Amount Of NO Research Articles

Experimental Study on SO2-to-SO3 Conversion Over Fe-Modified Mn/ZSM-5 Catalysts During the Catalytic Reduction of NOx

Mn–Fe/ZSM-5 catalysts with different Fe loading amounts were prepared using wet impregnation and the effects of these catalysts on SO3 formation during the catalytic reduction of NOx were assessed. Variations in the catalysts’ physicochemical properties with different Fe contents were also investigated using BET, XRD, SEM–EDS, FT-IR, H2-TPR and XPS techniques. The 9Mn9Fe catalyst gave the highest SO2-to-SO3 and NOx conversions, and adding Fe also improved the catalyst’s SO2 resistance. The presence of NO2 caused the formation of nitrate ions on the catalyst surface during fast SCR. These nitrate ions re-oxidized the active sites more rapidly than O2 at low temperatures, thereby promoting the redox reaction. BET, XRD and SEM–EDS showed that optimal Fe loading amount reduced MnOx crystallinity while improving surface dispersion. Adding excessive Fe caused the active compositions to accumulate on the catalyst surface. FT-IR, H2-TPR and XPS demonstrated that optimal Fe loading amount increased the quantity of Mn4+=O bonds while raising the concentrations of Mn4+ ions and lattice oxygen, thus enhancing SO2-to-SO3-conversion. Therefore, although suitable amounts of Fe and NO2 promoted NOx conversion, these species also significantly increased SO2-to-SO3 conversion.

Improved NOx Storage/Release Properties of Ceria-Based Lean NOx Trap Compositions with MnOx Modification

Ceria/spinel-based lean NOx trap compositions with and without barium were modified with MnOx via incipient wetness impregnation. The effect of the MnOx layer on the aged materials (850 °C) as to the NOx storage and release properties was investigated via NOx adsorption (500 ppm NO/5% O2/balance N2) carried out at 300 °C in a dual-bed with a 1% Pt/Al2O3 catalyst placed upstream of the samples to generate sufficient amounts of NO2 required for efficient NOx storage. Subsequent temperature programmed desorption (TPD) experiments were carried out under N2 from 300 °C to 700 °C. The addition of MnOx to the barium free composition led to a slightly reduced NOx storage capacity but all of the ad-NOx species were released from this material at significantly lower temperatures (ΔT ≈ 100 °C). The formation of a MnOx layer between ceria/spinel and barium had a remarkable effect on ageing stability as the formation of BaAl2O4 was suppressed in favour of BaMnO3. The presence of this phase resulted in an increased NOx storage capacity and lower desorption temperatures. Furthermore, NOx adsorption experiments carried out in absence of the Pt-catalyst also revealed an unexpected high NOx storage ability at low NO2/NO ratios, which could make this composition suitable for various lean NOx trap catalysts (LNT) related applications.

Combined use of calcium nitrate addition and anion exchange resin capping to control sedimentary phosphorus release and its nitrate‑nitrogen releasing risk

Calcium nitrate (Ca(NO3)2) addition can be used to control the release of phosphorus from sediments, however it can also cause an increase in the concentration of nitrate‑nitrogen (NO3−-N) in the water column. The risk of NO3−-N release from the Ca(NO3)2-injected sediments may be reduced by the placement of the anion exchange resin (AER) capping layer. In this study, the effectiveness of the combined use of Ca(NO3)2 addition and AER capping to prevent the liberation of phosphorus from sediments was investigated, and the reduction of the risk of NO3−-N released from the Ca(NO3)2-injected sediment by the AER capping was also evaluated. The combined application of Ca(NO3)2 addition and AER capping could tremendously reduce the amount of soluble reactive phosphorus (SR-P) in the overlying water, with SR-P reduction rates of 75.9–98.7%. Furthermore, it could cut down the contents of high-resolution diffusive gradients in thin films (DGT)-labile phosphorus in the sediments, resulting in the formation of phosphorus static layer in the upper sediments. The combined treatment using Ca(NO3)2 and AER had a relatively small effect on the contents of mobile phosphorus in the sediments, but it could greatly increase the amount of residual phosphorus in the top 30mm sediments (increased by 27.7–42.9%). The amount of NO3−-N in the overlying water under the action of the combined treatment method using Ca(NO3)2 and AER was much lower than that under the action of the single Ca(NO3)2 treatment during the early stage of sediment remediation. In conclusion, the combined use of Ca(NO3)2 addition and AER capping is a more promising strategy for the control of sedimentary phosphorus release than the single use of Ca(NO3)2 addition from the point of view of both the control efficiency of P release from sediments and the releasing risk of the added nitrate.

