Characterization of atmospheric aerosols over East Asia and the western North Pacific

To characterize atmospheric aerosols over East Asia and the western North Pacific, atmospheric aerosol were collected in the spring 1992 at: (1) Xi\u27an and Beijing in the interior of China, (2) Qingdao and Xiamen along the coast of the China Sea, and (3) during a research cruise in the East China Sea. Extended aerosol sampling was conducted at Beijing from December 1990 to April 1992. Temporal and geographical patterns of mineral aerosol over eastern Asia have been characterized. The highest concentrations of mineral aerosol were found in the Loess Plateau region, with decreasing trends to the south and east. Mineral aerosol concentrations in southern China are substantially lower than those in northern China. The mass particle size distribution of mineral aerosol varies as a function of distance from the source region, with mean mass-median diameters of ${\sim}5.0\ \mu$m in northern continental China and ${\sim}3.2\ \mu$m over the East China Sea resulting in different dry deposition velocities. Estimates based on atmospheric deposition models suggest that atmospheric fluxes of mineral aerosol over Loess Plateau are 260 (34-320) g m$\sp{-2}$ yr$\sp{-1}$; this is the highest of the regions studied in this project. With high concentrations and high fluxes of mineral aerosol, the atmosphere over northern continental China is characterized by its relatively strong acid-reducing capacity; this is reflected in relatively high ratios of Ca/SO$\sb4\sp{-2}$. The potential acid-reducing capacity of mineral aerosol is such that $\sim$0.46-1.4 neq H$\sp+$ could be reduced by each microgram of mineral aerosol in the spring if the water content in the atmosphere were sufficient. The atmospheric concentrations of non-sea-salt (nss) sulfate and nitrate are much higher along the coast of the China Sea than those over remote oceans. A strong correlation between nss-sulfate and Sb (r$\sp2$ = 0.92) suggests that coal combustion is the major source for nss-sulfate. Calculations based on the relationship of nss-sulfate to methanesulfonate (MSA) ratio indicate that anthropogenic sulfate accounts for $\ge$ 81-97% of the total nss-sulfate over the China Sea