Ratio Of NO Research Articles

Nitrous oxide in diesel aftertreatment systems including DOC, DPF and urea‐SCR

The formation of Nitrous oxide (N2O) over urea-based selective catalytic reduction (SCR) systems was scrutinized using exhaust gases from a 3.4-liter non-road diesel engine. Four catalysts were used for the SCR systems; Cu-zeolite (Cu/Fe = 4), Fe-zeolite (Fe only), vanadia and mixed (vanadia and Cu-zeolite) one. For all SCR systems, the N2O concentration at the SCR inlet (before SCR) was below 1 ppm, except for the low-load and low-speed engine conditions, where it was below 3 ppm. However, at the SCR outlet, the N2O concentration had risen to nearly 20 ppm, except for a few conditions. That is, N2O increased more than a dozen times by passing through the SCR systems. The amount of N2O formed within the SCR systems depended on the SCR catalysts; the vanadia catalyst had the lowest amount of N2O, while the Fe-zeolite catalyst as well as the Cu-zeolite catalyst had the highest. In addition, the formation of N2O was strongly involved in the ratio of nitrogen dioxide (NO2) to nitrogen oxides (NOx) at the SCR inlet, which was coupled to SCR inlet temperatures. The higher ratio of NO2 to NOx led to higher N2O at the SCR outlet. It was found that the start of N2O formation corresponded to the moment when nitric oxide (NO) was close to 0 ppm as the ratio of an ammonia (NH3) in aqueous urea solution to NOx increased. In other words, NO depletion played a crucial role in the start of N2O formation when NO and NO2 were simultaneously consumed. Therefore, the difference in N2O formation among the four catalysts for the SCR systems depended on how quickly NO was depleted. Results from α values of intersections of N2O and NO (α@N₂O = NO) for Cu- and Fe-zeolite catalysts showed that α@N₂O = NO for the Fe-zeolite catalyst are much smaller than that for the Cu-zeolite catalyst, and this implies that the Fe-zeolite catalyst can start N2O formation earlier or have faster NO depletion than the Cu-zeolite catalyst.

Efficacy optimization of plasma-activated water for food sanitization through two reactor design configurations

The chemistry, antimicrobial efficacy and energy consumption of plasma-activated water (PAW) was optimized by altering the discharge frequency, ground-electrode configuration, gas flow rate and initial water conductivity for two reactor configurations, i.e., air pin-to-liquid discharge and air plasma-bubble discharge in water. The ratio of NO2− and NO3− formation was altered to optimise the antimicrobial effects of PAW, tested against two Gram-negative bacteria. An initial solution conductivity of 0.2 S·m−1 and 2000-Hz discharge frequency with the ground electrode positioned inside the pin reactor showed the highest antimicrobial effect resulting in a 3.99 ± 0.13-log10 reduction within 300 s against Escherichia coli and 5.90 ± 0.24-log10 reduction within 240 s for Salmonella Typhimurium. An excellent energy efficiency of reactive oxygen and nitrogen species (RONS) generation of 10.1 ± 0.1 g·kW−1·h−1 was achieved. Industrial relevancePlasma-activated water (PAW) is deemed as an eco-friendly alternative to chemical disinfection because its bactericidal activity is temporary. Optimizing the design and operation of PAW reactors to achieve high inactivation rates of more than 5-log10 reductions, as demonstrated in this work, will support the industrial application of this technology and the scaleup at industrial level.

