We propose a coupled SOM-PMF framework to identify the sources and co-evolution of nitrate and fluoride in the Ganjiang River Basin. The results indicate that nitrate primarily originates from agricu....

Hypoxia in marine systems is expanding worldwide due to anthropogenic activities. Deep waters of the St. Lawrence Estuary and Gulf are rapidly deoxygenating (∼1 mmol O2 m−3 y−1), driven by changes in Atlantic water-mass intrusion and nutrient‐fueled remineralization, and are simultaneously acidifying (∼0.004 pH unit y−1). These changes alter biogeochemical cycles and degrade habitats, causing biotic and economic consequences. Using a coupled physical-biogeochemical model, we tested whether watershed-scale nitrate reductions could mitigate deep‐water deoxygenation and carbonate-system degradation. Three nitrate‐reduction scenarios reduced riverine St. Lawrence River nitrate loads by about 11%, 30%, and 50% (−2.8, −7.5, and −11.7 mmol N m−3, respectively). Relative to the baseline simulation, these scenarios increased dissolved oxygen concentrations (DO) (+1.6, +4.3, and +6.7 mmol O2 m−3), pH (+0.004, +0.010, and +0.016), and aragonite saturation state (Ωarag) (+0.003, +0.009, and +0.015) in the deep Laurentian Channel (⩾175 m). The volume of deep waters with DO saturation

Dual-isotope tracing in situ shows faster transport of water than nitrate from soil to canopy of mature trees, indicating effects of root function, soil texture and species traits. Douglas fir exhibi...

AbstractTraditional isotope ratio mass spectrometers are not optimally designed to analyze nonvolatile molecular solutes such as oxyanions or organics. Necessary sample conversion steps, often demanding micromole-scale samples, break chemical bonds and limit oxyanion analyses to elemental isotope ratios. Recent studies enthusiastically promote soft electrospray ionization coupled to high-resolution Orbitrap mass spectrometry (ESI-Orbitrap-MS) for intact-molecule isotopologue analysis. This combination uses widely accessible instrumentation to provide simultaneous multi-isotopologue and clumped isotope analyses using tens of nanomoles of dissolved sample. However, its isotopic capabilities have been evaluated primarily through technical assessments rather than on natural samples, despite the need for matrix sensitivity assessments and robust isotopic calibrations. Here, we establish a framework for natural-sample ESI-Orbitrap-MS isotopologue analysis of nitrate and sulfate, addressing matrix effects, isotopologue calibration, and instrumental stability. We demonstrate strong sensitivity to contaminants at concentrations 1000 times below target analytes and strong temperature-correlated drift over >30 min, highlighting the enhanced need for rigorous sample purification to suppress matrix effects, sample-reference bracketing to overcome drift, and isotopologue calibration to reduce biases and robustly quantify uncertainties. We achieve 0.4–1.3‰ precision and accurate measurements of δ15N-NO3–, δ18O-NO3–, Δ17O-NO3–, δ34S-SO42–, and Δ17O–SO42– relative to traditional techniques, consuming only 20 nmol nitrate or 10 nmol sulfate. We resolve relative nitrate clumped isotope values in ice core samples (Δ15N18O-NO3–: ±2.3‰; Δ18O18O-NO3–: ±3.3‰) yet observe no correlations with bulk nitrate isotopes. These results establish practical guidelines for applying ESI-Orbitrap-MS to isotopologue and clumped isotope analysis of trace analytes in challenging sample matrices under real-world conditions.

A symmetric cogeneration fuel cell integrating value-added chemical synthesis with electricity generation by coupling formaldehyde oxidation with the nitrate reduction was developed. This work highlights the broader potential of symmetric cogeneration fuel cells as a general platform for rational reaction pairing, offering a practical pathway to lower energy input, upgrade product value and advance electrochemical synthesis driven by renewable electricity. ABSTRACT Electrochemical synthesis offers a sustainable route to convert abundant feedstocks into value-added chemicals under mild conditions and couple chemical manufacturing with renewable electricity. However, its practical impact is often limited by system-level energy inefficiency, motivating rational reaction pairing to reduce energy input while upgrading product value. Here, we develop a symmetric cogeneration fuel cell that couples one-electron formaldehyde oxidation reaction with nitrate reduction to co-produce hydrogen, ammonia and formate while generating electricity. This symmetric cell was enabled by a FOR and NO 3 RR bifunctional Cu nano leaves coated with Co(OH) 2 catalyst, which constructs an interfacial hydrogen network capable of synchronizing NO 3 – reduction with active hydrogen delivery. As a result, the catalyst achieves an industrial current density of 2.35 A cm −2 at −1 V vs RHE with a high Faradaic efficiency of 96.38%. Operating at 35°C, the symmetric cell delivers a peak power density of 13.24 mW cm −2 , representing the highest value reported to date for unassisted ammonia synthesis systems. This work establishes a simple yet versatile strategy for integrating value-added chemical synthesis with electricity generation and offers a generalizable framework for other paired electrosynthesis processes.

