Impact of NH3 Emissions on Particulate Matter Pollution in South Korea: A Case Study of the Seoul Metropolitan Area

We analyzed the multi-year relationship between particulate matter (PM10 and PM2.5) concentrations and possible precursors including NO2, SO2, and NH3 based on local observations over the Seoul Metropolitan Area (SMA) from 2015 to 2017. Surface NH3 concentrations were obtained from Cross-track Infrared Sounder (CrIS) retrievals, while other pollutants were observed at 142 ground sites. We found that NH3 had the highest correlation with PM2.5 (R = 0.51) compared to other precursors such as NO2 and SO2 (R of 0.16 and 0.14, respectively). The correlations indicate that NH3 emissions are likely a limiting factor in controlling PM2.5 over the SMA in a high-NOx environment. This implies that the current Korean policy urgently requires tools for controlling local NH3 emissions from the livestock industry (for example, from hog manure). These findings provide the first satellite-based trace gas evidence that implementing an NH3 control strategy could play a key role in improving air quality in the SMA.