Naohiro Yoshida

Tokyo Institute of Technology | TITech · Earth-Life Science Institute

Stable isotopes of atmospheric nitrate (NO3−) are valuable tools for tracing nitrogen sources and processes; however, their signals in ice core records are often disrupted by post-depositional processes. The ice core from the southeastern Dome (SE-Dome) in Greenland is a potential record of variations in atmospheric chemistry that has experienced l...

Dissimilatory nitrate reduction to ammonium (DNRA), driven by nitrate-ammonifying bacteria, is an increasingly appreciated nitrogen-cycling pathway in terrestrial ecosystems. This process reportedly generates nitrous oxide (N2O), a strong greenhouse gas with ozone-depleting effects. However, it remains poorly understood how N2O is produced by envir...

The production by microorganisms of nitrous oxide (N2O), a trace gas contributing to global warming and stratospheric ozone depletion, is enhanced around the oceanic oxygen minimum zones (OMZs). The production constitutes an important source of atmospheric N2O. Although an OMZ is found in the northern part of the eastern Indian Ocean, the Bay of Be...

Temporal changes in the magnitude and geographic distribution of different sources of nitrous oxide (N2O) are not well constrained. To better understand the dynamics of N2O in the atmosphere over the last century, we have reconstructed the mole fraction, δ¹⁵Nbulk, δ¹⁸O, and δ¹⁵NSP values of N2O from ice cores, firn air archives, and modern atmosphe...

Carbon-13 position-specific isotope analysis of fatty acids from vegetable oils was performed using Nuclear Magnetic Resonance in the present study. The measured ¹³C patterns are not totally in accordance with the conventional view of the relative ¹³C-depletion of acetogenic lipids and their alternation of ¹³C-enriched and ¹³C-depleted carbon posit...

Understanding hydrocarbon cycling in the subsurface is important in various disciplines including climate science, energy resources and astrobiology. Mud volcanoes provide insights into biogeochemical processes occurring in the subsurface. They are usually associated with natural gas reservoirs consisting mainly of methane and other hydrocarbons as...

Rapid sea-ice retreat in the Arctic Ocean can promote the release of methane (CH4) from microbe and from sediment on the continental shelf. The released methane can be the cause or effect of strong climate feedback. Nevertheless, few observations have been reported of temporal changes of dissolved CH4 in the Arctic Ocean, especially in western coas...

Multiply substituted isotopic species of nitrous oxide (N2O), referred to as clumped isotopes, represent a promising new tool for distinguishing production pathways of this potent greenhouse gas. This work presents the first determination of enrichment factors of N2O clumped isotopes during bacterial denitrification. Samples of N2O obtained after 1...

Rationale: Information on the isotopic composition of nitrous oxide (N2 O) at natural abundance supports the identification of its source and sink processes. In recent years, a number of mass spectrometric and laser spectroscopic techniques have been developed and are increasingly used by the research community. Advances in this active research ar...

A new system was developed for measuring sulfur isotopes δ ³³ S and δ ³⁴ S from atmospheric carbonyl sulfide (COS) on small air samples of several liters, using pre-concentration and gas chromatography – isotope ratio mass spectrometry (GC-IRMS). Measurements of COS isotopes provide a tool for quantifying the COS budget, which will help towards bet...

Doubly substituted isotopic species of nitrous oxide (N2O), so called clumped isotopes, represent a new promising tool for distinguishing production paths of this potent greenhouse gas. This work presents first measurements of isotopic fractionation for clumped N2O isotopes during denitrification. Samples of N2O were obtained by incubation of a pur...

A new system was developed for measuring sulfur isotopes δ33S and δ34S from atmospheric carbonyl sulfide (COS or OCS) on small air samples of several liters, using a pre-concentration and gas chromatography – isotope ratio mass spectrometry (GC-IRMS) method. Measurements of COS isotopes provide a tool for quantifying the COS budget, which will help...

Recently developed methane clumped isotope techniques provides fresh and novel insights into methane biogeochemistry, which have been unobtainable through other techniques such as conventional stable isotope determinations and molecular composition measurements of hydrocarbons. Nonetheless, the governing processes and mechanisms which control the c...

