Determination of the inter-annual and spatial characteristics of the contribution of long-range transport to SO2 levels in Seoul between 2001 and 2010 based on conditional potential source contribution function (CPSCF)

► We introduce a method to estimate the contribution of long range transport based on CPSCF. ► This method was applied to investigate temporal variations of SO2 mixing ratio in Seoul. ► The change in the annual SO2 mixing ratio due to long-range transport ranged from 8 to 21%. ► This change increased from 2007 to 2010 and was high in spring and winter than other seasons. ► The uncertainty ranged from 24 to 62% of the estimated changes.