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

Qinhao Lin, Yuxiang Yang, Yuzhen Fu, Guohua Zhang, Feng Jiang, Long Peng, Xiufeng Lian, Fengxian Liu, Xinhui Bi, Lei Li, Duohong Chen, Mei Li (+5 others)
2019 Atmospheric Chemistry and Physics  
<p><strong>Abstract.</strong> 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&amp;thinsp;<span class="inline-formula">µm</span>) and supermicron (1.0–2.0&amp;thinsp;<span
more » ... an class="inline-formula">µm</span>) sea-salt-containing cloud residues (dried cloud droplets) at Mount Nanling, southern China. Seven cut sizes (7.5–14&amp;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&amp;thinsp;<span class="inline-formula">µm</span> (26&amp;thinsp;%, by number), followed by 14&amp;thinsp;<span class="inline-formula">µm</span> (17&amp;thinsp;%) and the other cut sizes (3&amp;thinsp;%–5&amp;thinsp;%). The submicron sea-salt-containing cloud residues contributed approximately 20&amp;thinsp;% (by number) at the cut size of 7.5&amp;thinsp;<span class="inline-formula">µm</span>, which was significantly higher than the percentages at the cut sizes of 8–14&amp;thinsp;<span class="inline-formula">µm</span> (below 2&amp;thinsp;%). This difference was likely involved in the change in the chemical composition. At the cut size of 7.5&amp;thinsp;<span class="inline-formula">µm</span>, nitrate was internally mixed with over 90&amp;thinsp;% of the submicron sea-salt-containing cloud residues, which was higher than sulfate (20&amp;thinsp;%), ammonium (below 1&amp;thinsp;%), amines (6&amp;thinsp;%), hydrocarbon organic species (2&amp;thinsp;%), and organic acids (4&amp;thinsp;%). However, at the cut sizes of 8–14&amp;thinsp;<span class="inline-formula">µm</span>, nitrate, sulfate, ammonium, amines, hydrocarbon organic species, and organic acids were internally mixed with &amp;gt;&amp;thinsp;90&amp;thinsp;%, &amp;gt;&amp;thinsp;80&amp;thinsp;%, 39&amp;thinsp;%–84&amp;thinsp;%, 71&amp;thinsp;%–86&amp;thinsp;%, 52&amp;thinsp;%–90&amp;thinsp;%, and 32&amp;thinsp;%–77&amp;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>
doi:10.5194/acp-19-10469-2019 fatcat:l5pe7xq4ofaidoktn4dpnpqmh4