Mulching and biochar are increasingly used individually in agriculture, but little is known about their combined effects on N2O distribution and dispersion in ridge and furrow profiles. We conducted ...a 2-year field experiment in northern China to determine soil N2O concentrations using the in situ gas well technique and calculate N2O fluxes from ridge and furrow profiles by the concentration gradient method. The results showed that mulch and biochar increased soil temperature and moisture and altered the mineral nitrogen status, leading to a decrease in the relative abundance of nitrification genes in the furrow area and an increase in the relative abundance of denitrification genes, with denitrification remaining as the main source of N2O production. N2O concentrations in the soil profile increased significantly after fertiliser application, and N2O concentrations in the ridge area of the mulch treatment were much higher than those in the furrow area, where vertical and horizontal diffusion occurred. Biochar addition was effective in reducing N2O concentrations but had no effect on the N2O distribution and diffusion pattern. Soil temperature and moisture, but not soil mineral nitrogen, explained the variation in soil N2O fluxes during the non-fertiliser application period. Compared to furrow-ridge planting (RF), furrow-ridge mulch planting (RFFM), furrow-ridge planting with biochar (RBRF) and furrow-ridge mulch planting with biochar (RFRB) resulted in 9.2%, 11.8% and 20.8% increases in yield per unit area and 1.9%, 26.3% and 27.4% decreases in N2O fluxes per unit of yield, respectively. The interaction between mulching and biochar significantly affected the N2O fluxes per unit of yield. Biochar costs aside, RFRB is very promising for increasing alfalfa yields and reducing N2O fluxes per unit of yield.
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•Soil N2O was higher in the furrow area than in the ridge area.•Soil temperature and moisture explained changes in N2O emissions.•Soil denitrification was the main source of N2O.•Mulching and biochar addition significantly reduced N2O flux per unit yield.
Vermicomposting is increasingly used to recycle organic wastes into highly-valued fertilizer. It is still unclear whether, and how, the feedstocks of vermicomposts affect soil N2O emissions. Thus, ...this study investigated the responses and relevant mechanisms of soil N2O emissions to the amendment of vermicomposts derived from the civil sludge and the cattle dung, using gas chromatography and microbial gene analysis. Compared to the cattle dung vermicompost, the civil sludge vermicompost increased soil N2O emission on an average of 14.5 times. This difference did not disappear when the concentrations of mineral N (NH4+ and NO3−) and metals (Zn and Fe) was adjusted to the same levels. This result indicated that the variations in mineral N and metal concentrations did not account for the difference in soil N2O emission between these two vermicomposts. The relative abundance of nirK-type denitrifying bacteria and the nirK gene expression were significantly higher in soil amended with the civil sludge vermicompost than those with the cattle dung vermicompost, suggesting that the promotion of nirK gene expression and the inhibition of N2O reduction potentially explained the higher N2O emissions under the civil sludge vermicompost amendment compared to the cattle dung vermicompost amendment. Controlling the nirK-type denitrifying bacteria and nirK gene expression at low levels and promoting N2O reduction will reduce soil N2O emission from vermicomposts.
The fertosphere, as the interfaces between fertilizer granular and soil particles, represents a key hotspot for nitrogen transformation processes, particularly for ammonia (NH3) and nitrous oxide ...(N2O) emissions. Understanding the heterogeneity of the fertosphere, especially when incorporating organic amendments like biochars, is crucial for predicting NH3 and N2O emissions after soil fertilization. In this study, we investigated the effects of three types of biochar (pristine, aged, and acid-washed biochar) on heterogeneity of fertosphere induced by localized urea application. pH-specific planar optodes were employed to visualize pH gradients in fertosphere hotspots with high spatial and temporal resolution. In addition, we conducted thorough measurements of the gradient distribution of electric conductivity (EC), mineral N, aqueous NH3 in soil and enzyme activities relevant to nitrification. Concurrently, NH3 and N2O emissions from the soil were continuously monitored at a high temporal resolution. Initially, urea-induced fertosphere exhibited significant NH3 emissions, primarily attributed to the pH elevation resulting from urea hydrolysis. However, after 6 days, NH3 emissions subsided, and there was a notable sharp increase in N2O emissions. Importantly, compared to urea application alone, the inclusion of pristine biochar led to a delay in soil pH decline with a 19% rise in NH3 emission. Aged biochar, characterized by a higher content of oxygen functional groups, demonstrated increased NH4+/NH3 adsorption capacity and enhanced ammonia monooxygenase (AMO) activity in soil, resulting in an 18% reduction in NH3 emission. While a slight decrease of 5% in NH3 cumulative emission was observed in the acid-washed biochar treatment. Notably, biochar could potentially promote nitrification-derived N2O emissions due to the accumulation of NH3 oxidation products (NH2OH). These findings could contribute to refining N transformation models for fertilized soils, and optimizing N fertilizer application strategies.