Urea treatment decouples intrinsic pH control over N2O emissions in soils

Soil N2O emission potential is commonly investigated under idealized denitrifying conditions (e.g. nitrate-N supplied and anaerobic soil), with pH commonly identified as a major determinant of N2O emission potential. However, under urine patch conditions in grazed pastures soils a more complex series of abiotic and biotic factors may influence emissions due to the complex N transformations that occur following urea hydrolysis. These transformations may decouple native and/or expected controls of N2O emissions encountered under classic denitrifying conditions. Here, we tracked O2, CO2, NO, N2O and N2 emissions from urine amended soils (i.e. simulating a urine patch) to determine putative controls of N2O emissions within 13 different pasture soils from northern (Ireland) and southern hemispheres (New Zealand). Incubations were performed under aerobic conditions±artificial urine (13.3 mg N vial−1) equivalent to field ruminant urine deposition rates of 1000 kg N ha−1. Results revealed that pH was not an important regulator of the emission ratio (N2O/(NO + N2O + N2)) in urine amended soils. Within urine affected soils, a new set of variables emerged as regulators of N2O emissions, likely due to the unique environment created within this system. We show that urine results in decoupling of the initial soil pH control of the emission ratio allowing other regulators such as nitrite to dominate. In addition, we observed that the emission ratio of N2O increased linearly with the rate of N- gas loss (NO + N2O + N2 μmol N h−1), O2 consumption was positively associated with ammonia oxidising bacteria (AOB) and that the production of NO and N2O were also enhanced under urine conditions.

Effective partial denitrification of biological effluent of landfill leachate for Anammox process: Start-up, influencing factors and stable operation

Partial denitrification combined with Anammox is a promising approach for simultaneous removal of ammonium and nitrate from wastewaters. In this study, the start-up, influencing factors and stable operation of partial denitrification for treating biological effluent from landfill leachate were investigated. High nitrate loads (3.85 kg N m−3 d−1) and short hydraulic retention time (0.66 h) were obtained in the partial denitrification process, yielding a suitable ratio of NO2−-N/NH4+-N in the effluent for downstream Anammox process. The study also revealed the importance of carbon sources, COD/NO3−-N ratio and salinity in the partial denitrification. Acetate-type carbon source, COD/NO3−-N ratio of about 3.0 and salinity lower than 1% favored high-efficient partial denitrification. The endogenous carbon sources from high-rate partial denitrification sludge contributed to low COD consumption in the process. During the partial denitrification, the dominant genus of Thauera was enriched, and shifted to Pseudomonas with the increase of organic removal rates.

N-type polysilicon passivating contacts using ultra-thin PECVD silicon oxynitrides as the interfacial layer

We describe the optimization of an ultra-thin silicon oxynitride (SiOxNy) layer deposited by plasma enhanced chemical vapor deposition (PECVD) as an interfacial layer for phosphorus doped polysilicon (poly-Si) passivating contacts. Our results demonstrate the possibility of depositing the thin interfacial layer and the intrinsic amorphous silicon (a-Si) film in a single PECVD process. We found that the gas flow rates strongly influence the properties of the SiOxNy layers, such as the refractive indices, chemical bond compositions and structural stabilities, which significantly affect the properties of the resulting polysilicon passivating contact structures. The passivation quality initially increased and then decreased with a decreasing N2O/SiH4 flow ratio, in the gas flow range of uniform deposition, while the contact resistivity decreased significantly. We found an optimal gas flow ratio of N2O:SiH4:N2 = 25:9:361, with which we obtained uniform polysilicon passivating contacts with a high implied open-circuit voltage (iVoc) of 711 mV and a low contact resistivity ρc of 6.6 mΩ cm2.

Model Based Design, Simulation and Experimental Validation of SCR Efficiency Model

<div class="section abstract"><div class="htmlview paragraph">Selective Catalytic Reduction is a key technology, used for NOx abatement. There are several models available for SCR system performance out of which most are experimentally verified only in flow reactors with simulated gaseous concentration and standard test conditions. But in the vehicle as well as in the engine test bench the conditions are very much dynamic compared to the simulated conditions of the lab. This transient behaviour emphasizes the need for a best fit model which accommodates the real-world dynamic conditions, thus reducing the overall effort in SCR catalyst selection for any given engine or vehicle application. The primary objective of this paper is to derive an empirical and mathematical efficiency model for SCR catalyst performance through a model-based design approach. The output from the model is compared with the experimental results from the vehicle and engine test bench, to validate the model accuracy. The model is a function of system specific parameters like space velocity, NO2 ratio, system efficiency, catalyst loading and ageing factors, temperature mapping, for various engine operating zones that are benchmarked from existing experimental results and chemical kinetics that are already incorporated in existing models. This model is fine-tuned by incorporating experimental data and simulated with different control strategies to further refine and optimize the catalyst performance and reduce DEF consumption and ammonia slip formation. The model output from numerical simulations and experimental results are used to derive the control strategy for the best overall efficiency model.</div></div>