As an important atmosphere constituent, sulfate aerosols exert profound impacts on climate, the ecological environment, and human health. The Tibetan Plateau (TP), identified as the “Third Pole”, contains the largest land ice masses outside the poles and has attracted widespread attention for its environment and climatic change. However, the mechan...

Nitrous oxide (N2O), an ozone-depleting greenhouse gas, is generally produced by soil microbes, particularly NH3 oxidizers and denitrifiers, and emitted in large quantities after N fertilizer application in croplands. N2O can be produced via multiple processes, and reduced, with the involvement of more diverse microbes with different physiological...

Increased use and improved methodology of carbonate clumped isotope thermometry has greatly enhanced our ability to interrogate a suite of Earth‐system processes. However, inter‐laboratory discrepancies in quantifying carbonate clumped isotope (Δ₄₇) measurements persist, and their specific sources remain unclear. To address inter‐laboratory differe...

After the 1980s, atmospheric sulfate reduction is slower than the dramatic reductions in sulfur dioxide (SO 2) emissions. However, a lack of observational evidence has hindered the identification of causal feedback mechanisms. Here, we report an increase in the oxygen isotopic composition of sulfate ( 17 O SO 4 2−) in a Greenland ice core, implyin...

Ocean–atmosphere gas exchange in the Arctic Ocean is sensitive to global warming because the decrease of sea‐ice covered area enhances the exchange. Melting sea ice affects the vertical transport of dissolved gases. Few reports of Arctic Ocean studies have described observations of dissolved N2O or temporal variation of sea‐to‐atmosphere N2O flux....

Previous studies on multiple sulfur isotopes (³²S, ³³S, and ³⁴S) in sedimentary pyrite at the end‐Permian suggested a shoaling of anoxic/sulfidic deep‐water contributing to the extinction. This scenario is based on an assumption that the sedimentary sulfur cycle was largely controlled by benthos activity, though a stratigraphic correlation between...

O‐excess (Δ¹⁷O = δ¹⁷O − 0.52 × δ¹⁸O) of sulfate trapped in Antarctic ice cores has been proposed as a potential tool for assessing past oxidant chemistry, while insufficient understanding of atmospheric sulfate formation around Antarctica hampers its interpretation. To probe influences of regional specific chemistry, we compared year‐round observat...

As an important atmosphere constituent, sulfate aerosols exert profound impacts on climate, ecological environment, and human health. The Tibetan Plateau (TP), identified as the Third Pole, contains the largest land ice masses outside the poles and has attracted wide attention on its environment and climatic change. However, the mechanisms of sulfa...

Position-specific isotope analysis has shown its potential to reveal information regarding formation, migration, and conversion procesess of hydrocarbons. The intramolecular isotope compositions of butane are promising to serve as a new thermometer and tracer. Therefore, position-specific isotope signatures in butane at equilibrium are needed for c...

The effects of cashew nut shell liquid (CNSL) feeding on the methane (CH4) emission and the ruminal microbiome of Lai Sind beef cattle were investigated. Changes in the methane production and rumen microbiome by CNSL feeding were monitored by a respiration chamber and 16S rRNA gene amplicon sequencing respectively. The results demonstrated that CNS...

We present analyses of nitrogen and oxygen isotopic ratios and site-preference (SP) values of atmospheric nitrous oxide samples obtained from Taiwan in west Pacific. Air samples were collected during from Keelung, located in the northeastern coast of Taiwan. The average values of δ 15 N, δ 18 O, and SP are 6.4 ± 0.3 ‰, 44.0 ± 0.4 ‰, and 17.1 ± 1.0...

This white paper describes the analytical capabilities of the Thermo Scientific™ Ultra™ High Resolution Isotope Ratio Mass Spectrometer (HR-IRMS) for the analysis of doubly substituted isotopologues (‘clumped isotopes’) of methane, including both ¹³CH₃D and ¹²CH₂D₂, and for analysis of the δ¹³C and δD signatures of methane with exceptional precisio...

