Mercury pollution, toxicity

Despite its availability and current use, coal is not as widely used today as the other fossil fuels. Coal s major weakness is that it does not burn cleanly. It often contains trace amounts of other elements, including mercury, arsenic, and sulfur, and when it burns, it releases these toxic substances into the air. Over time, coal pollution builds up in the environment. Mercury released during coal combustion, for example, settles in water and builds up in the bodies of fish and shellfish. When these fish and shellfish are eaten by humans and other animals, harmful amounts of mercury can be ingested. In 2008, bluefm tuna served in expensive New York restaurants was found to contain unacceptably high levels of mercury. These fish eat smaller organisms in the ocean, and when these small organisms contain mercury, the toxic element becomes concentrated in the body of the tuna. 

ANTIFOULING AGENTS. Various chemical substances added to paints and coatings to combat mildew and crustaceous formations, such as barnacles on the hull of a ship. In the past, large quantities of mercury compounds have been used in this manner. With growing environmental concern over possible mercury pollution, manufacturers have been turning to other, sometimes less efficacious compounds, Research continues to find compounds of a less toxic, but equally effective power of the mercury compounds. Bis(tributyltin) fluoride has been used on ship bottoms. See also Mercury. 

Mercury is ranked third by the CERCLA priority fist of toxic substances and has been found to be present in the environment in concentration that could be harmful [1]. Prevention measures for mercury pollution are primordial and the first proactive step is to identify the status of mercury pollution in high-risk areas. Though mercury is quite useful, it has long been known as a persistent, bio-accumulative toxic pollutant that adversely affects the central nervous system. Persistent, bio-accumulative,... 

Since the early 1960s, the growing awareness of environmental mercury pollution and its toxicity has stimulated the development of more accurate, precise and efficient methods for the determination of total mer-... 

Because of the sudden awareness of the toxic effects of mercury pollution problems in several parts of the world, many environmental studies were carried out in the early 1970 s. 

On Dec. 21, EPA issued the Mercury and Air Toxics Standards, the first national standards to protect American families from power plant emissions of mercury and toxic air pollution such as arsenic, acid gas, nickel, selenium, and cyanide. 

Jiang, G.-B., Shi, J.-B. Feng, X.-B. (2006) Mercury pollution in China. An overview of the past and current sources of the toxic metal. Environmental Science Technology, 40, 3672-3678. 

Environmental Protection Agency, National Emission Standards for Hazardous Air Pollutants, From Coal- and Oil-Fired Electric Utility Steam Generating Units and Standards of Performance for Fossil-Fuel-Fired Electric Utility, Industrial-Commercial-Institutional, and Small Industrial-Commercial-Institutional Steam Generatirtg Units, 76 Fed. Reg. 23,399 (2011) EPA Finalizes Rule to Reduce Mercury, Air Toxics Emissions From Power Plants, 42 BNA Env. Rept. 2877 (2011) Amy Harder, Mercurial, National Journal, September 17, 2011, at 54 (Obama Speech). 

The toxic nature of mercury and its compounds has caused concern over environmental pollution, and governmental agencies have imposed severe restrictions on release of mercury compounds to waterways and the air (see Mercury). Methods of precipitation and agglomeration of mercurial wastes from process water have been developed. These methods generally depend on the formation of relatively insoluble compounds such as mercury sulfides, oxides, and thiocarbamates. MetaUic mercury is invariably formed as a by-product. The use of coprecipitants, which adsorb mercury on their surfaces facihtating removal, is frequent. 

Although the petrochemical and metals industries were the primai y focus of the toxic air pollutants legislation, approximately forty of these substances have been detected in fossil power plant flue gas. Mercury, which is found in trace amounts in fossil fuels such as coal and oil, is liberated during the combustion process and these emissions may be regulated in the future. EPA issued an Information Collection Request (ICR) that required all coal-fired plants to analyze their feed coal for mercury and chlorine. Since these data will be used in making a regulatory decision on mercury near the end ot the year 2000, it is critical that the power industry provide the most accurate data possible. 

Table 13.8 identifies common pollutants in aqueous effluents. Of the metals, the most toxic are salts of the heavy metals beryllium, cadmium, chromium, copper, lead, mercury, nickel and zinc. 

There is a vast range of aqueous organic pollutants with a wide toxicity profile. Some, e.g. polychlorinated biphenyls, certain herbicides, fungicides and pesticides, and organo-mercury compounds, are persistent and may bioaccumulate in the food chain. Trace contaminants such as sodium chloride, iron and phenols (especially if chlorinated) may also impart a taste to water. Typical consent levels for industrial discharges are provided in Table 13.10. 

Scheuhammer AM. 1987. The chronic toxicity of aluminum, cadmium, mercury, and lead in birds a review. Environ Pollut 46 263-295. 

Toxic pollutants found in the mercury cell wastewater stream include mercury and some heavy metals like chromium and others stated in Table 22.8, some of them are corrosion products of reactions between chlorine and the plant materials of construction. Virtually, most of these pollutants are generally removed by sulfide precipitation followed by settling or filtration. Prior to treatment, sodium hydrosulfide is used to precipitate mercury sulfide, which is removed through filtration process in the wastewater stream. The tail gas scrubber water is often recycled as brine make-up water. Reduction, adsorption on activated carbon, ion exchange, and some chemical treatments are some of the processes employed in the treatment of wastewater in this cell. Sodium salts such as sodium bisulfite, sodium hydrosulfite, sodium sulfide, and sodium borohydride are also employed in the treatment of the wastewater in this cell28 (Figure 22.5). 

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