Search Results (634)

The increasing adoption of alternative fuels such as hydrogen and ammonia in energy systems has created a growing need for advanced diagnostic techniques capable of monitoring combustion products with high specificity and flexibility. In this context, Raman spectroscopy represents a promising optical approach for gas analysis, as it enables the simultaneous detection of multiple species without requiring sample preparation. In this work, the performance of a cost-effective Raman-based system on quantitative detection of nitrogen oxides (NO and NO₂) and nitrous oxide (N₂O) is presented. The experimental setup is based on a multi-pass optical configuration designed to enhance the Raman signal and employs off-the-shelf components, including an uncooled CMOS detector. Calibration measurements were carried out using gas mixtures at known partial pressures, and gas concentrations were retrieved through a nonlinear least-squares fitting procedure applied to the measured spectra. The results show that the system provides linear and repeatable responses for NO and N₂O over the investigated pressure ranges, with low mean errors and limited data dispersion, while NO₂ performance could not be fully quantified in a comparable manner due to the high reactivity of the species under the tested conditions. Overall, the proposed system represents a viable and cost-effective solution for multi-species gas analysis in emerging combustion applications. This work aims to extend the industrial applicability of Raman spectroscopy to NO_x and NO₂ diagnostics. Full article

Freshwater sediments play a central role in regulating methane (CH₄), carbon dioxide (CO₂) and nitrous oxide (N₂O) dynamics, yet the biogeochemical constraints shaping their short-term responses to redox change remain poorly resolved. Here, we used controlled aerobic and anaerobic slurry incubations of natural lake sediments to identify the environmental drivers governing early-stage greenhouse gas (GHG) dynamics. CH₄ exhibited minimal variation and no significant differences between live and sterilized treatments, indicating that methane turnover during the first hours of incubation is constrained primarily by rapid geochemical adjustments rather than by detectable microbial activity. In contrast, CO₂ and N₂O displayed clear biotic signals consistent with fast-responding respiratory and nitrogen-reducing processes. Across multivariate analyses and Random Forest models, redox-sensitive solutes (Fe³⁺, Fe²⁺, NO₃⁻, SO₄²⁻), together with dissolved organic carbon and NH₄⁺, emerged as key components of the biogeochemical framework structuring early GHG responses, highlighting coupled C–N–Fe controls on short-term gas dynamics. Microbial community analyses revealed the presence of methanogenic archaea (e.g., Methanomicrobiales, Methanofastidiosales), aerobic methanotrophs (Methylomonadaceae, Methylococcaceae) and nitrogen-transforming bacteria; however, their functional expression was limited during the short incubation period. Our results demonstrate that the earliest CH₄, CO₂ and N₂O responses in lake sediments are governed predominantly by rapid geochemical processes that regulate electron-acceptor availability and substrate chemistry, while microbial community composition plays a secondary role at short timescales. Full article

Background: Nitrous oxide (N₂O) is increasingly used as a recreational drug, leading to neurological and systemic toxicities. However, due to the rapid elimination and minimal alteration of nitrogen oxides, the short direct detection window complicates the assessment of N₂O exposure. Method: In this study, we investigated the effects of chronic N₂O exposure on plasma metabolites using an untargeted metabolomics approach in a mouse model. C57BL/6 mice were exposed to 90,000 ppm N₂O (1 h, twice daily for 28 days) or room air. Plasma samples were analyzed via UHPLC -Triple TOF -MS. Orthogonal partial least squares discriminant analysis (OPLS-DA) and receiver operating characteristic (ROC) curves were used to identify differential metabolites. Result: A total of 35 differential metabolites were identified. Eight metabolites with an area under the curve (AUC) > 0.90 were selected as candidate biomarkers, including up-regulated SOPC and PC(16:0/16:0) (suggesting disrupted phospholipid remodeling and membrane integrity), and down-regulated DL-tryptophan, creatine, ectoine, indole, His-Ser, and Ile-Pro. Pathway enrichment analysis revealed significant alterations in glycine, serine and threonine metabolism; phenylalanine, tyrosine and tryptophan biosynthesis; protein digestion and absorption; and tryptophan metabolism. Conclusions: Our data indicate that chronic N₂O exposure disrupts multiple amino acid-related metabolic pathways (e.g., tryptophan-kynurenine pathway) and phospholipid homeostasis. The identified metabolite changes, along with vitamin B₁₂, homocysteine, and methylmalonic acid, may constitute a specific metabolic fingerprint for N₂O exposure. These findings help reveal the intrinsic mechanistic links underlying metabolic disorders induced by N₂O exposure. Full article

