Isotopic measurements were carried out at the Biogeochemistry Stable Isotope Laboratory of Andalusian Earth Sciences Institute (CSIC). For total inorganic carbon (TIC) an aliquot of sample was injected into 12-ml vials prefilled with helium and five drops of 65% phosphoric acid, and shaken in a vortex agitator for 30 s. The vials were left at room temperature between 15 and 36 h to obtain a state of equilibrium [28 (link)]. The CO2 was separated from other residual gases by chromatography using a helium carrier gas in a Gas Bench (Thermo-Finnigan, Bremen, Germany) system interfaced with a mass spectrometer Delta XP isotope ratio mass spectrometer (Thermo-Finnigan, Bremen). Analytical precisions were estimated to be within 0.1‰ for TIC. For nitrates, water was filtered with a 0.45 μm (cellulose acetate membrane), poisoned with mercuric chloride, and stored in vials of 12 ml. Nitrogen and oxygen isotopic compositions of nitrate were analyzed by the denitrification method [29 (link)]. International reference materials (IAEA-N3, USGS-34, and USGS-35) and five in-house working standards were included within a batch of 96 bottles for a series of analysis. The N2O produced was then analyzed using a Thermo-Finnigan Delta V Plus. Analytical precisions were estimated to be within 0.3‰ for δ15N and δ18O.
Gasbench
Manufactured by Thermo Fisher Scientific
Sourced in Germany
The GasBench is a high-performance gas preparation and introduction system designed for stable isotope analysis. It automates the preparation of gas samples, ensuring precise and reproducible results for a variety of applications.
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Lab products found in correlation
Delta 5 plus, by Thermo Fisher Scientific (2 mentions)
Deltaxp isotope ratio mass spectrometer, by Thermo Fisher Scientific (1 mentions)
Delta 5 plus irms, by Thermo Fisher Scientific (1 mentions)
Delta 5 isotope ratio mass spectrometer, by Thermo Fisher Scientific (1 mentions)
Delta 5 mass spectrometer, by Thermo Fisher Scientific (1 mentions)
8 protocols using gasbench
1
Stable Isotope Analysis of Inorganic Carbon and Nitrates
2
Nitrate Nitrogen Isotope Ratio Analysis
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Nitrate nitrogen isotope ratios (15N/14N) were determined using the bacterial denitrification method (e.g., Sigman et al. 2001 (link); Casciotti et al. 2002 (link)) at the Stable Isotope Facility at the University of California—Davis. The isotope ratios of the resulting nitrous oxide were measured on a ThermoFinnigan GasBench and PreCon trace gas concentration system interfaced with a ThermoScientific Delta V Plus IRMS. The precision of the method (1σ) was 0.4‰ for δ15N (relative to N2 air).
3
Stable Isotopes of Tortoise Bone Apatite
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To understand bone apatite (structural carbonate) carbon and oxygen stable isotopes we homogenized a small sample of tortoise bone powder for analysis following standardized protocols (e.g., see36 ). This homogenized powder was cleansed with 3% hydrogen peroxide (H2O2) for 24 h to remove organics and then was rinsed to neutrality using deionized water and centrifugation. A second treatment of 0.1 M buffered acetic acid (CH3COOH) for 30 min (followed by rinsing to neutrality) occurred to remove labile carbonates. After drying, we measured approximately 8.0–10.0 mg of homogenized bone apatite powder into exetainer vials, flushed those vials with He to remove atmospheric CO2, and then reacted the sample with phosphoric acid at 50 °C for at least 6 h. This reaction produced CO2 for carbon (δ13Capatite) and oxygen (δ18Oapatite) stable isotope analysis. All samples were analyzed at UNM-CSI on a Thermo Scientific GasBench (Bremen, Germany) coupled to a Delta Plus isotope ratio mass spectrometer with a Conflo II. An in-house Carrara marble standard (δ13C = 2.0 and δ18O = − 1.8) was analyzed in every run and used to correct the data. All data are reported relative to Vienna Pee Dee Belemnite (V-PDB). Within-run standard precision (SD) is < 0.25‰ for δ13C and δ18O.
4
Carbonate Isotope Analysis in Sediments
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δ13Ccarb was measured using a GasBench coupled to a Thermo Finnigan Deltaplus XP mass spectrometer (Thermo Fisher Scientific) for 57 sediment and stromatolite samples (Supplementary Table S3 ). Sediment samples were first frozen and lyophilized to remove water, then rinsed with ultrapure water and centrifuged three times to remove the salt and once again frozen and lyophilized. The rinsed and lyophilized sediments were ground with an agate mortar and pestle.