Role of ammonia in secondary inorganic aerosols formation at an ammonia-rich city in winter in north China: A comparative study among industry, urban, and rural sites

Ammonia is essential for the generation of secondary inorganic aerosols (SIA) in particulate matter, which affects severely the air quality in north China. In this study, PM2.5 sampling was conducted as well as gaseous pollutant concentration and meteorological parameters were measured from November 2017 to January 2018. PM2.5 concentration was highest in the industrial site (94.8 ± 41.7 μg m−3), followed by urban (40.9 ± 24.1 μg m−3) and rural (35.6 ± 20.3 μg m−3) sites. The mass ratio of NO3−/SO42− exhibited clear site variations, with the highest average value of 1.2 was found at the urban site, likely due to the dense traffic volume resulting in higher emissions of NO2, and the lowest value of 0.9 at the industry site. The presence of Excess-NHx (E-NHx), raising the pH 24 by 1.4, 1.3, and 1.4 units in industry, urban, and rural sites, respectively, might be vital for raising the aerosol pH. Correlation coefficients of Nitrogen oxidation rate (NOR, NOR = [NO3−]/[NO3−] + [NO2]) vs. Photochemical oxidants (Ox, NO2 +O3 in our study) and NOR vs. aerosol water content (AWC) at three sites were implied that both homogeneous and heterogeneous reactions occurred for nitrate formation in industry site, while heterogeneous reactions were dominant in urban and rural sites. Oxidation rates were most sensitive to the variation of E-NHx concentration at rural site, followed by the urban and industry sites, which was shown by the fact that the increase in E-NHx concentration by 1.0 μg m−3 increased the SIA concentration by 1.21, 1.02, and 0.37 μg m−3 at rural, urban, and industry sites, respectively. With the increase in NHx emissions at present, the role of NHx in SIA formation at ammonia-rich atmosphere requires more attention, especially in the less-noticed rural areas.

Impacts of Anthropogenic Emission Reduction and Meteorological Conditions on PM2.5 Pollution in Typical Cities of Beijing-Tianjin-Hebei in Winter

This study used sampling analysis and a CAMx-PSAT coupling model to analyze the components, transmission, and source apportionment of PM2.5 in Beijing and Tangshan in January 2018. The results showed that in January 2018, water-soluble inorganic ions (WSⅡs) accounted for 49.59% and 39.13% of PM2.5 mass concentrations in Beijing and Tangshan, respectively. The ratios of NO3- to SO42- were 2.02 and 1.51, respectively, indicating that pollution in both cities was dominated by mobile sources. In Beijing and Tangshan, PM2.5 accounted for 48.74% and 30.67% of transmission, respectively. Regional transmissions were mainly contributed by neighboring areas, northwest masses, and southwest masses. However, the contribution of the southwest passage to pollution in the respective cities increased by 9.65% and 15.02% during pollution periods. The principal sources contributing to PM2.5 pollution in Beijing were mobile and dust sources. Secondary ions were more obviously affected by regional contributions, mobile and industrial sources had the most significant effect in Tangshan, and most particulate matter and sulfate were contributed by local emissions. From 2013 to 2018, the dominant component of WSⅡs changed from sulfate to nitrate while the main pollution sources changed from coal-fired and industrial sources to mobile and dust sources. Meanwhile, in January 2018, the meteorological factors were more favorable for pollution mitigation than in 2013. The meteorological impact of secondary ions is closely related to the lower relative humidity in 2018, compared to 2013.

