Analysis of Mercury Speciation Profiles Currently Used for Atmospheric Chemistry Modelling
Analysis of Mercury Speciation Profiles Currently Used for Atmospheric
Wisconsin Department of Natural Resources
Data obtained by the United States Environmental Protection Agency (USEPA) as part of an Information Collection Request (ICR) addressing Section 112 of the Clean Air Act, have been used to estimate speciation for every coal-fired utility boiler in the United States based on type of coal used, type of boiler, and type of controls. Paul Chu and Leonard Levin of EPRI gave a presentation to the Utility Work Group in Washington D.C. on December 18, 2001. The presentation, “EPRI ICR Data Analyses”, discusses the methods used to estimate mercury emissions and speciation for coal-fired boilers based on the data collected. It also discusses the limitations: many variables are not directly correlated (LOI, flue gas temperature, flue gas residence time, metal concentrations in coal, effect of SCR, SNCR, NH3), the analyses of coal defines mercury entering boiler, and the analyses assumed that there is no mercury in bottom ash. Despite the room for improvement, speciation for coal-fired boilers is in much better shape than any other category. This is good news if you are myopically interested in coal-fired boilers, but not good news if you are interested in the bigger picture of atmospheric mercury cycling in Wisconsin’s environment. Speciation largely determines the distance that mercury emitted from a source is transported [Hg(II) typically is removed from the atmosphere within 100km of the source] and its reactivity. Therefore, inaccurate speciation profiles can result in under or over estimating the contribution to local deposition of a particular source category.