Sulfur isotope signatures provide key information for the study of microbial activity in modern systems and the evolution of the Earth surface redox system. Microbial sulfate reducers shift sulfur isotope distributions by discriminating against heavier isotopes. This discrimination is strain-specific and often suppressed at sulfate concentrations in the lower micromolar range that are typical t...

The effects of dissolved salts (NaCI, KCI, MgCl,, CaCI,, Na,SO,, MgSO,, and their mixtures) on oxygen and hydrogen isotope partitioning between brines and coexisting phases (vapor and calcite) were experimentally determined at 50-350 C and 300 C, respectively. In liquid-vapor equilibration experiments, for all of the salts studied, the hydrogen isotope fractionation factors between the salt sol...

Individual-level diet variation can be easily quantified by gut-content analysis. However, because gut contents are a ‘snapshot’ of individuals’ feeding habits, such cross-sectional data can be subject to sampling error and lead one to overestimate levels of diet variation. In contrast, stable isotopes reflect an individual’s long-term diet, so isotope variation among individuals can be interpr...

Isotope effects, studied with precision isotope ratio mass spectrometry, have been used to locate critical steps in the H metabolism of plants. By manipulating the growth conditions of versatile microalgae, the discrimination of H isotopes between water in the growth medium and the organically bonded H in carbohydrates from these microalgae was -100 to -120 per thousand and was regulated by bot...

The persistent organic pollutant DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) is still indispensable in the fight against malaria, although DDT and related compounds pose toxicological hazards. Technical DDT contains the dichloro congener DDD (1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethyl]benzene) as by-product, but DDD is also formed by reductive degradation of DDT in the environment...

It has been reported in previous research that the lead isotopic composition of blood, urine and feces samples statistically differed from the given lead sources in Sprague-Dawley (SD) rats. However, the reason for this phenomenon is still unclear. An animal experiment was performed to investigate the lead isotope fractionation in diverse biological samples (i.e., lungs, liver, kidneys, bone) a...

Mass-independent sulfur isotope signatures are observed in Archean and early Paleoproterozoic sedimentary sulfate and sulfide minerals, and provide the most robust constraints on early atmospheric oxygen levels. Smaller mass-independent sulfur isotope anomalies are observed in ice cores and interpreted as a tracer of stratospheric volcanic loading. Photochemistry of sulfur dioxide (SO 2) has be...

Thermochemical sulfate reduction experiments with simple amino acid and dilute concentrations of sulfate reveal significant degrees of mass-independent sulfur isotope fractionation. Enrichments of up to 13‰ for (33)S are attributed to a magnetic isotope effect (MIE) associated with the formation of thiol-disulfide, ion-radical pairs. Observed (36)S depletions in products are explained here by c...

Stable isotope geochemistry is a branch of geology that investigates the age of natural materials, their origin and the processes they have undergone since formation [1]. Stable isotope analysis is also used in biogeochemical studies to monitor element cycling in ecosystems [2] and to identify geographical/regional differences for food provenance and archaeology. Of the elements of interest in ...

The global silicon (Si) cycle plays a critical role in regulating the biological pump and carbon oceans. A promising tool to reconstruct past dissolved silicic acid (DSi) concentrations is isotope signature of radiolaria (δ 30 Si rad ), siliceous zooplankton that dwells at subsurface intermediate water depths. However, date, only few studies on sediment δ records are available. To investigate i...