Superfund Research Program

Sources, Transport and Fate of Arsenic in Groundwater

Project Leaders: Carl E. Renshaw, Joel D. Blum (University of Michigan)
Grant Number: P42ES007373
Funding Period: 2000-2005

Project-Specific Links

Final Progress Reports

Year:   2004 

This project is examining the sources of arsenic and mercury in the environment and the mechanisms of their transport to drinking water wells and lakes where they pose potential hazards to humans. The studies related to arsenic have involved regional studies of the arsenic chemistry of groundwater throughout the state of New Hampshire, detailed site studies of arsenic speciation and hydrogeochemistry at several sites with especially high arsenic levels, investigations of the nanoscale properties of aquifer materials and how they affect arsenic sources and mobility, and laboratory studies to understand the physical and chemical processes operating in the natural systems.  The team’s regional study has been expanded from the 992 analyses included in their 1999 publication to over 3000 drinking water analyses and 300 rock analyses and has elucidated regional geologic controls on arsenic in groundwater. This was recently accepted for publication in the journal Chemical Geology. Site specific studies include analyses of the sources and transport mechanisms for arsenic in the groundwater at the Coakley landfill Superfund site and of the fate of the millions of pounds of lead arsenate pesticide applied to southern New Hampshire apple orchards during the first half of the last century, with a particular focus on the role of development on arsenic mobilization. The Coakley study is particularly focused on the role of the natural microbial degradation of organic contaminants in the release of naturally occurring arsenic.  A manuscript on this work is in review of the Journal of Environmental Science and Technology. The studies related to mercury involve three major research efforts. The first is the use of artificially enriched isotopes of mercury to trace the bioaccumulation of mercury in aquatic systems. This work has been in collaboration with Project 7 and has resulted in a series of recently published articles. The second is the study of mercury emissions form forest fires. This work suggests that up to 1/3 of US mercury emissions may come from wildfires and a manuscript is in preparation on this work. The third is the use of the natural variability in the isotopic composition of mercury in nature to trace the sources of mercury in the atmosphere and in aquatic systems. Project investigators have been developing new methods to measure the isotopic composition of mercury on small samples of various types with very high precision. They have completed studies of the natural variation of mercury isotope compositions in a wide variety of ore deposits, in many different industrial mercury compounds and in many standard reference materials; this work is in review in the journal Geology. They are currently analyzing the various sources of mercury to the atmosphere to characterize these endmembers—including mercury from coal and gas combustion, forest fires, and incinerators. They are also collecting and analyzing samples of atmospheric particles, reactive gases, precipitation, foliage, and lake sediments, with the goal of ascertaining the relative importance of different sources of mercury in contaminated lakes. Finally, they are carrying out studies in collaboration with researchers at Rutgers University and Project 7 to determine the effects of bacterial reduction and methylation on mercury isotope ratios. They have measured systematic rayleigh fractionation patterns and have determined fractionation factors for bacterial mercury reduction and a manuscript on these results is in preparation. The researchers have also observed systematic isotope fractionations in methyl mercury in freshwater fish and are continuing investigations of isotope fractionation during methylation.