Distribution and temporal behavior of particulate matter over the urban area of Buenos Aires

This paper contributes for the first time in Buenos Aires city to the temporal and horizontal distribution of the PM2.5 and PM10 concentrations. Their variations and relationships with relevant variables that characterize the air pollution potential of the urban air shed are also given. The measurements were carried out for one year from May 2006 to May 2007. During this period, particulate matter (PM) was continuously measured at one reference station and alternatively for shorter time periods at six different sites. The values and temporal variations on a daily and seasonal basis were consistent with the ventilation potential of the atmosphere. The cold season, which had the lowest values of the ventilation coefficient, indicated higher probabilities of poor air quality and this was confirmed by the higher concentrations of PM10 and PM2.5 measured. At the reference station, the daily EU limit value for PM10 was exceeded 36 times during one year while the Buenos Aires limit value was exceeded only once. The PM10 annual mean value was almost 70% of the Buenos Aires annual limit. The PM2.5 annual mean value (15 μg m-3) was same as the regulated one (15 μg m-3). The correlation between PM10 and PM2.5 concentrations and frequencies of wind directions showed that the highest concentrations were observed when the wind was from the city (land wind) and lowest concentrations when the wind was from Rio de La Plata (fluvial wind). The concentrations during land wind events exceeded the Buenos Aires PM2.5 annual limit value. The ratio of PM2.5 to PM10 was 0.44, which indicates the coarse particles (>2.5 μm) originated from road dust, soil re-suspension and abrasion processes are the dominated fractions of PM. Results of random PM measurements at 60 sites showed that PM2.5 was more homogeneously distributed over the city than PM10.