Mercury cycling in stream ecosystems. 1. Water column chemistry and transport.
ABSTRACT This paper is freely available via Open Access: http://pubs.acs.org/doi/abs/10.1021/es802694n
We studied total mercury (THg) and methylmercury (MeHg) in eight streams, located in Oregon, Wisconsin, and Florida, that span large ranges in climate, landscape characteristics, atmospheric Hg deposition, and water chemistry. While atmospheric deposition was the source of Hg at each site, basin characteristics appeared to mediate this source by providing controls on methylation and fluvial THg and MeHg transport. Instantaneous concentrations of filtered total mercury (FTHg) and filtered methylmercury (FMeHg) exhibited strong positive correlations with both dissolved organic carbon (DOC) concentrations and streamflow for most streams, whereas mean FTHg and FMeHg concentrations were correlated with wetland density of the basins. For all streams combined, whole water concentrations (sum of filtered and particulate forms) of THg and MeHg correlated strongly with DOC and suspended sediment concentrations in the water column.
- SourceAvailable from: Douglas A. Burns[Show abstract] [Hide abstract]
ABSTRACT: Inverse empirical models can inform and improve more complex process-based models by quantifying the principal factors that control water quality variation. Here, we developed a multiple regression model that explains 81% of the variation in filtered methylmercury (FMeHg) concentrations in Fishing Brook, a 4th-order stream in the Adirondack Mountains, New York, a known “hot spot” of Hg bioaccumulation. This model builds on previous observations that wetland-dominated riparian areas are the principal source of MeHg to this stream, and was based on 43 samples collected during a 33-mo period in 2007–09. Explanatory variables include those that represent the effects of water temperature, streamflow, and modeled riparian water table depth on seasonal and annual patterns of FMeHg concentrations. An additional variable represents the effects of an upstream pond on decreasing FMeHg concentrations. Model results suggest that temperature-driven effects on net Hg methylation rates is the principal control on annual FMeHg concentration patterns. Additionally, streamflow dilutes FMeHg concentrations during the cold dormant season. The model further indicates that depth and persistence of the riparian water table as simulated by TOPMODEL are dominant controls on FMeHg concentration patterns during the warm growing season, especially evident when concentrations during the dry summer of 2007 were less than half of those in the wetter summers of 2008 and 2009. This modeling approach may help identify the principal factors that control variation in surface water FMeHg concentrations in other settings, which can guide the appropriate application of process-based models.Journal of Geophysical Research: Biogeosciences 09/2014; · 3.02 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The U.S. EPA conducted a national statistical survey of fish fillet tissue with a sample size of 541 sites on boatable rivers =>5th order in 2008-2009. This is the first such study of mercury (Hg) in fish tissue from river sites focused on potential impacts to human health from fish consumption to also address wildlife impacts. Sample sites were identified as being urban or non-urban. All sample mercury concentrations were above the 3.33ugkg(-1) (ppb) quantitation limit, and an estimated 25.4% (±4.4%) of the 51663 river miles assessed exceeded the U.S. EPA 300ugkg(-1) fish-tissue based water quality criterion for mercury, representing 13144±181.8 river miles. Estimates of river miles exceeding comparable aquatic life thresholds (translated from fillet concentrations to whole fish equivalents) in avian species were similar to the number of river miles exceeding the human health threshold, whereas some mammalian species were more at risk than human from lower mercury concentrations. A comparison of means from the non-urban and urban data and among three ecoregions did not indicate a statistically significant difference in fish tissue Hg concentrations at p<0.05. Published by Elsevier Ltd.Chemosphere 11/2014; · 3.14 Impact Factor
- Journal of Hydrology 09/2013; 501:92-100. · 2.69 Impact Factor
Thank you for your interest in our paper Mercury cycling in stream ecosystems. 1. Water column
chemistry and transport.
This paper is open access, available for free download from Environmental Science and
Brigham, M.E., Wentz, D.A., Aiken, G.R., and Krabbenhoft, D.P., 2009, Mercury cycling in
stream ecosystems. 1. Water column chemistry and transport: Environmental Science and
Technology, v. 43, no. 8, p. 2720-2725. http://pubs.acs.org/doi/abs/10.1021/es802694n
denotes open access