Spatiotemporal distribution of marine aerosols and gaseous species over the North Pacific Ocean

Abstract

Observational studies of marine aerosols are essential for understanding the global aerosol budget and its environmental impacts. This study presents simultaneous in-situ measurements of major ionic components (Cl？, NO3？, SO42？, NH4+, K+, Ca2+, Na+, and Mg2+) in aerosols and gaseous species (HCl, HNO3, HONO, SO2, and NH3) over the North Pacific Ocean from July 4 to 15 and September 19 to October 3, 2022. Using high temporal resolution instruments aboard the Republic of Korea's icebreaker research vessel Araon, this study aimed to (1) report the spatial and temporal distributions of aerosols and gaseous species, (2) estimate the source contributions of continental anthropogenic pollutants, and (3) assess the influence of aerosol chemical composition and gaseous species on aerosol acidity and water content. Our results revealed a significant decline in anthropogenic contributions, from 72.4 ± 11.2 % in the Yellow Sea and East Sea to 32.0 ± 10.8 % in the remote Pacific, accompanied by an increase in natural aerosols from 27.6 ± 11.2 % to 68.0 ± 10.8 %. Elevated concentrations of ammonia (NH3) and nitrous acid (HONO) were observed in the remote ocean, likely associated with the marine environment and biological activities. This increase in NH3, along with a decrease in sulfate concentrations, contributed to the formation of more alkaline aerosols in the remote ocean. Despite the limited availability of previous studies for direct comparisons, our findings align with observed trends and highlight the unique physicochemical properties of marine aerosols. These results enhance our understanding for the interactions between continental pollutants and marine environments, emphasizing the distinct characteristics of marine aerosols and their potential role in modifying atmospheric processes and influencing climate change.