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•Localized urea application induced pH gradients along fertosphere up to 25 mm.•TAN and NO3−-N had opposite gradients across the fertosphere.•Biochar could attenuate the heterogeneity of fertosphere, but promote NH3 emissions.•Increased AMO and decreased HAO nitrification enzyme activities raised N2O emission.
Soil carbon dioxide (CO2) and nitrous oxide (N2O) emissions are two main greenhouse gases that play important roles in global warming. Studies have shown that microplastics, biochar, and earthworms ...can significantly affect soil greenhouse gas emissions. However, few studies have explored how their interactions affect soil CO2 and N2O emissions. A mesocosm experiment was conducted to investigate their interactive effects on soil greenhouse gases and soil microbial functional genes in vegetable-growing soil under different incubation times. Biochar alone or combined with microplastics significantly decreased soil CO2 emissions but had no effect on soil N2O emissions. Microplastics and biochar inhibited CO2 emissions and promoted N2O emissions in the soil with earthworms. The addition of microplastics, biochar, and earthworms had significant effects on soil chemical properties, including dissolved organic carbon, ammonia nitrogen, nitrate nitrogen, total nitrogen, and pH. Microplastics and earthworms selectively influenced microbial abundances and led to a fungi-prevalent soil microbial community, while biochar led to a bacteria-prevalent microbial community. The interactions of microplastics, biochar, and earthworms could alleviate the reduction of the bacteria-to-fungi ratio and the abundance of microbial functional genes caused by microplastics and earthworms alone. Microplastics significantly inhibited microorganisms as well as C and N cycling functional genes in earthworm guts, while biochar obviously stimulated them. The influence of the addition of exogenous material on soil greenhouse gas emissions, soil chemical properties, and functional microbes differed markedly with soil incubation time. Our results indicated that biochar is a promising amendment for soil with microplastics or earthworms to simultaneously mitigate CO2 emissions and regulate soil microbial community composition and function. These findings contribute to a better understanding of the interaction effects of microplastics, biochar, and earthworms on soil carbon and nitrogen cycles, which could be used to help conduct sustainable environmental management of soil.
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•Microplastics, biochar and earthworms influenced soil CO2 and N2O emissions.•Microplastics, earthworms and biochar altered soil microbial community.•Interactions of microplastics, biochar and earthworms regulated microbial function.•Microplastics and biochar affected microbial functional genes in earthworm guts.
The N2O + O reaction plays a critical role in NOx formation at high pressures and low peak temperatures, in the “dark zone” region of deflagration waves of organic energetic materials, and in N2O ...consumption in NH3 combustion. While the rate constant for N2O + O = NO + NO (R3) is considered reasonably well established, viewpoints regarding the rate constants for N2O + O = N2 + O2 (R2)—and even the main products of the N2O + O reaction—have not reached a consensus, with studies from the past few years continuing to reach drastically different conclusions. To date, no single model has been presented that can reproduce all key datasets on both sides of the debate. Using the MultiScale Informatics (MSI) approach, we identified a model consistent with a vast catalog of theoretical and experimental data previously used to determine rate constants for R2, R3, and other key reactions influencing experimental interpretations. Notably, this MSI model (presented herein) reproduces all experimental datasets previously used to anchor low-activation-energy k2 expressions that greatly favor R2 at intermediate temperatures. However, its kinetic parameters are also consistent with theoretical calculations that instead show high activation energy for R2 and k2 values many orders of magnitude lower—such that R3 is the main channel at essentially all temperatures. This model is also consistent with our new experimental data (presented in our companion paper) at optimally selected conditions that avoid the interpretation ambiguities that have hindered definitive conclusions from previous experimental data. The present analysis elucidates the role of secondary reactions that would have artificially inflated the apparent k2/k3 ratio previously deduced from experiments in a manner that may not have been detectable from even multi-species measurements at typical conditions—and may, therefore, explain the persistent historical difficulties in establishing the main products of N2O + O.
Novelty and significance statement
Despite decades of research, viewpoints regarding the rate constants for N2O + O = N2 + O2 (R2)—and even the main products of the N2O + O reaction—have not reached a consensus, with studies from the past few years still reaching drastically different conclusions. To date, no single model has been presented that can reproduce all key datasets on both sides of the debate. Here, we present a single model consistent with a vast catalog of theoretical and experimental data, including all experimental datasets previously used to anchor low-activation-energy expressions for k2 that greatly favor R2 as the main channel at intermediate temperatures—but with kinetic parameters consistent with theoretical calculations that instead show high activation energy for R2 and N2O + O = NO + NO (R3) as the main channel at essentially all temperatures.