Ammonia/Nitrate Analyzers are based on the principle of diffusion across a gas diffusion membrane coupled with electrical conductivity measurement as first described by Carlson. The pump directs the sample, caustic, and absorbing solutions into the Membrane Diffusion Cell. Within the cell, the sample is mixed with a caustic solution. The resulting solution has a pH sufficiently high to convert virtually all of the ammonium ion present in the sample to dissolved ammonia gas, as shown in below equation. The sample/caustic solution flows past one side of a membrane that is permeable to gases but not to liquids or ionic species.

Nitrate pollution in coastal aquifers poses growing environmental concerns, yet aquifer responses to coupled natural and anthropogenic drivers remain …

Climate warming alters biogeochemical cycles, especially in high-altitude forests where warming accelerates soil organic matter decomposition and CO2 …

A Cu-Ni-W tri-component catalyst enables efficient nitrate-to-ammonia conversion under pulsed electrolysis. Combined experimental and theoretical studies attribute its performance to component synergism and regulated intermediates. Its facile adaptation for glycerol valorization to formic acid underscores a versatile system design concept, advancing electrochemical coupling strategies for a broad spectrum of industrially relevant reactions. ABSTRACT Electrochemical nitrate reduction represents a promising route for sustainable ammonia (NH3) production, yet its practical deployment is constrained by the limited efficiency of state-of-the-art electrocatalysts and immature system architectures. Here, we report a generalist copper–nickel–tungsten tri-component tandem electrocatalyst via a sequential microwave-hydrothermal deposition route. Under pulsed electrolysis conditions, the catalyst delivers a remarkable Faradaic efficiency of 97.1% and a record-high ammonia yield rate of 43.87 mg h−1 cm−2. Online differential electrochemical mass spectrometry (DEMS) identifies key intermediates and associated pathways, while density functional theory (DFT) calculations elucidate the cooperative roles of each component: the copper component facilitates nitrate adsorption and deoxygenation, the nickel component promotes water dissociation for steady *H supply, and the tungsten component serves as a dynamic *H reservoir. This synergy efficiently suppresses hydrogen evolution and enhances ammonia selectivity. Furthermore, coupling with glycerol valorization (to formic acid) as the anodic reaction demonstrates the potential for energy-efficient ammonia electrosynthesis. Collectively, this work offers both design strategies and mechanistic understanding for next-generation multi-component tandem electrocatalysts targeting advanced nitrogen-based chemical synthesis.

The coupled process of ferric ammonium oxidation (Feammox) and nitrate-dependent ferrous oxidation (NDFO) is a cost-effective nitrogen removal strateg…

Proceedings of the National Academy of Sciences, Volume 123, Issue 2, January 2026. SignificanceElectrocatalytic nitrate reduction reaction (NO3RR) offers a sustainable route for ammonia synthesis and nitrogen recycling, but its complex network of proton-coupled electron transfer steps has hindered comprehensive mechanistic ...

Interactions between flow path variations and subsurface nitrogen cycling drive seasonally variable nitrate export regimes Interannual nitrate chemostasis is controlled by coupled responses of ni...

Published in Journal of environmental management

Modern eastern equatorial Pacific (EEP) upwelling influences nitrate utilization Coupled sediment d15N records are used to identify past EEP nitrate utilization Strong linear relationship between E...

Nitrate N and O isotopes are sensitive to organic matter remineralization Coupled isotopes track nitrate modification from Southern to North Pacific Nitrate N and O isotopes allow us to quantify re...

In anaerobic ammonium oxidation coupled with ferric iron reduction (Feammox) culture systems, the Feammox process coexists with nitrate-dependent ferr…

Nitrite- and nitrate-coupled anaerobic oxidation of methane (AOM), mediated by Candidatus Methylomirabilis-like bacteria and Methanoperedens-like archaea, respectively, are two recent additions of fre...

Leveraging SR images of ETM+, MSI, and UAV, the Mixture Density Network (MDN) model demonstrated superior performance,with coefficient of determination (R2) range from 0.50 to 0.99, root mean square error (RMSE) range from 0.05‰ to 2.31‰ and mean absolute error...

Domoic acid poisoning is stranding marine mammals as warnings are issued to beachgoers of the threat posed by animals that are transformed by their illness.