Electrical conductivity and dissolved oxygen as predictors of nitrate concentrations in shallow groundwater in Erhai Lake region

Elevated nitrogen (N) concentration in shallow groundwater is becoming increasingly problematic, putting water resources under pressure. For more effective management of such a resource, more precise predictors of N level in groundwater using smart monitoring networks are needed. However, external factors such as land use type, rainfall, and N loads from multiple sources (residential and agricultural) make it difficult to accurately predict the spatial and temporal variations of N concentration. In order to identify the key factors affecting spatial and temporal N concentration in shallow groundwater and develop a predictive model, 635 groundwater samples from drinking wells in residential areas and agricultural wells in croplands of a typical agricultural watershed in the Erhai Lake Basin, southwest China, in the period from 2018 to 2020, were collected and analyzed. The results showed that the type of land use and seasonal variations significantly affected the N forms and their concentrations in the shallow groundwater, as the ratios of ON and NO3−-N to TN were 30%–39% and 52%–59% for the two land uses and 25%–44% and 46%–66% for seasonal changes. Their variations were reflected by electrical conductivity (EC) and redox environment. EC and dissolved oxygen (DO) had a positive non-linear relationship with the concentrations of total nitrogen (TN) and nitrate (NO3−-N). The fitted non-linear quantitative models were established separately to predict TN and NO3−-N concentrations in groundwater using easily available indictors (EC and DO). The high accuracy and performance of the models were investigated and approved by rRMSE, MAE, and 1:1 line. These findings can provide technical support for the rapid prediction and evaluation of N pollution in shallow groundwater through easily available indicators.

The Breathe Easy Study: Impacts of Ventilation Improvements on IAQ and Adult Asthma in 40 Existing Homes in Chicago, IL

BACKGROUND AND AIM: This paper presents preliminary results of the Breathe Easy Project, which as designed to improve indoor air quality (IAQ) and asthma-related health outcomes by installing residential mechanical ventilation systems in forty existing homes in Chicago, IL. Each home had at least one self-reported adult resident with asthma and received one of three types of ventilation systems half-way through the study: exhaust-only system, central-fan-integrated-supply (CFIS) system, or balanced system with an energy recovery ventilator (ERV). METHODS: We conducted quarterly field measurements to monitor indoor and outdoor pollutants, including size-resolved particles (0.3-10 µm), ozone (O3), nitrogen dioxide (NO2), carbon dioxide (CO2), carbon monoxide (CO), and formaldehyde (HCHO). Monthly asthma control test (ACT) surveys were administered for each participant throughout the study. Wilcoxon signed-rank tests were used to evaluate the impacts of ventilation system retrofits on IAQ, indoor/outdoor (I/O) ratio, and ACT score. Chi-square tests for independence and multiple logistic regression were used to analyze associations between IAQ, asthma severity, and baseline characteristics of participants and homes. RESULTS:Indoor pollutant concentrations and I/O ratios were significantly lower after ventilation system retrofits for indoor concentrations of HCHO, CO2, PM1.0, PM2.5, and PM10, and I/O ratios of CO2, NO2, PM1.0, and PM2.5 (P 0.05). There was a small but significant increase in average ACT score of 1.04 across the entire study population after the ventilation system retrofits (P 0.001). Based on association analysis of the pre-intervention period, higher NO2 concentrations were associated with increased odds of poorly controlled asthma, with crude odds ratios (OR) (95% CI) of 2.8 (1.2−6.4). Also, Black participants showed OR (95% CI) of 5.7 (1.3−25.9) for poorly controlled asthma compared to White participants. CONCLUSIONS:The results can potentially provide information on the influence of exposure for many air toxics and will furnish an opportunity to evaluate exposure models for these compounds. KEYWORDS: Air pollution, asthma, exposures, occupational epidemiology

Ratio of nitrate to ammonium mainly drives soil bacterial dynamics involved in nitrate reduction processes

