Measurement of surface ozone and its precursors in an urban area in South Brazil

Weekly and seasonal variations of surface ozone and their precursors - nitrogen oxides, carbon monoxide-associated with meteorological parameters (wind direction, temperature, solar radiation) are reported. Measurements were performed continuously during 2006 at two sampling stations located in the metropolitan area of Porto Alegre, Brazil. Results have shown that O-3 concentrations remained almost constant between weekdays. Levels of NOx precursors decreased especially on Sundays, due to lighter traffic. The seasonal variation has shown a maximum O-3 concentration during summer and spring while NOx and NO2 have maxima at the colder months. The daily cycle of highest ozone concentrations reveals a lower nightly level and an inverse relation between O-3 and NOx, evidencing the photochemical formation of O-3. There are seasonal variation and source heterogeneity. (C) 2009 Elsevier Ltd. All rights reserved.