Impact of Municipal Solid Waste Landfill leachate on groundwater quality in Varanasi, India.

This study assesses the impact of municipal solid waste (MSW) landfill leachate on its surrounding groundwater quality of village Ramna, Varanasi, India. Leachate pollution index (LPI) of landfill leachate was evaluated with their physicochemical analysis that represents the overall leachate pollution potential and hazardous nature of MSW leachate. Physicochemical analysis of groundwater quality around the landfill site does not favour to drinking and domestic purposes as per the WHO and BIS standard. A considerable amount of NO3−, PO43−, Fe, electrical conductivity (EC) and total dissolved solid (TDS) were found in the groundwater samples near to the landfill site especially during post-monsoon, indicating that groundwater quality is being significantly affected by leachate percolation. Factor analysis signifies positive loading of most of the toxic pollutant that presenting MSW leachate impact on groundwater quality. WQI results also revealed that most of the groundwater samples were deteriorated from good and excellent water quality in pre-monsoon to fair water quality in post monsoon near the landfill site. Groundwater flow modeling simulation also showing that increase in the hydraulic head during the post-monsoon responsible for the downward flow of leachate pollutants from the landfill site. This Study suggests an urgent need for the sanitary landfill to control and minimize the impact of MSW leachate on groundwater quality around the Raman MSW landfill site.

Near-surface and path-averaged mixing ratios of NO<sub>2</sub> derived from car DOAS zenith-sky and tower DOAS off-axis measurements in Vienna: a case study

Abstract. Nitrogen dioxide (NO2), produced as a result of fossil fuel combustion, biomass burning, lightning, and soil emissions, is a key urban and rural tropospheric pollutant. In this case study, ground-based remote sensing has been coupled with the in situ network in Vienna, Austria, to investigate NO2 distributions in the planetary boundary layer. Near-surface and path-averaged NO2 mixing ratios within the metropolitan area of Vienna are estimated from car DOAS (differential optical absorption spectroscopy) zenith-sky and tower DOAS horizon observations. The latter configuration is innovative in the sense that it obtains horizontal measurements at more than a hundred different azimuthal angles – within a 360∘ rotation taking less than half an hour. Spectral measurements were made with a DOAS instrument on nine days in April, September, October, and November 2015 in the zenith-sky mode and on five days in April and May 2016 in the off-axis mode. The analysis of tropospheric NO2 columns from the car measurements and O4 normalized NO2 path averages from the tower observations provide interesting insights into the spatial and temporal NO2 distribution over Vienna. Integrated column amounts of NO2 from both DOAS-type measurements are converted into mixing ratios by different methods. The estimation of near-surface NO2 mixing ratios from car DOAS tropospheric NO2 vertical columns is based on a linear regression analysis including mixing height and other meteorological parameters that affect the dilution and reactivity in the planetary boundary layer – a new approach for such conversion. Path-averaged NO2 mixing ratios are calculated from tower DOAS NO2 slant column densities by taking into account topography and geometry. Overall, lap averages of near-surface NO2 mixing ratios obtained from car DOAS zenith-sky measurements, around a circuit in Vienna, are in the range of 3.8 to 26.1 ppb and in good agreement with values obtained from in situ NO2 measurements for days with wind from the southeast. Path-averaged NO2 mixing ratios at 160 m above the ground as derived from the tower DOAS measurements are between 2.5 and 9 ppb on two selected days with different wind conditions and pollution levels and show similar spatial distribution as seen in the car DOAS zenith-sky observations. We conclude that the application of the two methods to obtain near-surface and path-averaged NO2 mixing ratios is promising for this case study.

