Seasonal and regional variations of atmospheric ammonia across the South Korean Peninsula

This study aimed to identify the factors causing NH 3 emissions in the South Korean Peninsula and West Sea region. To analyze the trends of NH 3 and other air pollutants, such as NO x , CO, and NR-PM 1 , we collected samples from six supersites across the peninsula, a roadside in Seoul, and the West Sea over different sampling periods, ranging from 1 month to 1 year. The highest NH 3 concentrations were found at rural areas, ascribed to agricultural activities, particularly NH 4 NO 3 decomposition at high summer temperatures. Areas with low population densities recorded the lowest NH 3 concentrations, attributed to the lack of anthropogenic activities. A roadside field experiment confirmed the close link between ambient NH 3 and vehicle emissions in urban regions by showing a strong correlation between CO and NO x concentrations and that of NH 3 . Moreover, we examined oceanic emissions near the eastern coast of South Korea in the West Sea. Long-range transportation studies confirmed that most of the pollutants (NH 3 , CO, and PM 1 ) were transported by wind from the northeastern region of China. A maritime origin study showed that oceanic emissions and NH 4 NO 3 decomposition in the atmosphere owing to high temperatures were the causing NH 3 pollution. These findings provided valuable insights into the emission sources of NH 3 in primary air pollutants in South Korea, highlighting the contributions of land-based and oceanic sources. Our study can help inform policymakers and stakeholders for developing effective regional air pollution control strategies.