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Simultaneous analysis of nitrogen and triple oxygen isotopes in low-amount atmospheric samples on filters – How low can we go? Chemical preparation combined.

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Presentation on theme: "Simultaneous analysis of nitrogen and triple oxygen isotopes in low-amount atmospheric samples on filters – How low can we go? Chemical preparation combined."— Presentation transcript:

1 Simultaneous analysis of nitrogen and triple oxygen isotopes in low-amount atmospheric samples on filters – How low can we go? Chemical preparation combined with gold-furnace breaking of N 2 O – CF-IRMS Anna Smirnoff 1, Martine M. Savard 1, Robert Vet 2, Joelle Marion 1 and Marie-Christine Simard 1 1 Geological Survey of Canada, 490 rue de la Couronne, Quebec (Quebec), Canada G1K 9A9 2 Environment Canada, 4905 Dufferin Street, Toronto, Ontario, Canada M3H 5T4 ASITA-2013

2 Outline  Remind what we have been doing previously  Explain new challenges  Describe how we are trying to overcome them  Discuss pros and cons of our approach

3 Sample Preparation with Cd Reduction  Prepare a reduction column based on EPA method 4500-NO 3 -  Using EDTA (C 10 H 14 N 2 Na 2 O 8 ) as a chelate agent  Pass sample through Cd-reduction column  Reduce NO 2 - to N 2 O using NaN 3 (sodium azide)  Analyze N 2 O using slightly modified Pre-Con 18.5 cm 25 cm 10 cm 5-cm ID 85 mL 2-mm ID 3.5-mm ID Cu-Cd granules Glass wool plug

4 Analytical Setup vent He vent Mg(ClO 4 ) 2 + NaOH water trapMg(ClO 4 ) 2 He LH 2 manual Valco6 port vent U LH 2 auto He RT-Q Bond Plot, 15m LH 2 auto Modified from Brand,1995 Gold Furnace MoleSieve GC Column To IRMS U U Pre-Con

5 Preparation for Cd-reduction Modified and tested for: 0.10 mg/L N-NO 3 Developed for: 0.28 mg/L N-NO 3 80 mL – 04/2013

6 Objectives Analyze  new atmospheric samples with lower amount of material Assess  if lower concentrations affect accuracy of  15 N,  17 O and  18 O determinations

7 Western Canada N-cycle Research Sampling Atmospheric sources of nitrogen-bearing compounds  Characterized by  15 N,  17 O and  18 O TransportAgriculture Gas compressors and plants Coal-Fired Power Plants Upgraders OS Operations Desulphurization and hydrogen plants, boilers, heaters, turbines, vehicles, tailings ponds, etc.

8 Wet-only samplers - precipitation Filterpacks - dry material  1- Teflon filter  2- Nylon filter  3- Citrated cellulose filter  4- Maxxam cartridges

9 Sample details MethodTypeSample Wind Direction Sampling wet-only samplerprecipitationNO 3 -no wet-only samplerprecipitationNH 4 + no filterpack-TeflonparticulatesNO 3 -yes filterpack-TeflonparticulatesHN 4 + yes filterpack-nylongaseousHNO 3 yes filterpack-citrated cellulosegaseousNH 3 yes maxxam cartridgegaseousNO 2 ; NO x yes

10 Samples - Before and Now Reason  Filters from individual pumps were not combined 0.10 mg/L N-NO mg/L N-NO 3 50 mL 80 mL BeforeNow

11 Standards - As before Compound Name  15 N (‰) IAEA catalogue  18 O (‰) IAEA catalogue  18 O (‰) (Brand et al., 2008)  17 O (‰) (Bohlke et al., 2003) USGS- 32 (KNO 3 ) 180± ± ± USGS- 34 (KNO 3 ) -1.8± ± ± USGS-35 (NaNO 3 ) 2.7± ± ± IAEA-NO-3 (KNO 3 ) 4.7± ± ±

12  15 N Results Calibration Curves y = 2.04x y = 2.05x NOW Before

13  17 O and  18 O Results Calibration curves  17 O  18 O Now Before y = 1.62x y = 1.47x Before y = 1.45x Now y = 1.62x + 4.6

14 Why slope is different? Possible reason…  Replacement of Imidazole with EDTA?

15 Protocol modifications Replaced:  Imidazole with EDTA: C H NC C N H H H HO OH N N O O O O ImidazoleEthylenediaminetetraacetic acid (EDTA)

16 Validating results using standards Compound Name  17 O( ‰ ) known/calculated  18 O( ‰ ) known/calculated  15 N( ‰ ) known/calculated USGS /14.3 ± /26.4 ± USGS USGS /2.7 ± 0.2 IAEA-NO313.2/12.5 ± /24.9 ± /5.2 ± 0.1 KNO 3 -Lab

17  15 N,  17 O and  18 O analyses Which method? Bacterial method:  higher sample throughput  smaller amount of material Chemical preparation – Gold Furnace:  prompt return to analyzing sets of samples  more reliable  15 N results from analyzing N 2 in atmospheric samples as compared to analyzing N 2 O with contribution mass-independent 17 O

18 Further Details  Smirnoff, A., Savard, M. M., Vet, R., and Simard, M.C Nitrogen and triple oxygen isotopes in near-road air samples using chemical conversion and thermal decomposition. Rapid Communications in Mass spectrometry, v. 26,  This research is a part of the CORES project of the Geological Survey of Canada conducted within the Environmental Geoscience Program of Natural Resources Canada. The research is conducted in close collaboration with Environment Canada.


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