Ridge tillage (RC) has been proposed as a water-saving irrigation technique to mitigate greenhouse gas (GHG) emissions from paddy fields. To evaluate its effectiveness under cold-region climatic conditions, a two-year field experiment (2023–2024) was conducted in Northeast China. The study assessed the effects of RC on rice yield, methane (CH₄), nitrous oxide (N₂O), and total GHG emissions (expressed as CO₂e). A no-puddling treatment (NP) was additionally included in 2024. The results showed that compared to conventional cultivation (CK), RC significantly increased the number of effective panicles in 2023 (p < 0.05) but did not significantly affect yield in either year. CH₄ emissions exhibited a double-peak pattern, with peaks at the heading and grain-filling stages; the heading stage contributed the largest part (53.1–69.0%). N₂O emissions showed no distinct seasonal pattern, although N fertilization events stimulated N₂O peak. RC consistently reduced CH₄ emissions, with reductions of 50.8% in 2023 and 71.0% in 2024. NP in 2024 reduced CH₄ emissions by 27.0%. N₂O emissions showed no significant differences among treatments; however, their contribution from fertilization events varied with treatment and year. Total GHG was dominated by CH₄ (>99%). RC significantly lowered GHG and GHGI by 50.7–70.1% and 57.9–73.2% compared to CK, respectively. In conclusion, ridge tillage is an effective practice to reduce CH₄ and GHG emissions while maintaining rice yield in cold-region paddy fields. The large inter-annual variability strongly affects baseline emissions and underscores the needs for multi-year assessments. Full article

Understanding how external nitrogen sources regulate nitrogen fate in river water is critical for improving nitrogen removal and reducing greenhouse-gas risk. Here, short-term microcosm incubations were conducted using source water as the background matrix and seven representative source inputs. By integrating hydrochemical analyses, bacterial community profiling, metagenomics, RT-qPCR, and process-rate measurements, we evaluated source-dependent shifts in nitrogen-cycling pathways. Manure-related inputs generated the highest organic and nitrogen loading, suppressed nitrification, enhanced nrfA (cytochrome c nitrite reductase) abundance and transcription, and promoted DNRA, indicating a shift toward nitrogen retention via ammonium regeneration. In contrast, sewage-related inputs maintained relatively high NO₃⁻ availability, elevated nirS (cytochrome cd1 nitrite reductase) and nosZ (nitrous oxide reductase) expression, and enhanced denitrification, but also increased N₂O production. Metagenomic, transcriptional, and rate-based evidence consistently identified 12 h as a critical window for source-dependent pathway redistribution, highlighting the importance of short-term monitoring for detecting rapid nitrogen-cycle responses following pollution inputs. These findings support source-oriented nitrogen management that considers both nitrogen loading and hydrochemical controls on nitrate fate. Full article

Agricultural greenhouse gas (GHG) fluxes are often measured using chamber-based methods. However, comparisons among chamber-based methods are limited. This study compared the effects of chamber type and GHG concentration measurement method on GHG fluxes, emissions, global warming potential (GWP), and reduced two-gas GWP (GWP*) in conventionally tilled soybean (Glycine max L. [Merr]) on a silt-loam soil (Aeric Epiaqualfs) in southeast Arkansas. Carbon dioxide (CO₂) fluxes measured by optical feedback-cavity enhanced absorption spectroscopy (OF-CEAS, FT-LICOR) were greater (p < 0.01) than from the non-steady-state, non-flow-through, static, closed-chamber method analyzed by gas chromatography (NFT-GC), while methane (CH₄) and nitrous oxide (N₂O) fluxes were greater (p < 0.01) from the NFT-GC than the FT-LICOR method. Cumulative season-long CO₂ emissions were 36.2, 31.6, and 13.7 times greater (p < 0.01) from the FT-LICOR than the NFT-GC method for 0–15, 0–30, and 0–60 min gas sampling intervals, respectively. Methane N₂O emissions and GWP* did not differ (p > 0.05) between FT-LICOR and NFT-GC methods for the 0–15, 0–30, and 0–60 min intervals. Results suggest that differences in GHG flux, emissions, and GWP estimates reflect the combined influence of measurement methods rather than individual system components (i.e., chamber design, analyzer type, or closure time), which should be considered when designing and executing field studies. Full article

