New Particle Formation Events in Coastal and Marine Atmosphere From the Marginal Seas of China to Northwest Pacific Ocean

In this study, particle number size distributions were investigated during seven cruises from the marginal seas of China to the northwest Pacific Ocean (NWPO). New particle formation (NPF) events occurred in 25 days during the total of 162 days with the occurrence frequency the highest in fall (28%), followed by spring (14%) and summer (7%). In the marginal seas of China, the calculated formation rates and growth rates were the highest during the summer cruise (10.5±9.3 particles cm-3 s-1 and 7.3±4.9 nm h-1), which about twice as that in spring and fall cruises (6.9±3.8 particles cm-3 s-1 and 4.2±2.2 nm h-1 in spring, 5.3±5.4 particles cm-3 s-1 and 3.5±2.1 nm h-1 in fall). In the atmosphere of NWPO, the formation rates and growth rates of new particle were even larger (e.g., 15.7±7.9 particles cm-3 s-1 and 7.5±9.3 nm h-1), indicating the efficient gas to particle condensation mechanism in the open ocean. The geometric median diameter of new particles can grow to 77 nm in one day during the summer cruise, but can't grow to larger than 55 nm in the remaining 24 NPF days, indicating the low possibility of marine new particles grow to the CCN sizes. Three NPF events were suspected to be driven by the ocean emitted precursors, with the high chlorophyll-a concentrations and elevated mass concentrations of particulate dimethylamine (DMA+) and trimethylamine (TMA+) in particles less than 100 nm. The remain 22 NPF events was influenced by the continental air mass, character with more sulfate and nitrate in nanoparticles. The parallel measurements were conducted in a coastal site during three cruises, in which NPF events occurred on 17 days out of 59 days. The formation rates were only one third of that in the marine atmosphere, but the growth rates were larger, implying the difference in low volatility and semi-volatile species in the marine and coastal atmosphere. Thirteen NPF events were confirmed to be regional occurred covering the two sampling sites with the horizontal scale at least 47 km-475 km. On two days, the sizes of new particles at about 10 nm for 3-5 hours without further growth in the two sampling site with the horizontal scale >240 km. The air mass sourced from the land and the chemical limited growing of new particles needs further study.