The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Atmospheric deposition can provide abundant nutrients to the ocean, promote the growth of phytoplankton, and alter the community structure of phytoplankton, thereby enhancing the primary productivity and carbon storage capacity of the ocean. However, the impact of atmospheric deposition on marine ecosystems depends not only on its deposition flux but also on the settling velocity and residence time of atmospheric particles after entering the ocean. Here, we developed a hydrostatic sedimentation method using video imaging techniques to track particles of 5 - 20 μm in diameter falling into seawater and determine the particle settling velocities in relation to their diameter, shape, organic matter contained, and seawater salinity. The measured settling velocities ranged from 0.025 - 0.41 mm/s and were influenced by diameter and water salinity. Additionally, irregular particle shapes and organic matter in the particles also reduced settling velocity to some extent. It was also found that the dissolution process of particles in the water slowed down the settling velocity. Based on the experimental results, a formula for predicting the settling velocity of particles was proposed,which estimating settling velocity based on diameter, shape, and organic matter content is particularly well-suited for atmospheric particles. This result could serve studies on marine biogeochemical models.

atmospheric particles, settling velocity, organic matter, video imaging technique, predictive formula