Greenhouse gas (GHG) emissions from biomass combustion include carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O), which cause climate change and global warming. By measuring GHG emissions by biomass combustion, a potent protocol for the calculation of global warming potential (GWP), which is how much the global temperature has risen due to combustion processes, can be achieved, contributing to determining the mean reduction in global temperature rise and fostering a transition towards more sustainable energy systems. Additionally, warning can be given of the GHG and GWP risks associated with different species of biomass. This review includes the GHG emissions and GWP of biomass combustion and their measurement and estimation directly through biomass sample combustion, using unmanned aerial vehicles (UAVs) and satellite measurements of radiation interacting with atmospheric gases, or satellite-derived data and calculations according to IPCC guidelines. In addition, the relationship of lignocellulosic compounds and elements in biomass to HHV and GHG emissions is described. The key mechanism of molecular vibration of hydrogen bonds in biomass caused by NIR radiation related to GHG emissions is revealed and recorded regarding the possibility of using NIR spectroscopy for the prediction of GHG emissions and GWP. Calculation examples for sugarcane bagasse and other biomass species are shown. The comparative advantages and limitations of NIR spectroscopy with respect to other methods are included. These factors lead to elucidation of the possibility of using NIR spectroscopy for non-destructive prediction of GHG emissions. In this review, the feasibility of using NIR spectroscopy to evaluate GHG emissions, GWP and emission factors (EFs) as an alternative to IPCC estimation methods related to climate change by biomass combustion is confirmed. NIR spectroscopy is a novel methodology for predicting GHG emissions and GWP directly from intact chip or powder biomass spectral data without explicit gas measurement. This article records the essential spectroscopic knowledge of biomass polymer valorization that is of value in polymer science. Full article

Nitrification is a key process governing nitrogen (N) loss and greenhouse gas emissions in agricultural soils, and its regulation is strongly influenced by both chemical inhibitors and soil properties. Copper (Cu), a metal cofactor that is crucial for the function of ammonia monooxygenase (AMO), plays an important role in ammonia oxidation, whereas dicyandiamide (DCD) suppresses nitrification and may interact with Cu to inhibit AMO activity. However, the extent to which Cu availability and soil organic matter (SOM) jointly regulate DCD efficiency remains poorly understood. In this study, an incubation experiment was conducted using tropical paddy soils with contrasting SOM contents to explore how varying Cu levels (10 and 200 mg Cu kg⁻¹ soil) impact DCD efficiency in regulating the nitrification process and controlling nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions. Our results showed that DCD generally suppressed nitrification, as indicated by reduced NO₃⁻ accumulation and lower NO₃⁻/NH₄⁺ ratios. However, the response to Cu was strongly SOM-dependent. Under low SOM, Cu addition was associated with a partial restoration of nitrification activity, suggesting a potential reduction in DCD efficiency, whereas under high SOM, this effect appeared to be attenuated, likely due to Cu complexation and reduced bioavailability. Increasing Cu levels further weakened DCD inhibition, particularly in low SOM soils. DCD significantly reduced N₂O emissions, but this mitigation effect declined with Cu addition, suggesting a Cu-mediated influence on nitrification–denitrification pathways. On the other hand, CO₂ emissions were reduced under DCD application and appeared to be further reduced under Cu treatments. Changes in enzyme activities and nitrifier gene abundances supported these patterns, suggesting distinct responses of AOA and AOB communities under varying SOM and Cu conditions. This study provided evidence that the interaction of Cu availability and SOM may play an important role in governing the efficacy of nitrification inhibitors. This highlights the importance of considering soil-specific chemical environments when optimizing N management strategies to reduce environmental N losses. Full article

This study is the first to investigate volcanic ash (VA) as a soil amendment to mitigate nitrous oxide (N₂O) emissions, a potent greenhouse gas mainly produced through nitrification and denitrification processes in agricultural soils. The experiment assessed the effects of VA mixed with soil and combined with mineral (NH₄NO₃, N) or organic (poultry manure, O) fertilizer on N₂O emissions, soil mineral nitrogen (NO₃⁻ and NH₄⁺), trace metals (Zn, Cu, Mn), and crop yield in a 4-month pot experiment including treatments with and without VA. Results showed that VA reduced N₂O emissions by 55% in mineral fertilizer treatments and 71% in organic fertilizer treatments compared to soils without VA. This reduction was associated with significant changes in nitrogen availability. In mineral fertilizer treatments with VA, soil NO₃⁻ concentrations remained high, potentially limiting denitrifier activity, while in organic treatments VA appeared to inhibit nitrogen mineralization. Additionally, VA increased soil concentrations of Zn, Cu, and Mn, which were negatively correlated with N₂O emissions, suggesting an influence on microbial processes. Importantly, crop yields were not affected by VA application. Although promising, these preliminary findings highlight the need for further research to optimize application rates and evaluate long-term effects across soil types and management systems. Full article

