Why are variations in bromine isotope compositions in the Earth's history larger than chlorine isotope compositions?

In this paper we discuss the marked discrepancy in global chlorine and bromine isotope variations. While, based on experimentally and theoretically determined fractionation factors, it is expected that bromine isotope variations should be, depending on the process, 2 to 7 times less than chlorine isotope variations it is observed that in formation brines the isotope variations of bromine are at least of the same size as chlorine isotope variations, and regularly even larger. In this paper we argue that this is caused by the fact that oxidation-reduction processes play a more important role in bromine isotope geochemistry than in chlorine isotope geochemistry. Due to the fact that the bromide ion is more easily to oxidise than the chloride ion Rayleigh effects can cause the observed larger variations in bromine isotope geochemistry. In this paper we propose that biochemical reactions (oxidation of bromide ions to methyl bromide) may be the major cause for this effect. Although we do not yet understand the full processes that take place we show that oxidation-reduction processes must be the main effect to explain the differences between the two isotope systems and propose that more research is developed to understand how the processes cause the observed variations

Lithium in Portuguese Bottled Natural Mineral Waters—Potential for Health Benefits?

There is increasing epidemiologic and experimental evidence that lithium (Li) exhibits significant health benefits, even at concentrations lower than the therapeutic oral doses prescribed as treatment for mental disorders. The aim of this study is to determine the content of Li in 18 brands of bottled natural mineral waters that are available on the Portuguese market and from which the sources are found within the Portuguese territory, to provide data for Li intake from drinking water. Analyses of Li were performed by inductively coupled plasma-mass spectrometry. The results indicate highly different Li concentrations in natural mineral waters: one group with low Li concentrations (up to 11 µg Li/L) and a second group with Li concentrations higher than 100 µg/L. The highest Li concentrations (>1500 µg Li/L) were observed in the highly mineralized Na-HCO3 type waters that are naturally carbonated (>250 mg/L free CO2). As a highly bioavailable source for Li dietary intake these natural mineral waters have potential for Li health benefits but should be consumed in a controlled manner due to its Na and F− contents. The consumption of as little as 0.25 L/day of Vidago natural mineral water (2220 µg Li/L), can contribute up to 50% of the proposed daily requirement of 1 mg Li/day for an adult (70 kg body weight). In future, Li epidemiological studies that concern the potential Li effect or health benefits from Li in drinking water should consider not only the Li intake from tap water but also intake from natural mineral water that is consumed in order to adjust the Li intake of the subjects

Chlorine isotope fractionation between chloride (Cl<SUP>-</SUP>) and dichlorine (Cl<SUB>2</SUB>)

International audienceThe use of chlorine stable isotopes (35Cl and 37Cl) can help to constrain natural processes that involve chlorine species with different oxidation states. Theoretical studies based on thermodynamic and quantum mechanical approaches predict large isotope fractionation during redox reactions but to date, these reactions have not been studied experimentally. Here, we explore the chlorine isotope fractionation during the oxidation of hydrated Cl- (redox state of -I) to Cl2 (redox state of 0) at 25 °C and at 0 °C. Our apparatus consists of a sealed glass reactor where liquid HCl is mixed with liquid H2O2, a strong oxidant. Following complex reaction pathways, this mixture ultimately leads to the oxidation of Cl- and to the formation of Cl2 gas. As long as it is degassing, the Cl2 gas is flushed out of solution using N2 as a vector-gas from the glass-reactor to a potassium hydroxide (KOH) solution (pH 14) where it disproportionates into soluble species: Cl- and ClO-. After each experiment, the chlorine isotopic composition was measured in the recovered KOH-trap solution, as well as in the residual HCl solution. Consistent with theoretical predictions, the produced Cl2 gas is always enriched in the heavier 37Cl as compared to the initial Cl-reservoir. The following isotope fractionation factors are obtained: At 0 °C the isotopic fractionation 1000ln α(Cl2-Cl-) is 4.51 (+1.65/-0.49)‰ At 25 °C the isotopic fractionation 1000ln α(Cl2-Cl-) is 3.94 (+0.69/-0.18)‰. From the obtained data it is suggested that the production of Cl2 gas in our experiments is best described by a closed-system distillation. Our results are in agreement with published theoretical ab-initio calculations

