The effect of H2O2 treatment on stable isotope analysis (δ13C, δ18O and Δ47) of various carbonate minerals

Naizhong Zhang, Mang Lin, Keita Yamada, Akihiro Kano, Qi Liu, Naohiro Yoshida, Ryo Matsumoto

Research output: Contribution to journalArticle

Abstract

In carbonate isotopic measurements, H2O2 treatment is one of the most often used methods to remove organic matter contaminants from carbonate minerals for accurate analysis, but the interaction between H2O2 solution and carbonate minerals may also lead to analytical bias. In this study, we quantitatively tested the effect of H2O2 treatment for 7 types of carbonate minerals, and the influences on Δ47 values of calcium carbonate are systematically discussed for the first time. Most samples presented Δ47 offsets within the 2-SD of our analytical precision, except the methane derived authigenic carbonate (MDAC). The shift of Δ47 values in MDACs is attributed to the mixing effect of two types of carbonate minerals: original one and isotopically altered one, and the magnitude is determined by the differences of both δ13C and δ18O values between two endmembers. Regarding biogenic carbonate tested here, the analytical bias of H2O2 treatment is relative small in δ13C and δ18O values, and therefore the shift of Δ47 values is statistically neglectable. The δ13C and δ18O values for most samples tested in this study became positive (up to +1.7‰) after H2O2 treatment. Apart from previously well discussed mechanisms, such as removal of organic contamination, isotopic fractionation during the partial dissolution and dissolution of isotopic distinct carbonate compositions in the heterogeneous minerals, we experimentally demonstrated carbon and oxygen isotopic exchanges between carbonate minerals and H2O2 solution for the first time. The δ13C and δ18O values of carbonate were influenced by isotopic exchanges with atmospheric CO2 in the CO2-HCO3 -CO3 2− system and H2O in H2O2 solution, respectively. Rich transition metals in the authigenic carbonate minerals (e.g. MDAC, travertine), which catalyze H2O2 decomposition, can enlarge this effect by altering H2O isotopic compositions. Though the small shift of δ13C and δ18O in biogenic carbonate observed here (up to 0.6‰) would not change scientific interpretations and conclusions in most of previous studies, cautions should be taken in the future. Based upon our new experimental results, we suggest using a buffered H2O2 solution (pH≈8) isolated from atmospheric CO2 to remove potential organic contaminations in biogenic carbonate. For authigenic carbonate, H2O2 treatment is not recommended. If necessary, decreasing the H2O2 concentration, shortening the reaction time, leaving the solution in a CO2-free environment, and adjusting the solution to a basic condition will improve the accuracy in isotopic analysis of these minerals.

Original languageEnglish
Article number119352
JournalChemical Geology
Volume532
DOIs
Publication statusPublished - 20 Jan 2020

Fingerprint

Carbonate minerals
Carbonates
Isotopes
stable isotope
carbonate
mineral
Methane
Minerals
Dissolution
Contamination
analysis
effect
Calcium Carbonate
Fractionation
Chemical analysis
Biological materials
methane
Transition metals
dissolution
Ion exchange

Keywords

  • Aragonite
  • Calcite
  • Clumped isotope
  • Hydrogen peroxide
  • Pretreatment

Cite this

Zhang, Naizhong ; Lin, Mang ; Yamada, Keita ; Kano, Akihiro ; Liu, Qi ; Yoshida, Naohiro ; Matsumoto, Ryo. / The effect of H2O2 treatment on stable isotope analysis (δ13C, δ18O and Δ47) of various carbonate minerals. In: Chemical Geology. 2020 ; Vol. 532.
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The effect of H2O2 treatment on stable isotope analysis (δ13C, δ18O and Δ47) of various carbonate minerals. / Zhang, Naizhong; Lin, Mang; Yamada, Keita; Kano, Akihiro; Liu, Qi; Yoshida, Naohiro; Matsumoto, Ryo.