Globally, greenhouse gas (GHG) emissions have risen dramatically due to accelerated industrialization, excessive fossil fuel extraction, and agricultural activities, leading to global warming and ecosystem collapse. Achieving net-zero carbon emissions has therefore become a crucial global priority. Despite substantial international efforts, only a small number of countries have achieved carbon neutrality so far, with the majority aiming to do so by 2050 or 2060. Progress remains hindered by fragmented international coordination and inadequate integration of mitigation and adaptation co-benefits. However, agriculture is a major carbon emitter with significant mitigation potential. Attaining local carbon neutrality in agricultural landscapes is highly costly and strongly impacted by the spatial heterogeneity of GHG emissions and the diversity of available mitigation possibilities. This sector remains a major contributor to methane (CH₄) and nitrous oxide (N₂O) emissions, mainly through enteric fermentation and fertilizer use, and thus must be prioritized in global carbon neutrality strategies. Tactics such as improved livestock management, reduced use of synthetic fertilizers, conservation agriculture, afforestation, and renewable energy adoption can reduce emissions. These technical approaches should be supported by effective policy instruments, like carbon taxes, cap-and-trade schemes, low-carbon practice subsidies, and regulatory frameworks. Together, these measures can enable a transition toward long-term sustainability in agriculture by balancing emissions with removals through enhanced carbon sinks and credible offset mechanisms. Full article

N₂O (Nitrous oxide) is a potent greenhouse gas with a global warming potential nearly 300 times that of CO₂ and poses a critical environmental challenge, particularly in semiconductor and display manufacturing, where it is emitted during plasma processes. However, catalytic N₂O abatement in O₂-rich environments remains inefficient because O₂ competitively occupies active sites and hinders the turnover of surface oxygen species. To clarify how support properties govern this inhibition, Co-based catalysts supported on beta zeolite, CeO₂, and TiO₂, together with unsupported Co₃O₄, were comparatively evaluated for direct N₂O decomposition. Among them, Co/Beta exhibited the highest performance, achieving >95% N₂O conversion at 450 °C in the presence of 5% O₂ with excellent long-term stability. Co/Beta possessed a high specific surface area (649 m² g⁻¹) and a mesoporous framework that favored uniform Co dispersion and reactant accessibility, while its high Co²⁺/(Co²⁺ + Co³⁺) ratio (75.5%) and large fraction of chemisorbed oxygen species (79.9%) promoted oxygen-vacancy formation and facile oxygen exchange. These results indicate that the ability of Co/Beta to maintain high activity in the presence of oxygen stems from support-modulated cobalt surface states and enhanced oxygen turnover behavior. These findings provide a support-design principle for stable N₂O decomposition under oxygen-containing exhaust conditions. Full article

Growing concerns over food security and greenhouse gas emissions present a dual challenge, as mitigation strategies for one often intensify the other. Nitrification inhibitors (NIs) have emerged as a promising approach to simultaneously reduce nitrous oxide (N₂O) emissions and enhance crop productivity. However, their effectiveness is highly dependent on environmental conditions. To systematically evaluate the environmental controls and the economic trade-offs associated with NI application, this study presents a systematic data synthesis of 196 peer-reviewed articles, assessing the performance of three widely used NIs: dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP), and nitrapyrin. The analysis quantifies the influence of key environmental factors (e.g., temperature, soil pH, soil moisture, and soil organic carbon) on NI biodegradability, nitrogen dynamics, and N₂O emissions. The results indicate that soil organic carbon has a limited effect on NI performance, whereas temperature emerges as the dominant controlling factor. Among the NIs evaluated, DCD and DMPP demonstrate the highest mitigation efficiencies, achieving N₂O emission rates as low as 10⁻⁶ and 10⁻⁵ kg ha⁻¹ d⁻¹, respectively. An integrated economic analysis further evaluates the cost-effectiveness of NI application across major cropping systems, including corn, rice, and wheat. The findings show that DMPP and nitrapyrin applications yield the highest net economic returns in corn and rice systems (up to 860 USD and 880 USD, respectively), while wheat systems without NI application remain less profitable (approximately 330 USD). Ultimately, this study demonstrates that the practical viability of NIs depends heavily on balancing input costs with crop-specific yield gains, rather than environmental benefits alone. While NIs offer substantial greenhouse gas mitigation potential, their widespread adoption requires careful, site-specific economic evaluation to ensure that yield improvements sufficiently offset the added application costs to achieve truly sustainable agricultural practices. Full article

