Chemical characteristics of sulfur-containing aerosol particles across the western North Pacific and the Arctic Ocean

Abstract The characteristics of aerosol methanesulfonic acid (MSA), non-sea-salt sulfate (nss-SO42−) and MSA/nss-SO42− ratio, were measured at high-time resolution (1 h) over the East sea/sea of Japan (R1, 31° - 47°N, 121° - 145°E), western North Pacific Ocean (R2, 47° - 58°N, 145° - 176°E), subarctic western North Pacific (R3, 58° - 66°N, 176°E - 169°W) and Arctic Ocean (R4, 66° - 85°N, 150–174°W) during July–September 2018. The highest MSA levels were observed in R2, with an average of 0.22 ± 0.18 μg m−3. These levels were 3–10 times higher than in other regions, correlating with biological productivity. The concentration of nss-SO42− decreased with distance from Eurasia. The MSA/nss-SO42− ratios were 0.10 ± 0.27, 0.38 ± 0.43, 0.30 ± 0. 36 and 0.39 ± 0.48 over R1, R2, R3 and R4, respectively. Biological sources were larger contributors of nss-SO42− in R2 while nss-SO42− were affected more by continental anthropogenic sources in R1. Positive and negative relationships between the MSA/nss-SO42− ratio and temperature were observed, indicating that temperature may have a different influence on the MSA/nss-SO42− ratio. Four high level regions of MSA were observed over the R4, wind speed and temperature were critical factors that affected MSA levels over the R4. Significant depletion of chloride was observed and areas that were more affected by terrestrial sources had a greater chlorine depletion in this study, which means that the magnitude of the chlorine depletion followed the order R1 > R3 > R2 > R4.