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| Titel |
Particulate matter (PM) formation during summertime in the Po valley: mechanisms and source apportionment |
| VerfasserIn |
Federico Karagulian, Lorenza Emblico, Friedrich Lagler, Maurizio Barbiere, Richard Connolly, Claudio Belis |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057561
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| Zusammenfassung |
| In order to study the influence of photochemistry on PM levels in the Po Valley, diurnal trends
in the mass concentration, size distribution and chemical composition of PM2.5 were
measured during a field campaign in a suburban area near Milan (Limito di Pioltello).
Samples were collected in summer on a 4-hour time resolution. The inorganic fraction of
PM2.5 was dominated by NH4+ followed by NO3- and SO42-. NH4+ was the compound
to be better correlated with PM2.5 suggesting that the reaction of NH3 with H2SO4, and
HNO3 was responsible for the formation of SO42-, and NO3-. A photochemical episode
characterized by high nighttime PM2.5 concentrations was followed by high NOX and high
relative humidity. This could be responsible of the overall formation of sulfate. The
photochemical episode was also characterized by nighttime formation of VOCs followed
by daytime formation of carbonylic compounds. PM2.5 was correlated with the
lower end of the measured particle size range (0.25-0.58μm) suggesting a clear
accumulation of secondary ammonium nitrate and sulfate on the boundary layer of the
site.
Positive matrix factorization (EPA PMF 3.0) was used to retrieve the main factors
responsible for PM2.5 formation. Additional retrievals were carried out by using an
implemented version of the EPA PMF 3.0 program known as Multilienar-Engine (ME-2).
Results showed that primary emissions were associated with elemental carbon (EC) and to
the less volatile fraction of organic carbon, whereas secondary emissions were
associated with secondary inorganic aerosols (SIA) mainly formed by SO42-,
NO3-, and NH4+. EPA PMF 3.0 and ME-2 identified the same major sources
responsible for the PM2.5 in Limito di Pioltello. The three main sources were: traffic,
secondary nitrate and secondary sulfate with re-suspended soil. Comparison between the
two methods showed slightly differences. However, from ME-2 results we can see
the three factors were more distinguishable than from EPF PMF 3.0 results. The
traffic factor was better retrieved by ME-2 run, whereas the secondary nitrate and
sulfate factors showed less contamination from re-suspended soil and traffic factor,
respectively. |
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