Concept of small satellite UV/visible imaging spectrometer optimized for tropospheric NO2 measurements in air quality monitoring

Satellite observations at nadir can potentially facilitate a better understanding of the emissions and distribution of tropospheric nitrogen dioxide, NO2, which is a well-known pollutant. The identification of emissions requires adequate spatiotemporal resolution measurements of the total column amounts of NO2. The spatial resolution of previous and current observations is insufficient for the identification of NO2 hot-spots. Switching to a spatial resolution of ∼ 1 km × ∼ 1 km can improve the identification of local sources of NO2 and their emissions. To investigate the feasibility of observations with such a high spatial resolution, we simulated radiance spectra for different cases under varying parameters, such as area, season, satellite altitude, and surface reflectance by using the radiative transfer model SCIATRAN. We subsequently retrieved NO2 slant column densities (SCDs) using the differential optical absorption spectroscopy (DOAS) technique with several fit windows. For test cases associated with polluted conditions, we found that the conceptual nadir-observing instrument on a satellite at an altitude of ∼ 300 km involved the lowest retrieval errors for signal-to-noise ratios of around 1000 with accuracy better than the required 5% for tropospheric NO2 SCD and that the fit window of 425–497 nm met the scientific requirements for both surface reflectance cases.

Study on the contribution of different depth layers to N2O emission in subsurface wastewater infiltration system

Subsurface wastewater infiltration system (SWIS) is an eco-friendly technology treating domestic sewage. On the other hand, SWIS has been found to be a source of nitrous oxide (N2O) emission. Unfortunately, the contribution of different depth layers to N2O emission is still unclear. Therefore, this study sampled N2O samples in different layers using a stratified gas sampler. Three parallel SWISs were operated under low, medium and high hydraulic loads, respectively. The results showed that N2O emission and conversion rate of SWIS were 12.5–27.5 g/m2·y and 0.11–0.35%, respectively. Within the tested loads of 5, 10 and 15 cm/d, the amount of N2O produced decreased as the load increased. SWIS amended with 10% activated sludge degraded nitrogen effectively with effluent quality meeting the first class A standard of the “Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant” (GB/T18918-2002). Under varying influent load strengths, anaerobic zone was the main source for N2O emission. When the hydraulic load increased from 5 cm/d to 15 cm/d, the contributions of anaerobic zone increased from 43.56% to 65.09% for wetting period and from 38.01% to 78.8% for drying period, respectively.

Emissions of N2O and CO2 Following Short-Term Water and N Fertilization Events in Wheat-Based Cropping Systems

Greenhouse gas (GHG) emissions result from short-term perturbations of agricultural systems such as precipitation and fertilization events. We hypothesized those agricultural systems with contrasting management histories may respond differently to application events of water and N fertilizer with respect to GHG emissions. Studies with long-term management histories consisting of no-tillage (NT) and conventional tillage (CT) were coupled with high temporal resolution, automated chambers that monitored N2O and CO2 emissions for 22 hours following treatments. Treatments applied to NT and CT were a) control (no water or N additions), b) simulated precipitation to achieve approximately 80% water-filled pore space, and c) precipitation plus fertilizer additions of 150 kg N ha-1as ammonium nitrate. Emissions of CO2 increased with increase in moisture and temperature and decreased under fertilizer application. Water and nitrogen treatments in CT at the sites with 2 and 12-year history produced N2O fluxes greater than NT by 142% and 68%, respectively. The site with 10-year history of NT produced similar amounts of N2O from CT and NT treatments. The same treatments at the site with 31 yearlong no-till history, despite being one of the lowest among all sites, demonstrated 380% higher N2O fluxes from the NT than CT, which was likely due to higher levels of labile organic matter present in NT treatments. GHG emissions data regressed on measured soil C and N properties, fractionation, and mineralization data showed that N2O flux increased with reduction of acid-hydrolyzable N and increase of NH4-N in soil, which suggested that N2O production in the short-term water and water and N additions events is mostly produced via nitrification process. This indicates that neither the length of no-till treatment nor the fertilizer application rate define the rate of N2O emissions, but the soil N availability controlled by organic matter mineralization rate. The current study shows that the early stages of no-till adoption can result in reduction of N2O spikes during short-term precipitation events similar to some long-term no-till sites.