Automated platforms could enable the unprecedented pace required for modeling the countless proposed alternative fuels relevant to future technologies, but existing platforms rely exclusively on ...automatically generated computational data and lack experimental validation. Here, we introduce an experimental platform for rapid kinetic model refinement that combines optimal experimental design, computer-controlled experiments, and optimization—each of which are tailored in novel ways to form a cohesive platform together. The optimal experimental design considers (1) realistic uncertainties in both experimental conditions and measurements and (2) diverse reactant mixtures that can include “chemical sensitizers,” which are not necessarily reactants in a specified Quantity of Interest (QoI) but sensitize kinetic information relevant to a QoI. Similarly, our High-Throughput Jet-Stirred Reactor (HT-JSR) features (1) rapid multi-species diagnostics that can measure dozens of species within minutes, (2) a flow delivery system that can prepare up to ∼10-component reactant mixtures, and (3) computer-controlled operation of all components. Finally, a post-processing code automatically retrieves data from the instruments, quantifies uncertainties in both experimental conditions and measurements, and produces self-contained files usable for optimization in our MultiScale Informatics software. This platform is demonstrated for the rate constant for N2O + O ⇌ N2 + O2 as the QoI where, unlike for N2O + O ⇌ NO + NO, proposed values at ∼1000 K span ∼5 orders of magnitude yet give equally good agreement with previous experimental data—suggesting that previous experiments fail to constrain the branching ratio of N2O + O. The results show that optimal conditions with more species as both reactants and analytes—particularly NO2 as both a reactant and analyte—enable unambiguous discrimination of the main products of N2O + O. Specifically, the data preclude N2 + O2 as the main products at ∼1000 K—contrary to most recently proposed values.
Novelty and significance statement
We introduce a novel experimental platform for rapid kinetic model refinement that combines optimal design, computer-controlled experiments, and optimization—each uniquely tailored to form a cohesive platform. It notably employs high levels of automation, high-throughput multi-species diagnostics, and uniquely diverse reactant mixtures to accelerate scientific discovery. This platform is shown to achieve a goal that no previous experiment has: decipher the main products of N2O + O. This success—attributable to the platform’s unique design principles—demonstrates the effectiveness of this experimental platform as a tool for accelerating scientific discovery and kinetic model development.
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•Zeolite morphology greatly influences distribution of Fe species.•Monomer and dimers dominate in Fe/SSZ-13, but larger oligomers populate in Fe/Beta.•Strong correlation between Fe-O ...binding and N2O decomposition.•Fe/SSZ-13 displays one of the highest N2O decomposition activities among Fe/zeolites.•N2O + NH3 reaction is catalyzed by oligomeric Fe sites.
Fe/zeolites are important N2O abatement catalysts, efficient in direct N2O decomposition and (selective) catalytic N2O reduction. In this study, Fe/Beta and Fe/SSZ-13 materials were synthesized via solution ion-exchange and used to catalyze these two reactions. The nature of the Fe species was probed with UV–vis, Mössbauer and EPR spectroscopies and H2-TPR. These characterizations collectively indicate that primarily isolated and dinuclear Fe sites are present in Fe/SSZ-13, whereas Fe/Beta contains higher concentrations of oligomeric FexOy species. H2-TPR results suggest that Fe-O interactions are weaker in Fe/SSZ-13, as evidenced by the lower reduction temperatures by H2 and higher extents of autoreduction during high-temperature pretreatments in inert gas. Kinetic measurements show that Fe/SSZ-13 has higher normalized reaction rates in catalytic N2O decomposition, thus demonstrating a positive correlation between reaction rate and Fe-O binding, consistent with O2 desorption being rate-limiting for this reaction. However, Fe/Beta was found to display higher reaction rates in catalyzing N2O reduction by NH3. This latter result indicates that larger active ensembles (i.e., oligomers) are responsible for this reaction, consistent with the fact that both N2O and NH3 need to be activated in this case.
Although anaerobic ammonia oxidation (anammox) is a cost-effective nitrogen removal process, nitrous oxide (N2O) production will greatly reduce the advantages of this process. It is important to ...identify the N2O emission pathways and then reduce the N2O production in anammox system. To date, very limited research has been done to investigate the N2O production and N2O emission pathways in anammox biofilter. In this study, N2O production were investigated under different filtration rates in anammox biofilter for treating wastewater with low nitrogen concentrations, and N2O emission pathways were analyzed with batch tests using N2O microsensor and stable isotope mass spectrometry. The results showed N2O production increased with the increase of filtration rates in anammox biofilter, where the N2O emission factor increased from 0.012 % at 1.0 m/h to 0.496 % at 3.0 m/h. And the optimal operation condition was at filtration rate of 1.5 m/h, where NH4+-N and NO2−-N removal efficiencies reached 99 % and N2O concentration was the lowest. qPCR showed that anammox bacteria, nitrifying bacteria and denitrifying bacteria were all present in anammox biofilter, with anammox bacteria in the highest abundance. And nitrifying bacteria and denitrifying bacteria provided the possibility of N2O production. The batch tests and stable isotope mass spectrometry analysis indicated that nitrifier denitrification, hydroxylamine oxidation and endogenous heterotrophic denitrification were N2O production pathways in aerobic zone and anoxic zone of anammox biofilter, respectively. In addition, batch tests under different conditions showed no oxygen environment could reduce N2O production. Therefore, the production of N2O in anammox system is a problem that cannot be ignored and should be paid more attention to.
