Urban atmospheric particle size distribution in Santiago, Chile

A monitoring campaign of the atmospheric particulate matter (PM) size distribution (between 0.25 and 10 mu m in diameter (Dp)) in an urban area with high levels of air pollution between June 2018 and May, 2019 is presented. The relative contribution of 24 size fractions to the total number and mass concentration of PM was analyzed using an aerosol spectrometer. Local meteorological parameters and their effect on the PM concentrations were also evaluated. The size-fractionated particle mass concentrations showed the accumulation (Dp < 1 mu m) and coarse (1 mu m < Dp < 10 mu m) modes. The highest contribution of the accumulation mode was observed during autumn and winter (reaching 99.7 % and 35.2 % of the total number and mass concentrations, respectively). High relative humidity and low temperatures were strongly correlated with high concentrations for the smaller PM fractions, which can be connected to the increase of residential emissions of PM derived from wood burning sources in winter months. The larger PM fractions showed higher concentrations during the spring and summer months, potentially because of dust resuspension due to the high vehicular traffic in the vicinity. High PM concentrations of the larger fractions were favored by the lack of precipitation events and stronger winds during this time of the year. The results showed the importance of the PM1 fraction to improve the source apportionment studies in urban areas and provide information about the potential health effects associated to high PM concentration events.

Automated summary

The monitoring campaign analyzed the size distribution of atmospheric particulate matter in an urban area with high air pollution levels, showing accumulation and coarse modes. The higher concentrations of smaller particles during autumn and winter can be attributed to residential wood burning emissions, while larger particle concentrations in spring and summer may be due to dust resuspension from vehicular traffic. The results emphasize the importance of PM1 fraction in urban source apportionment studies and understanding the health impacts of high PM concentrations.