Atmospheric mercury concentrations from several observatory sites in the Northern Hemisphere
AbstractIn an effort to investigate both large-scale (spatial) and short/long-term (temporal) distribution characteristics of atmospheric mercury, we have combined and analyzed the Hg concentration data sets collected continuously by four different scientific groups for the areas and periods covering: (1) America (three sites near the Canadian Great Lakes (CGL): 1997-2000), (2) Asia (Seoul, Korea (SEL): 1997-2002), (3) Arctic (Alert, Canada (ALT): 1995-2001), and (4) Europe (Mace Head, Ireland (MH): 1996-2002). The mean concentrations of Hg data from those widely dispersed monitoring stations were computed to be: (1) 1.55+0.41 (ALT), (2) 1.76+0.31 (MH), (3) 1.58+0.23, 1.69+0.32, and 1.93+0.44 (three sites in CGL), and (4) 5.06+2.46 ng m-3 (SEL). Inter-site relationships were investigated among all different stations using the data groups divided in different temporal intervals. The analysis of diurnal variation patterns of Hg indicated differences in regional source/sink characteristics, with increasing amplitudes of variability toward areas under the strong influence of anthropogenic sources. When the analysis was made over different seasons, the patterns contrasted greatly between the Arctic and the other areas. It was found that the relative enhancement of Hg concentrations was dominant during winter/spring in most areas due to direct or indirect influences of anthropogenic emissions. However, the pattern for the Arctic area was distinguished pronouncedly from others with the spring minimum and summer maximum both of which reflect the potent effects of mercury depletion phenomenon (MDP). By contrast, no long-term trend, either being an increase or decrease, was evident from any of the stations during each respective study period. Although our initial attempts to examine the distribution characteristics of Hg analyzed by different scientific groups were successful, we feel that these efforts should be continued further to extend the compatibility of the global database of Hg.