Introducing an amine functionalized novel conjugate material for toxic nitrite detection and adsorption from wastewater

In the present study, 4-nitro-1-naphthylamine ligand functionalized porous conjugate material was prepared for efficient nitrite (NO2−) monitoring and removal from water samples. The proposed material was formed optical color upon addition of trace amount of NO2− at experimental conditions. Several experimental parameters such as material morphology, solution acidity, contact time, foreign ions, desorption, highest adsorption capacity was measured. The data were clarified that the materials could detect the ultra-trace level of NO2− according to the limit of detection was 0.45 μg/L. The solution acidity was exhibited the key role, and the suitable pH 3.50 were selected based on the signal intensity and adsorption efficiency. The foreign ions were not adversely affected in the NO2− monitoring and adsorption operation. In addition, the signal intensity was observed only for the NO2−, and these were clarified the high selectivity towards the NO2− at this experimental protocol. Moreover, the adsorption data were highly adjacent with the Langmuir adsorption model with monolayer coverage. The determined maximum adsorption was 124.36 mg/g, which was comparable to the other forms of materials. The material was exhibited the high reusability based on the desorption performances. The desorption was carried out using 0.10 M NaOH and then the material was ready to use after rinsing with water without loss in its functionality. Therefore, the data are promising to use the materials in the real wastewater. Moreover, the proposed materials will attract the scientific community as suitable nanomaterial for NO2− monitoring and removal from contaminated water as well as the production of value-added adsorbent for water treatments.

Equilibrium and kinetics of nitrous oxide, oxygen and nitrogen adsorption on activated carbon and carbon molecular sieve

To evaluate candidate adsorbents for the recovery of nitrous oxide (N2O) from adipic acid off-gases, the equilibrium and kinetics of N2O and O2 adsorption on activated carbon (AC) and of N2O, O2, and N2 adsorption on a carbon molecular sieve (CMS) were evaluated at 293, 308, and 323 K under pressures up to 1000 kPa using a high-pressure volumetric system. Adsorption amount of N2O on AC and CMS exceeded those of N2 and O2, and the adsorption isotherms for O2 and N2 were similar. The experimental N2O and O2 uptakes on AC and CMS were fitted to a non-isothermal adsorption model, whereas the model was ineffective for predicting N2 uptake on CMS. The isothermal dual-resistance model, considering surface barrier resistance and pore diffusion, adequately predicted N2 uptake on CMS. The rate of adsorption of N2O on AC was much lower than that of O2 and N2 whereas the rate of adsorption on CMS flowed the order: O2 > N2O ≫ N2, even though N2O has higher adsorption affinity and smaller kinetic diameter than O2. The Lewis structure of N2O was also found to influence the adsorption kinetics.

Characterization of Emission Factors Concerning Gasoline, LPG, and Diesel Vehicles via Transient Chassis-Dynamometer Tests

Gaseous emissions from vehicles contribute substantially to air pollution and climate change. Vehicular emissions also contain secondary pollutants produced via chemical reactions that occur between the emitted gases and atmospheric air. This study aims at understanding patterns concerning emission of regulated, greenhouse, and precursor gases, which demonstrate potential for secondary aerosol (SA) formation, from vehicles incorporating different engine technologies—multi-point injection (MPI) and gasoline direct injection (GDI)—and using different fuels—gasoline, liquefied petroleum gas (LPG), and diesel. Drive cycles from the National Institute of Environmental Research (NIER) were used in this study. Results obtained from drive cycle tests demonstrate a decline in aggregate gas emissions corresponding to an increase in average vehicle speed. CO2 accounts for more than 99% of aggregate gaseous emissions. In terms of concentration, CO and NH3 form predominantly non-CO2 emissions from gasoline and LPG vehicles, whereas nitrogen oxides (NOx) and non-methane hydrocarbons (NMHC) dominate diesel-vehicle emissions. A higher percentage of SO2 is emitted from diesel vehicles compared to their gasoline- and LPG-powered counterparts. EURO-5- and EURO-6-compliant vehicles equipped with diesel particulate filters (DPFs) tend to emit higher amounts of NO2 compared to EURO-3-compliant vehicles, which are not equipped with DPFs. Vehicles incorporating GDI tend to emit less CO2 compared to those incorporating MPI, albeit at the expense of increased CO emissions. The authors believe that results reported in this paper concerning regulated and unregulated pollutant-emission monitoring can contribute towards an accurate evaluation of both primary and secondary air-pollution scenarios in Korea.

