Cavity Ring-Down Spectroscopy Performance and Procedures for High-Throughput O and H Measurement in Water Using "Express" Mode.

Cavity ring-down spectroscopy (CRDS) is rapidly becoming an invaluable tool to measure hydrogen (δ²H) and oxygen (δO) isotopic compositions in water, yet the long-term accuracy and precision of this technique remain relatively underreported. Here, we critically evaluate one-year performance of CRDS δ²H and δO measurements at ETH Zurich, focusing on high throughput (~200 samples per week) while maintaining required precision and accuracy for diverse scientific investigations. We detail a comprehensive methodological and calibration strategy to optimize CRDS reliability for continuous, high-throughput analysis using Picarro's "Express" mode, an area not extensively explored previously.

Widespread occurrence of dissolved oxygen anomalies, aerobic microbes, and oxygen-producing metabolic pathways in apparently anoxic environments.

Nearly all molecular oxygen (O2) on Earth is produced via oxygenic photosynthesis by plants or photosynthetically active microorganisms. Light-independent O2 production, which occurs both abiotically, e.g.

Revised microbial and photochemical triple-oxygen isotope effects improve marine gross oxygen production estimates.

The biogeochemical fluxes that cycle oxygen (O) play a critical role in regulating Earth's climate and habitability. Triple-oxygen isotope (TOI) compositions of marine dissolved O are considered a robust tool for tracing oxygen cycling and quantifying gross photosynthetic O production. This method assumes that photosynthesis, microbial respiration, and gas exchange with the atmosphere are the primary influences on dissolved O content, and that they have predictable, fixed isotope effects.

Clay hydroxyl isotopes show an enhanced hydrologic cycle during the Paleocene-Eocene Thermal Maximum.

The Paleocene-Eocene Thermal Maximum (PETM) was an abrupt global warming event associated with a large injection of carbon into the ocean-atmosphere system, as evidenced by a diagnostic carbon isotope excursion (CIE). Evidence also suggests substantial hydrologic perturbations, but details have been hampered by a lack of appropriate proxies. To address this shortcoming, here we isolate and measure the isotopic composition of hydroxyl groups (OH) in clay minerals from a highly expanded PETM section in the North Sea Basin, together with their bulk oxygen isotope composition.

The triple oxygen isotope composition of marine sulfate and 130 million years of microbial control.

The triple oxygen isotope composition (Δ'O) of sulfate minerals is widely used to constrain ancient atmospheric O/CO and rates of gross primary production. The utility of this tool is based on a model that sulfate oxygen carries an isotope fingerprint of tropospheric O incorporated through oxidative weathering of reduced sulfur minerals, particularly pyrite. Work to date has targeted Proterozoic environments (2.

Climate control on terrestrial biospheric carbon turnover.

Terrestrial vegetation and soils hold three times more carbon than the atmosphere. Much debate concerns how anthropogenic activity will perturb these surface reservoirs, potentially exacerbating ongoing changes to the climate system. Uncertainties specifically persist in extrapolating point-source observations to ecosystem-scale budgets and fluxes, which require consideration of vertical and lateral processes on multiple temporal and spatial scales.

Vitamin B-dependent biosynthesis ties amplified 2-methylhopanoid production during oceanic anoxic events to nitrification.

Bacterial hopanoid lipids are ubiquitous in the geologic record and serve as biomarkers for reconstructing Earth's climatic and biogeochemical evolution. Specifically, the abundance of 2-methylhopanoids deposited during Mesozoic ocean anoxic events (OAEs) and other intervals has been interpreted to reflect proliferation of nitrogen-fixing marine cyanobacteria. However, there currently is no conclusive evidence for 2-methylhopanoid production by extant marine cyanobacteria.

Triple oxygen isotope insight into terrestrial pyrite oxidation.

The mass-independent minor oxygen isotope compositions (Δ'O) of atmospheric O and [Formula: see text] are primarily regulated by their relative partial pressures, [Formula: see text]/[Formula: see text] Pyrite oxidation during chemical weathering on land consumes [Formula: see text] and generates sulfate that is carried to the ocean by rivers. The Δ'O values of marine sulfate deposits have thus been proposed to quantitatively track ancient atmospheric conditions. This proxy assumes direct [Formula: see text] incorporation into terrestrial pyrite oxidation-derived sulfate, but a mechanistic understanding of pyrite oxidation-including oxygen sources-in weathering environments remains elusive.

Mineral protection regulates long-term global preservation of natural organic carbon.

The balance between photosynthetic organic carbon production and respiration controls atmospheric composition and climate. The majority of organic carbon is respired back to carbon dioxide in the biosphere, but a small fraction escapes remineralization and is preserved over geological timescales. By removing reduced carbon from Earth's surface, this sequestration process promotes atmospheric oxygen accumulation and carbon dioxide removal.

Microbial oxidation of lithospheric organic carbon in rapidly eroding tropical mountain soils.

Lithospheric organic carbon ("petrogenic"; OC) is oxidized during exhumation and subsequent erosion of mountain ranges. This process is a considerable source of carbon dioxide (CO) to the atmosphere over geologic time scales, but the mechanisms that govern oxidation rates in mountain landscapes are poorly constrained. We demonstrate that, on average, 67 ± 11% of the OC initially present in bedrock exhumed from the tropical, rapidly eroding Central Range of Taiwan is oxidized in soils, leading to CO emissions of 6.

Climate oscillations reflected within the microbiome of Arabian Sea sediments.

Selection of microorganisms in marine sediment is shaped by energy-yielding electron acceptors for respiration that are depleted in vertical succession. However, some taxa have been reported to reflect past depositional conditions suggesting they have experienced weak selection after burial. In sediments underlying the Arabian Sea oxygen minimum zone (OMZ), we performed the first metagenomic profiling of sedimentary DNA at centennial-scale resolution in the context of a multi-proxy paleoclimate reconstruction.

Polyparameter linear free energy relationship for wood char-water sorption coefficients of organic sorbates.

Black carbons, including soots, chars, activated carbons, and engineered nanocarbons, have different surface properties, but the extent to which these affect their sorbent properties is not known. To evaluate this for an environmentally ubiquitous form of black carbon, biomass char, the surface of a well-studied wood char was probed using 14 sorbates exhibiting diverse functional groups, and the data were fit with a polyparameter linear free energy relationship to assess the importance of the various possible sorbate-char surface interactions. Sorption from water to water-wet char evolved with the sorbate's degree of surface saturation and depended on only a few sorbate parameters: log K(d)L/kg) = [(4.