Assessment of Natural Source (Geologic and Vegetation) Mercury Emissions: Speciation, Mechanisms and SignificanceEPA Grant Number: R829800
Title: Assessment of Natural Source (Geologic and Vegetation) Mercury Emissions: Speciation, Mechanisms and Significance
Investigators: Gustin, Mae Sexauer , Schorran, David E. , Zehner, Richard E. , Rytuba, James J. , Johnson, Dale W. , Zhang, Hong , Lindberg, Steve
Current Investigators: Gustin, Mae Sexauer , Zehner, Richard E. , Rytuba, James J. , Johnson, Dale W. , Hatchett, Ben , Sedinger, Ben , Hanson, Brian , Peterson, Christianna , Weaver, Coty , Zhang, Hong , Stamenkovic, Jelena , Ericksen, Jody , Fay, Laura , Martindale, Lindsey , Engle, Mark , Xin, Mei , Markee, Melissa , Weisburg, Peter , Pillai, Rekha , Lyman, Seth , Lindberg, Steve , Kuiken, Todd , Ellis, Tyler
Institution: University of Nevada - Reno , University of Michigan , United States Geological Survey [USGS] , Desert Research Institute , University of Tennessee - Knoxville
Current Institution: University of Nevada - Reno , Desert Research Institute , Tennessee Technological University , United States Geological Survey [USGS] , University of Tennessee - Knoxville
EPA Project Officer: Chung, Serena
Project Period: January 1, 2003 through December 31, 2005 (Extended to December 31, 2007)
Project Amount: $891,545
RFA: Mercury: Transport, Transportation, and Fate in the Atmosphere (2001) RFA Text | Recipients Lists
Research Category: Mercury , Air Quality and Air Toxics , Safer Chemicals , Air
This study focuses on addressing gaps in our understanding of the role of natural sources in the atmospheric cycling of mercury (Hg) through a variety of field and laboratory studies. Our research will be conducted along interconnected avenues to reach consensus on the significance of natural sources of atmospheric Hg. The project will build upon a significant foundation of existing work and will use well established research protocols to fill these data gaps. Research will focus on quantifying Hg emissions from geologic sources, the speciation of the emitted Hg and the potential for local deposition, evaluation of the fraction of recently deposited Hg being re-emitted from such sources, and mechanisms of Hg release and emission from surface soils. The complication of vegetation emissions and of wildfires as natural sources of atmospheric Hg will also be investigated.
The proposed research will develop a database of Hg emissions from natural sources and a sound assessment of factors controlling these emissions that will be used to scale up fluxes and arrive at an estimate of natural source Hg emissions for the United States. This research focuses on information that is needed for assessment of the impact of natural source emissions on local, regional and global Hg cycles, and of the effectiveness of regulatory controls on point sources.
To better characterize the role of geologic and background sources, the proposed research includes a significant field component to characterize 1) Hg emissions from representative geologic settings, 2) the re-emission of Hg from soils, and 3) the speciation of those emissions. Site-related data needed for scaling up emissions temporally and spatially will also be collected. Mercury flux measurements will be made with field flux chambers and micro meteorological methods, and reactive gaseous Hg concentrations will be measured with annular denuders. This project will provide an understanding of the speciation of Hg being emitted from natural sources and the potential for dry deposition of elemental and reactive Hg to terrestrial surfaces near natural sources. Laboratory and field studies will provide a better understanding of the deposition and subsequent re-emission of Hg from soils. Mechanistic studies on the factors controlling emissions will be done and the information gained will be applied in models developed for scaling. The data base will build upon previous research providing a sound basis for modeling and scaling up emissions from natural sources. We will investigate the poorly-understood influence of vegetation on natural background and geologic source emissions, including role of vegetation and fires (both wild and prescribed) as sources of atmospheric Hg. These efforts will benefit from ongoing work. Our participation in three ongoing controlled-burn projects, will provide data on the magnitude of the release of Hg from geologic substrate, litter, and live vegetation associated with fires. We will similarly build upon an ongoing project investigating the role of live vegetation in Hg cycling. Using controlled growth plant chambers and a laboratory dynamic plant gas exchange chamber, the role of plants in controlling Hg cycling between soils and the atmosphere will be investigated. Recently developed plant chambers will allow us to measure Hg fluxes associated with vegetation growing in contaminated and non-contaminated soils in a field setting.
Based on our past work scaling up Hg emissions from local and regional areas, spatial data will be developed that characterizes Hg concentrations of geologic substrates, areas of Hg enrichment, and vegetation coverages for the U.S. that may be linked to Hg flux data and model parameters important in controlling Hg emissions. Using Geographic Information System Software we will build a database and model that will allow us to quantify the role of natural emissions of Hg to the atmosphere relative to anthropogenic emissions. Results of mechanistic studies will provide a framework for scaling emissions spatially and temporally, as a function of environmental conditions. Information derived in this project will allow for a much improved understanding of the local, regional and global impacts of Hg emitted from natural sources, many of which are beyond traditional control measures.