Hybrid rocket engines offer a compromise between safety, controllability, and performance, making them attractive for small-scale propulsion systems. However, oxidizer selection remains a critical early-stage design decision that cannot be determined solely from ideal thermodynamic metrics. This study presents a comparative analysis of three oxidizers—nitrous oxide (N₂O), gaseous oxygen (GOX), and liquid oxygen (LOX)—for a 1 kN-class hybrid rocket engine using HDPE fuel under identical operating conditions. Equilibrium combustion performance was first evaluated using NASA Chemical Equilibrium with Applications (CEA) to determine optimal oxidizer-to-fuel ratios and theoretical specific impulse. These results were subsequently refined using Rocket Propulsion Analysis (RPA) to incorporate finite combustion chamber geometry and non-ideal nozzle expansion effects. The equilibrium analysis predicts maximum specific impulses of approximately 260 s for N₂O/HDPE and nearly 300 s for oxygen-based systems. However, finite-geometry modelling indicates that practical performance is reduced by approximately 5–8%, yielding delivered specific impulses of about 275 s for GOX and 272 s for LOX. The results demonstrate that although oxygen (GOX and LOX) provides higher thermodynamic performance, the practical advantage of LOX over GOX becomes marginal at the kilonewton scale. Consequently, oxidizer selection for small hybrid engines should be treated as a system-level trade-off involving performance, infrastructure complexity, and operational safety. Full article

Nitrous oxide (N₂O) is a major agricultural greenhouse gas. Its direct emission factor (EF) is a key parameter for greenhouse gas inventories and developing mitigation strategies. However, the Intergovernmental Panel on Climate Change (IPCC) default EF may not reflect actual emissions from Chinese croplands. This study compiled extensive field observations from key agricultural regions in China. A systematic meta-analysis was conducted to evaluate annual N₂O emissions and nitrogen fertilizer-induced direct emission factors. Subgroup analyses revealed that fertilizer type, land use, soil texture, and climate zone all significantly influence EF. Univariate meta-regression indicated that EF is positively correlated with nitrogen (N) application rate and mean annual temperature but negatively correlated with soil pH, highlighting these factors as key drivers of N₂O emissions. The mean EF in Chinese croplands was about 0.68%, much lower than the 1% global default recommended by the IPCC. The combined effects of optimized agricultural management, cropping systems, and local environmental conditions help explain these lower emission factors. These findings provide a scientific basis for developing region-specific emission factors, improving cropland mitigation strategies, and enhancing the accuracy of greenhouse gas inventories. Full article

Detection of trace gases with high sensitivity and weak excitation power is highly desired for long-range remote sensing. Here, we report the detection of the greenhouse gas nitrous oxide (N₂O) with the power of excitation light down to picowatts, by converting the mid-infrared laser to near-infrared photons through an intra-cavity-enhanced sum-frequency upconversion system. The intra-cavity-enhanced pumping power of 1064.0 nm reaches about 200.0 W, resulting in the conversion of the 4514.6 nm mid-infrared laser to 861.1 nm with an efficiency up to 73.4% under optimal conditions. The upconverted light is then detected by a single-photon avalanche detector, followed by a time-correlated single-photon counting module, which can measure the arrival time of each upconverted photon. By performing discrete Fourier transformations of the arrival time of the detected photons, the frequency spectrum can be determined. By using frequency modulation, this method can suppress background noise significantly. Consequently, the excitation power can be brought down to about 100 pW with the concentration of N₂O being 10 ppm. As a demonstration of application, the presented system is also used for N₂O sensing in an open-path geometry, highlighting the potential for stand-off leak detection. Our proposal offers promising applications to monitor trace gases over long distances with weak excitation powers. Full article