Aerial observation of atmospheric nanoparticles on Fukue Island, Japan

Abstract

New particle formation (NPF) in the East Asian region is strongly influenced by photochemical processes during the long-range transport of air pollutants. Our previous measurements (Seto et al., 2013; Chandra et al., 2016) relating to the incomplete and weak NPF (onset diameter > 10 nm) on Fukue Island in Japan (downstream from the Asian continent) suggested nucleation in the upstream region. The vertical structure of atmospheric nanoparticle concentrations (particle size > 6 nm and altitude < 1.2 km) during NPF was observed using a Kite-Plane at Fukue Island. Three different event types were identified through aerial observations (different vertical profiles of nanoparticles), ground-based measurements (the initial detected diameter of nanoparticles, NPF starting time, and dominant chemical component in PM1), and air mass backward trajectory analysis. A stronger NPF event (Event I: > 35,000 particles cm–3) than in our previous measurements (from 2012 to 2016, ~20,000 particles cm–3) with a particle size as small as 5 nm, affected by the long-range transport of air pollutants under a high-pressure system, was detected. A sudden increase in particle number and SO2 concentrations with weak NPF caused by a change in the air mass origin (Event II: < 10,000 particles cm–3) as well as no NPF with aged sulfate particles during conditions with low particle number and SO2 concentrations (< 0.15 ppb) (Event III: < 2,000 particles cm–3) were also observed.