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Dissolved inorganic carbon (DIC) is the sum of aqueous species of inorganic carbon in solution which pass through a a filter (typically pore size of 0.45-0.7µm):

CO₂(g) + H₂CO₃(aq) + HCO₃^-(aq) + CO₃^2-(aq)

Radiocarbon dating of the DIC pool is a useful tool for exploring carbon cycling dynamics within systems such as air-water interface exchange, the microbial biological pump, and water-rock interactions.

Requirements:

• Samples should be submitted with zero headspace to minimize atmospheric CO2 equilibration into the sample.
• Each sample must yield a minimum of 1mgC; please sample accordingly.
• Concentration data (ppm C) is required prior to sample processing and is required with the submission form. If the concentration is unknown, we recommend collecting an additional aliquot of sample for concentration analysis. This can be coordinated independently with the Ján Veizer Stable Isotope Laboratory. Their water sampling and submission criteria are posted here. Please inform us if you have submitted to their lab.
• Water samples must be filtered in the field. Consult us if not possible.

Recommendations:

• We recommend glass bottles to prevent the exchange with atmospheric CO2 after collection. Plastic risks permeation by CO2. Before sampling, bottles should be soaked in 10% HCl for 1 hr, rinsed well with Milli-Q water and baked at 500 ˚C for 3 hours. Bottle caps and septa should be soaked in 10% HCl for 15 minutes, rinsed well and air dried (lightly covered in foil to avoid dust).

Recommended bottles

Recommended cap

More information

• Due to the sensitivity of 14C analysis, we recommend pre-combusted (500°C for 3 hours) glass fiber filters (GFF, nominal pore size 0.7µm).
• When sampling, use gentle filtration to minimize entrainment of air bubbles and allow sample bottles to overflow 3 times their volume before capping with zero headspace. If the particulate load is high, consider using prefilters or a larger filter diameter (larger surface area but still 0.45-0.7µm porosity) to prevent clogging.
• After sampling keep samples cool and away from light.
• We recommend preservation to inhibit microbial exchange after sampling. General consensus is that HgCl₂ is the best preservative, however due to its toxicity, some agencies and field sites do not allow its use.

In our lab, the sample is added to a baked and pre-cleaned round-bottom borosilicate glass reaction bottle with a CO2-free headspace. 85% Phosphoric acid is injected and the bottle is heated to 60°C for minimum 1 hour. Evolved CO2 is sparged from the headspace with helium, transferred to a vacuum line for cryogenic purification and trapped in a pre-baked 6 mm OD Pyrex breakseal containing a few grains of silver cobaltous (previously baked at 500°C for two hours) to remove S-bearing species or halogens. The sealed breakseal is baked overnight at 200°C so any sulfur is removed by the silver cobaltous (Palstra & Meijer, 2014).

For more information, please refer to Murseli et al., 2019 (PDF, 319 KB).

Ideal submission volume: enough to obtain a total yield of ≥2mgC (min. 1 mgC)

Dissolved organic carbon (DOC) is organic carbon in solution which passes through a filter (typically pore size of 0.45-0.7µm).

Radiocarbon dating of the DOC pool provides insight into carbon cycling dynamics within freshwater and marine environments. At this time, we do not provide ¹⁴C DOC analysis on saline samples.

Requirements:

• Each sample must yield a minimum of 1mgC; please sample accordingly.
• Concentration data (ppm C) is required prior to sample processing and is required with the submission form. If the concentration is unknown, we recommend collecting an additional aliquot of sample for concentration analysis. This can be coordinated independently with the Ján Veizer Stable Isotope Laboratory. Their water sampling and submission criteria are posted here. Please inform us if you have submitted to their lab.
• To prevent microbial degradation, samples stored beyond 24 hours should be frozen. Samples should be shipped overnight in coolers with plenty of blue ice. Do not use dry ice as this will fracture this bottles. If you intend to submit a large sample set, please coordinate with us ahead of time so we can ensure we have enough cold storage available.
• Samples must be filtered in the field (freezing unfiltered water samples will lead to cell lysing and subsequently introduce particulate organic matter into your dissolved pool). Please contact us if you have concerns.

Recommendations:

• Due to the sensitivity of 14C analysis, we recommend pre-combusted (500°C for 3 hours) glass fiber filters (GFF, nominal pore size 0.7µm).
• To minimize the risk of sample bottles fracturing when frozen, we recommend using polycarbonate bottles. Before sampling, bottles should be soaked in 10% HCl for 15 minutes, rinsed well with Milli-Q water and allowed to air dry, lightly covered in foil to avoid dust. Store dry and capped.

