Monitoring of tropospheric ozone in the ambient air with passive samplers

Two sampling campaigns in suburban places in the north zone of Santa Clara city, Cuba, have been carried out on a weekly base with the use of Radiello passive diffusion tubes in order to monitor the tropospheric ozone (O-3) levels in 2010. The first campaign was scheduled from February to April (cold season) and the second one in August and October (warm season), both of them at two sampling sites, i.e., Farm and School of Art Instructors. After aqueous extraction, the samples were analyzed by UV-VIS spectrophotometry. A seasonal trend was observed with the maximum O-3 concentrations in the cold season and the minimum levels in the warm season. Samples collected during the cold season showed the highest O-3 levels. Higher levels were reached at the Farm site with average values of about 58 +/- 12 mu g/m(3), which exceeded the limit of the Cuban Standard 99:1999. In the warm season, the O-3 concentrations were similar for both sites, but lower than those observed in the cold season. The overall, seasonal average value was found to be 24 mu g/m(3). Despite the higher weekly average temperatures in August, the O-3 concentrations during this month showed the lowest values of the whole sampling period, which finding is in agreement with that reported by the Meteorological Institute of Cuba. Mathematical models, based on the Cochrane-Orcutt algorithm, were fitted to the acquired data set to explain the change in the tropospheric ozone concentrations under various meteorological conditions during the two campaigns. The correlation coefficients for both the cold and the warm seasons demonstrated a strong correlation, i.e., 0.779 and 0.951, respectively. The high correlation of wind speed in the model from the first sampling campaign explains the sharp decrease in O-3 concentrations at the SAI sampling site from the sixth week of sampling. (C) 2011 Elsevier B.V. All rights reserved.