Identification and Characteristics of Long-Range Transport of PM2.5 Measured in Three Cities (Beijing, Seoul and Nagasaki)

Abstract

PM2.5 was sampled in Beijing from November 2014 through April 2015, in Seoul from September 2013 through May 2015, and in Nagasaki from February 2014 to May 2015 during the GRL (Global Research Lab) monitoring campaigns. Chemical species of PM2.5 including 3 water-soluble ions (NO3-, SO42-, NH4+), Organic Carbon (OC), Elemental Carbon (EC), and other 17 elements were analyzed. High Concentration Events (HCEs) of PM2.5 were classified according to the National Ambient Air Quality Standards (NAAQS) of 24-h PM2.5 standard in three countries (China, South Korea and Japan) over the monitoring campaigns. From the Residence Time Analysis (RTA) results, the HCEs of PM2.5 in Beijing were observed for 52 days (out of total 111 sampling days) and 14 days were determined as Long-Range Transport (LRT) events. In Seoul, HCEs were observed for 92 days (out of total 279 sampling days) and LRT events occurred for 64 days. In Nagasaki, only 15 days (out of total 245 days) were determined as the HCEs and LRT events occurred for 13 days. PM2.5 average concentrations of Beijing, Seoul, and Nagasaki were found to be 118, 44, and 18 μg/m3 over the study period. In terms of characteristics of PM2.5 chemical species during each classified events, for LRT event, PM2.5 mass levels were found to be 151, 79, and 48 μg/m3 in Beijing, Seoul, and Nagasaki, whereas for the Local event, PM2.5 levels were 238, 65, 48 μg/m3 in Beijing, Seoul, and Nagasaki. Cluster analysis showed that sulfate was significantly increased when air parcels moved towards the coastline of China and the Yellow Sea. In case of LRT event and Local event in three cities (Beijing, Seoul and Nagasaki), the PSCF results showed the different potential sources regions contributing to the elevated PM2.5 concentrations at each sampling site.