Mercury and methylmercury in aquatic sediment across western North America

Large-scale assessments are valuable in identifying primary factors controlling total mercury (THg) and monomethyl mercury (MeHg) concentrations, and distribution in aquatic ecosystems. Bed sediment THg and MeHg concentrations were compiled for >16,000 samples collected from aquatic habitats thro...

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Bibliographic Details
Published in:The Science of the total environment 2016-10, Vol.568, p.727-738
Main Authors: Fleck, Jacob A., Marvin-DiPasquale, Mark, Eagles-Smith, Collin A., Ackerman, Joshua T., Lutz, Michelle A., Tate, Michael, Alpers, Charles N., Hall, Britt D., Krabbenhoft, David P., Eckley, Chris S.
Format: Article
Language:English
Subjects:
Aquatic sediment
Environmental Monitoring - methods
Geologic Sediments - analysis
Mercury - analysis
Mercury methylation
Methylmercury Compounds - analysis
Northwest Territories
Northwestern United States
Spatial mercury patterns
Water Pollutants, Chemical - analysis
Western North American Mercury Synthesis
WNAMS
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Summary:Large-scale assessments are valuable in identifying primary factors controlling total mercury (THg) and monomethyl mercury (MeHg) concentrations, and distribution in aquatic ecosystems. Bed sediment THg and MeHg concentrations were compiled for >16,000 samples collected from aquatic habitats throughout the West between 1965 and 2013. The influence of aquatic feature type (canals, estuaries, lakes, and streams), and environmental setting (agriculture, forest, open-water, range, wetland, and urban) on THg and MeHg concentrations was examined. THg concentrations were highest in lake (29.3±6.5μgkg−1) and canal (28.6±6.9μgkg−1) sites, and lowest in stream (20.7±4.6μgkg−1) and estuarine (23.6±5.6μgkg−1) sites, which was partially a result of differences in grain size related to hydrologic gradients. By environmental setting, open-water (36.8±2.2μgkg−1) and forested (32.0±2.7μgkg−1) sites generally had the highest THg concentrations, followed by wetland sites (28.9±1.7μgkg−1), rangeland (25.5±1.5μgkg−1), agriculture (23.4±2.0μgkg−1), and urban (22.7±2.1μgkg−1) sites. MeHg concentrations also were highest in lakes (0.55±0.05μgkg−1) and canals (0.54±0.11μgkg−1), but, in contrast to THg, MeHg concentrations were lowest in open-water sites (0.22±0.03μgkg−1). The median percent MeHg (relative to THg) for the western region was 0.7%, indicating an overall low methylation efficiency; however, a significant subset of data (n>100) had percentages that represent elevated methylation efficiency (>6%). MeHg concentrations were weakly correlated with THg (r2=0.25) across western North America. Overall, these results highlight the large spatial variability in sediment THg and MeHg concentrations throughout western North America and underscore the important roles that landscape and land-use characteristics have on the MeHg cycle. [Display omitted] •THg and MeHg concentrations of aquatic sediment compiled from >11000 western sites•Geospatial attributes were integrated with Hg and MeHg concentrations•MeHg concentrations differed among landscape categories, trends differed from THg•THg - MeHg relationship was weak (r2 = 0.25) but significant across the landscape•51% of MeHg variation explained by within-site variability and landscape categories
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2016.03.044