Exploratory data analysis of PAH, nitro-PAH and hydroxy-PAH concentrations in atmospheric PM10-bound aerosol particles. Correlations with physical and chemical factors

A method is proposed to determine PAHs, OH-PAHs and nitro-PAHs in samples of PM10 particulate matter based on liquid chromatography with fluorescence detection, and applied to quantify such compounds over a 14-month period in a semiurban area of a large city (Madrid, Spain). A clear seasonal trend was observed in the levels of the compounds. The mean overall concentration of all the PAHs determined was 1250 pg m−3; with levels rising in the colder months to 2062 pg m−3 and descending in the warm months to 725 pg m−3. The same effect was observed for the OH-PAHs, showing a mean of 83 pg m−3 and values of 153 pg m−3 and 36 pg m−3 in the colder and warmer months, and for the nitro-PAHs, with a mean of 132 pg m−3 and levels of 162 pg m−3 and of 112 pg m−3 in the colder and warmer months, respectively. These trends were confirmed in the statistical analysis, which clearly revealed the difference between PAH levels in the months April–September compared to October–December or January–March. Correlations were also found between PAH patterns and those of their hydroxy- and nitro derivatives, as well as between both derivatives. Negative correlation was observed between O3 and OH-PAH levels and direct correlation between the presence of nitrogen oxides in the atmosphere and nitro-PAHs in the particulate matter.