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•N2O concentration increased with the increase of filtration rates in AN-biofilter.•Optimal filtration rate was 1.5 m/h for better nitrogen removal and lower N2O production.•Anammox bacteria predominated, but nitrifier and denitrifier caused N2O production.•AOB denitrification, NH2OH oxidation, heterotrophic denitrification caused N2O production.•Anaerobic environment could reduce the production of N2O in AN-biofilter.
•Soil and biochar pH was an important factor that controls N2O and CO2 fluxes.•Biochar’s N2O mitigation potential in acidic soils dependent on soil NO3− content.•Effect of different biochar addition ...on enzymes activities varied at different soils.
Emissions of greenhouse gases (GHGs), such as carbon dioxide (CO2) and nitrous oxide (N2O) have great impact on global warming and atmospheric chemistry. Biochar addition is a potential option for reducing GHGs emissions through carbon (C) sequestration and N2O mitigation. However, the influences of biochar on C and nitrogen (N) transformations in soil are still unclear, resulting in a poor understanding of the mechanisms of N2O mitigation effects of biochar. Here we carried out two soil incubation experiments to investigate the influence of two common biochars addition (corn cob and olive pulp) with ammonium sulfate on CO2 and N2O emissions from two contrasting soil types (acidic sandy and alkaline clay soil). Furthermore, four extracellular enzymes activities that related to C and N cycling, i.e. cellobiohydrolase, chitinase, xylanase and β-glucosidase, were analyzed to gain insights into the underlying mechanisms of biochar’s effects on CO2 and N2O evolutions. Contrasting effects of two biochars on CO2 and N2O emissions were observed in the two different soils. The corn biochar addition had no significant effect on CO2 and N2O emissions in the alkaline clay soil, but significantly decreased CO2 emissions by 11.8% and N2O emissions by 26.9% in the acidic sandy soil compared to N-fertilizer only treatment. In contrast, olive biochar addition showed no significant effect on CO2 emissions but decreased N2O emissions by 34.3% in the alkaline clay soil, while in the acidic sandy soil addition of olive biochar triggered about a twofold higher maximum CO2 emission rate and decreased N2O emissions by 68.4%. Up to 50–130% higher specific CO2 emissions (per unit of C-related enzyme activity: cellobiohydrolase, chitinases and β-glucosidase) were observed after addition of olive biochar compared to corn biochar addition in the acidic sandy soil. We concluded that biochar’s effects on N2O and CO2 emissions are more pronounced in acidic soils. Alkaline biochar’s N2O mitigation potential in acidic soils seems to be dependent on soil NO3− content as drastically higher N2O emissions were measured in early phase of the experiment (where soil NO3− was high) and significantly lower N2O fluxes were obtained in later phases (with lower soil NO3− content).
The main objective of this research is to investigate the relationship between the green finance, Fintech, ecological footprints of Mineral rich developing economies namely Peru, Indonesia, ...Kazakhstan, Argentina, Philippines, Ghana, India, Mexico, Zambia, Turkey, Chile, Saudi Arabia, South Africa, Brazil, Russia, China. The This study investigates the role of Fintech and green finance in influencing the environmental landscape of mineral-rich developing nations. This study analyses data from Mineral rich developing economies states spanning the period from 2003 to 2022. The main areas of investigation are digital governance, Fintech, environmental degradation, and green finance. Three distinct regression models were employed to investigate the impact of FinTech, and green finance on, CO2 emissions, NO2 emissions, and ecological footprints. The ecological footprint was introduced as a means of evaluating the state of the environment, taking into account both ecological and biological factors. Promoting green and financial technologies is critical for disentangling environmental degradation and economic success. Finally, the report suggests an inclusive policy framework for mineral-rich developing nations that protects the environment while promoting economic development. The findings of the study imply that the mineral rich developing economies can incorporate the study's significant findings into their policies. The text emphasises the importance of improving Fintech, prioritising green finance, and pursuing prudent economic growth as means of fostering sustainable and environmentally conscious development.
•Relationship between green finance and Fintech in Mineral rich developing economies.•The role of Fintech and green finance in influencing the environmental landscape.•Three distinct regression models to investigate the relationship.•Protection of mineral resources is dependent on inclusive policy framework.
