4:45 PM - 5:00 PM
[AAS11-29] Individual particle analysis of aerosols from biomass burning over Asia and their mixing with sea salt
Keywords:aerosol, biomass burning, sea salt, observation
Forest and agricultural fires (i.e., biomass burning, BB) emit large amounts of aerosols in the form of smoke. This BB-derived aerosol degrades the environment and air pollution near the source. Its long-range transport affects air quality, weather, and climate on regional and global scales. On the other hand, if we focus on the composition of these BB aerosol particles, their physicochemical properties changes as they are transported over long distances from the source, through reactions with gaseous components and mixing with other aerosols. Such changes in the chemical composition of individual particles are important for estimating the effects of BB aerosols on health, climate, and meteorology. In this study, aerosol samples obtained mainly from observations in Asia (aircraft observations around Japan and ground and aircraft observations in Thailand) were analyzed by transmission electron microscopy (TEM), focusing on the components of BB to analyze at the individual particle scale. In addition, we found that these components mix with sea salt components by long-range transport.
Aerosol samples from three campaigns were used for this presentation: 1) ground-based observations in Thailand (Nakhon Pathom) in February 2029 (Adachi et al., 2025), 2) aircraft observations at the south coast of Hokkaido in July and August 2022 (A-force 2022 campaign, Adachi et al., in preparation), and 3) aircraft observations in Thailand in March 2024 (ASIA-AQ campaign) (Adachi, to be presented at the aircraft session in JpGU 2025). Compositional analysis of these samples was performed using TEM, focusing on potassium (K), a tracer of BB components, and sodium (Na), a tracer of sea spray components.
TEM analysis revealed that the number fraction of K-bearing particles increased in samples with strong BB influence. The K-bearing particles existed mainly as potassium sulfate salts and were commonly internally mixed with organic matter or sea salt particles. The K-bearing particles frequently mixed with Na, especially in the air masses over and through the ocean, and existed as K-Na-bearing particles, i.e., mixing of BB and sea spray components in individual particles. Both components are important sources of naturally occurring aerosols, suggesting that mixing of both also affects physicochemical properties such as their cloud condensation nuclei properties, optical properties, and viscosity. For example, sulfates containing Na and K in arbitrary proportions have different hygroscopic properties and viscosities depending on their ratios (Adachi et al., 2025). Therefore, their mixing may also affect the reproducibility of aerosol physicochemical properties in model calculations.
Adachi, K., Sun, C., Onchang, R., & Takegawa, N. (2025). Homogeneous mixing of sea spray and biomass burning tracer elements within single particles observed over Southeast Asia. Journal of Geophysical Research: Atmospheres, 130, e2024JD042328. https://doi.org/10.1029/2024JD042328
Aerosol samples from three campaigns were used for this presentation: 1) ground-based observations in Thailand (Nakhon Pathom) in February 2029 (Adachi et al., 2025), 2) aircraft observations at the south coast of Hokkaido in July and August 2022 (A-force 2022 campaign, Adachi et al., in preparation), and 3) aircraft observations in Thailand in March 2024 (ASIA-AQ campaign) (Adachi, to be presented at the aircraft session in JpGU 2025). Compositional analysis of these samples was performed using TEM, focusing on potassium (K), a tracer of BB components, and sodium (Na), a tracer of sea spray components.
TEM analysis revealed that the number fraction of K-bearing particles increased in samples with strong BB influence. The K-bearing particles existed mainly as potassium sulfate salts and were commonly internally mixed with organic matter or sea salt particles. The K-bearing particles frequently mixed with Na, especially in the air masses over and through the ocean, and existed as K-Na-bearing particles, i.e., mixing of BB and sea spray components in individual particles. Both components are important sources of naturally occurring aerosols, suggesting that mixing of both also affects physicochemical properties such as their cloud condensation nuclei properties, optical properties, and viscosity. For example, sulfates containing Na and K in arbitrary proportions have different hygroscopic properties and viscosities depending on their ratios (Adachi et al., 2025). Therefore, their mixing may also affect the reproducibility of aerosol physicochemical properties in model calculations.
Adachi, K., Sun, C., Onchang, R., & Takegawa, N. (2025). Homogeneous mixing of sea spray and biomass burning tracer elements within single particles observed over Southeast Asia. Journal of Geophysical Research: Atmospheres, 130, e2024JD042328. https://doi.org/10.1029/2024JD042328