Mercury sampling procedure

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. 

After the firing was completed, the permanganate solution was analyzed by the same procedure used for the volatile mercury samples. Mercury in coal samples from the National Bureau of Standards and the United States Bureau of Mines were analyzed simultaneously as controls. At least duplicate analyses were performed on all samples. Empty crucibles were fired into acidic permanganate solutions by an identical procedure to obtain solutions for blank determinations. 

A) Pressure-controlled mercury porosimetry procedure. It consists of recording the injected mercury volume in the sample each time the pressure increases in order to obtain a quasi steady-state of the mercury level as P,+i-Pi >dP>0 where Pj+i, Pi are two successive experimental capillary pressure in the curve of pressure P versus volume V and dP is the pressure threshold being strictly positive. According to this protocol it is possible to calculate several petrophysical parameters of porous medium such as total porosity, distribution of pore-throat size, specific surface area and its distribution. Several authors estimate the permeability from mercury injection capillary pressure data. Thompson applied percolation theory to calculate permeability from mercury-injection data. 

Open Ocean Mercury Determinations. In our initial studies concerned with the marine geochemistry of mercury, we obtained open ocean smrface samples by hand from a small work boat away from any adverse influence of the oceanographic research vessel. The concentrations of mercury in the open-ocean surface waters (western Sargasso Sea) were small (ca. 10 ng/1.) and rather imiformly distributed (26). However, to collect seawater to determine the concentrations of mercury at other depths, we needed an artifact-free sampling procedure. 

An automatic analysis system has been used regularly over the past three years for the determination of mercury in natural waters. Some results will be presented to show the possible applications of this system to determine directly, without the use of sample vessels, the concentration of mercury and its species in natural waters. In this way, contamination - mainly due to sampling procedure - can be considerably reduced. 

A more rigorous sampling procedure was developed and is detailed in Table V. To test this procedure, a comparison of the total mercury concentration in the water in the sampling vessels and that obtained by direct determination was carried out. 

The various sampling procedures must be appropriate to the sample type and methylmercury concentration. Organic mercury is present at much lower concentrations than total mercury, except in fish or seafood. Therefore, apart from the methylmercury-specific separation and detection techniques, careful... 

In order to calculate the true volume intrusion of mercury into the pores of a sample, a correction must be made to account for the compression of mercury, sample cell and sample [69]. The usual procedure is to carry out a blank experiment in the absence of a sample or with a non-porous sample [70]. During the course of calibration measurements on non-porous nylon it was found that a normal blank correction procedure led to erroneous mercury penetration volumes [71]. In particular it was found that the shape of the intrusion curve varied with the size of the sample. 

Automated analyzers may be used for continuous monitoring of ambient poUutants and EPA has developed continuous procedures (23) as alternatives to the referenced methods. Eor source sampling, EPA has specified extractive sampling trains and analytical methods for poUutants such as SO2 and SO [7446-11-9] sulfuric acid [7664-93-9] mists, NO, mercury [7439-97-6], beryUium [7440-41-7], vinyl chloride, and VOCs (volatile organic compounds). Some EPA New Source Performance Standards requite continuous monitors on specified sources. 

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. 

Stripping voltammetry procedure has been developed for determination of thallium(I) traces in aqueous medium on a mercury film electrode with application of thallium preconcentration by coprecipitation with manganese (IV) hydroxide. More than 90% of thallium present in water sample is uptaken by a deposit depending on conditions of prepai ation of precipitant. Direct determination of thallium was carried out by stripping voltammetry in AC mode with anodic polarization of potential in 0,06 M ascorbic acid in presence of 5T0 M of mercury(II) on PU-1 polarograph. 

To determine the purity of a sample of a mercury(II) salt, the following procedure in which the compound is reduced with phosphorous (phosphonic) acid may be used to assay a sample of a mercury(I) salt, the reduction with phosphorous acid is omitted. 

The following procedure is recommended. The sample solution is de-aerated, then, with the tip of the capillary in the air, the mercury pressure is raised at least 10 cm above the previously found equilibrium height, the capillary is inserted into the cell, and the mercury level is finally adjusted to the desired value. After completion of the measurements the capillary is withdrawn from the cell and washed thoroughly with a stream of water from a wash bottle while the mercury is still issuing from the tip and is being collected in a microbeaker. 

This procedure has been utihzed to determine metal cations and anions in water sample [48,50,51], titanium in high-speed steel at a concentration level of 25 3 mg/g [22], heavy metals (20 to 400 mg/1) in electroplating waste waters [25], copper and nickel (5 mg/1) in metal electroplating baths on wedge-shaped plates [44], copper, lead, cadmium, or mercury in vegetable juices [29], and nickel (1 to 3.8 mg/1) in electroplating waste water of lock industries [42,47]. 

A waste is toxic under 40 CFR Part 261 if the extract from a sample of the waste exceeds specified limits for any one of eight elements and five pesticides (arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver, endrin, methoxychlor, toxaphene, 2,4-D and 2,4,5-TP Silvex using extraction procedure (EP) toxicity test methods. Note that this narrow definition of toxicity relates to whether a waste is defined as hazardous for regulatory purposes in the context of this chapter, toxicity has a broader meaning because most deep-well-injected wastes have properties that can be toxic to living organisms. 

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