PM2.5-bound PAHs and hydroxy-PAHs in atmospheric aerosol samples: Correlations with season and with physical and chemical factors

Over a one-year period, the concentrations of ten polycyclic aromatic hydrocarbons (PAHs) and two of their hydroxy derivatives (OH-PAHs) were monitored in a suburb of Madrid (Spain). The levels of other chemical indicators of urban pollution (nitrogen oxides, sulphur oxides, etc.), as well as a series of meteorological variables (temperature, atmospheric pressure, etc.) were determined simultaneously. PAH concentrations varied according to the environmental conditions such that depending on the wind direction and speed, levels exceeded those expected for outside the central city area. Concentrations of 2-hydroxyphenanthrene ranged from 12 to 200 pg m−3 and those of 1-hydroxypyrene from 3 to 60 pg m−3. Their variations were directly related to levels of phenanthrene and pyrene and also found to depend on the weather conditions, especially temperature and atmospheric pressure. Through multivariate analysis (factor and cluster analyses) a clear link was detected between the concentrations of PAHs or hydroxy-PAHs and those of other chemical pollutants (nitrogen and sulphur oxides). We also observed an inverse relationship with temperature, ozone concentration, solar radiation and UV radiation intensity. Changes in both PAHs and OH-PAHs were clearly seasonal, increasing in the colder months and undergoing a reduction in the warmer months of the year.