>C-14 Sample Selection and Prep Protocol
Home » Research » Methods » C-14 Sample Selection and Prep Protocol

C-14 Sample Selection and Prep Protocol

Background

The protocols described here apply to dating of samples by the liquid scintillation counting method. Sample sizes and treatment steps are described for each of the types of material that are commonly dated using this method. The analysis involves three major steps:

  • pretreatment (to remove contaminants)
  • chemical preparation (to convert the sample's carbon to a datable form)
  • and the actual counting process.

Purpose

To determine how old a sample is.

Materials

Datable materials include:

The sample sizes listed below are the minimum needed to produce 3 ml of benzene equivalent to 2.41 gm of carbon), which is the minimum volume of benzene required by the counter. Samples yielding less than 3 ml of benzene can still be counted, but must be diluted first with dead benzene to bring the total volume up to 3 ml, which tends to increase the magnitude of the counting deviation (the ± figure in the date).

Please note: Except in the case of charcoal, these are minimum sizes. A larger quantity of material may be required if the carbon content of the material is unusually low.

  • Charcoal: 5-6 gm of clean charcoal (actual pieces of charcoal, not counting any included dirt).
  • Wood: 6-7 gm of hardwood or 10 gm of softwood.
  • Peat: 15-20 gm if silt-free, or proportionally more if there is a significant silt content.
  • Other organic materials: Varies depending on the proportion of carbon to other constituents.
  • Shell: 20-100 gm of clean shell, depending on the degree of weathering. In the case of badly weathered shell as much as 90% of the outer part of the shell may have to be discarded.
  • Other carbonates (including mortar): 20-30 gm if silt-free, or proportionally more if there is a significant silt content.
  • Bone: 1 kg of clean bone, or proportionally more if the bone is badly weathered. As with shell, as much as 90% of the original sample may have to be discarded if the bone is badly weathered. It is desirable to date both the apatite and collagen fractions, if possible, although it frequently is not possible to extract enough collagen to obtain meaningful results.
  • Soil: Two one-gallon ziplock bags (or the equivalent) of soil if only a total humate date is required; twice that amount if humin or humic acid dates also are to be run.
  • Ground water: To date ground water, carbon suspended in the water must be precipitated out as strontium carbonate by a separate chemical process, which the Radiocarbon Lab is not equipped to perform. 60-70 gm of clean, dry precipitate are required.

Pre-treatment Procedure

Charcoal & Wood 

  1. All adhering dirt and other foreign matter is removed by washing the sample with hot water through a USGS screen of appropriate mesh. For charcoal samples, any large chunks are broken up with a knife (preferred size is ca. 1 cm.); wood samples are cut into shavings.
  2. The dirt-free sample is placed in a 1-liter beaker, immersed in 2% HCl, and boiled for 10-60 minutes, depending on the size of the sample. This step removes any CaCO3 in the sample. The sample is left in the cold HCl solution to digest overnight. It is then washed repeatedly with distilled H2O until the pH is 5.5 (near neutral).
  3. The sample is washed into a clean beaker. 2% NaOH is added and the sample is boiled to remove possible humic acid contaminants. The sample is again left standing overnight and then is washed repeatedly with distilled H2O until the pH is 5.5 (near neutral). The NaOH is decanted, and saved if the humic acid fraction is to be dated. Otherwise, it is discarded.
  4. Because NaOH tends to imbibe modern and ultra-modern CO2 from the atmosphere during the removal of the humic acid fraction, to form Na2CO3, the sample is again immersed in cold 2% HCl to ensure the removal of atmospheric CO2. When the sample is again freed of HCl by washing with distilled H2O, it is dried in an oven overnight at approximately 100°C. The dried sample is then visually inspected under low magnification to remove any rootlets and other contaminating foreign matter.

Peat

Normally, no pretreatment is required except to break the sample into small pieces, and remove any obvious concentrations of silt.
However, pretreatment may be required if there is evidence of significant carbonate deposits

