Measuring isotopes accurately for a safer, healthier and sustainable world

Transcription

1 Measuring isotopes accurately for a safer, healthier and sustainable world Manfred Gröning Environment Laboratories International Atomic Energy Agency

2 Acknowledgment Thanks to my colleagues at, especially to: Sergey Assonov Monika Horsky Sandor Tarjan Joanna Izewska Debbie van der Merwe Ahmed Meghzifene and to our colleagues at BIPM: Robert Wielgosz Joële Viallon Philippe Moussay Steven Judge

3 International Atomic Energy Agency Technical Agency associated to the UN System Atoms for Peace and Development The Agency shall seek to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world.

4 Overview Long term cooperation with BIPM: 1. Dosimetry and MRA 2. MoU between and BIPM 3. Trace Element Analysis and Nuclear Data 4. Stable Isotope Ratios and Radionuclides

5 1. Dosimetry and the Mutual Recognition Agreement Secondary Standard Dosimetry Laboratories: Provision of calibration for dosimetry equipment. Dosimeters are used to determine dose level for patients, staff or the public importance that measurement results are consistent with SI system (radiation measurements) Formal agreement to establish a Network of SSDLs signed by & WHO (1976) Since 1987, activities of the network are assessed by an independent SSDL Scientific Committee (includes BIPM) MRA signed in 1999 Currently 26 CMCs 86 SSDLs in 71 countries

6 /WHO dose audits for radiotherapy centres How is the audit carried out? Small dosimeters are sent to radiotherapy centres for irradiation to verify the beam output used for patients treatments. Dose audit services : 49 years of the /WHO postal dose audits >13000 beam checks ~2300 radiotherapy centres in 136 Member States BIPM has provided reference irradiations for the /WHO dose audits for >20 years 6

7 Reference irradiations for dose audits : N = 404, m = 1.001, SD =

8 2. Memorandum of Understanding MOU formally signed in 2012, defines the main areas of cooperation: Mutual exchange of data and information in the area of metrology of ionizing radiation and chemical measurements representation in CCRI (full member 2011) participation - as a signatory - in activities related to CIPM MRA BIPM participation in the SSDL Scientific Committee BIPM support to the /WHO dosimetry audits and calibration services through reference irradiations and calibration of reference standards Collaboration for measurement standards and reference materials Publication and dissemination of nuclear data Participation in scientific events (e.g. conferences), education and training, etc. The Dosimetry Laboratory Cs-137 irradiator will be made available to BIPM staff for calibration purposes as of 2019

9 3. Trace Element Analysis & Nuclear Data CCQM Key Comparison K75 (and Pilot Study P118) Determination of toxic metals in algae Platinum and Nickel, 2010 Shakhashiro et al. Nuclear data decay data evaluations with BIPM Attendance at CCRI Neutron standard cross sections

10 4. Stable Isotope Ratios, and Radionuclides 100 Reference Materials available at

11 Stable Isotopes: - e.g. oxygen in water H 2 O Oxygen 16 O

12 16 O 8 Protons + 8 Neutrons 16 O

13 18 O 8 Protons + 10 Neutrons 18 O

14 Ratio of 18 O to 16 O 18 O 16 O ~ Oxygen: ( 18 O/ 16 O) = (2005.2±0.45) 10-6 Hydrogen: ( 2 H/ 1 H) = (155.76±0.05) 10-6

15 Range of Stable Isotopes in Nature Hydrogen: 2 H H Carbon: Oxygen: 13 C 12 C O O from Coplen et al. 2002

16 Why to measure Stable Isotopes in Nature Chemical analysis: Stable isotopes?

17 Why to measure Stable Isotopes in Nature Chemical analysis: Stable isotopes?

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19 Stable Isotopes are the Colors for the Elements

20 Global Network Isotopes in Precipitation

21 Standards required for any lab operation Length: Meter Mass: Kilogram Kilogram new definition, still requiring measurements Isotopes: Reference materials

22 δ 2 H vs. VSMOW [ ] δ 2 H vs. VSMOW [ ] δ 2 H ( ) VSMOW2 Vienna Standard Mean Ocean Water Its isotopic composition is used for the triple point of water Kelvin -300 VSMOW2 and VSMOW ± 0.02 Raw water for VSMOW2 production GSF USGS UEA CIO VSMOW2-4 δ 18 O vs. VSMOW [ ] -1 δ 18 O ( ) δ 18 O vs. VSMOW [ ] VSMOW VSMOW2 routine lab uncertainty calibration data uncertainty combined uncert.(+bias)

