Measurement of 18 O18 O and 17 O18 O in atmospheric O2 using the 253 Ultra mass spectrometer and applications to stratospheric and tropospheric air samples

High-accuracy measurement of 36SF5 + signal using an ultrahigh-resolution isotope ratio mass spectrometer

RATIONALE

The Δ36S standard deviation measured in a conventional isotope ratio mass spectrometer such as MAT 253 is ca 0.1‰ to 0.3‰. At this precision, it is difficult to resolve the origin of non-mass-dependent sulfur isotope fractionation in tropospheric sulfate aerosol and in Martian meteorites or small deviations from the canonical mass-dependent fractionation laws. Interfering ions with m/z at 131 of 36SF5 + are suggested by the community as the cause of the poor precision, but the exact ion species has not been identified or confirmed.

METHODS

Here we examined the potential interfering ions by using a Thermo Scientific ultrahigh-resolution isotope ratio mass spectrometer to measure SF6 working gas and SF6 gases converted from IAEA-S1/2/3 Ag2S reference materials.

RESULTS

We found that there are two resolvable peaks to the right of the 36SF5 + peak when a new filament was installed, which are 186WF4 2+ followed by 12C3F5 +. However, only the 12C3F5 + interference peak was observed after more than three days of filament use. 12C3F5 + is generated inside the instrument during the ionization process. Avoiding the interfering signals, we were able to achieve a Δ36S standard deviation of 0.046‰ (n = 8) for SF6 zero-enrichment and 0.069‰ (n = 8) for overall measurement start from silver sulfide IAEA-S1.

CONCLUSIONS

Aging the filament with SF6 gas can avoid the interference of 186WF4 2+. Minimizing the presence of carbon-bearing compounds and avoiding the interfering signals of 12C3F5 + from 36SF5 +, we can improve Δ36S measurement accuracy and precision, which helps to open new territories for research using quadruple sulfur isotope composition.

Managing argon interference during measurements of 18O/16O ratios in O2 by continuous-flow isotope ratio mass spectrometry

Abstract

Monitoring changes in stable oxygen isotope ratios in molecular oxygen allows for studying many fundamental processes in bio(geo)chemistry and environmental sciences. While the measurement of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{18}$$\end{document}18O/\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{16}$$\end{document}16O ratios of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {O}_{2}$$\end{document}O2 in gaseous samples can be carried out conveniently and from extracting moderately small aqueous samples for analyses by continuous-flow isotope ratio mass spectrometry (CF-IRMS), oxygen isotope signatures, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\updelta ^{18}$$\end{document}δ18O, could be overestimated by more than 6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\permille$$\end{document}‱ because of interferences from argon in air. Here, we systematically evaluated the extent of such Ar interferences on \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{18}$$\end{document}18O/\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{16}$$\end{document}16O ratios of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {O}_{2}$$\end{document}O2 for measurements by gas chromatography/IRMS and GasBench/IRMS and propose simple instrumental modifications for improved Ar and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {O}_{2}$$\end{document}O2 separation as well as post-measurement correction procedures for obtaining accurate \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\updelta ^{18}$$\end{document}δ18O. We subsequently evaluated the consequences of Ar interferences for the quantification of O isotope fractionation in terms of isotope enrichment factors, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upepsilon _{\mathrm {O}}$$\end{document}ϵO, and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{18}$$\end{document}18O kinetic isotope effects (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{18}$$\end{document}18O KIEs) in samples where \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {O}_{2}$$\end{document}O2 is consumed and Ar:\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {O}_{2}$$\end{document}O2 ratios increase steadily and substantially over the course of a reaction. We show that the extent of O isotope fractionation is overestimated only slightly and that this effect is typically smaller than uncertainties originating from the precision of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\updelta ^{18}$$\end{document}δ18O measurements and experimental variability. Ar interferences can become more relevant and bias \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upepsilon _{\mathrm {O}}$$\end{document}ϵO values by more than \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2\permille$$\end{document}2‱ in aqueous samples where fractional \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {O}_{2}$$\end{document}O2 conversion exceeds 90%. Practically, however, such samples would typically contain less than 25 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu$$\end{document}μM of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {O}_{2}$$\end{document}O2 at ambient temperature, an amount that is close to the method detection limit of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{18}$$\end{document}18O/\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{16}$$\end{document}16O ratio measurement by CF-IRMS.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00216-022-04184-3.