The Himalayas and Tibetan Plateau, identified as the Third Pole (TP), is a unique region because of its insertion into global environmental and climatic changes. Deposition of atmospheric nitrate in this region is one of the most important sources of reactive nitrogen to glacial‐hydrologic system and ecosystems. The isotopic composition of atmosphe...

Although eutrophic urban rivers receiving loads of wastewater represent an important anthropogenic source of N2O, little is known as to how temperature and other environmental factors affect temporal variations in N2O emissions from wastewater treatment plants (WWTPs) and downstream rivers. Two-year monitoring at a WWTP and five river sites was com...

Significance Carbonyl sulfide (OCS) is a key proxy of the global photosynthesis rate, but the greatest uncertainty in the OCS cycle is its missing source. Our unique method of measuring sulfur isotope ratios ( ³⁴ S/ ³² S) of OCS was used in this study to distinguish oceanic and anthropogenic OCS sources. A north–south latitudinal gradient in the ³⁴...

Inorganic particulate nitrate (p-NO—3), gaseous nitric acid (HNO3(g)) and nitrogen oxides (NOx=NO+NO2), as main atmospheric pollutants, have detrimental effects on human health and aquatic/terrestrial ecosystems. Referred to as the ‘Third Pole’ and the ‘Water Tower of Asia’, the Tibetan Plateau (TP) has attracted wide attention on its environmental...

The isotopic composition of nitrous oxide (N2O) provides useful information for evaluating N2O sources and budgets. Due to the co‐occurrence of multiple N2O transformation pathways, it is, however, challenging to use isotopic information to quantify the contribution of distinct processes across variable spatiotemporal scales. Here, we present an ov...

Rationale Unravelling the biogeochemical cycle of the potent greenhouse gas nitrous oxide (N2O) is an underdetermined problem in environmental sciences due to the multiple involved source and sink processes, which complicates mitigation of its emissions. Measuring the doubly isotopically substituted molecules (isotopocules) of nitrous oxide can add...

We present a laser spectroscopic technique to selectively and simultaneously measure the eight most abundant isotopocules of N2O, including three doubly substituted species – so called “clumped isotopes”. For the absolute quantification of individual isotopocule abundances, we propose a new calibration scheme that combines thermal equilibration of...

A single-step method allowing the measurement of ¹³C intramolecular distribution of butane isomers (n- and i-butane) from natural gas samples was developed. The method builds up on the one that has been developed for propane, using on-line pyrolysis followed by isotope analysis of the pyrolytic fragments. The isotopic filiation between n-butane and...

Acetonitrile (CH3CN) is a volatile organic compound (VOC) and a potential tracer of biomass burning. We evaluated the capability of using observations derived from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station (ISS) to measure CH3CN profiles. The error in a CH3CN vertical profile from the L...

Plain Language Summary HO 2 radical, a key atmospheric oxidant in the mechanisms that influence the atmospheric composition of our planet, has been predicted to be generated by lightning‐induced upper atmospheric discharge, called sprites, from water vapor. However, there has been no observational evidence of sprite‐producing active radicals due to...

MicroRNAs are important genes in biological processes. Although the function of microRNAs has been elucidated, the relationship between the sequence and the disease is not sufficiently clear. It is important to clarify the relationship between the sequence and the disease because it is possible to clarify the meaning of the microRNA genetic code co...

Ocean acidification, induced by the increase in anthropogenic CO2 emissions, has a profound impact on marine organisms and biogeochemical processes1. The response of marine microbial activities to ocean acidification might play a crucial role in the future evolution of air–sea fluxes of biogenic gases such as nitrous oxide (N2O), a strong GHG and t...

In carbonate isotopic measurements, H2O2 treatment is one of the most often used methods to remove organic matter contaminants from carbonate minerals for accurate analysis, but the interaction between H2O2 solution and carbonate minerals may also lead to analytical bias. In this study, we quantitatively tested the effect of H2O2 treatment for 7 ty...

Sulfate aerosol (SO42−) preserved in Antarctic ice cores is discussed in the light of interactions between marine biological activity and climate since it is mainly sourced from biogenic emissions from the surface ocean and scatters solar radiation during traveling in the atmosphere. However, there has been a paradox between the ice core record and...

