| Abstract |
The particulate organic compounds, of the atmospheric aerosols, play an important role on human health, in atmospheric chemistry and climate. The substantial problems that are caused to the human respiratory tract by these organic particles, and their connection with many other diseases (cancer and mutations), make more visible their harmful effects. Furthermore the gas-particle distribution of the organic aerosols constituents is the factor that controls their "fate" in the environment, because the atmospheric reactions and the atmospheric processes (transport and deposition), are different for the two phases of the semi-volatile compounds. The subject of the present research is to study the organic composition of the particulate matter PM2,5, at urban sites. The specific aims of the study were (i) the accurate and correct (reliable) assessment of the concentrations of organic compounds PM2,5 (in particulate phase), (ii) the identification of the contribution of anthropogenic activities at the emissions of these organic particles in the environment (iii) the estimation of the artifact that presents at classical studies because of the volatilization losses of some organic compounds (from the particulate phase), which leads to a wrong assessment of the emission sources. The selection of the diameter of the particles that we studied (<2,5 μm), is based on the fact that recently epidemiological studies have shown a strong correlation between increased mortality rates (from ischemic heart disease, respiratory tract diseases) and PM2,5 concentration. Moreover the carcinogenic and mutagenic organic particles (PAH's, O-PAH's) have generally much smaller diameter than 2,5 μm. These data have direct the attention of the World Health Organism (WHO) and the Environmental Protection Agency (EPA) to the study of PM2,5 particles. The sampling areas were two cities in Chile (S.America): Santiago and Temuco. In these two cities the problem of atmospheric pollution have become substantial at the late years. This is associated with a growing economy, a very rapid increase of the population, intense industrial activities, an excessive increase of automobiles vehicles and mostly with the emissions of the sizable diesel powered bus fleet (12000 buses at Santiago) operating in these cities, and also their geographic location. In order to make an accurate assessment of the organic composition of the particulate matter and also a correct estimation of the sources, we have to minimize the sampling artifacts. Until now, all the classic studies that have been done, have remarkable sampling artifacts, which lead either to underestimation or to overestimation of the concentrations of particulate phase and furthermore to a wrong estimation of the emission sources. The sampler of the present study, consist of a diffusion denuder to remove gas phase organics prior to particle collection, a Teflon filter, and a PUF cartridge downstream of the filter. This sampler allow us to avoid the sampling artifact that leads to underestimation of the concentrations of some compounds in particulate phase (losses of the more volatile compounds due to the high pressure drop across the collecting filter) and also avoid the sampling artifact that leads to overestimation of the concentrations of some compounds in particulate phase. Furthermore reaction of organic compounds such us PAHs with ozone to form O-PAHs doesn't happen.
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Μελέτη της οργανικής σύστασης των σωματιδίων ΡΜ2,5 στην ατμόσφαιρα αστικών περιοχών της Χιλής (Ν. Αμερική)
