Observation of aerosol size distribution and new particle formation under different air masses arriving at the northwesternmost South Korean island in the Yellow Sea

Abstract

Particle number size distribution (PNSD) was measured with scanning mobility particle sizers from January 2014 to December 2016 at the Baengnyeong-do Comprehensive Monitoring Observatory, located on a rural island between China and the Korean Peninsula. Five different typical air mass transport pathway types were identified using the fuzzy c-means clustering method. Aerosols from the Shandong Province (Type 3) and South Korea (Seoul Metropolitan Area; Type 4) generally showed larger modal diameters than those transported from Mongolia and West Manchuria through the free troposphere (Type 1), which is attributable to the coagulation and condensational growth of preexisting particles. New particle formation (NPF) events, identified from the first mode of cyclostationary empirical orthogonal function analysis of the PNSD were observed in 42.2% (strong NPF [16.9%], weak NPF [25.3%]) of the days included in this study. Strong NPF events were frequently observed from October to March under the influence of pristine free tropospheric air masses transported along the Type 1 pathway, which can be characterized as NPF supported by meteorological conditions and a small condensation sink (3.77 × 10−3 s−1) under a limited precursor gas supply (i.e., SO2). Some occasional strong NPF events occurred under the influence of Type 3 air masses, primarily in spring (April to May), with a relatively high particle growth rate (6.95 nm h−1) and condensation sink (6.74 × 10−3 s−1), attributed to the relatively high preexisting particle concentration and abundant gaseous precursors.