New particle formation in the marine atmosphere during seven cruise campaigns

Abstract

We measured the particle number concentration, size distribution, and new particle formation (NPF) events in the marine atmosphere during six cruise campaigns over the marginal seas of China in 2011-2016 and one campaign from the marginal seas to the Northwest Pacific Ocean (NWPO) in 2014. We observed relatively frequent NPF events in the atmosphere over the marginal seas of China, i.e., on 23 out of 126 observational days, with the highest frequency of occurrence in fall, followed by spring and summer. In total, 22 out of 23 NPF events were found to be associated with the long-range transport of continental pollutants based on 24 h air mass back trajectories and pre-existing particle number concentrations, which largely exceeded the clean marine background, leaving one much weaker NPF event that was likely induced by oceanic precursors alone, as supported by multiple independent pieces of evidence. Although the longrange transport signal of continental pollutants can be clearly observed in the remote marine atmosphere over the NWPO, NPF events were observed on only 2 out of 36 days. The nucleation-mode particles (<30 nm), however, accounted for as high as 35 % ± 13 % of the total particle number concentration during the NWPO cruise campaign, implying the existence of many undetected NPF events in the near-sea-level atmosphere or above.To better characterize NPF events, we introduce a term called the net maximum increase in the nucleation-mode particle number concentration (NMINP) and correlate it with the formation rate of new particles (FR). We find a moderately good linear correlation between NMINP and FR at FR ≤ 8 cm −3 s −1 , but no correlation exists at FR>8 cm −3 s −1 . The possible mechanisms are argued in terms of the roles of different vapor precursors. We also find that a ceiling exists for the growth of new particles from 10 nm to larger sizes in most NPF events. We thereby introduce a term called the maximum geometric median diameter of new particles (D pgmax ) and correlate it with the growth rate of new particles (GR). A moderately good linear correlation is also obtained between the D pgmax and GR, and only GR values larger than 7.9 nm h −1 can lead to new particles growing with a D pgmax beyond 50 nm based on the equation. By combining simultaneous measurements of the particle number size distributions and cloud condensation nuclei (CCN) at different super saturations (SS), we observed a clear increase in CCN when the D pg of new particles exceeded 50 nm at SS = 0.4 %. However, this case did not occur for SS = 0.2 %. Consistent with the results of previous studies in the continental atmosphere, our results imply that particles smaller than 50 nm are unlikely activated as CCN at SS = 0.4 % in the marine atmosphere. Moreover, κ decrease from 0.4 to 0.

Investigating three patterns of new particles growing to cloud condensation nuclei size in Beijing's urban atmosphere

“…The growth rate of newly formed particles is mainly determined by concentrations of condensable vapors such as sulfuric acid, organics in various volatilities, nitric acid and ammonia (Zhang et al, 2012;Ehn et al, 2014;Man et al, 2015;Lee et al, 20 2019). The Dpgmax are, however, determined by the total amount of vapors condensed on grown new particles, which may or may not have a positive correlation with the concentrations of these vapors (Zhu et al, 2019). When the values of Dpgmax are plotted against those of GR in Fig.…”

Variations in &lt;i&gt;N&lt;/i&gt;&lt;sub&gt;cn&lt;/sub&gt; and &lt;i&gt;N&lt;/i&gt;&lt;sub&gt;ccn&lt;/sub&gt; over marginal seas in China related to marine traffic emissions, new particle formation and aerosol aging

“…The CPC was used to report the N cn ranging from 4 nm (50 % efficiency) to 3000 nm (N cn ) in 2 s time resolution with an inlet flow of 1.5 L min −1 . The N cn was then used to calibrate the particle number size distributions simultaneously measured by the FMPS on the basis of the procedure proposed by Zimmerman et al (2015). Due to the severe oceanic conditions and humid weather conditions, the FMPS and CPC were out of service after DOY 118 and DOY 122, respectively.…”

Tracer-based investigation of organic aerosols in marine atmospheres from marginal seas of China to the northwest Pacific Ocean

“…The concentrations of SOAM tracers were almost one magnitude lower than those of SOAI tracers. Due to the unique contribution of terpene-derived SOA to nucleation and growth of newly formed particles in the atmospheres (Gordon et al, 2017;Zhu et al, 2019;Ehn et al, 2014), the SOAM may primarily cause indirect climate effects rather than direct effects of aerosols in the marine atmosphere. The difference in mean SOAM concentration between the SCS and NWPO narrowed to a factor of two, in contrast to the differences of approximately one order of magnitude in mean SOAI between the two types of atmospheres.…”