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) influence the nitrate (NO3−) reduction and its final fate in the environment. However, it is unclear how denitrifying and DNRA bacterial communities respond to different environment conditions. Here, we investigated the effects of fertilization and sampling time (April, July and November) on the abundances of nitrogen (N) cycling genes in processes of denitrification and DNRA at different soil depths (0–20, 20–40 and 40–60 cm) based on a long-term fertilization experiment station (initiated in 1987). The abundances of genes involved in NO3− reduction process were determined using quantitative PCR (qPCR) analysis method. Sampling time showed a stronger effect on the abundances of denitrifying and DNRA genes than fertilization. And the effect of fertilization on the abundances of genes involved in NO3− reduction process was decreased with soil depths. Compared with no fertilizer (CK), the application of mineral N fertilizer (N2 and N4) reduced the abundances of denitrification and DNRA genes at 0–20 cm soil depth, regardless of sampling time. However, the application of organic manure combined with mineral N fertilizer (M2N2) clearly increased the abundance of specific denitrifying genes, including napA (NO3− to NO2−) and nosZ (N2O to N2) genes compared with N2 and N4 treatments at 0–20 and 20–40 cm soil depths. Although the abundance of nrfA gene was the highest, the abundance of norB gene was the most sensitive to environmental variation among all the tested N cycling genes. Ratio of NO3− to ammonium (NO3−/NH4+) was significantly correlated with all the denitrifying and DNRA genes. In general, long-term application of organic manure combined with mineral N fertilizer has a potential to mitigate the NO3− leaching and N2O production, and NO3−/NH4+ ratio is an important factor driving the dynamics of bacterial communities involved in the NO3− reduction process.

Iodide CIMS and <i>m</i>∕<i>z</i> 62: the detection of HNO<sub>3</sub> as NO<sub>3</sub><sup>−</sup> in the presence of PAN, peroxyacetic acid and ozone

Abstract. Chemical ionisation mass spectrometry (CIMS) using I− (the iodide anion), hereafter I-CIMS, as a primary reactant ion has previously been used to measure NO3 and N2O5 both in laboratory and field experiments. We show that reports of large daytime mixing ratios of NO3 and N2O5 (both usually present in detectable amounts only at night) are likely to be heavily biased by the ubiquitous presence of HNO3 in the troposphere and lower stratosphere. We demonstrate in a series of laboratory experiments that the CIMS detection of HNO3 at m/z 62 using I− ions is efficient in the presence of peroxy acetyl nitric anhydride (PAN) or peroxyacetic acid (PAA) and especially O3. We have characterised the dependence of the sensitivity to HNO3 detection on the presence of acetate anions (CH3CO2-, m/z 59, from either PAN or PAA). The loss of CH3CO2- via conversion to NO3- in the presence of HNO3 may represent a significant bias in I-CIMS measurements of PAN and PAA in which continuous calibration (e.g. via addition of isotopically labelled PAN) is not carried out. The greatest sensitivity to HNO3 at m/z 62 is achieved in the presence of ambient levels of O3 whereby the thermodynamically disfavoured, direct reaction of I− with HNO3 to form NO3- is bypassed by the formation of IOx-, which reacts with HNO3 to form, for example, iodic acid and NO3-. The ozone and humidity dependence of the detection of HNO3 at m/z 62 was characterised in laboratory experiments and applied to daytime, airborne measurements in which good agreement with measurements of the I−(HNO3) cluster ion (specific for HNO3 detection) was obtained. At high ozone mixing ratios, we show that the concentration of I− ions in our ion–molecule reactor (IMR) is significantly depleted. This is not reflected by changes in the measured I− signal at m/z 127 as the IOx- formed does not survive passage through the instrument but is likely detected after fragmentation to I−. This may result in a bias in measurements of trace gases using I-CIMS in stratospheric air masses unless a calibration gas is continuously added or the impact of O3 on sensitivity is characterised.

