Nearshore seawater-column measurements of coastal groundwater discharge, Ofu, American Samoa, February 2020

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Frequently anticipated questions:

What does this data set describe?

Title:
Nearshore seawater-column measurements of coastal groundwater discharge, Ofu, American Samoa, February 2020
Abstract:
In-situ nearshore seawater measurements of dissolved radon and water level were used to determine the advection rate of groundwater onto the fringing reef off Ofu, American Samoa.
Supplemental_Information:
Additional information about the field activity from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2020-620-FA Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    Oberle, Ferdinand K., Prouty, Nancy G., and Storlazzi, Curt, 20250508, Nearshore seawater-column measurements of coastal groundwater discharge, Ofu, American Samoa, February 2020: data release DOI:10.5066/P13RJCAJ, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Oberle, F.K., Prouty, N.G., and Storlazzi, C.D. 2025, Nearshore seawater-column measurements of coastal groundwater discharge, Ofu, American Samoa, February 2020: U.S. Geological Survey data release, https://doi.org/10.5066/P13RJCAJ.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -169.666217
    East_Bounding_Coordinate: -169.658219
    North_Bounding_Coordinate: -14.181312
    South_Bounding_Coordinate: -14.185000
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 01-Feb-2020
    Ending_Date: 07-Feb-2020
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: comma-delimited text
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference:
      Data were collected continuously at a single point at Papaloloa Point and Fatuana Point, Ofu, American Samoa.
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (776)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
  7. How does the data set describe geographic features?
    Ofu20_Rn_data_200off_1.csv, Ofu20_Rn_data_200on_2.csv, Ofu20_Rn_data_300off_6.csv, Ofu20_Rn_data_300on_5.csv, Ofu20_Rn_data_200east_off_4.csv, and Ofu20_Rn_data_200east_on_3.csv
    Comma Separated Value (CSV) file containing data. (Source: Producer Defined)
    Date
    Date and time referenced to Universal Coordinate Time (Source: Global Positioning System)
    Range of values
    Minimum:2/1/2020 16:08
    Maximum:2/7/2020 9:49
    Units:MM/DD/YY hour:minutes
    Resolution:1
    Excess_Radon_(dpm/m3)
    Excess Radon (Source: Producer Defined)
    Range of values
    Minimum:-8.7000
    Maximum:147987.9773
    Units:Disintegrations per minute (dpm) per cubic meter (m3)
    Resolution:0.0001
    Water_Level_(m)
    Water Level (Source: Producer Defined)
    Range of values
    Minimum:0.031073130
    Maximum:1.084792501
    Units:meters
    Resolution:0.000000001
    Latitude_(Decimal_Degrees)
    Latitude in decimal degrees (Source: Global Positioning System)
    Range of values
    Minimum:-14.185000
    Maximum:-14.181312
    Units:decimal degrees
    Resolution:0.000001
    Longitude_(Decimal_Degrees)
    Longitude in decimal degrees (Source: Global Positioning System)
    Range of values
    Minimum:-169.666217
    Maximum:-169.658219
    Units:decimal degrees
    Resolution:0.000001
    Entity_and_Attribute_Overview: The first line of the csv file is a header line.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Ferdinand K. Oberle
    • Nancy G. Prouty
    • Curt Storlazzi
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-460-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

Radon (Rn-222) data were collected to characterize the advection rate of groundwater onto the nearshore reef. When analyzed in conjunction with measurements of changing water levels from tides the data can be used to assess the potential for terrestrial groundwater intrusion and the sources and fate of these water masses.

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: 03-Aug-2016 (process 1 of 1)
    Radon (Rn-222) concentration data were collected with a DURRIDGE RAD7 radon detector. The alpha decay of Rn-222 was detected at 3-minute intervals with the RAD7 in SNIFF mode. In SNIFF mode, the instrument detects radon entry points and gushers, and it recovers from high radon exposures in minutes. At the end of each run, the detector printed out a complete report. The RAD7 data were QA/QC’d, and raw counts of radon were exported using the manufacturer’s CAPTURE software. Conductivity and water level (CTD) data were collected with a YSI Castaway CTD Profiler.
  3. What similar or related data should the user be aware of?

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

  1. How well have the observations been checked?
    No formal attribute accuracy tests were conducted. DURRIDGE RAD7 radon detectors were calibrated using Durridge services to achieve a reproducibility of better than ±2% and an overall calibration accuracy of better than ±5%. Calibrations are carried out with a National Institute of Standards and Technology radon standard supplied through the U.S. EPA.
  2. How accurate are the geographic locations?
    A formal accuracy assessment of the horizontal positional information in the data set has not been conducted. The stated accuracy of the GPS unit used to determine the location of the instruments is +/- 5 m.
  3. How accurate are the heights or depths?
    A formal accuracy assessment of the vertical information in the data set has not been conducted. The stated accuracy of the Hastelloy pressure sensor used to determine the depth of the instrument is +/- 1 cm.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the metadata for each part of this data release carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    Data fall within expected ranges.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No restrictions or legal prerequisites for accessing the dataset.
Use_Constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? These data are available in comma-delimited (csv) format contained in a single zipped folder (Ofu20_Rn_Data.zip) accompanied by CMGDS FGDC-compliant metadata.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with any text editor software.

Who wrote the metadata?

Dates:
Last modified: 08-May-2025
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-460-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P13RJCAJ/Ofu20_Rn_metadata.faq.html>
Generated by mp version 2.9.51 on Fri May 9 14:39:01 2025