Acetonitrile (CH3CN) is one of the volatile organic compounds (VOC) and a potential tracer of biomass burning. We evaluated the capability of using observations derived from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station (ISS) to measure CH3CN profiles. The error in a CH3CN vertical profile...

The Hokuriku district of central Japan receives high levels of precipitation during winter, largely in the form of snow. This study aimed to elucidate the internal nitrogen dynamics in this temperate forested region with heavy snowfall using the triple oxygen and nitrogen isotopic compositions of NO3-. The isotopic compositions of NO3- in atmospher...

The authors became aware of a mistake in the data and axis labeling in Fig. 2 in the original version of the Article. Specifically, the authors mistakenly copied and pasted a formula for background correction instead of the actual values. As a result of this, Fig. 3 was updated to replace the incorrect label ‘sulfate flux (kg km−2)’ with the correc...

Despite widespread applications of sulfur isotope mass-independent fractionation (MIF) signals for probing terrestrial and extra-terrestrial environments, there has been no international sulfur isotope reference material available for normalization of Δ33S and Δ36S data. International reference materials to anchor isotope values are useful for inte...

One of the most plausible scenarios of the origin of life assumes the preceding prebiotic autotrophic metabolism in sulfide-rich hydrothermal vent environments. However, geochemical mechanisms to harness the reductive power provided by hydrothermal systems remain to be elucidated. Here, we show that, under a geoelectrochemical condition realizable...

Nitrous oxide (N2O) contributes to global warming and stratospheric ozone depletion. Although its major sources are regarded as bacterial or archaeal nitrification and denitrification in soil and water, the origins of ubiquitous marine N2O maximum at depths of 100–800 m and N2O dissolved in deeper seawater have not been identified. We examined N2O...

Satellite observations at nadir can potentially facilitate a better understanding of the emissions and distribution of tropospheric nitrogen dioxide, NO 2 , which is a well-known pollutant. The identification of emissions requires adequate spatiotemporal resolution measurements of the total column amounts of NO 2 . The spatial resolution of previou...

The chemical and stable isotopic composition of methane-derived authigenic carbonate (MDAC) can be used to document paleoclimate and biogeochemical information in methane cold seeps, such as temperature records determined through clumped isotope (Δ 47 ) analyses. Previous investigations of MDACs, however, have noted isotopic disequilibrium values,...

We present a numerical study conducted using a regional Lagrangian model to account for the transport, deposition and radioactive decay of ³⁵S in sulfur dioxide and sulfate aerosols emitted into the atmosphere during the Fukushima Dai-ichi Nuclear Power Plant incident. The model is a Eulerian-Lagrangian hybrid system that accounts for chemical conv...

This paper presents isotopic compositions (δ ¹⁵ N and Δ ¹⁷ O values) of atmospheric particulate nitrate (p-NO 3⁻ ) collected over the Pacific Ocean between 40°S and 68°N on two cruises using the Research Vessel Hakuho Maru. Six marine regions over the Pacific Ocean were categorized using backward trajectory analysis, and various ion concentrations...

Significance Microorganisms can oxidize hydrocarbons anaerobically, but the detection and quantification of this process in natural settings remains difficult, impeding reliable estimation of these processes at the global scale. We have used the technique of position-specific isotope analysis of propane and show that anaerobic biological degradatio...

Rationale Biochar amendments often decrease N2O gas production from soil, but the mechanisms and magnitudes are still not well characterized since N2O can be produced via several different microbial pathways. We evaluated the influence of biochar amendment on N2O emissions and N2O isotopic composition, including ¹⁵N site preference (SP) under the a...

Knowledge related to sulfur isotope ratios of carbonyl sulfide (OCS or COS), the most abundant atmospheric sulfur species, remains scarce. An earlier method developed for sulfur isotopic analysis for OCS using S+ fragmentation by an isotope ratio mass spectrometer is inapplicable for ambient air samples because of the large samples required (approx...

High quality records of stratospheric volcanic eruptions, required to model past climate variability, have been constructed by identifying synchronous (bipolar) volcanic sulfate horizons in Greenland and Antarctic ice cores. Here we present a new 2600-year chronology of stratospheric volcanic events using an independent approach that relies on isot...