Nitrate sources and transformations in surface water of a mining area due to intensive mining activities: Emphasis on effects on distinct subsidence waters

The increase in NO3− content in surface water caused by intensive mining activities in Huainan City, China, has attracted considerable attention owing to the deterioration of water quality and the degradation of ecosystems in recent years. The Huainan mining area, which is highly disturbed by anthropogenic activities, was selected as a typical observation area, and the surface water was classified as open subsidence water (OSW), closed subsidence water (CSW), and river water (RW). Moreover, the hydrochemical parameters and the δ15N and δ18O values of nitrate were employed to quantitatively trace the sources and biochemical transformation of NO3−, and the contribution ratios of different NO3− sources were estimated using the stable isotope analysis in R based on the Bayesian model. There was evident nitrification in the study area, but no significant denitrification has occurred. A substantial portion of δ15N–NO3- demonstrated complex sources of NO3−. Compared with those of CSW, the NO3− compositions of the OSW approached to those of the RW due to river recharge and discharge, and were greatly affected by anthropogenic activities. The proportional contribution of manure and sewage in the OSW was found to be the highest with a mean value of 39.5 % ± 12.3 %, which was followed by that of mine drainage (mean: 22.1 % ± 13.1 %), chemical fertilizer (mean: 17.5 % ± 10.6 %), and soil organic nitrogen (mean: 17.5 % ± 11.6 %). In the RW, the highest mean contribution of manure sewage was 35.2 % ± 9.7 %, which was followed by that of chemical fertilizer (mean: 29.3 % ± 7.2 %), mine drainage (mean: 23.4 % ± 13.0 %), and soil organic nitrogen (mean: 10.9 % ± 8.3 %). In contrast, the contribution of chemical fertilizer to the CSW was the highest with a mean value of 33.9 % ± 13.6 %, which was followed by that of soil organic nitrogen (mean: 26.5 % ± 13.8 %), mine drainage (mean: 18.1 % ± 11.6 %). Therefore, NO3− in the surface water of the mining area primarily originates from chemical fertilizers and manure sewage. In addition, the contribution of mine drainage to nitrate in the study area indicates the potential impact of mining activities on surface water. These findings highlight the value of classifying different types of surface water in tracing NO3− contamination sources, and provide relevant theoretical basis for tracing nitrate sources in other areas.

Simulation of Denitrification of Vehicle Exhaust over Cu-CHA Bazite Catalyst for a Monolith Reactor

A CFD model with chemical reaction kinetic and heat and mass transfer for a monolith reactor is established by COMSOL Multiphysics to investigate the influence of different operating conditions and water on denitrification efficiency for Cu-CHA. At the low temperature range, water has little effect on the denitrification efficiency over the Cu-CHA catalyst while NO conversion is increased by about 30% at the medium temperature. The concentration of O2 (CO2) has no significant effect on the performance of Cu-CHA catalyst. The best ratio of NO2 to NOx in feed gases may be 1/2, which improves the denitrification efficiency and the yield of N2 but it produces relatively little N2O. The optimal ammonia-nitrogen ratio is 1.1, where Cu-CHA catalyst has fairly great denitrification efficiency and low NH3 leakage. Increasing inlet flow velocity and cross area of channels have negative effect on NO conversion, while longer channels and thicker substrate have the opposite effect.

Phytoplankton Bloom Dynamics in Incubated Natural Seawater: Predicting Bloom Magnitude and Timing

