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...

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....

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...

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...

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.

Enrichments from bioreactors find a single bacterium capable of methane oxidation coupled to nitrate reduction via nitrite to dinitrogen, a process previously thought to rely on syntrophy.

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

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...

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

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

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

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.

Published in Journal of environmental management

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

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...

Increasing studies have recognized that the enzymatic nitrate–nitrite isotopic exchange reaction may be a potential breakthrough to update our understanding of the nitrogen cycle. However, fundamental aspects of this reaction remain poorly understood, limiting our comprehensive understanding of the nitrogen cycle. In this study, we present the first coupled measurements of nitrate and nitrite dual isotopes at natural abundance across the Antarctic summer to uncover the environmental factors influencing enzymatic isotopic exchange. East Antarctic surface waters exhibit the most anomalous nitrate and nitrite isotope signatures and a more pronounced equilibrium isotope effect compared to West Antarctica. This feature may be attributed to the regulation of enzymatic isotopic exchange reaction by temperature, and we infer that there might be a tipping point in the expression of its intensity. Given the warming of Antarctic waters due to global climate change, particularly in West Antarctic, we hypothesize that such reaction could have an amplified impact on nitrogen isotope dynamics. Further analyses incorporating data from beyond the Southern Ocean also suggest that functional differences in the nitrite oxidoreductase enzyme itself are a critical contributing factor. Overall, our study provides new insights into the mechanisms underlying the enzymatic isotopic exchange reaction, with broad implications for models of the modern upper ocean nitrogen cycle and paleoceanographic reconstructions of ancient nitrogen cycle dynamics.

The NRT1/PTR family of proton-coupled transporters are responsible for nitrogen assimilation in eukaryotes and bacteria through the uptake of peptides. However, in most plant species members of this family have evolved to transport nitrate as well as additional secondary metabolites and hormones....

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...

An anaerobic methanotroph (ANME-2d) can perform nitrate-d...