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| Titel |
Secondary Organic Aerosol Formation from the Photooxidation of Naphthalene |
| VerfasserIn |
S. Zhou, Y. Chen, J. Wenger |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250019387
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| Zusammenfassung |
| Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous air pollutants that are released into
the atmosphere as a by-product of combustion processes. The gas-phase PAHs can be
chemically transformed via reaction with the hydroxyl radical to produce a range of oxidised
organic compounds and other pollutants such as ozone and secondary organic aerosol
(SOA). Epidemiological studies have established that exposure to this type of air
pollution is associated with damaging effects on the respiratory and cardiovascular
systems, and can lead to asthma, oxidative stress, health deterioration and even
death.
The major anthropogenic source of SOA in urban areas is believed to be aromatic
hydrocarbons, which are present in automobile fuels and are used as solvents. As a result,
research is currently being performed on the characterisation of SOA produced from aromatic
hydrocarbons such as toluene, the xylenes and trimethylbenzenes. However, significant
amounts of PAHs are also released into urban areas from automobile emissions and the
combustion of fossil fuels for home heating. Naphthalene is regularly cited as the most
abundant PAH in polluted urban air, with typical ambient air concentrations of 0.05 - 0.20
parts per billion (ppbV) in European cities, comparable to the xylenes. Since naphthalene
reacts in an analogous manner to monocyclic aromatic compounds then it is also expected to
make a significant contribution to ambient SOA. However, the yield and chemical
composition of SOA produced from the atmospheric degradation of naphthalene is not well
known.
In this presentation, the effects of NOx level and relative humidity on the SOA formation
from the phootooixdation of naphthalene will be presented. A series of experiments has
been performed in a large atmospheric simulation chamber equipped with a gas
chromatograph and analyzers for monitoring nitrogen oxides (NOx) and ozone. SOA
formation from the photooxidation of naphthalene was measured using a scanning
mobility particle sizer. The effect of NOx concentration on SOA formation was
evaluated by varying the initial naphthalene and NOx concentrations. The results
clearly show that a higher hydrocarbon to NOx ratio produces a higher yield of
SOA. The SOA mass yields were also found to increase as the relative humidity
was raised from 0 to 50%. A recently developed denuder-filter sampling technique
was used to investigate the gas/particle partitioning behavior of the photooxidation
products. This work is the first study of the formation of SOA from naphthalene and
the results will be compared to those obtained from other aromatic compounds. |
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