This meant that the marine aerosol at the remote areas over the East China Sea was highly related to the regional and/or long-range transport. SNA accounted for 24% of PM2.5 during ND_HN and 31% during PD_HN, respectively. The mass ratio of SNA to PM2.5 at the Huaniao Isle was close to that in Beijing, a city far away from the isle, but much lower than that in Shanghai, the adjacent city to the isle, which suggested that the marine aerosol over the East China Sea was more influenced by the long-range transport (more discussion in Section 3.3). Also, the mean Kþ concentration increased from 0.1 mg m3 in ND_HN to 0.9 mg m3 in PD_HN, and the nss-Kþ accounted for ~96% of the total Kþ in both ND_HN and PD_HN, which indicated that Kþ at the Huaniao Isle was mostly from the regional/long-range transport of the anthropogenic emissions in the mainland China.