RELATIONSHIPS AMONG AEROSOL CONSTITUENTS FROM ASIA AND THE NORTH PACIFIC DURING PEM-WEST-A

Aerosol particle samples collected from Asia and the North Pacific wer e analyzed to investigate the relationships among atmospheric sea salt , mineral aerosol, biogenic emissions (methanesulfonate (MSA)), and se veral anthropogenic substances (sulfate, nitrate, and various trace el ements), These studies specifically focused on the sources for aerosol SO4 = and on the long-range transport of continental materials to the North Pacific. Ground-based aerosol sampling was conducted at four co astal-continental sites: Hong Kong, Taiwan, Okinawa, and Cheju; and at three remote Pacific islands, Shemya, Midway, and Oahu. Non-sea-salt (nss) SO4= and MSA were uncorrelated at the East Asian sites presumabl y because pollution sources overwhelm the biogenic emissions of nss SO 4=. At the coastal-continental sites, marine biogenic emissions accoun ted for only 10 to <5% of the total nss SO4=. In contrast, over the oc ean the concentrations of nss SO4= and MSA were correlated (Midway r = 0.70; Oahu r = 0.54), and higher percentages of biogenic nss SO4= occ urred, 55 and 70% at Oahu and Midway, respectively. The concentrations of nss SO4= and NO3- were correlated at Cheju, Hong Kong, Taiwan, Oki nawa, Midway, and Oahu, indicating some similarities in their sources and the processes governing their transport; however, differences in t he nss SO4=/NO3- ratios among sites suggest regional differences in th e pollution component of the aerosol. At Shemya the concentrations of MSA during the summer (100 ng m(-3) or more) are about 2 orders of mag nitude higher than those in winter. The dimethylsulfide-derived fracti on of the nss SO4= is highest in the summer when the monthly median ns s SO4=/MSA ratios range from 2.7 to 4.5, i.e., comparable to the ratio s observed over Antarctica and other high-latitude locations. However, the monthly median nss SO4=/MSA ratios increase, reaching 50 to 200 i n the winter as productivity nearly ceases, and the biogenic fraction of nss SO4= at Shemya decreases dramatically; this suggests a strong s easonal pollution component to the sulfate aerosol. The meteorological conditions favoring the long-range transport of Asian dust to the Nor th Pacific also lead to transport of anthropogenic materials. At Oahu the correlation between NO3- and Al (dust) was highly significant (r = 0.75; p < 0.001), while the correlations between nitrate and Al at th e continental sites were low, These differences indicate that the comp osition of the air sampled at the coastal-continental stations may be quite different from the air transported to the remote ocean. This phe nomenon also appeared to affect the relationship between nss SO4= and antimony. The correlations between nss SO4= and Sb were weak at the As ian sites but strong at the open ocean sites where the nss SO4=/Sb rat ios were higher than those over the continent.