Atmospheric mercury species

Munthe J., and Berg T. (2001) Reply to comment on Atmospheric mercury species in the European Arctic measurement and modeling by Berg et al. Atmos. Environ. 35(31), 5379-5380. 

Petersen G., Iverfeldt A., and Munthe J. (1995) Atmospheric mercury species over central and northern Europe model calculations and comparison with the observations from the Nordic air and precipitation network for 1987 and 1988. Atmos. Environ. 29(1), Al-61. 

Johnson DC, Bramen RS. 1974. Distribution of atmospheric mercury species near the ground. Environ Sci Technol 8 1003-1009. 

Sommar j, Sprovieri E, Stevens RK, Stratton W, Tungel G and Urba A (2001) Intercomparison of methods for sampling and analysis of atmospheric mercury species. Atmos Environ 35 3007—3017. 

Driscoll et al. (1994) have studied the mercury species relationships among water, sediments, and fish (yellow perch) in a series of Adirondack lakes in New York state, USA. In most lakes, approximately 10% of the total mercury loading was in the form of C2HsHg+. Mercury concentrations increased as pH fell, but the best correlation was found between [dissolved Al] and [dissolved Hg] suggesting that the same factors are responsible for mobilizing both these metals. Methylmercury concentrations correlated strongly with the dissolved organic carbon content in the water. Fish muscle tissue was analyzed for mercury and showed an increase with age. However, the study was unable to resolve the question of whether the principal source of mercury to these lakes was atmospheric deposition or dissolution from bedrock due to acid rains. 

It was quickly realized that the mercury species to be found in greatest abundance in precipitation was ionic mercury (e.g., Fogg and Fitzgerald, 1979). Some typical values of total mercury in precipitation are shown in Table 10. Extensive databases of precipitation mercury concentrations are available from monitoring networks in the US, Canada, and Nordic countries (e.g., US Mercury Deposition Network http //nadp.sws.uiuc.edu/ mdn). The discrepancy between the dominant gas and precipitation phase species implied a process of oxidation of elemental mercury in the atmosphere and its subsequent scavenging as being a major component of the mercury cycle. Since the initial work, and partially in response to... 

Lamborg C. H., Fitzgerald W. F., Vandal G. M., and Rolfhus K. R. (1995) Atmospheric mercury in northern Wisconsin sources and species. Water Air Soil Pollut. 80, 198-206. 

Mercuiy in the Arctic cycles with the seasons between the atmosphere and snow on the ground. In the spring, as the sun reappears after the winter darkness, mercury levels in the troposphere decline for about 3 months. At the same time, the level of mercury in the snow increases 100-fold, both as methylmercury and as inorganic compounds of mercury. Later in the year, as the snow melts, the levels in the snow drop and mercury reappears in the troposphere. The elemental mercury in the atmosphere is converted to particulates or reactive species, parallelling a decrease in atmospheric ozone, and is then deposited in the snow. Later in the summer, the mercury levels in the atmosphere increase, probably due to temperature- or sunlight-induced emission of volatile mercury species from the surface. 

N. S. Bloom, E. M. Prcstbo, J. S. Tokos, E. von dcr Geest, E. S. Kuhn, Distribution and origins of mercury species in the Pacific northwest atmosphere. Abstract, World Mercury Conference, Hamburg, August 1996. 

Schroeder WH, Yarwood G, Niki H. 1991. Transformation processes involving mercury species in the atmosphere - results from a literature survey. Water, Air, Soil Pollution 56 653-666. 

Main mercury species in ambient air are elemental mercury (Hg°), reactive gaseous mercury (Hg(II)), mercury bound to aerosols, and methylmercury. Though dimethyl-mercury is together with Hg° the most volatile form of Hg, it has not been detected unequivocally in the atmosphere. Elemental mercury represents >95% of Hg in the atmosphere with ambient concentrations at the order of 1-5 ng m whereas MeHg in air was found to be in the range of 1 to 20 pg m (Pirrone et al. 2001). For this reason, in most cases mercury is pre-con-centrated on solid absorbers (gold, silver, activated carbon traps, etc.) prior to analysis (Drabaeck and Iverfeldt 1992, Horvat 1996). 

Mercury Species in the Environment Most of the mercury encountered in water/ soil/sediments/biota (all environmental media except the atmosphere) is in the form of inorganic mercuric salts and orga-nomercurics. The presence of a covalent C—Hg bond differentiates organomercurics from inorganic mercury compounds that merely associate with the organic material in the environment but do not have the C—... 

Mercury in Water Systems There are a number of pathways by which mercury can enter the water systems Hg(II) and methylmercury from atmospheric deposition (wet and dry) can enter water bodies directly they can be transported to water bodies in run-off or can leach into the water body from groundwater flow in the upper soil layers. Once in the water system, the same complexation and transformation processes that occur to mercury species in soil will occur along with additional processes due to the aqueous environment. 

Lamborg CH, Fitzgerald WF, Vandal GM and Rolfhus K (1995) Atmospheric Mercury in Northern Wisconsin Sources and Species. Water Air Soil Pollut 80 189-198. 

Crude oil is known to contain volatile mercury because mercury is found concentrated in the liquefied petroleum gas (LPG) and naphtha fractions of the atmospheric distillation when oil is refined. It is known conclusively that elemental mercury is at least one of the volatile mercury species in crude oil because it sometimes is found condensed in trays in refinery distillation towers and condensed in cryogenic heat exchangers that liquefy petroleum gases. What is not known is whether elemental mercury is the only volatile species. 

Improvements have been made recently for the preconcentration of gaseous methylmercury in air by preconcentration in mist chambers and subsequent determination by aqueous-phase ethylation, precollection on carbotrap columns, separation by GC, and detection by cold vapor atomic fluorescence spectrometry (CV-AFS). In order to understand the behavior and fate of mercury compounds in the atmosphere and their role in environmental mercury cycling, there is an urgent need for further development of analytical methods to afford identification of mercury species in the atmosphere by compound-specific analytical methods (as opposed to operationally defined protocols). 

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