Investigation of adsorption characteristics of four toxic gases (nitric oxide, nitrogen dioxide, sulfur dioxide, and hydrogen chloride) on the inner surface of nickel-coated manganese steel cylinders and aluminum cylinders

ABSTRACT To develop standard toxic gas mixtures, it is essential to identify adsorption characteristics of each toxic gas on the inner surface of a gas cylinder. Thus, this study quantified adsorbed amounts of the four toxic gases (nitric oxide [NO], nitrogen dioxide [NO2], sulfur dioxide [SO2], and hydrogen chloride [HCl]) on the inner surface of aluminum cylinders and nickel-coated manganese steel cylinders. After eluting adsorbed gases on the inside of cylinders with ultrapure water, a quantitative analysis was performed on an ion chromatograph. To evaluate the reaction characteristics of the toxic gases with cylinder materials, quantitative analyses of nickel (Ni), iron (Fe), and aluminum (Al) were also performed by inductively coupled plasma optical emission spectrometry (ICP-OES). It was found that the amounts of NO, NO2, and SO2 adsorbed on the inner surface of aluminum cylinders were less than 1.0% at the level of 100 μmol/mol mixing ratio, whereas the signal for most heavy metal elements were below their respective detection limits. This study found that the amounts of HCl adsorbed on the inner surface of nickel-coated manganese steel cylinders were less than 5% at the level of 100 μmol/mol mixing ratio, whereas Ni (86 μmol) and Fe (28 μmol) were detected in the same cylinders. It was revealed that the adsorption mainly took place via the reaction of HCl with inner surface material of nickel-coated manganese steel cylinders. On the other hand, in the case of aluminum cylinders, the amounts of the adsorption were determined to be less than 1% at the level of HCl 100 μmol/mol mixing ratio, whereas most of Ni, Fe, and Al were detected at levels similar to their limits of detection. As a result, this study found that aluminum cylinders are more suitable for preparing HCl gas mixtures than nickel-coated manganese steel cylinders. Implications: To develop a standard toxic gas mixture, it is essential to understand the adsorption characteristics of each toxic gas inside a gas cylinder. It was found that the amounts of NO, NO2, and SO2 adsorbed inside aluminum cylinders were less than 1.0% at the level of 100 μmol/mol mixing ratio. The amounts of HCl adsorbed inside nickel-coated manganese steel cylinders were less than 5% at the level of 100 μmol/mol mixing ratio, whereas those inside aluminum cylinders were less than 1%, indicating that aluminum cylinders are more suitable for preparing HCl gas mixtures.

Analysis of carbon sink effects for saline constructed wetlands vegetated with mangroves to treat mariculture wastewater and sewage

In this study, two saline mangrove artificial wetlands, Datang Saline Constructed Wetland (DSCW) created for treating mariculture wastewater and sewage, vegetated with Avicennia marina, and Mangrove Wetland Park (MWP) created for mangrove conservation, vegetated with Rhizophora stylosa, were selected for assessment of carbon sequestration and carbon budget based on measuring greenhouse gas (GHG) emissions and net primary productivities. The average GHG flux and net carbon sequestration flux as carbon dioxide equivalent (CO2 eq.) were measured. The results showed that the GHG flux emitted from DSCW and MWP were 2,128 and 2,148 g CO2 eq./m2-yr, respectively, while the flux of net sequestered carbon was 2,909 and 3,178 g CO2 eq./m2-yr, respectively, which achieved carbon budget values of -676 and -230 g CO2 eq./m2-yr, respectively, exhibiting carbon source effects. Some amounts of N2O, with a high global warming potential of 265, emitted from both artificial wetland systems might cause high GHG flux as CO2 eq. emitted from the wetland systems. It was concluded that both the nitrogenous contents and environmental conditions suitable for microbial production of N2O might be the main factors to change the wetland systems from carbon sinks to carbon sources.

