Journal
ATMOSPHERIC ENVIRONMENT
Volume 164, Issue -, Pages 289-298Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.atmosenv.2017.06.001
Keywords
Long-term CCN study; Cloud condensation nuclei; New particle formation events; Urban aerosol
Funding
- Austrian Science Fund (FWF) [P19515-N20]
- Austrian Science Fund (FWF) [P19515] Funding Source: Austrian Science Fund (FWF)
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Many studies have indicated New Particle Formation (NPF) events as an important source of CCN in the atmosphere. However, most of these studies are based on indirect determination of CCN concentrations or were of rather short duration. In this study, we present long-term measurements of CCN concentrations and particle number size distributions performed in the urban background of Vienna, Austria, spanning a period of two years. NPF events occurred on 70 of the 539 measurement days. For 38 of these events, concurrent CCN concentrations (measured at 0.5% supersaturation) are available. Direct comparisons of absolute CCN concentrations before and after an event, however, are inconclusive as other influences can lead to changes in CCN concentrations. In this study, we developed criteria to take local emissions of ultrafine particles, atmospheric mixing conditions and changes in air mass into account. A new normalization procedure (CCN/PM2.5) is introduced to account for dilution and concentration effects due to changes in boundary layer height. Other possible influences, such as weather conditions and traffic emissions were accounted for by tracking wind direction and velocity, as well as black carbon (BC) mass concentrations. On 15 event days, all criteria to exclude other influences were met. On 14 days, NPF was found to be a source of CCN (at 0.5% supersaturation), with concentration increases by up to 143%. (C) 2017 Elsevier Ltd. All rights reserved.
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