Natural sources, mercury deposition

Schuster PF, Krabbenhoft DP, Naftz DL, Cecil FD, Olson ML, Dewild IF, Susong DD, Green JR, Abbott ML. 2002. Atmospheric mercury deposition during the last 270 years a glacial ice core record of natural and anthropogenic sources. Env Sci Technol 36 2303-2310. 

As a rule, simulations consider emissions of heavy metals from anthropogenic and natural sources, transport in the atmosphere and deposition to the underlying surface (Figure 6). It is assumed that lead and cadmium are transported in the atmosphere only as a part of aerosol particles. Besides, chemical transformations of these metals do not change removal properties of their particles-carriers. On the contrary, mercury enters the atmosphere in different physical and chemical forms and undergoes numerous transformations during its pathway in the atmosphere (Ilyn et al., 2002 2004 Ilyin and Travnikov, 2003). 

Mercury emissions from European anthropogenic sources in 2002 totaled 180 tons this is 11 % lower than those in 2001. The input from natural emission and re-emission from European soils and the marginal seas is estimated at about 150 tons. More than 65% of emitted mercury was transported beyond the boundaries of Europe. The total mercury depositions to Europe were about 100 tons. Of this amount, 50 tons originated from anthropogenic sources of European countries the rest was the input from natural sources, re-emission and global anthropogenic sources. 

About one third of the total deposition is from Kazakhstan and 10% is from other Asian sources. In both cases about 20% is contributed by natural sources. The total annual deposition of mercury to Kazakhstan amounts to 28 t/yr and to Kyrgyzstan—2.9 t/yr. 

The primary repository of methylmercury in the diet is fish. Natural sources of inorganic mercury, such as volcanoes, and human contributions from fossil fuel and waste combustion contribute to a global mercury cycle that deposits the mercury in waterways. Microorganisms in the bottom sediment convert the inorganic form into methylmercury,... 

With the exception of mercury ore deposits, the amount of mercury that naturally exists in any one place is usually very low. In contrast, the amount of mercury that may be found in soil at a particular hazardous waste site because of human activity can be high (over 200,000 times natural levels). The mercury in air, water, and soil at hazardous waste sites may come from both natural sources and human activity. 

The natural global bio-geochemical cycling of mercury is characterized by degassing of the element from soils and surface waters, followed by atmospheric transport, deposition of mercury back to land and surface waters, and sorption of the compound to soil or sediment particulates. Mercury deposited on land and open water is in part revolatilized back into the atmosphere. This emission, deposition, and revolatilization creates difficulties in tracing the movement of mercury to its sources (WHO 1990). Particulate-bound mercury can be converted to insoluble mercury sulfide and precipitated or bioconverted into more volatile or soluble forms that re-enter the atmosphere or are bioaccumulated in aquatic and terrestrial food chains (EPA 1984b). 

Recent estimates indicate that of the approximately 200000 tons of mercury emitted to the atmosphere since 1890, about 95% resides in terrestrial soils, about 3% in the ocean surface waters, and 2% in the atmosphere (Expert Panel on Mercury Atmospheric Processes 1994). Some 20-30% of the current oceanic emissions are from mercury originally mobilized by natural sources (Eitzgerald and Mason 1996). Similarly, a potentially large fraction of terrestrial and vegetative emissions consists of recycled mercury from previously deposited anthropogenic and natural emissions (Expert Panel on Mercury Atmospheric Processes... 

Virtually all mercury in the Florida Everglades from natural sources (39% of the total mercury deposited) is attributed to release from the soil through natural processes, including microbial transformations of inorganic... 

An explosion rupturing an ammonia separator (still) in an ammonia production unit, probably because mercury vapour from geological sources entered with hydrogen syngas originating from natural gas and reacted to give explosive nitride deposits. The separator remains crackled when scraped [1]. For a more academic study of the effects of mercury on ammonia plants, including embrittlement and corrosion, as well as explosive deposits [2],... 

---