Atmospheric deposition as a pathway for microplastic transport to the marine environment: Temporal variation and...

Although understanding microplastic transport from terrestrial to marine environments presents a significant challenge, studies on their temporal variation in atmospheric deposition are lacking. This study investigated an intra-annual variation in the amount and characteristics of atmospheric microplastic deposition in an urbanized coastal bay, Masan Bay, and estimated its annual input load to the bay. Additionally, we explored the relationships between atmospheric deposition and various environmental factors. The average deposition rate of microplastic was 75.4 ± 29.2 n/m²/day, with an estimated annual input of 1.94 trillion particles into the bay. The deposition rate showed a significant negative correlation with temperature, reflecting seasonal variations. The microplastic deposition rate increased in spring and winter due to winds blowing from inland areas, while it decreased in summer under the influence of winds blowing from the oceanic regions. The deposition rate was significantly positively correlated with fine particulate matter (PM_2.5), which is predominantly associated with anthropogenic emissions in urban areas. This study highlights that a significant amount of microplastic can enter the marine environment via atmospheric transport, which supports the notion that atmospheric deposition is a crucial pathway for microplastics. The transport of air masses across urbanized areas in South Korea combined with the predominance of fragment-type microplastics in atmospheric deposits-consistent with patterns observed in other environmental media within the country-suggests that microplastics deposited in the coastal bay predominantly originate from intense anthropogenic activity in domestic urban areas.