Radiochemistry (210Pb and 137Cs) of cores BC01 and BC02 obtained in 2024 off Alameda and Point Isabel in San Francisco Bay, California

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Frequently anticipated questions:

What does this data set describe?

Title:
Radiochemistry (210Pb and 137Cs) of cores BC01 and BC02 obtained in 2024 off Alameda and Point Isabel in San Francisco Bay, California
Abstract:
This data release provides radiochemistry data (210Pb and 137Cs) of two sediment cores, BC01 and BC02, collected during USGS Field Activity 2024-662-FA in 2024 in San Francisco Bay, California, U.S.A., off Alameda and Point Isabel, respectively.
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=2024-662-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?
    McGann, Mary, and Lorenson, Thomas D., 2025, Radiochemistry (210Pb and 137Cs) of cores BC01 and BC02 obtained in 2024 off Alameda and Point Isabel in San Francisco Bay, California: data release DOI: 10.5066/P1VG9X8Q, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: McGann, M. and Lorenson, T.D., 2025, Radiochemistry (210Pb and 137Cs) of cores BC01 and BC02 obtained in 2024 off Alameda and Point Isabel in San Francisco Bay, California: U.S. Geological Survey data release, https://doi.org/10.5066/P1VG9X8Q.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.34480
    East_Bounding_Coordinate: -122.27956
    North_Bounding_Coordinate: 37.89334
    South_Bounding_Coordinate: 37.76284
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 08-Nov-2024
    Ending_Date: 08-Nov-2024
    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?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (37)
    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 0.00001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.978698214.
  7. How does the data set describe geographic features?
    SFB_Cores_BC01_and_BC02_data_radiochemistry.csv
    Results of 210Pb and 137Cs analyses of fine sediment. (Source: Producer defined.)
    State
    State in the United States in which the core was obtained (Source: Producer defined.)
    ValueDefinition
    CaliforniaState in the United States in which the core was obtained.
    General_Location
    Generalized geographic location (Source: Producer defined.) General geographic location where the core was taken.
    Coring_Location
    Name of the coring location. (Source: Producer defined)
    ValueDefinition
    AlamedaMore precise description of coring location.
    Point IsabelMore precise description of coring location.
    USGS_Field_Activity_Number
    Name of the field activity (Source: Producer defined) Unique alphanumeric identifier for a U.S. Geological Survey field activity, in FFFF-FFF-FF format. The FFFF-FFF-FF format (e.g., 1997-609-FA) represents the year of the field activity (e.g., FFFF equals 1997), the number assigned to the field activity (FFF equals 609), and the last two digits (FF) representing a USGS field activity (FA).
    Core_ID
    Name of the core (Source: Producer defined) Unique alphanumeric identifier for the core.
    Coring_Device
    Type of device used to collect the core (Source: Producer defined)
    ValueDefinition
    BobcorerBobcorer indicates the sample was collected with a bobcorer from a vessel.
    Date_Collected_YYYY_MM_DD
    Date in year, month, and day (YYYY-MM-DD) (Source: Producer defined.)
    Range of values
    Minimum:2024-11-08
    Maximum:2024-11-08
    Units:day
    Resolution:1
    Latitude
    Latitude of the site at which the push core was collected. (Source: Producer defined.)
    Range of values
    Minimum:37.76284
    Maximum:37.89334
    Units:decimal degrees
    Resolution:0.00001
    Longitude
    Longitude of the site at which the push core was collected. (Source: Producer defined.)
    Range of values
    Minimum:-122.27956
    Maximum:-122.34480
    Units:decimal degrees
    Resolution:0.00001
    Core_Length_cm
    Length of core recovered. (Source: Producer defined)
    Range of values
    Minimum:123.5
    Maximum:128.0
    Units:centimeters
    Resolution:0.5
    Water_Depth_m
    Water depth of core collected. (Source: Producer defined.)
    Range of values
    Minimum:2.6
    Maximum:2.8
    Units:meters
    Resolution:0.1
    Sample_Upper_Depth_Limit_cm