Soil Total Humate

  1. About one gallon of the sample is placed in a 5-gallon stainless steel pot. Deionized water is added, the sample is stirred well, and it is allowed to stand overnight to disaggregate.
  2. The following day, the contents of the pot are stirred well a second time and any floating particles are skimmed off with a 60-mesh or more appropriate size USGS screen. The stirring and skimming is repeated until no floating material remains.
  3. The material remaining in the pot is passed through a 230-mesh sieve into a second 5-gallon pot, stirring the original pot and adding deionized water as needed to keep fine material in suspension. Two full pots will result from this transferring and sieving. The water and sediment remaining in the bottom of the original pot is discarded.
  4. If any floating material is observed in the new pots, it is skimmed off with a 230-mesh or finer sieve. The sample is allowed to stand until settling has occurred, or centrifuged in several 1-liter batches to separate out the solids.
  5. The pots are decanted, and the sediment is flushed into 3-liter beakers using distilled water.
  6. Steps 1 through 5 are repeated for each gallon of the sample until all have been processed.
  7. A small amount (1-2 ml) of concentrated HCl is added to one of the beakers to check for carbonates. If the material is not reactive, it is acidified to a pH of about 5. If there is a reaction, HCl is added about 5 ml at a time, alternating with distilled water, until the reaction appears to have stopped. The acidified sample is allowed to stand overnight to ensure neutralization of any dolomite that may be present.
  8. The sample is stirred, transferred to wide-mouth, 1-liter centrifuge bottles, centrifuged, and decanted, discarding the supernatant. Distilled water is added, and the sample is agitated and then centrifuged; this is repeated several times to rinse the sediment. During this process the sample is kept at a pH of about 5 by the addition of a few drops of HCl as needed.
  9. The sediment is transferred into clean beakers, and allowed to stand until all solids have settled out. The supernatant is siphoned off, and the solid residue is dried in an oven at approximately 100°C.
  10. The solid residue is pulverized in a mill. The resulting powder is the total humate fraction, which can be dated as is, or given additional processing to separate out the humic acid and humin fractions.
>C-14 Sample Selection and Prep Protocol
  • Home
  • About Me
  • Research
    • Scientific Highlights
    • Projects
      • Near-Census River Science
        • 2DMUs
        • Hydraulic Topography
        • Topographic Change Detection
        • Topographic Change Processes
        • Floodplain Inundation
        • Streamwood Storage
        • Upper South Yuba
        • Salmonid Migration
        • North Yuba River
        • Salmon Migratory Habitat
      • Geomorphic Covariance Structures
      • Synthetic River Valleys
      • Watershed Processes
        • Watershed Sediment Transport
        • Watershed Streamwood
        • Watershed Sedimentation
      • River Rehabilitation
        • Spawning Habitat Rehabilitation
        • Cobble/Gravel Injection
        • Streamwood Jams
        • Geomorphologist's Guide
      • Waterfalls
        • Horseshoe Falls
        • NSEAM 1.0
        • Hydraulic Jumps
        • Small Step Mapping
        • Small Step Hydraulics
      • Tidal Freshwater Deltas
        • TFD Introduction
        • TFD Vegetation
        • TFD Sediment Cycles
        • TFD Ecogeomorphology
        • TFD Hydrometeorology
        • TFD Sediment Transport
        • TFD Modeling
        • TFD Animal Response
        • Bush River, MD
        • Winter's Run, MD
      • Estuarine Processes
        • Salinas River Estuary
        • San Joaquin-Sacramento Delta
        • Blackwater National Wildlife Refuge
        • Long Island Sound
      • Functional Flows Model
      • Volcanic Lakes
        • VL Classification & Modeling
        • VL Bibliography
        • Keli Mutu
          • Remote Sampling Strategy
        • Lake Batur
        • Other Volcanic Lakes
      • Agricultural Sediment
      • Urban Rivers
      • Chaos in Hydrology
      • Channel Types
    • Methods
      • Net Sedimentation Tile (NST) Protocol
      • Sediment Core Processing Protocol
      • Vibracoring Protocol
      • Loss-On-Ignition Protocol
      • C-14 Sample Selection and Prep Protocol
      • Cation Sample Prep and Analysis Protocol
      • Grain Size Distirbution Protocol
      • MS Word Fig. code
      • Kite Blimp Method
      • Laser Granulometer Protocol
    • Software
      • River Builder
    • Sponsors
  • Teaching
    • SAS 004Y : Water in Popular Culture
      • Course Logistics
      • Sections
      • Syllabus
        • SAS004 Introduction
        • Water Scarcity
        • Water Scarcity Discussion
        • Floods
        • Flood Insurance Discussion
        • Water Quality
        • Water Quality Discussion
        • Water & Psychology
        • Water Psychology Discussion
        • Conquering Nature
        • Conquering Nature Discussion