Formation of Nitrogen Oxides by Nanosecond Pulsed Plasma Discharges in Gas–Liquid Reactors

A gas–liquid-film flow reactor with a nanosecond pulsed power supply was utilized to produce nitrogen oxides from Ar/N2 mixtures (gas phase) and deionized water (liquid phase). Chemical analysis of the stable products found in both the gas and liquid phases was performed and chemical quenching was incorporated for the liquid phase samples in order to eliminate post plasma reactions. Significant amounts of NO and NO2 in the gas phase and $${\text{NO}}_{2}^{ - }$$ and $${\text{NO}}_{3}^{ - }$$ in the liquid phase were determined using FTIR spectroscopy and ion chromatography, respectively. The production rate of all nitrogen oxides produced increased significantly with N2 concentration while H2O2 formation decreased slightly. The gas temperature of the plasma was approximately 525 K and was unaffected by N2 concentration while the electron density ranged from 1 × 1017 cm−3 in pure Ar to 5.5 × 1017 cm−3 in 28% N2. The role of the $${\cdot {\text{OH}}}$$ in the reaction pathway was assessed by adding CO as a gas phase radical scavenger showing that $${\cdot {\text{OH}}}$$ is essential for conversion of the gas phase NO and NO2 into water soluble $${\text{NO}}_{2}^{ - }$$ and $${\text{NO}}_{3}^{ - }$$ . Conversely, atomic oxygen originating from water is likely responsible for NO and NO2 generation. Experiments with N2/O2/Ar mixtures and air showed a significant increase in NO2 production caused by the additional generation of reactive oxygen species. An overall energy yield for all nitrogen oxides produced in the most efficient case was 50 eV/molecule.

Impact of Biogas and Waste Fats Methyl Esters on NO, NO2, CO, and PM Emission by Dual Fuel Diesel Engine

The aim of this study was to perform a comparative analysis of the unit gas emission value in the exhaust of a dual fuel diesel engine. The results of the effects of a diesel engine’s applications in biogas plants and the method for calculating mass gas emissions per unit of produced electricity are shown. The test was performed using a two-cylinder, naturally aspirated, liquid-cooled diesel engine. The diesel engine powered a generator connected to the grid. The engine was fed with liquid fuels—waste cooking oil methyl ester (UCOME) and diesel fuel (DF)—and with a gas fuel, biogas (BG). The engine ran at a constant rotational speed (2000 rpm ± 30 rpm) with variable load. The gas analyzer measured the amount of CO, NO, NO2, and PM (particulate matter) in exhaust gas. This gas content share was then converted to mass per engine generated energy unit. This experiment showed the effect of BG introduced to the intake manifold on fuel combustion, as well as an increase in CO and NO2 emission and decrease in NO and PM. In terms of dependence of exhaust emissions on the type of liquid fuel used, the use of UCOME as opposed to diesel fuel resulted in PM reduction and increase of NO emissions.

Dye‐Sensitized Core/Shell Upconversion Nanoparticles for Detecting Nitrites in Plant Cells

AbstractA fluorescent nanoprobe is reported for rapid detection of nitrites (NO2−) in plant cells. The probe is fabricated by linking neutral reds (NR) to the surface of upconversion fluorescent core/shell nanocrystalline with the bridging of polyethylene glycol (PEG) molecules. The fluorescence of upconversion nanoparticles (UCNPs) is stored by NR through fluorescence resonance energy transfer (FRET) under 980 nm excitation that can be released by further linking to NO2−. It is observed that the intensity rate of green to red emission of NR‐modified UCNPs changes linearly with increasing the amount of NO2−. So that concentration of NO2− can be accordingly addressed. Worth mentioning is that, comparing with bare core upconversion nanoparticles (NPs), core/shell UCNPs can greatly reduce the surface quenching of the fluorescence induced by solvents instead of NR and thus leading to the enhancement of signal‐to‐noise ratios. Moreover, excitation of core/shell UCNPs requires only a much lower power (0.06 W cm−2) than bare cores which is beneficial to reducing the decomposition of NR to stabilize the FRET processes. Under the optimum conditions, the detection limit of nitrite in plant cells was 0.1 µg mL−1.

Optimization of Ammonia Oxidation Using Response Surface Methodology

In this paper, the design of experiments and response surface methodology were proposed to study ammonia oxidation process. The following independent variables were selected: the reactor’s load, the temperature of reaction and the number of catalytic gauzes, whereas ammonia oxidation efficiency and N2O concentration in nitrous gases were assumed as dependent variables (response). Based on the achieved results, statistically significant mathematical models were developed which describe the effect of independent variables on the analysed responses. In case of ammonia oxidation efficiency, its achieved value depends on the reactor’s load and the number of catalytic gauzes, whereas the temperature in the studied range (870–910 °C) has no effect on this dependent variable. The concentration of nitrous oxide in nitrous gases depends on all three parameters. The developed models were used for the multi-criteria optimization with the application of desirability function. Sets of parameters were achieved for which optimization assumptions were met: maximization of ammonia oxidation efficiency and minimization of the N2O amount being formed in the reaction.

