Total gaseous Hg

The most volatile forms present in water are Hg° and DMHg. These should be removed from the samples immediately after collection by aeration with collection on gold (for total gaseous Hg) and Carbotrap or Tenax (for DMHg). After filtration, samples should be preserved prior to storage. For total Hg, samples can be acidified with HCl or HNO3 or with the addition of an oxidant (BrCl), whereas for MMHg the samples can be acidified with HCl or stored unpreserved deep frozen. ... 

There are, however, some new instruments that do not require pre-concentration for elemental mercury in air, such as AAS with Zeeman background correction (Pogarev etal. 2002) and mobile laser systems for remote measurements (Edner etal. 1992). In general, total gaseous Hg in air can be determined with high precision and accuracy. 

Table 1 Levels (ng of total gaseous Hg (TGM) in the atmosphere in Mexico and selected other areas worldwide...

Figure 6 Depletion of Hg° in the atmosphere during Arctic spring as observed by Schroeder et al. (1998) at Alert. The traces, from top to bottom, are surface air temperature, total gaseous mercury, and ozone. The inset illustrates the correlation between mercury and ozone during the spring depletion period (source Schroeder et al, 1998).

In 1995, approximately 1900 metric tons of anthropogenic mercury entered the atmosphere (mostly 75%) from the combustion of fossil fuels. About 56% of global mercury atmospheric emissions came from Asian countries, with Europe and North America combined contributing less than 25% gaseous elemental mercury (Hg) comprised 53% of total atmospheric emissions, gaseous Hg+ 37%, and particle-associated mercury the remainder. 

The Henry s law constant for the solubility of radon in water at 30°C is 9.57 X 10-6 Mlmm Hg. Radon is present with other gases in a sample taken from an aquifer at 30°C. Radon has a mole fraction of 2.7 X 10-6 in the gaseous mixture. The gaseous mixture is shaken with water at a total pressure of 28 atm. Calculate the concentration of radon in the water. Express your answers using the following concentration units. 

The products were collected after 6 hr reaction at room temperature. The total pressure was 300 mm Hg. Gaseous products were obtained by condensing the gas phase in a liquid nitrogen trap. Surface product was the strongly adsorbed propylene obtained by degassing at 125°C. 

Atmospheric deposition is an important source of mercury for surface waters and terrestrial environments that can be categorized into two different types, wet and dry depositions. Wet deposition during rainfall is the primary mechanism by which mercury is transported from the atmosphere to surface waters and land. Whereas the predominant form of Hg in the atmosphere is Hg° (>95%), is oxidized in the upper atmosphere to water-soluble ionic mercury, which is returned to the earth s surface in rainwater. In addition to wet deposition of Hg in precipitation, there can also be dry deposition of Hg°, particulate (HgP), and reactive gaseous mercury (RGM) to watersheds [9-11]. In fact, about 90% of the total Hg input to the aquatic environment is recycled to the atmosphere and less than 10% reaches the sediments [12]. By current consensus, it is generally accepted that sulfate-reducing bacteria (SRB)... 

Figure 12 Vertical profiles of total dissolved mercury and mercury species in the South Atlantic, from station 8 of the IOC Baseline South Atlantic Cruise. MonomethylHg was below detection at all depths, while measurable dimethylHg was found within and below the thermocline. Dissolved gaseous mercury, dominated by Hg°, represents the majority of mercury at many depths at this location (source Mason and Sullivan, 1999).

A gaseous mixture consisting of 50 mol % hydrogen and 50 mol % acetaldehyde (C2H4O) is initially contained in a rigid vessel at a total pressure of 760 mm Hg abs. The formation of ethanol (C2H6O) occurs according to... 

After a time it was noted that the total pressure in the rigid vessel had dropped to 700 mm Hg abs. Calculate the degree of completion of the reaction using the following assumptions (1) all reactants and products are in the gaseous state and (2) the vessel and its contents were at the same temperature when the two pressures were measured. 

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