Diurnal and day-to-day characteristics of ambient particle mass size distributions from HR-ToF-AMS measurements at an urban site and a suburban site in Hong Kong
Mass-concentration-based particle size distributions measured by a high-resolution aerosol mass spectrometer were systematically analyzed to assess long and short-term temporal characteristics of ambient particle size distributions sampled at a typical urban environment close to emission sources...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/13605/2017/acp-17-13605-2017.pdf |
| Summary: | Mass-concentration-based particle size distributions measured by a
high-resolution aerosol mass spectrometer were systematically analyzed to
assess long and short-term temporal characteristics of ambient particle size
distributions sampled at a typical urban environment close to emission
sources and a suburban coastal site representing a regional and local
pollution receptor location in Hong Kong. Measured distributions were
bimodal and deconvoluted into submodes, which were analyzed for day-to-day
variations and diurnal variations.<br><br>
Traffic and cooking emissions at the urban site contributed substantially to
particle mass in both modes, while notable decreases in mass median diameters
were limited to the morning rush hour. Inorganic particle components
displayed varying diurnal behavior, including nocturnal nitrate formation and
daytime photochemical formation evident in both modes. Suburban particle size
distributions exhibited notable seasonal disparities with differing influence
of local formation, particularly in spring and summer, and transport which
dominated in the fall season leading to notably higher sulfate and organic
accumulation-mode particle concentrations. Variations in particle mixing
state were evaluated by comparison of interspecies mass median diameter
trends at both measurement sites. Internal mixing was prevalent in the
accumulation mode in spring at the urban site, while greater frequency of
time periods with external mixing of particle populations comprising
different fractions of organic constituents was observed in summer. At the
suburban site, sulfate and nitrate in the accumulation mode more frequently
exhibited differing particle size distributions in all seasons, signifying a
greater extent of external mixing.<br><br>
At the urban site, periods of greater submicron inorganic mass concentrations
were more likely to be caused by increases in both Aitken- and accumulation-mode particle mass in summer, while at the suburban receptor location, organic
and nitrate Aitken-mode particle mass contributed more regularly to higher
total submicron species mass concentrations in most seasons (spring, summer,
and winter). |
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| ISSN: | 1680-7316 1680-7324 |