements obtained inside the Planetary Boundary Layer (PBL) and the lower free troposphere. The measurements took place during the period May 2005-February 2007, at the National Technical University of Athens Campus (200 m above sea level (asl.), 37.96°N, 23.78°E). The SO_2 and NO_2 DOAS measurements showed maximum 1-hour mean values (around 20 μg/m~3 and 74 μg/m~3, respectively) in winter and did not exceed the current European Union (EU) air quality stan dards (European Council Directive 2008/50/EC), in contrast to ozone, which shows its maximum (around 128 μg/m~3) in summer and frequently exceeds the EU standard for human health protection (120 μg/m~3). If the measurements are classified according to the two most frequent flow-patterns of the air masses in the Athens basin (northern-southern circulation), it is observed that in general the atmospheric concentra tions of all measured pollutants including ozone are higher when the southern circulation occurs, in compar ison to the corresponding values under the northern circulation. The vertical ozone profiles obtained by DIAL were also higher under the southern circulation. During the summer months a mean difference (between the southern-northern circulations) of the order of 15-20 μg/m~3, maximized at the 0.9-1.1 km and 1.7-1.8 km height, was observed within the PBL It was also observed that the summer surface ozone levels remained rel atively high (around 80-110 μg/m~3) even during strong northerly winds, verifying the high levels of rural surface ozone in the surrounding area reported by previous studies.