Mercury in ambient air

Feng X, Sommar J, Gardfeldt K, Lindqvist O. 2000. Improved determination of gaseous divalent mercury in ambient air using KCl coated denuders. Fresenius J Anal Chem 366(5) 423 28. 

Lindberg SE, Stratton WJ. 1998. Atmospheric mercury speciation concentrations and behavior of reactive gaseous mercury in ambient air. Environ Sci Technol 32 49-57. 

Lu JY, Schroeder WH, Berg T, Munthe J, Schneeberger D, Schaedlich F. 1998. A device for sampling and determination of total particulate mercury in ambient air. Anal Chem 70 2403-2408. 

Lu JY, Schroeder WH. 1999. Sampling and determination of particulate mercury in ambient air a review. Water Air Soil Pollut 112 279-295. 

Development and characterization of an annular denuder methodology for the measurement of divalent inorganic reactive gaseous mercury in ambient air. Environ. Sci. Technol. 36(13), 3000-3009. 

Tumer RR, Bogle MA, Heidel LL, et al. 1992. Mercury in ambient air at the Oak Ridge Y-12 Plant, July 1986 through December 1990. Govt Reports Announcements and Index (GRA I) Issue 02. 

Measure the impact of specific plant operation and maintenance events on the concentration of mercury in ambient air in surrounding areas (Ambient Air Sampling and Analysis Plan)... 

European Union (2004) Directive 2004/107/EC of the European Parliament and of the Council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel, and polycyclic aromatic hydrocarbons in ambient air. Official Journal of the European Communities, L23/3, 3-15. 

A method has been proposed which is amenable for use for sampling of all atmospheres for merciuy in all forms (5). The method as it has been used does not allow for the differentiation between the various forms of airborne mercury possible. Ambient air is drawn over silica wool held at a temperature of 400°C and then passed through silver wool by a pump. The combined species of mercury, if present, are pyrolyzed on the silica... 

Analyses of Particulate Matter. For mercury, as an example, analysis of particulate matter is a fruitless task since one expects that less than 10% of the total mercury (which is itself not very high in ambient air) is in a combined form and therefore a component of particulate matter. That is not to say that only 10% of the mercury will be collected, however, since the particulate matter can serve as a holding agent for mer-... 

Potential sources of human exposure to mercury include food contaminated with mercury, inhalation of mercury vapors in ambient air, and exposure to mercury through water, soil and sediment. Dietary intake is by far the most important source of exposure to mercury for the general population. Fish and other seafood products are the main source of methylmercury in the diet studies have shown that methylmercury concentrations in fish and shellfish are 10-100 times greater than in other foods, including cereals, potatoes, vegetables, fruits, meats, poultry, eggs, and milk. As of December 1998, mercury was the chemical contaminant responsible, at least in part, for the issuance of 1931 fish consumption advisories by 40 states, including the US territory of American Samoa. Almost 68% of all advisories issued in the United States are a result of mercury contamination in fish and shellfish. Advisories for mercury have increased steadily by 115% from 899 advisories in 1993 to 1931 advisories in 1998. The number of states that have issued mercury advisories also has risen steadily from 27 states in 1993 to 40 states in 1997, and remains at 40 states for 1998. Advisories for mercury increased nearly 8% from 1997 (1782 advisories) to 1998 (1931 advisories). 

The SI unit of P is the pascal (Pa). However, millimeters of mercury (also called torr) has continued to remain popular (see Box 27-2 for conversion factors). Use of SI units does have a practical advantage in that 1 atm almost equals 100 kPa (1 atm = 101.325 kPa). Partial pressures expressed in kilopascals are therefore very close estimates of percentages of the gases in the mixture at 1 atm. Pressure, P (or p), may mean either total pressure, as in the expression P(Amb) for the mixture of gases in ambient air, or partial pressure in blood, as in P02(aB). Numerical value and units of R differ depending on the units used for P, so that ... 

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). 

A number of units are used to express a pressure measurement. Some are based on a force per unit area for e.xample, pound (force) per square inch (psi) or dyne per square centimeter (dyne/enr). Otliers are based on a fluid height, such as inches of water (in H O) or millimeters of mercury (iimiHg) units such as these are convenient when tlie pressure is indicated by a difference between two levels of a liquid, as in a imuiometer or barometer. Barometric pressure is a measure of the ambient air pressure. Standard barometric pressure is 1 atm and is equivalent to 14.696 psi and 29.921 in Hg. 

Brosset C, Lord E. 1991. Mercury in precipitation and ambient air a new scenario. Water Air Soil Pollut 56 493-506. 

For gases and vapors, exposure concentrations are traditionally expressed in parts per million (ppm). The calculation for the ppm of a gas or vapor in an air sample is based on Avogadro s Law, which states that Equal volumes contain equal numbers of molecules under the same temperature and pressure. In other words, under standard temperature and pressure (STP), one gram-molecular weight (mole) of any gas under a pressure of one atmosphere (equivalent to the height of 760 mm mercury) and a temperature of 273 K has the same number of molecules and occupies the same volume of 22.4 liters. However, under ambient conditions, the volume of 22.4 liters has to be corrected to a larger volume based on Charles Law, which states that at constant pressure the volume of gas varies directly with the absolute temperature. Thus, at a room temperature of 25° C, one mole of a gas occupies a volume of 24.5 liters. 

The analytic principles that have been applied to accumulate air quality data are colorimetry, amperometry, chemiluminescence, and ultraviolet absorption. Calorimetric and amperometric continuous analyzers that use wet chemical techniques (reagent solutions) have been in use as ambient-air monitors for many years. Chemiluminescent analyzers, which measure the amount of chemiluminescence produced when ozone reacts with a gas or solid, were developed to provide a specific and sensitive analysis for ozone and have also been field-tested. Ultraviolet-absorption analyzers are based on a physical detection principle, the absorption of ultraviolet radiation by a substance. They do not use chemical reagents, gases, or solids in their operation and have only recently been field-tested. Ultraviolet-absorption analyzers are ideal as transfer standards, but, as discussed earlier, they have limitations as air monitors, because aerosols, mercury vapor, and some hydrocarbons could, interfere with the accuracy of ozone measurements made in polluted air. 

Evaluating the quantitative effect of these factors on the volatile mercury concentration requires determining how much of the initial mercury found in the coal is 1. not volatilized from the coal during combustion, 2. recovered in the various ash collection mechanisms by some adsorption phenomena, and 3. released to the atmosphere. With this information, a mercury mass balance can be calculated in which the amount of mercury consumed during the combustion process is compared with the amount in the stack gas and the various ashes. During this study, this was accomplished by comparing the stack gas concentration with the amount of mercury initially in the coal, corrected for the amounts recovered in the ashes. Differences between these two values would represent adsorption and/or desorption onto and off the walls of the ducts and stack and any significant contribution from the ambient air used in the combustion process. 

Monitoring of the mercury concentrations and flow rate of the ambient air used in the combustion process... 

Two disparate translation methods are investigated for the measurement of sulfur dioxide. Both involve interaction with an aqueous solution. In the first, collected S(IV) is translated by the enzyme sulfite oxidase to which is then measured by an enzymatic fluorometric method. The method is susceptible to interference from i CWg) efforts to minimize this interference is discussed. The second method involves the translation of SO2 into elemental Hg by reaction with aqueous mercurous nitrate at an air/liquid interface held in the pores of hydrophobic membrane tubes. The liberated mercury is measured by a conductometric gold film sensor. Both methods exhibit detection limits of 100 pptv with response times under two minutes. Ambient air measurements for air parcels containing sub-ppbv levels of SO2 show good correlation between the two methods. 

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