Recommended Bottle = Nalgene Square Polycarbonate Bottle with Closure

In our lab, the sample is added to a baked and pre-cleaned round-bottom borosilicate glass reaction bottle with 85% phosphoric acid and heated to 60°C for minimum 1 hour. The sample is sparged with helium to remove any CO₂(aq) evolved from DIC. ~8ml of sodium persulfate oxidant solution (400g/L) and 1mL of 0.5N AgNO₃ catalyst are added, and the vessel is heated to 95°C for minimum 60 minutes to oxidize organics compounds (technique modeled from Zhou et al. (2015) and Lang et al. (2016)). CO₂ is sparged from the headspace with helium, transferred to a vacuum line for cryogenic purification and trapped in a pre-baked 6 mm OD Pyrex breakseal containing a few grains of silver cobaltous (previously baked at 500°C for two hours) to remove S-bearing species or halogens. The sealed breakseal is baked overnight at 200°C so any sulfur is removed by the silver cobaltous (Palstra & Meijer, 2014).

For more information  please refer to Murseli et al., 2019 (PDF, 319 KB).

Ideal submission volume: enough to obtain a total yield of ≥2mgC (min. 1 mgC)

Requirements:

• Please consult with us prior to sampling and submission.
• Samples should be submitted in:
  • gastight bottles with septa
  • gastight canisters with a ¼" stainless steel Swagelok^® tube fitting
  • gastight canisters with a ¼" stainless steel Swagelok^® tube adapter
  • Please consult with us prior to sampling if you require a different inlet/adaptor.
• Concentration data (ppm C) is required prior to sample processing and is required with the submission form. Ideally each sample will yield ≥2 mgC; please sample accordingly.
• Please consult with us prior to sampling/submission if your gas mixture is not clean air or soil gas. For samples that do not have a clean air composition, we may require that a gas analysis report is completed.
• Natural gas clients: please contact us before submission - for mixtures containing hydrocarbons heavier than ethane we will need a gas analysis report before accepting your samples.
• We do not accept “sour” gas samples. Please consult with us prior to sampling if you suspect trace presence of H₂S, SO₂, NO_x, NH₄, VOC’s or other pollutants.

CO₂ is cryogenically trapped on a U-trap packed with silver wool, either by flushing the sample bottle with ultra-high purity He, or slowly metering the gas through the trap to vacuum. After concentration, the sample CO₂ is cryogenically purified using a -80°C ethanol slurry to remove water and other non-condensable gases and transferred to a pre-baked 6 mm OD Pyrex breakseal containing a few grains of silver cobaltous (previously baked at 500°C for two hours). The sealed breakseal is baked overnight at 200°C so any sulfur is removed by the silver cobaltous (Palstra & Meijer, 2014).

For more information  please refer to Murseli et al., 2019 (PDF, 319 KB).

Ideal submission volume: enough to obtain a total yield of ≥2mgC (min. 0.5 mgC)

Requirements:

• Please consult with us prior to sampling and submission. Samples should be submitted in gastight bottles with septa.
• Concentration data (ppm C) is required prior to sample processing and is required with the submission form. Ideally each sample will yield ≥2 mgC; please sample accordingly.
• Please note: we can only accommodate samples in the % CH4 range (>10000ppm CH4). We do not accept “sour” gas samples. Please consult with us prior to sampling if you suspect trace presence of H₂S, SO₂, NO_x, NH₄, VOC’s or other pollutants. We may require that a gas analysis report is completed.

In our lab, sample CH₄ is combusted to CO₂ following the methods of Pack et al. (2015). In summary, CH₄ in headspace is sampled from a septum-capped bottle via gas-tight syringe. The syringe and dead volume in the needle are flushed with He to eliminate atmospheric contamination. The sample is injected into a combustion line with a carrier of ultra-zero  air at a flow rate of 10 ml/min. CO₂ is first cryogenically separated from the sample, followed by a CO trap (300°C oven packed with CuO to oxidize CO to CO₂) followed by a second CO₂ trap. The methane is combusted in a 975°C tube furnace packed with CuO (regenerated by the constant flow of UZ air). Any water produced from the combustion is separated from the CO₂, and then is transferred to a vacuum line and trapped in a pre-baked 6 mm OD Pyrex breakseal containing a few grains of silver cobaltous (previously baked at 500°C for two hours). The sealed breakseal is baked overnight at 200°C so any sulfur is removed by the silver cobaltous (Palstra & Meijer, 2014).

For more information  please refer to Murseli et al., 2019 (PDF, 319 KB).

Ideal submission volume: enough to obtain a total yield of ≥2mgC (min. 0.5 mgC)

CONSULTATION REQUIRED: After a sample preparation laboratory has been validated as an external laboratory (by prior testing of QA/QC standards), we can accept purified CO₂ sealed within a pyrex breakseal. Consultation is required to ensure the external laboratory poses no risk of tracer contamination, and the proper pre-treatment protocols are followed. We will not accept purified CO₂ without QA/QC standards that have been treated and extracted alongside the unknown samples (analyzed at no charge). We can provide aliquots of standards.

