PM 2.5 Simulations for the Seoul Metropolitan Area: ( I ) Contributions of Precursor Emissions in the 2013 CAPSS Emissions Inventory

Abstract

CMAQ (Community Multiscale Air Quality Model) simulations were carried out to estimate the potential range of contributions on surface PM 2.5 concentrations over the Seoul Metropolitan Area (SMA) with the gaseous precursors and Primary Particulate Matters (PPM) available from a recent national emissions inventory. In detail, on top of a base simulation utilizing the 2013 Clean Air Policy Supporting System (CAPSS) emission inventory, a set of Brute Force Method (BFM) simulations after reducing anthropogenic NO x, SO₂, NH₃, VOCs, and PPM emissions released from area, mobile, and point sources in SMA by 50% were performed in turn. Modeling results show that zero-out contributions (ZOC) of NH₃ and PPM emissions from SMA are as high as 4~5 μg/m 3 over the region during the modeling period. On the contrary, ZOC of local NO x and SO₂ emissions to SMA PM 2.5 are less than 1 μg/m 3. Moreover, model analyses indicate that a wintertime NOx reduction at least up to 50% increases SMA PM 2.5 concentrations, probably due to increased HNO₃ formation and conversion to aerosols under more abundant ozone and radical conditions after the NO x reduction. However, a nation-wide NO x reduction decreased SMA PM 2.5 concentrations even during winter, which implies that nation-wide reductions would be more effective to curtail SMA PM 2.5 concentrations than localized efforts.