In: Chemical Geology, Vol. 532, 119352, 20.01.2020.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The effect of H2O2 treatment on stable isotope analysis (δ13C, δ18O and Δ47) of various carbonate minerals

AU - Zhang, Naizhong

AU - Lin, Mang

AU - Yamada, Keita

AU - Kano, Akihiro

AU - Liu, Qi

AU - Yoshida, Naohiro

AU - Matsumoto, Ryo

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N2 - In carbonate isotopic measurements, H2O2 treatment is one of the most often used methods to remove organic matter contaminants from carbonate minerals for accurate analysis, but the interaction between H2O2 solution and carbonate minerals may also lead to analytical bias. In this study, we quantitatively tested the effect of H2O2 treatment for 7 types of carbonate minerals, and the influences on Δ47 values of calcium carbonate are systematically discussed for the first time. Most samples presented Δ47 offsets within the 2-SD of our analytical precision, except the methane derived authigenic carbonate (MDAC). The shift of Δ47 values in MDACs is attributed to the mixing effect of two types of carbonate minerals: original one and isotopically altered one, and the magnitude is determined by the differences of both δ13C and δ18O values between two endmembers. Regarding biogenic carbonate tested here, the analytical bias of H2O2 treatment is relative small in δ13C and δ18O values, and therefore the shift of Δ47 values is statistically neglectable. The δ13C and δ18O values for most samples tested in this study became positive (up to +1.7‰) after H2O2 treatment. Apart from previously well discussed mechanisms, such as removal of organic contamination, isotopic fractionation during the partial dissolution and dissolution of isotopic distinct carbonate compositions in the heterogeneous minerals, we experimentally demonstrated carbon and oxygen isotopic exchanges between carbonate minerals and H2O2 solution for the first time. The δ13C and δ18O values of carbonate were influenced by isotopic exchanges with atmospheric CO2 in the CO2-HCO3 −-CO3 2− system and H2O in H2O2 solution, respectively. Rich transition metals in the authigenic carbonate minerals (e.g. MDAC, travertine), which catalyze H2O2 decomposition, can enlarge this effect by altering H2O isotopic compositions. Though the small shift of δ13C and δ18O in biogenic carbonate observed here (up to 0.6‰) would not change scientific interpretations and conclusions in most of previous studies, cautions should be taken in the future. Based upon our new experimental results, we suggest using a buffered H2O2 solution (pH≈8) isolated from atmospheric CO2 to remove potential organic contaminations in biogenic carbonate. For authigenic carbonate, H2O2 treatment is not recommended. If necessary, decreasing the H2O2 concentration, shortening the reaction time, leaving the solution in a CO2-free environment, and adjusting the solution to a basic condition will improve the accuracy in isotopic analysis of these minerals.

AB - In carbonate isotopic measurements, H2O2 treatment is one of the most often used methods to remove organic matter contaminants from carbonate minerals for accurate analysis, but the interaction between H2O2 solution and carbonate minerals may also lead to analytical bias. In this study, we quantitatively tested the effect of H2O2 treatment for 7 types of carbonate minerals, and the influences on Δ47 values of calcium carbonate are systematically discussed for the first time. Most samples presented Δ47 offsets within the 2-SD of our analytical precision, except the methane derived authigenic carbonate (MDAC). The shift of Δ47 values in MDACs is attributed to the mixing effect of two types of carbonate minerals: original one and isotopically altered one, and the magnitude is determined by the differences of both δ13C and δ18O values between two endmembers. Regarding biogenic carbonate tested here, the analytical bias of H2O2 treatment is relative small in δ13C and δ18O values, and therefore the shift of Δ47 values is statistically neglectable. The δ13C and δ18O values for most samples tested in this study became positive (up to +1.7‰) after H2O2 treatment. Apart from previously well discussed mechanisms, such as removal of organic contamination, isotopic fractionation during the partial dissolution and dissolution of isotopic distinct carbonate compositions in the heterogeneous minerals, we experimentally demonstrated carbon and oxygen isotopic exchanges between carbonate minerals and H2O2 solution for the first time. The δ13C and δ18O values of carbonate were influenced by isotopic exchanges with atmospheric CO2 in the CO2-HCO3 −-CO3 2− system and H2O in H2O2 solution, respectively. Rich transition metals in the authigenic carbonate minerals (e.g. MDAC, travertine), which catalyze H2O2 decomposition, can enlarge this effect by altering H2O isotopic compositions. Though the small shift of δ13C and δ18O in biogenic carbonate observed here (up to 0.6‰) would not change scientific interpretations and conclusions in most of previous studies, cautions should be taken in the future. Based upon our new experimental results, we suggest using a buffered H2O2 solution (pH≈8) isolated from atmospheric CO2 to remove potential organic contaminations in biogenic carbonate. For authigenic carbonate, H2O2 treatment is not recommended. If necessary, decreasing the H2O2 concentration, shortening the reaction time, leaving the solution in a CO2-free environment, and adjusting the solution to a basic condition will improve the accuracy in isotopic analysis of these minerals.

KW - Aragonite

KW - Calcite

KW - Clumped isotope

KW - Hydrogen peroxide

KW - Pretreatment

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