ABSTRACT
In this study, a chemical transport model (i.e., Community Multi-scale Air Quality (CMAQ) modeling system with brute-force method (BFM)) was used in combination with atmosphere-ocean coupling to evaluate the impact of natural emissions (e.g., marine dimethyl sulfide (DMS), sea salt aerosol (SSA), and biogenic compounds) on the air quality of South Korea in the spring of 2019 (May 1-31). Overall, the coupled simulation results exhibited good agreement with the observations for meteorological fields and air quality (fine particulate matter (PM2.5) and ozone (O3)) compared to those obtained using the non-coupled simulation. The coupling effect in the study area tended to be strong in the presence of relatively strong winds (≥4 m s-1). The mean contributions of natural marine (DMS and SSA) and biogenic emissions to total PM2.5 mass reached ~8.2 % over the marine area and ~ 9.1 % over the land area, respectively. On average, biogenic emissions contributed 8.6 %, 29.3 % (and 27.3 %) to the concentrations of O3, secondary organic aerosol (SOA) (and organic carbon (OC)), respectively, over the land area. Isoprene and monoterpene contributed 40 % and 20 %, respectively, to biogenic SOA production over the land area and biogenic SOA accounted for 1.7 % and 7.8 % of the total O3 and PM2.5, respectively. Secondary aerosol formation was enhanced by gas-to-particle conversion processes due to the coupling effect. Therefore, this modeling study confirmed the non-negligible impact of natural emissions on the air quality in the study area. In addition, the study area is likely to be associated with VOC-limited conditions because of significantly enhanced photochemical O3 production owing to biogenic emissions.
ABSTRACT
The impacts of natural dimethyl sulfide (DMS) and ship emissions on marine environments and particulate matter (PM) over the western and southern sea areas around South Korea were studied based on field campaigns from August-September 2017 and May-June 2018 using the Community Multi-scale Air Quality v5.3.2 modeling system. DMS oxidation enhanced the concentrations of both sulfur dioxide (SO2) and sulfate (SO42-) in PM2.5 by 6.2-6.4% and 2.9-3.6%, respectively, in the marine atmosphere during the study period, whereas it slightly decreased nitrate (NO3-) concentrations (by -1.3%), compared to the simulation without DMS oxidation chemistry. Furthermore, ship emissions increased the concentrations of SO42-, NO3-, and NH4+ by 4.5%, 23%, and 7.3%, respectively. Methane sulfonic acid concentration was 0.17 µg m-3, suggesting the importance of the addition channel in the DMS oxidation pathway. The model simulation indicated that ship emissions in the target area contributed dominantly to non-sea-salt SO42-, and the marine DMS emission source was non-negligible. The geographical distribution of PM toxicity (aerosol oxidative potential) was assessed in the marine atmosphere during the study period.
