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Particle Growth and Variation of Cloud Condensation Nucleus Activity on Polluted Days with New Particle Formation: A Case Study for Regional Air Pollution in the PRD Region, China

Category: Aerosol and Atmospheric Chemistry

Volume: 16 | Issue: 2 | Pages: 323-335
DOI: 10.4209/aaqr.2015.06.0381
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Dingli Yue1, Liuju Zhong 1, Tao Zhang1, Jin Shen1, Luan Yuan1, Siqi Ye1, Yan Zhou1, Limin Zeng2

  • 1 Guangdong Environmental Monitoring Center, State Environmental Protection Key Laboratory of Regional Air Quality Monitoring, Guangzhou 510308, China
  • 2 College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China

Highlights

NPF events and their impact on CCN activity in the PPD region were investigated.
SO42–, NH4+ and organic matters were produced continuously during particle growth.
κ dominated by SO42–, NO3 and NH4+ was larger than that composed of more organics.
NCCN/EC with S ≥ 0.46% on NPF days was significantly higher than that on non-NPF day.


Abstract

New particle formation (NPF) events on polluted days at a regional supersite in the Pearl River Delta (PRD) region and its impact on the abundance and properties of cloud condensation nuclei (CCN) were investigated. Nucleation and subsequent significant growth of nanoparticles on a regional scale was observed and representative events on 2 and 6 October 2013 were chosen in this study. The measurements showed that the primary components of the particles were sulfate, ammonium, and organics as they were added continuously to secondary aerosol mass and that particles show inversion from growth to shrink if the particles comprise primarily of organics due to evaporation of semi-volatile species under favorable meteorological conditions. The effective hygroscopicity parameter κ of fine particles on 2 October composed of sulfate, nitrate and ammonium (κ = 0.26–0.42) was larger than that of fine particles on 6 October containing more organics (κ = 0.19–0.36). Particles in the nucleation mode were observed to grow rapidly to the CCN sizes and dominate the CCN number concentrations at a water vapor supersaturation (S) over 0.46%. At an S range of 0.26–0.86%, the CCN number concentrations reached maximum values of (1.3–2.6) × 104 cm–3 after the NPF event on 2 October. The sulfate component in the particles was found to increase significantly, about 50% higher than that before NPF. Results from events on 6 October showed a significant increase of the organic component and the CCN number concentrations after the NPF event were comparable or slightly lower than those before the event. Nevertheless, the average CCN number concentrations scaled with EC mass concentration with S over 0.46% in the daytime of 2 and 6 October were significantly higher than those on a non-NPF event day.

Keywords

New particle formation Secondary aerosol formation Particle growth Cloud condensation nucleus activity


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