        • Pro Poor Water
        • Pro Poor Water Discussion
        • Arctic Socio-Ecology
        • Indigenous Knowledge
        • Earth Stewardship
        • Earth Stewardship Discussion
        • Global Climate Change
        • Global Climate Change Discussion
        • Coastal Zone in Crisis
        • Coastal Zone Crisis Discussion
        • Course Review
      • Readings
      • Instructor
      • Classroom Behavior
      • Grading Policy
      • Movie Logs
      • Discussion Activities
      • Expository Essay
      • Study Guide
      • Online TA Help
    • ESM 125: River Conservation
      • Syllabus
        • River Conservation Introduction
        • Navigability For Title - Law
        • River Segmentation
        • Historical Hydrology
        • Indigenous River Conservation
        • Habitat Conservation Law
        • Aquatic Habitat
        • Riparian Habitat
        • Water Temperature
        • Sediment Sampling
        • Water Quality
        • CA State Water Boards
        • Biological Opinions
        • Setting Biological Goals
        • County-Level Water Management
        • River Restoration
        • Fish Passage & Fishways
        • Beaver-Assisted Restoration
        • Water Management Lessons
      • Instructor
      • Grading Policy
      • Readings
      • Exams
      • Individual Assignments
      • River Presentations
      • Video Response Canvas Quizzes
      • Reading Response Canvas Quizzes
    • HYD 143 : Ecohydrology
      • Instructor
      • Grading Policy
      • Syllabus
        • Chapter 1
        • Chapter 2
        • Chapter 3
        • Chapter 4
        • Chapter 5
        • Group Activity 1
        • Group Presentations 1
        • Chapter 6
        • Chapter 7
        • Chapter 8
        • Chapter 9
        • Group Activity 2
        • Group Presentations 2
        • Chapter 10
        • Chapter 11
        • Chapter 12
        • Chapter 13
        • Chapter 14
        • Chapter 15
        • Group Activity 3
        • Group Presentations 3
        • Chapter 16
        • Chapter 17
        • Chapter 18
        • Chapter 19
        • Chapter 20
        • Chapter 21
      • Online TA Help
      • Video Response Quizzes
      • Group Presentations
      • In-class Assignments
    • HYD 151 : Field Methods in Hydrology
      • Instructor
      • TA Info
      • Grading Policy
      • Syllabus
        • Chapter 21
        • Chapter 1
        • Chapter 2
        • Chapter 3
        • Chapter 4
        • Assignment 1
        • Chapter 5
        • Chapter 6
        • Assignment 2
        • Chapter 7
        • Chapter 8
        • Chapter 9
        • Assignment 3
        • Chapter 10
        • Chapter 12
        • Chapter 11
        • Chapter 13
        • Chapter 14
        • Assignment 4
        • Chapter 15
        • Chapter 16
        • Chapter 16b
        • Chapter 17
        • Field Equipment Showcase
        • Chapter 18
        • Chapter 19
        • Chapter 20
        • Chapter 22
        • Chapter 23
        • Chapter 24
        • Course Review
      • Readings
      • Online TA Help
      • Field Safety
    • HYD 252: Hillslope Geomorphology and Sediment Budgets
      • Instructor
      • Grading Policy
      • Syllabus
        • Week 1
        • Week 2
        • Week 3
        • Week 5
        • Week 6
        • Week 7
        • Week 8
        • Week 9
        • Week 10
        • Week 4
      • Readings
      • Safety
    • HYD 254Y: Ecohydraulics
      • Instructor
      • Grading Policy
      • Syllabus
        • Introduction to Near-Census River Science
        • Introduction to 2D Modeling
        • 2D Modeling Training
        • 2D modeling discussion & synthesis
        • 2D Modeling Terrain Variability
        • 2D Model Validation
        • Fluvial Landform Assessment
        • Ecological Analysis of Structure and Function
        • Hydrogeomorphic Processes
        • Parameterizing Boundary Roughness
        • Frontiers of River Science
      • Readings
      • Online TA Help
      • Lab Tutorials
    • HYD 256: Geomorphology of Estuaries and Deltas
      • Syllabus
        • Week 1
        • Week 2
        • Week 3
        • Week 4
        • Week 5
        • Week 6
        • Week 7
        • Week 8
        • Week 9
        • Week 10
      • Readings
      • Lab
      • Field Safety
      • Online TA Help
      • Grading Policy
    • Virtual River Methods
      • Syllabus
      • Instructor
      • Grading Policy
      • Readings
      • Assignments
      • Game Setup
  • People
    • MS Students
    • PhD Students
    • Postdocs
    • Committee Advisees
    • Technicians
    • Undergrads
    • Visitors
    • Collaborators
    • Furry Friends
  • Info for Applicants
  • Service
    • Past Service
    • Professional Service
  • Outreach
  • Curriculum Vitae

GET IN TOUCH

  • 223 Veihmeyer Hall
    LAWR Dept., UC Davis
    One Shields Avenue
    Davis, CA 95616
  • (530) 302-5658
  • (530) 752-1552
  • gpast@ucdavis.edu
  • Google Scholar
  • Research Gate
  • ORCID: 0000-0002-1977-4175
  • Dr. Gregory B. Pasternack - Watershed Hydrology, Geomorphology, and Ecohydraulics
UC Davis