Seawater pH, pCO2 and [CO2−3] variations in the Caribbean Sea over the last 130 kyr: A boron isotope and B/Ca study of planktic foraminifera

The isotopic systems of boron and magnesium are increasingly being used as proxies for a number of environmental variables and processes. The isotopic composition of seawater for both systems plays a central role in these studies and is an important interlaboratory standard. Given the long residence times of both elements (∼10 7 years) it is commonly assumed that seawater is isotopically homogenous for these systems, yet no systematic studies currently exist. Here we present the B and Mg isotopic composition of 26-28 seawater samples from a number of ocean basins that encompass a significant range in salinity (32 to 38 psu), temperature (-0.3 to +25.9C) and water depth (0 to 1240 m). We find no significant or systematic variation for either system in accordance with their long residence times. We recommend that the mean values we report (δ 11 B = 39.61 0.04 ‰ (2 s.e.; n = 28), δ 25 Mg = -0.43 0.01 ‰ (2 s.e.; n = 26), δ 26 Mg = -0.82 0.01 ‰ (2 s.e.; n = 26)) be used in future studies involving Mg and B isotopes. Copyright © 2010 by the American Geophysical Union.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2010GC003201

Boron and magnesium isotopic composition of seawater

https://cyberleninka.org/article/n/862582.pdf

Calibration and correction of LA-ICP-MS and LA-MC-ICP-MS analyses for element contents and isotopic ratios

The geochemical cycle of boron: Constraints from boron isotope partitioning experiments between mica and fluid

In 1999 the Istituto di Geoscienze e Georisorse (IGG), with the support of the International Atomic Energy Agency (IAEA), undertook the collection, preparation and distribution of eight geological materials intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials came from Italian sources and consist of three natural waters (Mediterranean seawater and two groundwaters) and five rocks and minerals (tourmaline, basalt, obsidian, limestone and clay). The solid materials were crushed, milled and mixed, in preparation for distribution. Extensive assays performed at the IGG on these materials demonstrated that their boron isotopic and chemical compositions are homogeneous.



Additional homogeneity tests were carried out on solid material fragments at the GeoForschungsZentrum Potsdam, with the specific objective of investigating the suitability of some of them for the calibration in situ of micro-analytical techniques. Two materials, B4 (tourmaline) and B6 (obsidian), proved to be isotopically homogeneous and may become excellent references for in situ microanalyses of boron isotopes.



The materials described here were used as the basis of a major laboratory intercomparison study and are now available for further distribution from either the IAEA (solid materials) or the IGG (waters).



L'Istituto di Geoscienze e Georisorse (IGG), avec le soutien de l'Agence Internationale de l'Energie Atomique (AIEA), a entrepris en 1999 la recolte, la preparation et la distribution de huit materiaux geologiques dans le but de conduire une comparaison en aveugle des mesures de composition isotopique et de concentration du bore entre differents laboratoires. Les materiaux, qui derivent tous de sites italiens, comprennent trois eaux naturelles (une eau de la Mer Mediterranee et deux eaux souterraines) et cinq roches et mineraux (tourmaline, basalte, obsidienne, calcaire et argile). Pour la distribution, les materiaux solides ont ete reduits en fragments, broyes et melanges et leur homogeneite de composition isotopique et chimique du bore a ete verifiee par des essais exhaustifs.



D'autres essais d'homogeneite ont ete effectues au GeoForschungsZentrum Potsdam sur des fragments des materiaux solides avec le but particulier d'etudier la possibilite d'utilisation de ces materiaux pour la calibration in situ des techniques microanalytiques. Deux materiaux, le B4 (tourmaline) et le B6 (obsidienne), se sont reveles isotopiquement homogenes et donc peuvent devenir d'excellents materiaux de reference pour les microanalyses isotopiques in situ du bore.



Les materiaux, qui sont decrits dans cette note, ont ete utilises pour une etude d'intercomparaison des mesures isotopiques et chimiques du bore entre differents laboratoire. Ils sont maintenant a disposition a l'AIEA (materiaux solides) et a l'IGG (eaux) pour leur distribution ulterieure.

Intercomparison of Boron Isotope and Concentration Measurements. Part I: Selection, Preparation and Homogeneity Tests of the Intercomparison Materials

The Istituto di Geoscienze e Georisorse (IGG), on behalf and with the support of the International Atomic Energy Agency (IAEA), prepared eight geological materials (three natural waters and five rocks and minerals), intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials were distributed to twenty seven laboratories - virtually all those performing geochemical boron isotope analyses in the world -which agreed to participate in the intercomparison exercise. Only fifteen laboratories, however, ultimately submitted the isotopic and/or concentration results they obtained on the intercomparison materials. The results demonstrate that interlaboratory reproducibility is not well reflected by the precision values reported by the individual laboratories and this observation holds true for both boron concentration and isotopic composition. The reasons for the discrepancies include fractionations due to the chemical matrix of materials, relative shift of the zero position on the δ11B scale and a lack of well characterized materials for calibrating absolute boron content measurements. The intercomparison materials are now available at the IAEA (solid materials) and IGG (waters) for future distribution.



L'Istituto di Geoscienze e Georisorse (IGG), pour le compte et avec le soutien de l'Agence Internationale de l'Energie Atomique (AIEA), a prepare huit materiaux geologiques (trois eaux naturelles et cinq roches et mineraux) destines a la conduite d'une comparaison en aveugle des mesures de composition isotopique et de concentration du bore entre differents laboratoires. Vingt-sept laboratoires -pratiquement tous ceux qui travaillent sur les isotopes du bore en geochimie - ont accepte de participer a cette intercomparaison, mais quinze seulement ont finalement envoye leurs donnees de composition isotopique et/ou de concentration du bore. Les resultats demontrent que la precision des valeurs indiquee par les laboratoires reflete mal la reproductibilite entre laboratoires des mesures de composition isotopique comme de concentration du bore. Les raisons de ces discordances peuvent comprendre l'existence de fractionnements isotopiques dus aux matrices chimiques des materiaux, un deplacement relatif du zero de l'echelle de δ11B, ainsi que le manque de materiaux bien caracterises pour calibrer les mesures de concentration du bore. Les materiaux utilises pour l'intercomparaison des mesures sont maintenant a disposition a l'AIEA (materiaux solides) et l'IGG (eaux) pour etre distribues.

Sabine Tonn

Papers

Intercomparison of boron isotope and concentration measurements : Part II: Evaluation of results