We report on mercury in the atmosphere of east Asia (Japan, Korea, and China) as measured from sea level to ∼7000 m during 16 research flights in the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) C‐130 aircraft during the Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) campaign (http://saga.pmel.noaa.gov/aceasia/). The air at all altitudes contained concentrations of atmospheric mercury above the global background. The atmosphere was highly stratified with plumes originating from massive dust storms carried out of China, from local industrial pollution, from volcanoes, and, less well defined, from biomass burning. Most often the air masses were mixtures, e.g., dust layers contained anthropogenic emissions or volcanic plumes were embedded in anthropogenic pollution; thus the total data set showed no significant correlations of gaseous mercury with the most common anthropogenic pollutants in the area (CO and SO2), but good correlations were observed for identifiable plumes. Highest mixing ratios for gaseous elemental mercury (GEM) were found in industrial plumes exiting China (∼6.3 ng/m3), Korea (∼3 ng/m3), and Japan (∼3 ng/m3). The core of the plume from Miyake Jima volcano contained ∼3.7 ng/m3 of GEM. Crustal mercury was also present, emitted and subsequently deposited during the outbreak of the spring dust storms. Some of the nondust aerosols contained soluble mercury in highly variable ratios with the gas‐phase mercury contained in the same plume. Preliminary estimates for the export from China are 5–15 t of crustal mercury during the dust storms, ∼150 t/yr of gas‐phase mercury from biomass/biofuel combustion, and ∼600 t/yr from industrial sources, mostly from coal combustion. Gaseous mercury is a useful tracer for industrial, volcanic, and biomass‐burning sources, but in most cases, robust plume identification required one or more cotracers. Because of the inertness of GEM and the ease of its measurement it is well suited for the tracking of long‐range transport.

[1] Smoke plumes from large wildfires burning in late August 2001 in the temperate forests along the eastern slopes of the Cascade Mountains in Washington State and from a wheat stubble fire on the northeastern plain of Oregon were sampled for mercury from the University of Washington's Convair 580 research aircraft. Total gaseous mercury (TGM) concentrations as high as 7.5 ng/m 3 , a six-time enhancement over background, were measured. The TGM was linearly correlated with CO (R 2 = 0.805, where R is a 95% confidence level regression coefficient). Mercury was speciated as elemental mercury (>95%) and as mercury contained in the particulate fraction of the smoke. Emission factors (EF) were calculated from TGM and CO emissions and from a combustion efficiency of 0.9, adjusted for mercury contained in particulates, to yield an EF for total mercury of (113 ± 59) mg Hg per kilogram consumed fuel.

No abstract