Enrichment of submicron sea-salt-containing particles in small cloud droplets based on single-particle mass spectrometry

• Main Authors: Q. Lin, Y. Yang, Y. Fu, G. Zhang, F. Jiang, L. Peng, X. Lian, F. Liu, X. Bi, L. Li, D. Chen, M. Li, J. Ou, M. Tang, X. Wang, P. Peng, G. Sheng
• Format: Article
• Language: English
• Published: Copernicus Publications 2019-08-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://www.atmos-chem-phys.net/19/10469/2019/acp-19-10469-2019.pdf

<p>The effects of the chemical composition and size of sea-salt-containing particles on their cloud condensation nuclei (CCN) activity are incompletely understood. We used a ground-based counterflow virtual impactor (GCVI) coupled with a single-particle aerosol mass spectrometer (SPAMS) to characterize chemical composition of submicron (dry diameter of 0.2–1.0&thinsp;<span class="inline-formula">µm</span>) and supermicron (1.0–2.0&thinsp;<span class="inline-formula">µm</span>) sea-salt-containing cloud residues (dried cloud droplets) at Mount Nanling, southern China. Seven cut sizes (7.5–14&thinsp;<span class="inline-formula">µm</span>) of cloud droplets were set in the GCVI system. The highest number fraction of sea-salt-containing particles was observed at the cut size of 7.5&thinsp;<span class="inline-formula">µm</span> (26&thinsp;%, by number), followed by 14&thinsp;<span class="inline-formula">µm</span> (17&thinsp;%) and the other cut sizes (3&thinsp;%–5&thinsp;%). The submicron sea-salt-containing cloud residues contributed approximately 20&thinsp;% (by number) at the cut size of 7.5&thinsp;<span class="inline-formula">µm</span>, which was significantly higher than the percentages at the cut sizes of 8–14&thinsp;<span class="inline-formula">µm</span> (below 2&thinsp;%). This difference was likely involved in the change in the chemical composition. At the cut size of 7.5&thinsp;<span class="inline-formula">µm</span>, nitrate was internally mixed with over 90&thinsp;% of the submicron sea-salt-containing cloud residues, which was higher than sulfate (20&thinsp;%), ammonium (below 1&thinsp;%), amines (6&thinsp;%), hydrocarbon organic species (2&thinsp;%), and organic acids (4&thinsp;%). However, at the cut sizes of 8–14&thinsp;<span class="inline-formula">µm</span>, nitrate, sulfate, ammonium, amines, hydrocarbon organic species, and organic acids were internally mixed with &gt;&thinsp;90&thinsp;%, &gt;&thinsp;80&thinsp;%, 39&thinsp;%–84&thinsp;%, 71&thinsp;%–86&thinsp;%, 52&thinsp;%–90&thinsp;%, and 32&thinsp;%–77&thinsp;% of the submicron sea-salt-containing cloud residues. The proportion of sea-salt-containing particles in the supermicron cloud residues generally increased as a function of cut size, and their CCN activity was less influenced by chemical composition. This study provided a significant contribution towards a comprehensive understanding of sea-salt CCN activity.</p>