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

This study aimed to identify the factors causing NH₃ emissions in the South Korean Peninsula and West Sea region. To analyze the trends of NH₃ and other air pollutants, such as NO_x, CO, and NR-PM₁, 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 NH₃ concentrations were found at rural areas, ascribed to agricultural activities, particularly NH₄NO₃ decomposition at high summer temperatures. Areas with low population densities recorded the lowest NH₃ concentrations, attributed to the lack of anthropogenic activities. A roadside field experiment confirmed the close link between ambient NH₃ and vehicle emissions in urban regions by showing a strong correlation between CO and NO_x concentrations and that of NH₃. 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 (NH₃, CO, and PM₁) were transported by wind from the northeastern region of China. A maritime origin study showed that oceanic emissions and NH₄NO₃ decomposition in the atmosphere owing to high temperatures were the causing NH₃ pollution. These findings provided valuable insights into the emission sources of NH₃ 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.