Requirements:

• pCO₂ must be calculated by manometry and is required at time of submission
• CO₂ must be pure. Any impurities in the gas could lead to sample loss.
• Breakseals must be 6mm OD Pyrex sealed at 15cm length

Ideal concentration: 1mgC (min. 0.5mgC)

CONSULTATION RECOMMENDED: To conduct a swipe, a pre-combusted quartz fiber filter wetted with methanol is rubbed over a pre-cleaned surface (i.e. dusted, dirt wiped away) suspected of being contaminated with 14C tracer (lab counters, fume hoods, fridge/freezers, door handles, common science store counters, etc.). The user should take care to wear gloves and change them between swipe locations. The filters are allowed to air dry, then wrapped in non-stick aluminum foil and placed in a Ziploc bag labelled with the swipe location and shipped to the lab for testing, along with a printed copy of the submission form. Blank filters (only wetted with methanol) should also be sent. A swipe kit can be sent out upon request. Please contact us first prior to conducting a swipe test.

Radiocarbon analyses are performed on an Ionplus AG MICADAS (Mini Carbon Dating System). The 12,13,14C+1 ions are measured after tandem acceleration by a terminal at 185 kV and equipped with He stripping. Data is processed using the BATS data reduction software as described in Wacker et al. (2010). The fraction-modern (F14C) is calculated according to Reimer et al. (2004) as the ratio of the sample 14C/12C to that of primary standard Ox-II, measured quasi-simultaneously. Both 14C/12C ratios are background-corrected and fractionation-corrected (occurring both from spectrometer and sample preparation fractionation) to δ13C_PDB = -25 permille. Conventional radiocarbon ages (14C yrs. BP) are calculated as -8033ln(F14C) and reported in 14C yr BP (where BP=AD 1950), as described in Stuiver and Polach (1977). Quoted uncertainties (1σ) are based on Poisson counting statistics, variability among repeated 14C/12C and 13C/12C measurements, and blank variability based on historical laboratory performance. We do not report online AMS δ13C as it contains machine-induced fractionation.

We follow the conventions recommended by Millard (2014) for reporting radiocarbon results.

Conventional radiocarbon ages (CRA) are rounded in line with the conventions in Stuiver and Polach (1977):

Reported errors are typically ± 15-25 14C yrs. for samples younger than 5,000 14C yrs. BP.

D14C (defined as permille depletion or enrichment relative to standard normalized for isotope fractionation, equivalent to stable isotope δ notation) is calculated as:

(F14C – 1) · 1000

Δ14C (defined as the absolute amount of 14C in the sample in the year it was measured) is calculated as:

F14C · (e(1950-y)/8267) – 1) · 1000

Please note: If the year of measurement (y) is not the same as the year of collection (z), calculate as:

F14C · (e(1950-z)/8267) – 1) * 1000)

Calibrated ages are provided upon request.

Calibration is performed using the most recent version of OxCal (Bronk Ramsey, 2009). Calibrated results are given as a range (or ranges) with an associated probability, as point estimates (mean, median) cannot represent the uncertainties involved (Millard, 2014).

Where the F14C is less than 1, the IntCal20 calibration curve is used for Northern Hemisphere samples (Reimer et al., 2020) and ShCal20 for Southern Hemisphere samples (Hogg et al., 2020). For samples with an F14C greater than 1, the post-bomb atmospheric curve is used (Hua et al., 2022). Post-bomb samples have two age ranges due to calibration on both sides of the bomb pulse. There are methods for deciding which side of the bomb pulse to select as the more appropriate date, so feel free to contact us for further information.

Samples that calibrate between the 1700’s and early 1950’s will always result in a calibrated age range covering the majority of this period. This is due to the “Seuss Effect”, which is a flat portion of the calibration curve caused by the burning of fossil fuels.

For marine samples, the Marine20 calibration curve is used with the appropriate marine reservoir correction (Heaton et al., 2020). The ∆R values (regional difference from the average global marine reservoir correction) are provided by the user or determined using 14CHRONO Queen’s University Belfast marine reservoir correction database and incorporated into the calibrated dates. Marine samples with a radiocarbon age minus ΔR that is less than 460 14C yr BP should not be calibrated due to high atmospheric 14C levels from nuclear weapons testing (Reimer et al. 2004). Please note, the Marine20 curve is not intended for calibration in polar regions (<40°S or >40/50°N latitude) due to variability in sea ice extent (Heaton et al. 2020). Recent guidance states that the use of the Marine20 curve with an appropriate regional ΔR correction is likely suitable for Holocene-aged samples; however, for samples falling outside of the Holocene, a bracketed age approach is recommended using low- and high-depletion scenarios with “boosted” ΔR values assessed latitudinally. For more information, please see Heaton et al. 2020, 2022, and 2023.