Chlorine isotope and Cl–Br fractionation in fluids of Poás volcano (Costa Rica): Insight into an active volcanic–hydrothermal system

OVSICORIHalogen-rich volcanic fluids issued at the surface carry information on properties and processes operating in shallow hydrothermal systems. This paper reports a long-term record of Cl–Br concentrations and δ37Cl signatures of lake water and fumaroles from the active crater of Poás volcano (Costa Rica), where surface expressions of magmatic-hydrothermal activity have shown substantial periodic changes over the last decades. Both the hyperacid water of its crater lake (Laguna Caliente) and subaerial fumaroles show significant temporal variability in Cl–Br concentrations, Br/Cl ratios and δ37Cl, reflecting variations in the mode and magnitude of volatile transfer. The δ37Cl signatures of the lake, covering the period 1985–2012, show fluctuations between + 0.02 ± 0.06‰ and + 1.15 ± 0.09‰. Condensate samples from adjacent fumaroles on the southern shore, collected during the interval (2010–2012) with strong changes in gas temperature (107–763°C), display a much larger range from − 0.43 ± 0.09‰ to + 14.09 ± 0.08‰. Most of the variations in Cl isotope, Br/Cl and concentration signals can be attributed to interaction between magma-derived gas and liquid water in the volcanic–hydrothermal system below the crater. The δ37Cl were lowest and closest to magmatic values in (1) fumarolic gas that experienced little or no interaction with subsurface water and followed a relatively dry pathway, and (2) water that captured the bulk of magmatic halogen output so that no phase separation could induce fractionation. In contrast, elevated δ37Cl can be explained by partial scavenging and fractionation during subsurface gas–liquid interaction. Hence, strong Cl isotope fractionation leading to very high δ37Cl in Poás’ fumaroles indicates that they followed a wet pathway. Highest δ37Cl values in the lake water were found mostly in periods when it received a significant input from subaqueous fumaroles or when high temperatures and low pH caused HCl evaporation. It is concluded that combined monitoring of δ37Cl and Br/Cl in Laguna Caliente and adjacent fumaroles provides valuable information on activity in the subsurface hydrothermal system with significant relevance for volcanic surveillance of Poás.Los fluidos volcánicos ricos en halógenos emitidos en la superficie transportan información sobre propiedades y procesos que operan en sistemas hidrotermales poco profundos. Este artículo reporta un registro a largo plazo de concentraciones de Cl-Br y firmas de δ37Cl en el agua del lago y fumarolas del cráter activo del volcán Poás (Costa Rica), donde las expresiones superficiales de la actividad magmático-hidrotermal han mostrado cambios periódicos sustanciales durante las últimas décadas. . Tanto el agua hiperácida de su lago del cráter (Laguna Caliente) como las fumarolas subaéreas muestran una variabilidad temporal significativa en las concentraciones de Cl-Br, relaciones Br / Cl y δ37Cl, lo que refleja variaciones en el modo y magnitud de la transferencia de volátiles. Las firmas de δ37Cl del lago, que cubren el período 1985-2012, muestran fluctuaciones entre + 0.02 ± 0.06 ‰ y + 1.15 ± 0.09 ‰. Las muestras de condensado de fumarolas adyacentes en la costa sur, recolectadas durante el intervalo (2010-2012) con fuertes cambios en la temperatura del gas (107–763 ° C), muestran un rango mucho mayor de - 0.43 ± 0.09 ‰ a + 14.09 ± 0.08 ‰ . La mayoría de las variaciones en el isótopo de Cl, Br / Cl y las señales de concentración se pueden atribuir a la interacción entre el gas derivado del magma y el agua líquida en el sistema volcánico-hidrotermal debajo del cráter. Los δ37Cl fueron los más bajos y cercanos a los valores