23 -603 Marble - Carbon isotope standard Combined standard uncert. u(δ 13 C)= ±0.01 (homog. & calibration versus NBS19) nearly ideal material for δ 13 C VPDB scale realization

24 New Instruments requiring novel standards for CO 2 Isotope Analysis ~ 99% of 12 C 16 O 16 O ~ 1% of 13 C 16 O 16 O I 0 (n) I 0 (n)e (-a(n)l) L R 13 = x 636 x 626 R 18 = x 628 x is 13 C 16 O 16 O 626 is 12 C 16 O 16 O 628 is 12 C 18 O 16 O Commercially available Optical instruments Measure infrared absorption of individual isotopologues Measure directly at concentration range of interest Absorption can be modelled Flow rates 0.1 to1 L/min 24 (Slide courtesy BIPM)

25 Spread in isotope ratios of CO 2 Standards in CCQM-K120, coordinated by BIPM 25 (Slide courtesy BIPM)

26 Calibration Strategies for Optical Instrument Isotope Ratio Measurements developed by BIPM 1. Calibration in delta scale space and correction for mole fraction effects δ 13 C 1 δ 13 C 2 x (CO 2, A ) x (CO 2, B ) 2. Calibration of mole fractions and conversion to delta scale x (626, A ) x (636, A ) x (626, B ) x (636, B ) 26 (Slide courtesy BIPM)

27 BIPM Stable Isotope Reference Mixture Generator Facility Lower end d 13 C Mix target d 13 C Filling aliquots with known pure CO 2 Higher end d 13 C 27 (Slide courtesy BIPM)

28 CO 2 isotope ratio comparison (2020) (BIPM and Coordinators) Comparison samples produced at BIPM δ 13 C (VPDB) Atmospheric CO 2 Stability and homogeneity measured at BIPM ((1σ) δ 13 C = 0.04 (1σ) δ 18 O = 0.1 ) Reference Value assigned at ((1σ) δ 13 C = 0.01 (1σ) δ 18 O = 0.02 Fossil Fuels Natural Gas Well Blended with enriched 13 CO 2 δ 18 O (VPDB) 28 (Slide courtesy BIPM)

29 Carbonate - CO 2 isotope analysis system

30 Aliquoting CO 2 from BIPM vessels Dosing valves BIPM vessels (~2 bar) CO2 reference gases at -lab

31 d 18 O, VPDB-CO2 Tests at on BIPM mixed CO 2 -vessels (last week) Successful Performance check d 13 C, VPDB Aliquots Average d 13 C= ±0.006 (n=10) d 18 O= ±0.029 (n=10)

32 CO 2 concentration in the atmosphere IPCC Report: SRIPPS; NOAA

33 Carbon Cycle

34 Carbon Cycle - reference materials Annual change in mean δ 13 C: ~0.02 Precision required for any laboratory: ±0.02 for 40 years!!! Ultra-stable reference material -603 ±0.01

35 Carbon Flux (GtC/ yr) Carbon Isotopes CO 2 partition between Land and Ocean Total f lux to Land and Ocean~4.5 GtC More Share for Land 0.5 Positive Bias More Share for Ocean -1.0 Negative Bias Uncertainty in d 13 C ( ) Gt C Ultra-stable reference material -603 ±0.01

36 Carbon Cycle BIPM and New laser instruments require new standardisation BIPM developed a CO 2 calibration strategy Measurement precision is achieved for CO 2 Initiative for Comparison of CO 2 isotope ratios in 2020 CO 2 / CO 2 -in-air isotope ratio reference materials CCQM Isotope Ratio Working Group established Excellent cooperation for benefit of environmental monitoring worldwide

37 Habitats / endangered species Timber from concessions versus illegal sources validation of origin Work on Reference materials & on Sampling Guidelines IvoryID webpage Ivory origin CITES

38 Radionuclides: ALMERA Network Analytical Laboratories for the Measurement of Environmental Radioactivity: Network of 177 laboratories in 89 countries Proficiency Tests Validated Analytical Procedures ALMERA Network Core Activities Training Courses and Workshops Forum for Sharing Knowledge

39 Radionuclides: Support for Member State laboratories Proficiency tests for 400 laboratories annually Bq/kg Cooperation with CCRI?

40 Thanks for your attention