This study investigated the dry deposition fluxes of particulate inorganic nitrogen in PM_2.5 at four islands in East Asia, including Penghu, Dongsha, Okinawa, and Green Islands. Consecutive seven-day 24-h PM_2.5 per season were initially sampled in four seasons. The nitrate (NO₃^-) and ammonium (NH₄⁺) in PM_2.5 were further analyzed to estimate pNH₄⁺-N and pNO₃⁻-N in PM_2.5. The dry deposition fluxes of particulate nitrogen at the islands in East Asia ranged from 0.140-0.674 mg N m⁻² day⁻¹. Seasonally, the highest deposition fluxes of particulate nitrogen were observed in winter, and followed by fall and spring, while the lowest fluxes were found in summer. In winter, strong northeastern monsoons and high atmospheric stability both elevated PM_2.5 concentrations, secondary inorganic species, and particulate nitrogen deposition fluxes. In summer, clean marine air, better air dispersion, and rain washout reduced particulate nitrogen deposition fluxes to the lowest level. Spatially, Penghu Island had higher dry deposition fluxes of particulate nitrogen than those at other three islands. The highest seasonal particulate nitrogen flux of 0.674 mg N m⁻² day⁻¹ was observed at Penghu Island in winter, showing that the western channel was strongly influenced by long-range transport (LRT) via channel effect in the Taiwan Strait. Dongsha Island showed the second highest fluxes of 0.444 mg N m⁻² day⁻¹ in fall and 0.500 mg N m⁻² day⁻¹ in winter, respectively. It suggested that Dongsha Islands were affected by Asian continental outflow, regional transport over the South China Sea, and ship emissions. The winter nitrogen deposition flux at Green Island increased up to 0.507 mg N m⁻² day⁻¹, showing that the eastern channel was affected by LRT during the strong northeastern monsoon periods, even though it was influenced by clean marine air. In contrast, Okinawa Island had lower fluxes with particulate nitrogen deposition fluxes of 0.172-0.338 mg N m⁻² day⁻¹, suggesting lower input from anthropogenic sources. In terms of nitrogen species, dry deposition flux of pNO₃⁻-N was higher than pNH₄⁺-N at most islands and in most seasons. Overall, the dry deposition of particulate inorganic nitrogen at four islands showed similar spatiotemporal variation trend. The western channel, especially Penghu Island, is a high-flux area of particulate nitrogen dry deposition. It showed that the Taiwan Strait is an important pathway for LRT during the northeastern monsoon seasons. The results provided valuable scientifical information for understanding particulate nitrogen input, biogeochemical cycles, and nutrient loading to marine ecosystems in East Asia, showing the strong influences of LRT on atmospheric deposition of particulate nitrogen over islands and nearby seas.
 

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