[Parameters: Topic='SOLID EARTH', Term='ROCKS/MINERALS/CRYSTALS', Variable_Level_1='SEDIMENTS']
Methylmercury Degradation RatesEntry ID: USGS_SOFIA_MeHg_degrad_rates
Abstract: The spreadsheet contains the data for 12 sites for sediment methylmercury degradation potential rate measurements.
High concentrations of methyl-mercury (CH3Hg+), a toxic substance to both animals and humans, recently have been measured in a number of top predators (including panthers and game fish) native to the Florida Everglades. The objective of this research was to provide ecosystem managers with CH3Hg+ degradation rate data from a number of study sites that represent a diversity of hydrologic and nutrient regimes common to the Everglades. The focus was on better understanding the microbial and geochemical controls regulating CH3Hg+ degradation. At the time of the study, little was known about the specific factors influencing this process in natural systems.
Data Set Citation
Dataset Originator/Creator: Ronald Oremland Mark Marvin-DiPasquale
Dataset Title: Methylmercury Degradation Rates
Dataset Release Date: 2005
Data Presentation Form: spreadsheetOnline Resource: http://sofia.usgs.gov/exchange/marvin-dipasquale/mmdindex.html
ISO Topic Category
Quality Data were collected at a suite of sites between 1995 and 1998 in the Water Conservation Areas and Everglades National Park. Due to changes in methodology, only data collected since June 1996 is included in the dataset.
Not all sites have data for all dates.
... Periodic field measurements of methylmercury (MeHg) degradation potential rates in sediment were conducted between 1995 and 1998, at a suite of study sites in the Water Conservation Areas and Everglades National Park. Intact sediment cores were collected by hand with polycarbonate core tubes (8 cm i.d. x 15-30 cm). The unconsolidated surface floc layer was treated as one discrete interval for June 1996, December 1996, and January 1998. Sediment below this zone was sectioned into 2 cm to 4 cm discrete depth intervals. Discrete depths were sampled for the whole core during April 1997, July 1997, and June 1998. For each interval, sediment from 3-6 cores was pooled for a homogenized composite sample. Subsamples (3 cc) were amended with radiolabeled 14C-MeHg (0.5 to 10 nCi) and incubated anoxically for 0.2 to 7 days at 18-25 deg C in 13 cc serum bottles. Incubations were arrested by adding 1 ml of 3 M NaOH. All incubations were initiated within 10 hours of sample collection, except during April 1997, which were initiated three days after collection. All site/depth discrete sample sets included n=3 replicates and one autoclave killed control. The gaseous 14 C endproducts (14 CH4 and 14 CO2) were assayed by a CH4 combustion/CO2 trapping assay as described in Marvin-DiPasquale and Oremland (1998) Environ. Sci. Tech. 32:2256-2263.
All MeHg production and degradation rates were calculated as potential rates (i.e. based on the amount of radiolabel added) and not as in-situ rates.
Access Constraints None
Use Constraints None.
Data Set Progress
Distribution Size: 0.041
Distribution Format: MS Excel
Role: TECHNICAL CONTACT
Email: mmarvin at usgs.gov
U.S. Geological Survey Bldg 15, McKelvey Building 345 Middlefield Road, MS 480
City: Menlo Park
Province or State: CA
Postal Code: 94025
Role: DIF AUTHOR
Email: alicia.m.aleman at nasa.gov
Goddard Space Flight Center Code 610.2
Province or State: MD
Postal Code: 20771
Marvin-DiPasquale, Mark C., Oremland, Ronald S. 1998; Bacterial methylmercury degradation in Florida Everglades peat sediment; Environmental Science and Technology, v. 32, n. 17, American Chemical Society All users may view the abstract of this article. If you are a subscriber, you may view the article. If you are not a subscriber, you may purchase and download the PDF version of the article.
Marvin-DiPasquale, Mark C., Agee, Jennifer; McGowan, Chad; Oremland, Ronald S.; Thomas, Martha; Krabbenhoft, David; Gilmour, Cynthia C. 2000; Methyl-mercury degradation pathways: a comparison among three mercury-impacted ecosystems; Environmental Science and Technology, v. 34 , n. 23, American Chemical Society All users may view the abstract of this article. If you are a subscriber, you may view the article. If you are not a subscriber, you may purchase and download the PDF version of the article.
Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2008-01-22
Last DIF Revision Date: 2016-01-27