Environmental Biogeochemical Cycling of Mercury

Fif ure 17. Field of anthropogenic emi.ssion of mercury in /996 with. spatial rc.solution 50 X 50 km, g/krn per year (Ryabo.shapko et al, 1999). 

The consideration of these budget components shows the predominant emission of the gaseous elemental mercury to the atmosphere from both natural and anthropogenic sources. The dry deposition is represented also by elemental mercury, however the wet deposition is mainly connected with gaseous and particulate Hg- . 

Mercury deposition field is formed by wet and dry deposition of three different mercury forms (DMM is scavenged only by photochemical decomposition). A pronounced gradient of depositions is observed from Central Europe to the north. Maximum values of depositions reach 500 g/km /year. With the distance from pollution sources, the deposition intensity is abruptly decreased and in the periphery of domain it is 5-20 g/km /year. The lowest values are shown for the northern periphery of Europe. 

Much of the Hgt pool was found in the upper part of the soil, which is rich in organic matter. This pattern is likely due to an elevated atmospheric deposition of Hgt over the extended period and immobilization of mercury by organic functional 

The runoff export of mercury was about 0.03 g/ha of Hgt per year. This value lies within the range of 0.008 to 0.059 g Hg/ha/year, derived from a number of catchment studies in Sweden. The output of methylmercury from catchment area was 0.0015 g/ha/year of Hg. This is substantially lower than the input to the catchment. There appears to be an ongoing net accumulation of Hgm in the terrestrial ecosystems, similar to the pattern previously shown for the total mercury. 

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A similar comparison can be conducted with results of the environmental biogeochemical cycle of mercury. The most important anthropogenic emission sources of mercury are listed in Table 11. 

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