Publication Date:
2014-10-24
Description:
Particle size distributions in the range of 1.34–615.3 nm were recorded from 25 November 2013 to 25 January 2014 in urban Shanghai, using a combination of one nano Condensation Nucleus Counter system (nCNC), one nano-Scanning Mobility Particle Sizer (SMPS), and one long-SMPS. Measurements of sulfur dioxide by an SO2 analyzer with pulsed UV fluorescence technique allowed calculation of sulfuric acid proxy. In addition, concentrations of ammonia were recorded with a Differential Optical Absorption Spectroscopy (DOAS). During this 62-day campaign, 13 NPF events were identified with strong burst of sub-3 nm particles and subsequent fast growth of newly formed particles. The observed nucleation rate (J1.34), formation rate of 3 nm particles (J3), and condensation sink (CS) were 112.4–271.0 cm−3 s−1, 2.3–19.2 cm−3 s−1, and 0.030–0.10 s−1, respectively. Subsequent cluster/nanoparticle growth showed a clear size dependence, with average values of GR1.35~1.39 (from the bin of 1.34–1.37 nm to the bin of 1.37–1.41 nm), GR1.39~1.46 (from 1.37–1.41 to 1.41–1.52 nm), GR1.46~1.70 (from 1.41–1.52 to 1.52–1.89 nm), GR1.70~2.39 (from 1.52–1.89 to 1.89–3.0 nm), GR2.39~7 (from 1.89–3.0 to 7 nm), and GR7~20 (from 7 to 20 nm) being 1.6 ± 1.0, 1.4 ± 2.2, 7.2 ± 7.1, 9.0 ± 11.4, 10.9 ± 9.8, and 11.4 ± 9.7 nm h−1, respectively. Correlation between nucleation rate (J1.34) and sulfuric acid proxy indicates that nucleation rate J1.34 was proportional to a 0.64 power of sulfuric acid proxy. Correlation between nucleation rate (J1.34) and gas-phase ammonia suggests that ammonia was associated with NPF events. The calculated sulfuric acid proxy was sufficient to explain the subsequent growth of 1.34–3 nm particles, but insufficient for particles exceeding this size range. Qualitatively, NPF events in urban Shanghai likely occur on days with low levels of PM2.5.
Electronic ISSN:
1680-7375
Topics:
Geosciences
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