magmáticos en (1) gas fumarólico que experimentó poca o ninguna interacción con el agua subterránea y siguió una vía relativamente seca, y (2) agua que capturó la mayor parte de la producción de halógeno magmático de modo que ninguna separación de fases pudo inducir el fraccionamiento. Por el contrario, el δ37Cl elevado puede explicarse por la eliminación parcial y el fraccionamiento durante la interacción gas-líquido del subsuelo. Por lo tanto, un fuerte fraccionamiento de isótopos de Cl que conduce a un δ37Cl muy alto en las fumarolas de Poás indica que siguieron una vía húmeda. Los valores más altos de δ37Cl en el agua del lago se encontraron principalmente en períodos en los que recibió una entrada significativa de fumarolas subacuáticas o cuando las altas temperaturas y el pH bajo causaron la evaporación del HCl. Se concluye que el monitoreo combinado de δ37Cl y Br / Cl en Laguna Caliente y fumarolas adyacentes proporciona información valiosa sobre la actividad en el sistema hidrotermal subsuperficial con relevancia significativa para la vigilancia volcánica de Poás.Fluidos vulcânicos ricos em halogênio emitidos na superfície carregam informações sobre propriedades e processos que operam em sistemas hidrotérmicos rasos. Este artigo relata um registro de longo prazo das concentrações de Cl-Br e assinaturas de δ37Cl da água do lago e fumarolas da cratera ativa do vulcão Poás (Costa Rica), onde as expressões de superfície da atividade magmático-hidrotérmica mostraram mudanças periódicas substanciais nas últimas décadas . Tanto a água hiperácida de seu lago de cratera (Laguna Caliente) quanto as fumarolas subaéreas mostram uma variabilidade temporal significativa nas concentrações de Cl-Br, razões Br / Cl e δ37Cl, refletindo variações no modo e magnitude da transferência de voláteis. As assinaturas de δ37Cl do lago, cobrindo o período 1985–2012, mostram flutuações entre + 0,02 ± 0,06 ‰ e + 1,15 ± 0,09 ‰. Amostras condensadas de fumarolas adjacentes na costa sul, coletadas durante o intervalo (2010–2012) com fortes mudanças na temperatura do gás (107–763 ° C), exibem uma faixa muito maior de - 0,43 ± 0,09 ‰ a + 14,09 ± 0,08 ‰ . A maioria das variações no isótopo Cl, Br / Cl e sinais de concentração podem ser atribuídas à interação entre o gás derivado do magma e a água líquida no sistema vulcânico-hidrotérmico abaixo da cratera. Os δ37Cl foram os mais baixos e mais próximos dos valores magmáticos em (1) gás fumarólico que experimentou pouca ou nenhuma interação com água subterrânea e seguiu um caminho relativamente seco, e (2) água que capturou a maior parte da saída de halogênio magmático de modo que nenhuma separação de fase poderia induzir o fracionamento. Em contraste, o δ37Cl elevado pode ser explicado pela eliminação parcial e fracionamento durante a interação gás-líquido subterrâneo. Portanto, o forte fracionamento de isótopos de Cl levando a δ37Cl muito alto nas fumarolas de Poás indica que eles seguiram um caminho úmido. Os maiores valores de δ37Cl na água do lago foram encontrados principalmente em períodos em que recebeu uma entrada significativa de fumarolas subaquáticas ou quando altas temperaturas e baixo pH causaram a evaporação de HCl. Conclui-se que o monitoramento combinado de δ37Cl e Br / Cl em Laguna Caliente e fumarolas adjacentes fornece informações valiosas sobre a atividade no sistema hidrotérmico subterrâneo com relevância significativa para a vigilância vulcânica de Poás.Utrecht University, The NetherlandsOnderzoek & Beleving, The NetherlandsLa Sorbonne, FranceUniversidad Nacional, Costa RicaObservatorio Vulcanológico y Sismológico de Costa Ric

Bromine Isotope Variations in Magmatic and Hydrothermal Sodalite and Tugtupite and the Estimation of Br Isotope Fractionation between Melt and Sodalite