Several tests were carried out with samples only washed and ground, and with the same samples from which organic matter was removed by low-temperature oxygen-plasma ashing75 (link) using a POLARON PT7160 RF system (Polaron Equipment Limited, Watford, UK). These tests showed that the organic matter in the untreated sample did not affect the isotope signature of the carbonates (Supplementary TableS3 ). Hence, the preparation and analysis of the carbonate samples was similar to that of the carbonate standards used for the isotopic calibration described above for DIC and δ13CDIC. The isotopic compositions are expressed in the delta notation, in ‰, relative to VPDB with a reproducibility of ± 0.2‰ (1σ) (Supplementary Table S3 ).
Several tests were carried out with samples only washed and ground, and with the same samples from which organic matter was removed by low-temperature oxygen-plasma ashing75 (link) using a POLARON PT7160 RF system (Polaron Equipment Limited, Watford, UK). These tests showed that the organic matter in the untreated sample did not affect the isotope signature of the carbonates (Supplementary Table
5
Stable Isotopes Analysis of Seawater
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For δ18Osw analysis, 60 ml serum vials with butyl rubber caps were filled with seawater during CTD operations on board. These were sealed and stored cool until analysis. For δ13CDIC water analysis, 5 drops of 100% phosphoric acid (H3PO4) was added to the 12 ml exetainer vials using a 1 ml single-use syringe and flushed on the Gas Bench with Helium before ship departure at FARLAB laboratory. Then 1 ml of water sample was added into the exetainer vials during the cruise and stored at fridge temperatures (2–5 °C) before measuring samples after cruise return.
The stable isotope analyses for δ18O and δ13CDIC in the seawater were performed on a Thermo Scientific Gasbench connected to a Thermo Scientific Delta V+ isotope ratio mass spectrometer at the Norwegian National Infrastructure FARLAB (Facility for advanced isotopic research and monitoring of weather, climate, and biogeochemical cycling) at the University of Bergen, Norway. The results are provided in the conventional δ-notation in ‰ relative to VSMOW for δ18Oseawater and VPDB for δ13CDIC. The analytical error of the measurements is 0.09 ‰ for δ18O, and 0.05 ‰ for δ13CDIC (1 standard deviation).
The stable isotope analyses for δ18O and δ13CDIC in the seawater were performed on a Thermo Scientific Gasbench connected to a Thermo Scientific Delta V+ isotope ratio mass spectrometer at the Norwegian National Infrastructure FARLAB (Facility for advanced isotopic research and monitoring of weather, climate, and biogeochemical cycling) at the University of Bergen, Norway. The results are provided in the conventional δ-notation in ‰ relative to VSMOW for δ18Oseawater and VPDB for δ13CDIC. The analytical error of the measurements is 0.09 ‰ for δ18O, and 0.05 ‰ for δ13CDIC (1 standard deviation).
6
DIC Analysis via Gas Chromatography-Mass Spectrometry
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DIC measurements were made using a Thermo Gas Bench attached to a Delta V Mass Spectrometer. Three or four drops of orthophosphoric acid (100%) were preloaded into a reaction vial, which was capped, sealed and the headspace flushed with Helium gas. Approximately 1.5 ml of sample water was injected into the vial through the butyl rubber septa using a syringe and left to react for 1 h. The sample tubes were transferred to the Gas Bench and CTC CombiPal Autosampler and the resulting CO2 in the headspace analysed using a Thermo Delta V Mass Spectrometer. A series of standards and reference samples distributed throughout the run were used to calibrate to the international standard VPDB. Results have a reproducibility of better than 0.1 per mille.
7
Groundwater Sampling and Isotopic Analysis
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Twenty-four groundwater samples were collected from about 8.5 m below ground surface in the geyser borehole using a peristaltic pump and copper pipe. Samples were collected in 12 mL glass vials. The vials were flushed with fresh geyser water and were filled underwater in a bucket that was overflowing with groundwater to avoid atmospheric contact; this was confirmed by gas chromatography analyses that did not detect contamination by atmospheric gases (N2, O2, or Ar; unpublished data). The stable carbon isotopic composition of the dissolved inorganic carbon was analyzed by Continuous Flow Isotope Ratio Mass Spectrometry (CF-IRMS) using a Thermo Finnigan GasBench coupled to a DeltaVPlus. Water pressure, temperature, and electrical conductivity were measured in situ at the same depth using a Solinst LTC Levelogger Edge.
8
Measuring δ13C of Inorganic Carbon
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The δ13C content of all inorganic carbon (mineral and dissolved inorganic carbon) was determined after conversion to CO2 through acidification by addition of excess phosphoric acid in Helium-flushed hermetically sealed vials, and incubation at 60 °C in a multiprep heating block. All sample inorganic carbon ends up in the headspace, where the CO2 δ13C is equivalent to that of the carbonate or dissolved Ci. CO2 from the headspace was sampled using a Thermo GasBench, and δ13C values obtained in an interfaced MAT 253 mass spectrometer
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