    The upper depth at which the sediment sample was obtained below the sediment surface in a core. (Source: Producer defined.)
    Range of values
    Minimum:0.0
    Maximum:50.0
    Units:centimeters
    Resolution:1.0
    Sample_Lower_Depth_Limit_cm
    The lower depth at which the sediment sample was obtained below the sediment surface in a core. (Source: Producer defined.)
    Range of values
    Minimum:1.0
    Maximum:51.0
    Units:centimeters
    Resolution:1.0
    Sample_Middle_Depth_Limit_cm
    The middle of the depth range at which the sediment sample was obtained below the sediment surface in a core. (Source: Producer defined.)
    Range of values
    Minimum:0.5
    Maximum:50.5
    Units:centimeters
    Resolution:0.5
    Dry_Bulk_Density_per_cubic_g
    Measurement of the density of bulk dry sediment per cubic gram. (Source: Producer defined.)
    Range of values
    Minimum:0.5937
    Maximum:1.2233
    Units:per cubic gram
    Resolution:0.0001
    Cumulative_Mass_g_per_square_cm
    Measurement of the cumulative mass of the sediment in grams per square centimeter. (Source: Producer defined.)
    Range of values
    Minimum:0.9259
    Maximum:25.2121
    Units:grams per square centimeter
    Resolution:0.0001
    Total_210Pb_dpm_per_g
    Measurement of the total 210Pb in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0.0000
    Maximum:5.6575
    Units:disintegrations per minute per gram
    Resolution:0.0001
    Total_210Pb_Error_dpm_per_g
    Error in the measurement of the total 210Pb in disintegrations per minute per gram of sediment. 9999 represents no error could be determined because no disintegrations per minute per gram of sediment were measured. (Source: Producer defined.)
    Range of values
    Minimum:0.4009
    Maximum:1.0141
    Units:disintegrations per minute per gram.
    Resolution:0.0001
    226Ra_dpm_per_g
    Measurement of 226Ra in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0.9603
    Maximum:1.9328
    Units:disintegrations per minute per gram
    Resolution:0.0001
    226Ra_Error_dpm_per_g
    Error in the measurement of 226Ra in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0.0743
    Maximum:0.2133
    Units:disintegrations per minute per gram
    Resolution:0.0001
    Excess_210Pb_dpm_per_g
    Measurement of the excess 210Pb in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:-0.303
    Maximum:4.134
    Units:disintegrations per minute per gram
    Resolution:0.001
    Excess_210Pb_Error_dpm_per_g
    Measurement of the error in the excess 210Pb in disintegrations per minute per gram of sediment. 9999 represents no error could be determined because no disintegrations per minute per gram of sediment were measured. (Source: Producer defined.)
    Range of values
    Minimum:0.4100
    Maximum:1.0230
    Units:disintegrations per minute per gram.
    Resolution:0.0001
    137Cs_dpm_per_g
    Measurement of the 137Cs in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0.0000
    Maximum:0.2830
    Units:disintegrations per minute per gram
    Resolution:0.0001
    137Cs_Error_dpm_per_g
    Measurement of the error of 137Cs in disintegrations per minute per gram of sediment. 9999 represents no error could be determined because no disintegrations per minute per gram of sediment were measured. (Source: Producer defined.)
    Range of values
    Minimum:0.0330
    Maximum:0.0660
    Units:disintegrations per minute per gram
    Resolution:0.001
    Linear_Sedimentation_Rate_cm_per_year
    The linear sedimentation rate in centimeters of sediment per year. 9999 represents no linear sedimentation rate could be determined from the available data. (Source: Producer defined.)
    Range of values
    Minimum:9999
    Maximum:9999
    Units:centimeters per year
    Mass_Accumulation_Rate_mg_per_squared_cm_per_year
    The mass accumulation rate in milligrams per squared centimeter of sediment per year. 9999 represents no mass accumulation rate could be determined from the available data. (Source: Producer defined.)
    Range of values
    Minimum:9999
    Maximum:9999
    Units:milligrams per squared centimeter per year
    Entity_and_Attribute_Overview:
    The first line of the comma-separated values 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)
    • Mary McGann
    • Thomas D. Lorenson
  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