Phytoplankton blooms can cause imbalances in marine ecosystems leading to great economic losses in diverse industries. Better understanding and prediction of blooms one week in advance would help to prevent massive losses, especially in areas where aquaculture cages are concentrated. This study has aimed to develop a method to predict the magnitude and timing of phytoplankton blooms using nutrient and chlorophyll-a concentrations. We explored variations in nutrient and chlorophyll-a concentrations in incubated seawater collected from the coastal waters off Yeosu, South Korea, seven times between May and August 2019. Using the data from a total of seven bottle incubations, four different linear regressions for the magnitude of bloom peaks and four linear regressions for the timing were analyzed. To predict the bloom magnitude, the chlorophyll-a peak or peak-to-initial ratio was analyzed against the initial concentrations of NO3 or the ratio of the initial NO3 to chlorophyll-a. To predict the timing, the chlorophyll-a peak timing or the growth rate against the natural log of NO3 or the natural log of the ratio of the initial NO3 to chlorophyll-a was analyzed. These regressions were all significantly correlated. From these regressions, we developed the best-fit equations to predict the magnitude and timing of the bloom peak. The results from these equations led to the predicted bloom magnitude and timing values showing significant correlations with those of natural seawater in other regions. Therefore, this method can be applied to predict bloom magnitude and timing one week in advance and give aquaculture farmers time to harvest fish in cages early or move the cages to safer regions.

N2 and N2O mitigation potential of replacing maize with the perennial biomass crop Silphium perfoliatum—An incubation study

AbstractSustainability of biogas production is strongly dependent on soil‐borne greenhouse gas (GHG) emissions during feedstock cultivation. Maize (Zea mays) is the most common feedstock for biogas production in Europe. Since it is an annual crop requiring high fertilizer input, maize cropping can cause high GHG emissions on sites that, due to their hydrology, have high N2O emission potential. On such sites, cultivation of cup plant (Silphium perfoliatum) as a perennial crop could be a more environmentally friendly alternative offering versatile ecosystem services. To evaluate the possible benefits of perennial cup plant cropping on GHG emissions and nitrogen losses, an incubation study was conducted with intact soil cores from a maize field and a cup plant field. The 15N gas flux method was used to quantify N source‐specific N2 and N2O fluxes. Cumulated N2O emissions and N2+N2O emissions did not differ significantly between maize and cup plant soils, but tended to be higher in maize soil. Soils from both systems exhibited relatively high and similar N2O/(N2+N2O) ratios (N2Oi). N2O emissions originating from sources other than the 15N‐labelled NO3 pool were low, but were the only fluxes exhibiting a significant difference between the maize and cup plant soils. Missing differences in fluxes derived from the 15N pool indicate that under the experimental conditions with high moisture and level, and without plants, the cropping system had little effect on N fluxes related to denitrification. Lower soil pH and higher bulk density in the cup plant soil are likely to have reduced the mitigation potential of perennial biomass cropping.

Nitrogen removal performance using anaerobic ammonium oxidation considering variable conditions.

The anaerobic nitrogen removal performance of anammox at 30°C, 25°C, and 16°C were studied by using the UASB (Up flow Anaerobic Sludge Blanket) reactor and the influent concentration of NH4+-N and NO2--N were 16.9 and 20.6 mg L-1 respectively. Experimental results showed that high-efficiency anammox nitrogen removal could be achieved at 30°C, when hydraulic retention time (HRT) was 0.14 h, the nitrogen removal rate (NRR) was 5.73 kg N m-3 d-1. The anammox reactor operated stably for more than 80 days under the condition of 16°C-20°C, and the high NRR of 2.78 kg N m-3 d-1 was obtained. In this experiment, DO had little effect on the activity of anammox granular sludge, and the nitrogen removal performance could be quickly recovered in a short period of time after being affected by DO. Moreover, the stoichiometric ratio of NO2--N and NH4+-N consumption (ΔNO2--N/ΔNH4+-N) and the stoichiometric ratio of NO3--N production and NH4+-N conversion (ΔNO3--N/ΔNH4+-N) were 1.21 ± 0.11and 0.25 ± 0.06 respectively at 30°C, which were very close to the theoretical value, it indicated that anammox bacteria were the dominant bacteria at 30°C.