Role of Vehicular Catalytic Converter Temperature in Emission of Pollutants: An Assessment Based on Isotopic Analysis of CO2 and N2O

Vehicular catalytic converters are used to regulate, reduce, and convert toxic and environmentally unfriendly compounds in exhaust gases into relatively inert and less harmful chemical species. The efficiency, however, is largely affected by the operating temperature of the converter which is set by the hot exhaust gas released from the combustion chamber. A major gas released during combustion is CO₂, and its multiply substituted isotopocule, namely, ¹³C¹⁶O¹⁸O, provides a window of opportunity to probe directly the effective temperature of the converter in operation. Here, we report multiple isotopic measurements in exhaust CO₂ (δ¹³C, δ¹⁷O, δ¹⁸O, and Δ₄₇) of diesel (trucks and buses) and gasoline (sedans, trucks, and two-wheel motorcycles)-powered vehicles. For investigating the efficiency of a converter in reducing toxic compounds, we studied NO_x processes through isotopic analysis of the exhaust N₂O. We found that the degree of N₂O reduction to N₂ in gasoline-powered vehicles is high when the temperature is above 200 °C (inferred by Δ₄₇). In contrast, diesel-powered vehicles produce N₂O in abundance, probably a consequence of selective catalytic reduction of NO_x, and the reduction efficiency depends on the converter temperature. In other words, the catalytic converters act as sinks and sources of N₂O to the atmosphere in gasoline- and diesel-operated vehicles, respectively. We also report a new set of field data by measuring the isotopic compositions of CO₂ and N₂O in the Hsuehshan tunnel, a ∼13 km long highway tunnel in Taiwan. Elevated N₂O concentrations inside the tunnel indicate that the emission of N₂O by heavy-duty diesel vehicles is much higher compared to the reduction by gasoline-operated passenger cars, making the vehicular exhausts a net source of N₂O to the atmosphere. The combined study of clumped isotopes and N₂O concentration in exhaust gases suggests that it is useful to probe the operational temperature of catalytic converters and monitor the pollution level in operation, thus providing an opportunity for manufacturers to optimize the catalytic efficiency to reduce the level of toxic pollutants to the environment.

A new perspective of probing the level of pollution in the megacity Delhi affected by crop residue burning using the triple oxygen isotope technique in atmospheric CO2

Air quality in the megacity Delhi is affected not only by local emissions but also by pollutants from crop residue burning in the surrounding areas of the city, particularly the rice straw burning in the post monsoon season. As a major burning product, gaseous CO₂, which is rather inert in the polluted atmosphere, provides an alternative solution to characterize the impact of biomass burning from a new perspective that other common tracers such as particulate matters are limited because of their physical and chemical reactiveness. Here, we report conventional ([CO₂], δ¹³C, and δ¹⁸O) and unconventional (Δ¹⁷O) isotope data for CO₂ collected at Connaught Place (CP), a core area in the megacity Delhi, and two surrounding remote regions during a field campaign in October 18-20, 2017. We also measured the isotopic ratios near a rice straw burning site in Taiwan to constrain their end member isotopic compositions. Rice straw burning produces CO₂ with δ¹³C, δ¹⁸O, and Δ¹⁷O values of -29.02 ± 0.65, 19.63 ± 1.16, and 0.05 ± 0.02‰, respectively. The first two isotopic tracers are less distinguishable from those emitted by fossil fuel combustion but the last one is significantly different. We then utilize these end member isotopic ratios, with emphasis on Δ¹⁷O for the reason given above, for partitioning sources that affect the CO₂ level in Delhi. Anthropogenic fraction of CO₂ at CP ranges from 4 to 40%. Further analysis done by employing a three-component (background, rice straw burning, and fuel combustion) mixing model with constraints from the Δ¹⁷O values yields that rice straw burning contributes as much as ∼70% of the total anthropogenic CO₂, which is more than double of the fossil fuel contribution (∼30%), during the study days.