| dc.description.abstract | Methane, as one of the greenhouse gases, plays an important role in global warming. Observational data from both global and Taiwan sources have shown a steady increase in methane concentration over the years, with more substantial growth rates in recent times. Currently, research on the characteristics of methane in Taiwan is relatively limited. Understanding the variations in emission sources in different fields can effectively guide emission reduction strategies and improve the pollution of methane.
To gain insight into Taiwan′s methane emission characteristics and pollution sources in different regions, we utilized data from EPA stations and NOAA’s background stations to explore the long-term trends and seasonal variations of methane in Taiwan. Additionally, we analyzed satellite data to assess the impact of East Asian source regions on methane concentration in Taiwan. Furthermore, using PAMS data, we examined air mass aging levels to identify potential characteristics of methane sources in different regions and used wind field data to determine the main directions of high-concentration events.
The results indicate that methane concentration in different regions of Taiwan has exhibited similar growth trends as background stations, with a significant increase observed in 2021. The seasonal variations in all regions follow a pattern of higher methane concentration in winter and spring, and lower in summer. The diurnal variations of methane worsen at midnight. The seasonal oscillations are more pronounced in March. Satellite data revealed a contribution of East Asian source regions to methane levels in Taiwan and its neighboring areas. The metropolitan area exhibited smaller diurnal variations due to differing contributions from traffic and natural gas. A better correlation between methane and VOCs in the metropolitan area suggests a higher consistency in their sources. The non-methane hydrocarbon (NMHC) ratios pointed out that high methane concentrations occur in aged air masses, indicating a greater influence of regional emissions on methane levels in the metropolitan area. In contrast, industrial areas exhibited a worse correlation with traffic emissions, showing more diverse pollution sources. The NMHC ratios suggested that high methane concentrations in industrial areas are derived from both local and regional emissions.
In summary, this study provides valuable insights into the characteristics of methane emissions in Taiwan and sheds light on the pollution sources in different regions. The findings contribute to the formulation of effective emission reduction strategies and the improvement of methane pollution. | en_US |