Open‐Path Dual‐Comb Spectroscopy for Multispecies Trace Gas Detection in the 4.5–5 µm Spectral Region

AbstractOpen‐path dual‐comb spectroscopy provides multispecies atmospheric gas concentration measurements with high precision. Here, open‐path dual‐comb spectroscopy is extended to the mid‐infrared 5 µm atmospheric window, enabling atmospheric concentration retrievals of the primary greenhouse gases, N2O, CO2, and H2O, as well as the criteria air pollutants O3 and CO across 600 m and 2 km round‐trip paths. Measurements are demonstrated over a five‐day period at 2 min temporal resolution with 80% uptime. The achieved precision is sufficient to resolve the atmospheric concentration variations of the multiple gas species; retrieved dry mixing ratios of CO and N2O are in good agreement with a colocated point sensor. In addition, the retrieved ratio of excess CO versus CO2 agrees with similar urban studies but disagrees with the US National Emission Inventory by a factor of 3. The retrieved ratio of excess N2O versus CO2 exhibits a plume‐dependent value, indicating the variability of sources of the greenhouse gas N2O.

Nitrate/ammonium ratio effect on the growth, yield and foliar anatomy of grafted tomato plants

The vigorous behaviour of a rootstock modifies the growth and yield of a plant variety or hybrid, altering the plant nutritional requirements. The purpose of this work was to study four ratios of NO3–/NH4+ (100/0, 92/8, 85/15 and 80/20%) over the growth, leaf anatomy and yield of grafted and ungrafted tomato plants. We used a fully randomised experimental block design with factorial arrangement of 2 × 4 (grafted and ungrafted plants and four ratios of NO3–/NH4+), on eight treatments in total with four replicates each, using Tukey’s mean comparison test (P ≤ 0.05). The rootstock was ‘Silex’ by Fito Seeds, with the ‘El Arrojado’ graft (variety) by Gene Seeds. The graft produced an increase in growth, dry biomass production, stomatal density, trichome number, epidermal cell density, fruits per plant, average fruit weight, fruit size and total soluble solids, in comparison with the ungrafted tomato plants. In most of the assessed variables, the grafted tomato plants gave their best response at an 85/15% NO3–/NH4+ ratio; while the ungrafted plants performed better at a 92/8% NO3–/NH4+ ratio. The response of the grafted plants to the different NO3–/NH4+ ratios suggests that grafting induces tolerance to NH4+.

Potential Sources, Formation Routes, and Health Effects of Nitrogen Dioxide (NO2) on Indoor Air Quality, Human Health, Safety, and the Environment: A Review

Since human beings spend 80-90% of the day inside houses, educational and recreation centers, office blocks, or automobiles, the quality of air within these buildings or structures is crucial for human health and safety. Hence, indoor air quality (IAQ) highlights the general characteristics of indoor air that affect the state of health, thermal comfort, and well-being of humans. Despite numerous regulatory standards, framework policies, and monitoring plans proposed for IAQ, the occurrence of indoor pollutants including radon (Rn), ozone (O3), and oxides of carbon, sulfur, and nitrogen have become common. Many studies contend that nitrogen dioxide (NO2) is a major indoor air pollutant and one of the most poisonous on Earth. It is a reddish-brown gas generated from the oxidation of nitrogen oxides (NOx) and molecular oxygen or O3 or the high-temperature combustion of solid fuels. This paper presents an overview of the potential sources, formation routes, and health effects of NO2. According to reviewed literature, the occurrence, concentrations, and ratios of NO2 in the indoor environment are affected by residential factors, weather/climate, and proximity to NO2 sources indoors, such as burners, ovens, and stoves. Furthermore, long-term exposure to NO2 causes diabetes, heart, cardiovascular, hypertension diseases, severe cough, hemoptysis, pediatric lung edema and, more recently, fatalities arising from COVID-19. Therefore, the overdependence on polluting fuels that generate NO2 must be minimized or eliminated to improve IAQ and protect human health, safety, and the environment. Future design plans for constructing kitchens, homes, offices, automobiles, factories, and power plants must incorporate smart sensors or ventilation systems for detecting, monitoring, or removal of exhaust gases, including NO2.