Total particulate mercury

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. 

A series of mercury mass balances was obtained at a coal-fired power plant by comparing the volatile and particulate mercury in the stack gas stream to the mercury initially in the coal, corrected for the mercury adsorbed and retained by the various ashes. These data were used to determine the fate of the mercury in the combustion process and to check the accuracy of the volatile mercury sampling procedure (gold amalgamation). The bottom ash had the lowest mercury concentration of the ash samples collected, and the mercury concentration increased as one proceeded through the ash collection system from the initial mechanical ash to the electrostatic ash. The mercury recovered in the various ashes represented about 10% of the total mercury introduced in the raw coal. 

This method is used for the determination of total chromium (Cr), cadmium (Cd), arsenic (As), nickel (Ni), manganese (Mn), beiylhum (Be), copper (Cu), zinc (Zn), lead (Pb), selenium (Se), phosphorus (P), thalhum (Tl), silver (Ag), antimony (Sb), barium (Ba), and mer-cuiy (Hg) stack emissions from stationaiy sources. This method may also be used for the determination of particulate emissions fohowing the procedures and precautions described. However, modifications to the sample recoveiy and analysis procedures described in the method for the purpose of determining particulate emissions may potentially impacl the front-half mercury determination. 

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)... 

Babiarz et al. (2001) examined total mercury (Hg) and methyhnercury (Me-Hg) concentrations in the colloidal phase of 15 freshwaters from the upper Midwest and Southern United States. On average, Hg and Me-Hg forms were distributed evenly between the particulate (0.4 jm), colloidal, and dissolved (lOkDa) phases. The amount of Hg in the colloidal phase decreased with increasing specific electric conductance. Furthermore, experiments on freshwater with artificially elevated electric conductance suggest that Hg and Me-Hg may partition to different subfractions of colloidal material. The two colloidal Hg phases act differently with the same type of adsorbent. For example, the colloidal phase Hg correlates poorly with organic carbon (OC) but a strong correlation between Me-Hg and OC was observed. 

Choe, K.Y., Gill, G.A., and Lehman, R. (2003) Distribution of particulate, colloidal, and dissolved mercury in San Francisco Bay estuary. 1. Total mercury. Lirnnol. Oceanogr. 48, 1535-1546. 

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-... 

In the atmosphere, particulate bound mercury constitutes only 2% of total mercury in the air and has normally been found to be less than 0.1 ngm in regions unaffected by local sources. Some other mercury compounds, which may exist in the atmosphere, are mercuric chloride, mercuric bromide, mercuric hydroxide, mercuric sulfide, and mercuric cyanide. The rest is elemental mercury in the gaseous phase. In remote areas over the Atlantic and Pacific oceans, mercury bound to particulate matter concentrations are generally at or below the picogram per cubic meter level. 

The natural occurrence of mercury in the environment means that mercury is likely to occur in surface waters, even when anthropogenic sources of mercury are absent. Freshwaters without known sources of mercury contamination generally contain less than 5 ng/L (ppt) of total mercury in aerobic surface waters (Gilmour and Henry 1991). Mercury levels in water-borne particulates in the St. Louis River estuary... 

Dust. Williston 26) mentioned the possibility of mercury removal by dust particles. He based his assumption on the observation that an open silica gel container adsorbed up to 1 /Ltg/gram from laboratory air after several months of exposure (7). In laboratory air, half of the total mercury was found on suspended particulate matter when the latter was collected on a membrane filter at 40-60% relative humidity (24). The settled dust had a lower mercury content (Table IV). Thus, mercury on suspended particulate matter appears to be associated mainly with the submicron particles. Other examples in Table IV show higher levels of mercury collected on urban dust. Apparently some samples from... 

Current methods for sampling and analysis are known to be problematic and prone to error. Several wet chemical impinger-based methods have been approved for the determination of total Hg in flue gas. These include US EPA method 29 and lOlA. More recently, diese methods have been modified to enable the speciation of particulate, oxidized, and elemental mercury. The most commonly used procedure is the ASTM Standard Test Method for Elemental, Oxidized, Particle-Bound and Total Mercury in Flue Gas Generated from Coal-Fired Stationary Sources (D 6784-02) known as the Ontario Hydro Method. This method was developed by public consultation with ASTM membership. 

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