Fifteen-year trends in carbon species and PM2.5 in Seoul, South Korea (2003–2017)

This study focused on particulate matter (PM2.5) and carbon species in Seoul, South Korea, to quantitatively evaluate their long-term trends and assess the main correlating factors. Ambient PM2.5 samples were collected over a 24 h period every third or sixth day from March 2003 to December 2017. The mean concentrations of PM2.5, organic carbon (OC), elemental carbon (EC), primary and secondary OC (POC and SOC) in Seoul over 15 years were 32.2 μg/m3 and 7.28 μg/m3, 1.85 μg/m3, 4.29 μg/m3 and 3.54 μg/m3 respectively. The long-term concentration trends in PM2.5, OC, EC, POC, and SOC decreased significantly at rates of −2.09, −3.13, −6.31, −2.86, and −3.88 per year, respectively from 2003 to 2017 (p