Dust aerosols transported across continents and oceans undergo complex atmospheric processing, including mixing with anthropogenic pollutants and atmospheric aging, which can substantially modify their chemical composition. However, how these transformations influence the health risks associated with dust over populated regions and the capacity of dust to supply bioavailable nutrients to marine ecosystems remains poorly understood. In this study, we investigated the environmental consequences of two strong Asian dust events in March 2021 through integrated observations at an inland urban site in Beijing and a coastal marine site on Tuoji Island in the Bohai Sea. By combining multi-platform atmospheric observations, chemical composition measurements, oxidative potential (OP) assays, and iron solubility analyses, we characterized the evolution of dust properties during long-range transport and evaluated their implications for terrestrial and marine environments.
The results showed that dust substantially increased atmospheric particulate matter concentrations in Beijing, while atmospheric aging modified the toxicity of dust particles. During the return-flow period of Dust-1, PM_2.5 mass concentration decreased by 79% compared with the initial dust arrival, whereas mass-normalized oxidative potential (OP_m) increased by a factor of 5.3. This enhancement was mainly attributed to the mixing of mineral dust with anthropogenic aerosols, which contributed 34% of PM_2.5 during the return-flow period. The mixing with anthropogenic pollutants also clearly enhanced iron solubility during the Dust-1 return-flow period. In contrast, during the land-to-ocean transport of Dust-2, atmospheric processing promoted iron mobilization. The formation of secondary acidic species, particularly oxalic acid, enhanced iron dissolution, resulting in a 173% increase in iron solubility at Tuoji Island compared with Beijing. Satellite, lidar, and biogeochemical Argo float observations further revealed that transported dust events can influence regional atmospheric composition and marine ecosystem responses.
This study demonstrates that long-range transport does not simply redistribute dust aerosols but can modify their chemical properties, leading to enhanced oxidative toxicity over urban areas while increasing the bioavailability of iron to marine ecosystems. These findings highlight the dual roles of atmospheric dust aging in affecting human health risks and ocean biogeochemical processes.

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