We determined the bromine isotope compositions of magmatic and hydrothermal sodalite (Na8Al6Si6O24Cl2) and tugtupite (Na8Al2Be2Si8O24Cl2) from the Ilímaussaq intrusion in South Greenland, in order to constrain the Br isotope composition of the melt and hydrothermal fluids from which these minerals were formed. Early formed magmatic sodalite has high Br contents (138 ± 10 µg/g, n = 5) and low δ81Br values (+0.23 ± 0.07‰). Late stage hydrothermal sodalite has lower Br contents (53±10 µg/g, n = 5) and higher δ81Br values (+0.36 ± 0.08‰). Tugtupite that forms at even later stages shows the lowest Br contents (26 ± 2 µg/g, n = 2) and the highest δ81Br values (+0.71 ± 0.17‰). One hydrothermal sodalite has a Br concentration of 48 ± 9 µg/g and an exceptionally high δ81Br of 0.82 ± 0.12‰, very similar to the δ81Br of tugtupites. We suggest that this may be a very late stage sodalite that possibly formed under Be deficient conditions. The data set suggests that sodalite crystallises with a negative Br isotope fractionation factor, which means that the sodalite has a more negative δ81Br than the melt, of −0.3 to −0.4‰ from the melt. This leads to a value of +0.5 to +0.6‰ relative to SMOB for the melt from which sodalite crystallises. This value is similar to a recently published δ81Br value of +0.7‰ for very deep geothermal fluids with very high R/Ra He isotope ratios, presumably derived from the mantle. During crystallisation of later stage hydrothermal sodalite and the Be mineral tugtupite, δ81Br of the residual fluids (both melt and hydrothermal fluid) increases as light 79Br crystallises in the sodalite and tugtupite. This results in increasing δ81Br values of later stage minerals that crystallise with comparable fractionation factors from a fluid with increasingly higher δ81Br values

Chlorine isotope variations in the hyper-acid lake system of Poás volcano, Costa Rica

Utrecht University, The NetherlandsUniversidad Nacional, Costa RicaUniversidade Técnica de Lisboa, Portuga

Geochemical and multi-isotopes (δ18O, δ2H, δ13C, 3H and δ37Cl) evidences to karst development and flow directions in transboundary aquifer, Northeast of Iran

The first systematic research of the geo-hydrogeological and hydrogeochemical characteristics and isotopic signatures was carried out in the transboundary karstic aquifer in northeast of Iran, in order to investigate the groundwater origin, flow directions and karst development. The karstic springs of the area are characterized by discharge rate of 50–500 L/s, EC values of 370–1050 μS/cm and the Ca–Mg–HCO3 water type. Stable isotope values of the precipitations resulted in a LMWL (δ2H = 7.2 × δ18O+8.6, R2 = 0.96, n = 96) with a lower slope and a lower intercept than the global meteoric water line (GMWL) due to isotope kinetic fractionation effects during precipitation. The δ18O precipitation gradient is −0.32‰ per 100 m of altitude. Isotopes data reveals that recent Mediterranean meteoric water (rain and/or snow) is the main origin of groundwater in the study area. The depleted isotope composition of some of the springs can be attributed to their higher catchment area and more recharge by snow. Groundwater budget analysis reveals that a large amount of water migrates toward the neighboring country. Fold and fault zones can be important variables on groundwater local and regional flows in the karstic aquifer. In terms of karst development, the Sarani spring in transboundary karstic aquifer with lower δ18O, δ37Cl and EC values and higher δ13CDIC has conduit flow regime and more karst development in its catchment area. In comparison, the isotopic values as well as physic-chemical characteristics of the springs confirm larger residence times (>30 years) and lower karst development in the other karstic springs. Consequently, the geo-hydrogeological and tectonic settings as well as isotopic approaches enhances knowledge in both groundwater flow direction and karst development and, ultimately, to better evaluate and manage water resources in the study area, and also in other transboundary karstic regions