Atmospheric Ammonia Research Articles

Removal of ammonia nitrogen from residual ammonium leaching solution by heterotrophic nitrification-aerobic denitrification process

ABSTRACT The aftermath of mining weathered crust elution-deposited rare earth ore produces a large amount of residual ammonium leaching solution, which causes ammonia and nitrogen pollution to the mine site. Recently, denitrification by heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria has attracted much attention. However, limited studies exist regarding the denitrification process of HN-AD bacteria. In this study, we combined four strains of HN-AD bacteria, Pseudomonas fulva K3, Pseudomonas mosselii K17, Klebsiella oxytoca A12, and Enterobacter hormaechei A16, obtained from rare earth element leaching sites, to select the best microbial consortium for ammonia nitrogen removal. We designed an ammonia removal process applicable to HN-AD bacteria to directly remove ammonia nitrogen from acidic leaching solutions. The experimental results demonstrated that the most efficient microbial consortium for ammonia nitrogen removal to be K3 + K17 + A16, with a removal efficiency of 89.68% for 8 h. In this process, considering the influencing factors of the ammonia removal process, the larger the influent flow rate and influent ammonia nitrogen concentration, the greater the ammonia nitrogen accumulation and pH decrease in the reactor. In consecutive multi-batch experiments, the ammonia removal process was used to remove ammonia nitrogen, at concentrations of 100–600 mg/L, from the simulated leaching solution at pH 4–7, whereby the effluent ammonia nitrogen concentration was lower than 15 mg/L. The results demonstrate that the ammonia removal process is highly feasible and stable. These findings will provide new ideas for the application of HN-AD bacteria and new methods for the removal of ammonia nitrogen from acidic leaching solutions.

Spatiotemporal Distribution of Ammonia Emissions from Poultry Farming in the Yangtze River Delta Based on Online Monitoring Derived Local Emission Factors

In order to obtain the ammonia emission level and space-time distribution characteristics of the poultry production industry in the Yangtze River Delta, an online high-resolution monitoring system was used to continuously monitor the atmospheric ammonia concentration in the breeding house and compost shed in a typical large-scale layer farm. By obtaining the ammonia emission level and emission factor during each growth stage, we established the localized ammonia emission inventory for the poultry production industry in the Yangtze River Delta. The results showed that the average daily ρ(NH3) in the breeding house and compost shed for spring, summer, autumn, and winter were (1.85±0.38), (4.58±0.33), (3.87±0.12), and (2.83±0.47) mg·m-3 and (2.04±0.50), (4.04±1.04), (2.51±0.67), and (1.55±0.16) mg·m-3 respectively. Ammonia emissions showed a significant daily hourly change trend. The highest hourly ammonia concentration in the layer house appeared from 13:00-14:00 in the afternoon, and the minimum appeared from 01:00-03:00 in the morning. The highest hourly ammonia concentration in the compost shed occurred between 16:00-19:00 in summer and autumn, whereas the diurnal changes in spring and winter were not significant. Hourly changes in ammonia emissions during the day were mainly affected by daily temperature, poultry activities, and manure management. Ammonia concentrations at different growth stages of laying hens showed significant differences. ρ (NH3) from young chickens, laying hens, and pre-eliminated chickens were (1.85±0.38), (2.83±0.47), and (1.61±0.32) mg·m-3, respectively. The ammonia emission rate from laying hens reached 1.53 times and 1.65 times that of young chickens and pre-eliminated chickens, respectively. Metabolism levels and feed intake at different growth stages were the main reasons for the differences in ammonia emissions. Ammonia emission factors for the layer house and compost shed in spring, summer, autumn, and winter were (0.13±0.02), (0.54±0.01), (0.39±0.01), and (0.17±0.01) g·(bird·d)-1 and (0.07±0.01), (0.17±0.02), (0.08±0.01), and (0.04±0.01) g·(bird·d)-1, respectively. Annual ammonia emission factors reached (0.11±0.06) kg·(bird·a)-1 and (0.03±0.02) kg·(bird·a)-1, respectively. Our results suggest that ambient temperature, ventilation mode, chicken house type, and manure removal frequency were the main influencing factors of ammonia emissions from poultry production. The uncertainty ranges of the ammonia emission coefficients reached±122%,±79%, and±74%, and±56%, respectively. Great uncertainties were generated when empirical emission factors were used for emission inventory establishment. Based on the results of online monitoring, model simulation, and literature analysis, we established an ammonia emission inventory for the poultry production industry within the Yangtze River Delta region by adopting the emission factors of (0.16±0.08) kg·(bird·a)-1. In 2019, the total ammonia emission from poultry production was (108.81±54.41) kt. In terms of spatial distribution, ammonia emission intensities in the northern regions were significantly higher than those in the southern parts. The ammonia emission intensities during summer were 3.38-3.56 times higher than those in spring and winter.

Water quality assessment and pollution threat to safe water supply for three river basins in Malaysia

Pollution in raw water poses increasing threats to safe water supply in many developing countries. Therefore, a comprehensive water quality assessment is essential to provide various stakeholders the information to deal with this problem. This study applies chemometrics to interpret a recent 10-year water quality data from three major river basins (Selangor River basin, Langat River basin, and Klang River basin) frequented by water supply disruptions in Selangor, Malaysia. We present the application of selected chemometrics approaches, namely agglomerative hierarchical cluster analysis, principal component analysis, factor analysis and Man-Kendall trend analysis. The results showed three spatial groups of monitoring stations with similar land use practices and pollution characteristics. Besides spatial differences, periodic variations were observed when similar pollutants exhibited different pollution loads during rainy and dry periods. We found that nitrogen species, total suspended solids, and dissolved solids represented the major pollution loads in the studied basins. The results further confirmed a significant increasing trend in ammonia pollution. Our study demonstrates how ammonia pollutant is likely to pose a threat to water supply and highlights the vulnerability of Selangor's water resource system to water pollution. The results of this study could facilitate decision making towards more holistic strategies, specifically, incorporating ammonia treatment facilities into the conventional water treatment plant will help achieve smooth water supply operations.

