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Investigating the Effects of Mercury Emissions in the Four Corners Area on Local Deposition Levels and Ambient Concentrations

Weidner, Kristin
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project Formato: 6998431 bytes; application/pdf
Publicado em 11/09/2007
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In 2005, the United States Environmental Protection Agency (EPA) issued the Clean Air Mercury Rule (CAMR) as a means for regulating mercury emissions from coal-fired utility boilers in the United States. However, there is concern that this rule may result in local ‘hot spots’ of increased mercury in the environment surrounding these facilities. Citizens of the Four Corners region in the southwest are particularly concerned about this rule due to the presence of two of the highest mercury-emitting facilities in the country. While studies have shown that an increase in atmospheric levels of mercury lead to a global increase in mercury deposition, little is known on the effects air emissions from point sources on local mercury levels in the environment. In this study, mercury emissions from the Four Corners Power Plant and the San Juan Generating Station of New Mexico were investigated for their possible impacts on local mercury levels in the environment. The analysis included statistical and back trajectory analysis of deposition data at a nearby monitoring site, as well as SCREEN dispersion modeling of mercury emissions to calculate mercury concentrations in the ambient air. Results of the statistical analysis of the deposition data showed a relationship between precipitation and deposition levels...

Sources and Biogeochemical Transformation of Mercury in Aquatic Ecosystems

Deonarine, Amrika
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011
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Mercury contamination in aquatic ecosystems is a concern as anaerobic aquatic sediments are the primary regions of methylmercury production in freshwater and coastal regions. Methlymercury is a bioaccumulative neurotoxin, and human exposure to methylmercury can result in impaired functioning of the central nervous system and developmental disabilities in children. To minimize the risk of human exposure to methylmercury, it is important to be knowledgeable of the various sources which can supply mercury to aquatic ecosystems as well as have a complete understanding of the biogeochemical processes which are involved in methylmercury production in aquatic systems. In this dissertation work, both mercury biogeochemical speciation in anaerobic aquatic sediments and sources of mercury to aquatic systems were addressed.

The biogeochemical speciation of mercury is a critical factor which influences the fate and transformation of mercury in aquatic environments. In anaerobic sediments, mercury chemical speciation is controlled by reduced sulfur groups, such as inorganic sulfide and reduced sulfur moieties in dissolved organic matter (DOM). The formation of mercury sulfide nanoparticles through stabilization by dissolved organic matter (DOM) was investigated in precipitation studies using dynamic light scattering. Mercury sulfide nanoparticles (particle diameter < 100 nm) were stabilized through precipitation reactions that were kinetically hindered by DOM. To further investigate the interaction between DOM and metal sulfides...