No abstract

Ozone, NO 2 , SO 2 , CO, PM 10 and meteorological parameters were measured simultaneously during the summer-autumn season 2007 in Osijek-the eastern, flat, agricultural part of Croatia. Fourier analysis confirms the existence of variation in ozone volume fractions with periods ranging from the usual semi-daily and daily to 7 and 28 daily cycles. The relationships between O 3 and other variables were modelled in three ways: principal component analysis, multiple linear regression and principal component regression. The results of the principal component analysis detected underlying relationships among ozone concentrations and meteorological variables. An extremely simple meteorological model is suitable for the prediction of ozone levels. The meteorological factors, temperature and cloudiness played a main role in the MLR model (R 2 =0.83). The application of the principal component regression approach confirmed that the original variables associated with the valid principal components were meteorological variables (R 2 =0.82).

Indicators were devised to classify air pollution monitoring sites according to the type of expected photochemical pollution. The indicators are based on measured ozone volume fractions, the most frequently monitored component of photochemical pollution, and in particular on two contributions: one due to the ratio of daily maximum-to-minimum ozone volume fractions and the other to observed peak values. The two contributions regarded as independent are logically connected by "and" and therefore mathematically combined by multiplication. The criterion of classification is mainly described by the mentioned ratio and incidences of ozone volume fractions exceeding the limit of 80 ppb. Twelve monitoring stations within the European network (Cooperative programme for monitoring and evaluation of long-range transmission of air pollutants in Europe, EMEP) were classified according to this indicator predicting what ozone levels can be expected at the particular sites during the growth season (April through September) into three groups: clean, medium, and polluted, based on the data for the 7 years (1997 to 2003).

The purpose of this study was to investigate the ozone, carbon monoxide, and nitrogen dioxide variations and their correlation with meteorological parameters in Osijek (Eastern Croatia) during the summer seasons of 2002, 2007, and 2012. The measured data are discussed in relation to the EU guidelines (Directive 2002/3/EC, Directive 2008/50/EC). In order to characterize ambient air with respect to ozone photochemical pollution we calculated three photochemical pollution indicators. These indicators may also be a valid measure for harmful effects on living organisms. The influence of local meteorological parameters on the measured concentrations of ozone, carbon monoxide, and nitrogen dioxide was also investigated. We have attempted to establish correlations between measured pollutant concentrations and meteorological parameters using the technique of multivariate principal component analysis (PCA).

Ozone (O3) is a secondary gaseous pollutant in the urban environment, and its variation correlates well with nitrogen oxides (NOx = NO + NO2). Continuous monitoring has been done in the Campo Grande city urban area, using ozone 49C and NO-NO2-NOx 42CTL gas analyzers. The results show that the maximum concentrations of O3 and oxidant (Ox = O3 + NO2) in Campo Grande often appear in the early afternoon around 15:00 hours. The daily variation of NO concentrations shows a very clear cycle with two peaks, one appearing around 07:00 a.m. and the other at 11:00 p.m. At the lowest level, NO2 is the main component of NOx, while NO dominates the higher mixing ratio. It is also shown that the level of Ox is composed of two factors: the regional and the local contributions. The former is affected by the regional O3 level, while the latter is effectively correlated with the primary pollution level. The daily variation also appears in the concentrations of oxidant components.