Nitrous oxide emission from upland soil amended with different animal manures

The nitrous oxide (N2O) emission of from arable soil following the application of manure is expected to vary by different animal manure types used. This study was conducted to determine the relationship between the type of animal manure used to amend soil and the amount of N2O emitted during the cultivation of sweet potato (Ipomoea batatas). An additional objective was to study the characteristics of nitrogen (N) and carbon (C) in different animal manures. Composted manures from chickens, cows, and pigs were applied to the soil at rates of 0, 10, and 20 Mg ha−1, respectively. The availability and concentration of N and C varied by manure type. The concentration of NH4+ was greater in pig manure (4638 mg kg−1) than in chicken (551 mg kg−1) and cow manure (147 mg kg−1). The mean cumulative N2O emission rate across soil application rates was also the highest with pig manure (11.9 kg ha−1 year−1), followed by chicken and cow manure, with emission rates of 10.8 and 10.1 kg ha−1 year−1, respectively. The majority of N2O measured during the sweet-potato-growing season was produced from aerobic nitrification. Dissolved organic carbon (DOC) concentrations in animal manures did not affect cumulative N2O emission rates, and no significant relationship was observed throughout the growing season between the concentration of DOC in soil and daily N2O emission. Cumulative N2O emission rates depended on the type of animal manure and might be governed by NH4+ concentration, rather than by total N concentration in animal manure type.

Au-TiO2/SiO2 photocatalysts with NOx depolluting activity: Influence of gold particle size and loading

The air pollution is becoming one of most important health problems around the world. Thus, the development of depolluting building materials is a crucial challenge. TiO2 is a photocatalyst with demonstrated performance for degradation of NOx and other typical pollutants. However, its limited absorption of solar light reduces its performance. In this study, Au-TiO2NPs are integrated into a silica matrix in order to produce long-lasting coatings with de-pollutant performance and applicability in building. The interaction between Au and TiO2 improves the photoactivity of TiO2 and it promotes a considerably increase in visible light absorption. A significant role of the AuNPs size and their loading on the material photoactivity has been also demonstrated. The lowest AuNPs size enhances the activity due to their better dispersion and subsequently, the higher Au-TiO2 interaction observed. Regarding the Au loading, the maximum photoactivity, in terms of NO conversion and dye degradation, was reached for the intermedium Au loading. It can be mainly associated to the abrupt increase of Au-TiO2 agglomeration for the highest loading evaluated. Finally, it has been stablished that AuNPs also increased the selectivity of the NO oxidation to nitrates and nitrites, reducing the amount of NO2 released.

Nitrous oxide in vivo emission may regulate nitrogen stoichiometry in earthworm body tissues

There is growing evidence that earthworms maintain strict homeostasis in their nitrogen (N) stoichiometry, but the mechanisms employed remain poorly understood. Herein, we examined whether the endogeic earthworm Aporrectodea turgida regulates N stoichiometry in its body (1) by changing the quantity of N excreted from urine and mucus secretion, and (2) regulating the amounts of N2O and N2 emitted from their body by the aid of gut-microbiota. These objectives were evaluated in a laboratory experiment using 15N-labeled adults of A. turgida and tracking the 15N lost from their body during a 48 h period in microcosms containing soil-plant litter mixtures varying in N content and C:N ratio. The quantity of 15N excreted by A. turgida after 48 h was about 3.7 ± 0.3 μg and was composed of 50% 15N-mineral N and 34% 15N-DON. The N excretion rate varied, on average, from 507 to 699 μg N g−1 fw d−1 with no effect of the litter treatment (P > 0.05). It is unlikely that N release through urine and mucus regulated N stoichiometry in the body tissue of A. turgida. However, the net change in N2O production with earthworms and the quantity of 15NN2O was 8–12 times greater in microcosms amended with the N-rich red clover than N-poor litters and the control (no litter). This suggests that in vivo N2O emission from A. turgida may regulate the N stoichiometry of its body tissues.