Comparison of New Prticle Formation in Marine and Coastal Atmosphere under Outflow of City Clusters in North China

Abstract:

Simultaneous measurements of new particle formation (NPF) events were conducted during two cruises over China Seas and at a coastal site. NPF events occurred in thirteen days out of 38 sampling days over China Seas, and the NPF events in eleven days were confirmed to be regional occurred with the spatial scale at least 47 km-475 km. The formation rates of new particles were 5.3±5.0 particles cm^-3s^-1 in marine NPF events while 2.4±1.2 particles cm^-3s^-1 in coastal NPF events. The reason for the lower formation rates in coastal atmosphere might be the higher number concentration of pre-existing particles and larger condensation sinks. However, the growth rates of new particles in marine NPF events (3.3±2.2 nm h^-1) were lower than in coastal NPF events (4.3±2.2 nm h^-1), which might be caused by more precursors for new particles growth in the coastal city. In the marine atmosphere, new particles can grow from nucleation mode (<30 nm) to Aitken mode (30-100 nm) in seven days. However, the largest geometric median diameter of new particles (D_pg) was 50 nm in two days with the low number concentration, indicating the negligible contribution of marine new particles to CCN production. In the coastal atmosphere, new particles can grow to about 100 nm in two days, but the second-stage growth of new particles seemed to be generated from mixing process with pre-existing particles rather than gas-particle condensation. The measurement of particular chemical composition during the marine NPF days showed the important role of organic acids in new particles.