PM2,5 and PM2,5-10 samples were collected at São José dos Campos (São Paulo) from February 2004 to February 2005. During this time there were two periods of drought, one lasting for 25 consecutive days and a second one for 38 days. The later exhibited higher PM concentrations values than the first one. Data were divided into two groups, one comprising all measurements carried out during the 63 days without rain (dry period) and a second one comprising the remaining data (regular period). The PM2,5 and PM2,5-10 average concentrations were respectively 23 ± 7.5 and 19 ± 7.9 µg m-3 during dry period and 14 ± 7.9 and 13 ± 7.9 µg m-3 during regular period. There was a day-of-week variation with highest average concentrations on Wednesday (PM2.5) and Thursday (PM2.5-10) and lowest on Sunday. The PM2,5-10 exhibited the most pronounced variation suggesting an association with vehicular emissions. During both dry and regular periods, average SO4-2 and NH4+ concentrations were about 5 times higher in the fine than in the coarse fraction. PM2,5 ionic concentrations, especially that of K+, were higher in the dry period compared to regular one (except for Cl-, Na+ and Mg2+). Hierarchical cluster analysis and backward air mass trajectories indicate that during the dry period NO3-, SO4(2-), NH4+ and K+ associated with PM2.5 are significantly influenced by continental sources.
atmospheric particulate matter; inhalable particles; fine particulate matter; coarse particulate matter; long-range transport