    650-329-4979 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

San Francisco Bay is one of the most highly-invaded estuaries in the world. A species of benthic foraminifera, Trochammina hadai Uchio, was first found in the bay in 1993 in a core collected in the southern embayment of the bay (known a South Bay) offshore of San Francisco International Airport. It has now been three decades since Trochammina hadai was first recognized as a non-indigenous species in San Francisco Bay. To update the record of the species’ arrival and presence in the bay, cores were collected at sites in the vicinity of Alameda and Point Isabel. Radiochemistry (210Pb and 137Cs) was analyzed in two cores (BC01 and BC02) to provide an age model and aid in determining the first arrival of the species at those locations.

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: 2024 (process 1 of 2)
    A metal core barrel, approximately 6 cm in diameter, was driven into the sediment surface by means of a bobcorer at three locations (one off Alameda and two off Point Isabel) in San Francisco Bay off the USGS R/V Jewell. The cores were brought to the the USGS facility in Santa Cruz, California and housed in a core refrigerator.
    Date: 2024 (process 2 of 2)
    Sixteen sediment samples from core BC01 and twenty-one from core BC02 were prepared for 210Pb and 137Cs following the methods of Swarzenski and others (2006) and Swarzenski (2014). For core BC01, samples weighing 15-20 grams were taken every 2 cm continuously down through 20 cm and then approximately every 5 cm to a depth of 51 cm. For core BC02, samples weighing 15-20 grams were taken every 1 cm continuously down through 20 cm and then approximately every 5 cm to a depth of 37 cm. Sediment samples for 210Pbc dating were weighed before and after drying at 105 degrees celsius for at least 24 hours, disaggregated in a mortar and pestle, transferred to a plastic test tube, then placed in a gamma radiation detector and counted. Total 210Pb activities were directly determined by measuring the 46.52-KeV gamma peak using ORTEC High Purity Germanium (HPGe) radiation detectors. Supported levels of 210Pb from 226Ra were determined by measuring the gamma activity of 214Pb (at 295 and 352 KeV) and of 214Bi (609 KeV), the short-lived daughter products of 226Ra (351.87 and 609.31 KeV). 137Cs activities in this study were determined by measurement of the 661.6-KeV gamma peak. Precision in these measurements was less than 5 percent.
  3. What similar or related data should the user be aware of?
    Swarzenski, P.W., Baskaran, M., Rosenbauer, R.J., and Orem, W.H., 2006, Historical trace element distribution in sediments from the Mississippi River Delta..

    Online Links:

    Other_Citation_Details:
    Swarzenski, P.W., Baskaran, M., Rosenbauer, R.J., and Orem, W.H., 2006, Historical trace element distribution in sediments from the Mississippi River Delta: Estuaries and Coasts, v. 29. p. 1094–1107.
    Swarzenski, P.W., 2014, 210Pb dating..

    Online Links:

    Other_Citation_Details:
    Swarzenski, P.W., 2014, 210Pb dating, in Rink, W., Thompson, J., eds., Encyclopedia of Scientific Dating Methods, Springer, Dordrecht, p. 1–11.

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

  1. How well have the observations been checked?
    Because of the inverse relationship between particle surface area and particle size, the finest sediment available was analyzed. The thinnest possible sediment layers were sampled to provide better time resolution of sedimentation rates. NIST radioactive spikes and material and International Atomic Energy Agency (IAEA) radioactive standards were used for calibrating the counting equipment. Precision in the activities of 210Pb and 226Ra was typically better than 5 percent. Since our spikes are primary standards and our counting equipment was well calibrated, our accuracy was similar to our precision.
  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 horizontal accuracy was determined with a a Garmin GPSmap XSV chartplotter and a Garmin GPS19x antenna on the R/V Jewell. The system can determine the location to within 3 m (9.84 ft).
  3. How accurate are the heights or depths?
    A formal accuracy assessment of the vertical positional information in the data set has not been conducted. Depth was determined using a Furuno FCV585 depth sounder for R/V Jewell.
  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 were checked for logical consistency by the laboratory staff before release to confirm that numerical values were not outside a reasonable range for a particular field.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints
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 originators 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 a comma-delimited text file (SFB_Cores_BC01_and_BC02_data_radiochemistry.csv) which provides radiochemistry data (210Pb and 137Cs) of two sediment cores, BC01 and BC02, collected in 2024 in San Francisco Bay, California off Alameda and Point Isabel, respectively.
  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: 30-Apr-2025
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (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_P1VG9X8Q/SFB_Cores_BC01_and_BC02_data_radiochemistry_metadata.faq.html>
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