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Methylmercury Degradation Rates

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Frequently-anticipated questions:

What does this data set describe?

Title: Methylmercury Degradation Rates
Abstract:
The spreadsheet contains the data for 12 sites for sediment methylmercury degradation potential rate measurements
  1. How should this data set be cited?

    Ronald Oremland Mark Marvin-DiPasquale, 2005, Methylmercury Degradation Rates.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -81
    East_Bounding_Coordinate: -80
    North_Bounding_Coordinate: 26.75
    South_Bounding_Coordinate: 25

  3. What does it look like?

    <http://sofia.usgs.gov/exchange/marvin-dipasquale/mmdsitemap.gif> (GIF)
    map showing location of sampling sites

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: Jun-1996
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: spreadsheet

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference: Water Conservation Areas and Everglades National Park

    2. What coordinate system is used to represent geographic features?

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    Data collected for each site contain site id, date, sediment depth interval (cm), incubation time (days), 14C-MeHG injected (ng/cc wet sed), MeHg degradation first-order rate constant (k), and Me-Hg degradation potential rate (ng/cc set sed/d)
    Entity_and_Attribute_Detail_Citation: USGS personnel

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Mark Marvin-DiPasquale
    U.S. Geological Survey
    Project manager
    345 Middlefield Road,

    Building 15, McKelvey Building
    Menlo Park, CA 94025
    USA

    650 329 4442 (voice)
    650 329-4463 (FAX)
    mmarvin@usgs.gov

Why was the data set created?

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.

How was the data set created?

  1. From what previous works were the data drawn?

  2. How were the data generated, processed, and modified?

    Date: 1998 (process 1 of 1)
    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.

    Person who carried out this activity:

    Mark Marvin-DiPasquale
    U.S. Geological Survey
    Project manager
    345 Middlefield Road,

    Building 15, McKelvey Building
    Menlo Park, CA 94025
    USA

    650 329 4442 (voice)
    650 329-4463 (FAX)
    mmarvin@usgs.gov

  3. What similar or related data should the user be aware of?

    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, Washington, DC.

    Online Links:

    Other_Citation_Details:
    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, Ch, 2000, Methyl-mercury degradation pathways: a comparison among three mercury-impacted ecosystems: Environmental Science and Technology v. 34 , n. 23, American Chemical Society, Washington, DC.

    Online Links:

    Other_Citation_Details:
    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.

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Not all sites have data for all dates

  5. How consistent are the relationships among the observations, including topology?

    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

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: none
Use_Constraints:
none 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.

  1. Who distributes the data set? (Distributor 1 of 1)

    Heather S.Henkel
    U.S. Geological Survey
    600 Fourth St. South
    St. Petersburg, FL 33701
    USA

    727 803-8747 ext 3028 (voice)
    727 803-2030 (FAX)
    hhenkel@usgs.gov

  2. What's the catalog number I need to order this data set?

    Everglades Sediment Methylmercury Degradation Potential Rate Measurements

  3. What legal disclaimers am I supposed to read?

    The data have no explicit or implied guarantees.

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 22-Jan-2008
Metadata author:
Heather Henkel
U.S. Geological Survey
600 Fourth Street South
St. Petersburg, FL 33701
USA

727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
sofia-metadata@usgs.gov

Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <http://sofia.usgs.gov/metadata/sflwww/MeHg_degrad_rates.faq.html>

U.S. Department of the Interior, U.S. Geological Survey
Comments and suggestions? Contact: Heather Henkel - Webmaster
Generated by mp version 2.8.18 on Tue Jan 22 11:59:38 2008