Exploring global changes in agricultural ammonia emissions and their contribution to nitrogen deposition since 1980.

SignificanceAgricultural systems are already major forces of ammonia pollution and environmental degradation. How agricultural ammonia emissions affect the spatio-temporal patterns of nitrogen deposition and where to target future mitigation efforts, remains poorly understood. We develop a substantially complete and coherent agricultural ammonia emissions dataset in nearly recent four decades, and evaluate the relative role of reduced nitrogen in total nitrogen deposition in a spatially explicit way. Global reduced nitrogen deposition has grown rapidly, and will occupy a greater dominant position in total nitrogen deposition without future ammonia regulations. Recognition of agricultural ammonia emissions on nitrogen deposition is critical to formulate effective policies to address ammonia related environmental challenges and protect ecosystems from excessive nitrogen inputs.

Atmospheric ammonia causes histopathological lesions, cell cycle blockage, and apoptosis of spleen in chickens

This experiment was conducted to investigate the effect of atmospheric ammonia (NH3) on histological changes, cell cycle distribution, and apoptosis of the spleen in chickens. Two hundred forty chickens were randomly allocated to the control group (without NH3 challenge) and NH3 group (70 ± 5 ppm NH3). The experiment lasted for 8 days. The results showed that NH3 exposure caused decreased relative weight ( P < 0.05), dysplasia of white pulps, obvious ultrastructural lesions, upregulation of G0G1 phase cells, excessive apoptosis, and oxidative stress ( P < 0.05) in the spleen. The mechanisms of cell cycle blockage were closely related to the upregulation of the P53 and P21 genes ( P < 0.05), the downregulation of the cyclin D1 and CDK6 genes ( P < 0.05), and the decrease of proliferating cell nuclear antigen (PCNA) protein ( P < 0.05). The activated apoptosis resulted from the increased gene and protein expression of Bax and caspase-3 ( P < 0.05), and the decreased gene and protein expression of Bcl-2 ( P < 0.05). The results suggested that 70 ± 5 ppm NH3 caused the spleen dysplasia, which was closely related to the cell cycle arrest and mitochondrial apoptotic pathway activation.

Self-supporting nitrogen-doped reduced graphene oxide@carbon nanofiber hybrid membranes as high-performance integrated air cathodes in microbial fuel cells

The traditional air cathode in microbial fuel cell (MFC) usually consists of catalyst layer (CL), supporting layer (SL) and conductive gas diffusion layer (GDL), the overall MFC performance is inevitably affected by the additional and expensive adhesives and conductive agents. Here, we developed an integrated air cathode in MFC without any additional SL, GDL or adhesives. The integrated air cathode was self-supporting nitrogen-doped reduced graphene oxide@carbon nanofiber (N-rGO@CNF) hybrid membranes fabricated by electrospinning with subsequent heat-treatment under ammonia atmosphere. The as-fabricated N-rGO@CNFs possessed far superior MFC performance and oxygen reduction reaction (ORR) activity to the pristine nitrogen-doped carbon nanofibers (NCNF) and commercial activated carbon (CAC). The amount of rGO embedded into CNF had prominent influence on their ORR activities and MFC performances. N-5-rGO@CNF had the lowest resistance and the maximal exchange current density, exhibiting desirable oxygen reduction performance via a four-electron pathway. The maximum power density of N-5-rGO@CNF can reach 826 mW m−2 in MFC, which is approximately 9, 2.53 and 1.82 times of pristine NCNF, CAC and Pt/C with values of 91, 327 and 454 mW m−2. The outstanding performance of the integrated air-cathodes originates from the integrality, brevity and hybrid composition of the electrospun nanofiber membrane. The appropriate embedded rGO not only improves the bulk conductivity of the rGO@CNF to promote ion adsorption, but also provides vacancies to accommodate ions, the doped nitrogen atoms facilitate O2 adsorption and/or subsequent O–O bond breaking, thus improving the electrochemical performance of N-rGO@CNF in MFC.

Productive performance, lipid profile, immunity, and antioxidant parameters of quail breeders fed low protein diets supplemented with different zinc sources

The current study was conducted to study the impact of low-CP protein diets with different sources of zinc (zinc oxide-ZnO and zinc methionine-Zn-Met) on performance, lipid profile, immune and antioxidant parameters of quail breeders. A total number of 216 Japanese quail at 8 weeks of age were randomly distributed into nine (3 × 3) groups, with four replicates, each of six quails (four females and two males). Quails were fed three levels of CP (16, 18, and 20%) and three sources of Zn (0, 0.1 g ZnO, and 0.1 g Zn-Met/kg diets). No significant differences in daily feed intake (FI), feed conversion ratio (FCR), and egg mass are due to the main effect of protein levels or zinc sources at all ages. Dietary CP (16 and 20%) in growing quail diets increased SOD and GSH, while IgG levels were improved by 18%. Finally, it can be recommended that 16% CP and zinc source (Zn-Met or ZnO) can maintain egg mass, as well as lipid profile, immunological and antioxidant parameters in Japanese quails breeders. This level (16% CP) is enough during the production stage and a valuable way for mitigating ammonia pollution and reducing feeding costs.

Facile preparation of TPU conductive nanocomposites containing polypyrrole-coated multi-walled carbon nanotubes for a rapid and selective response in volatile organic compounds applications

Thermoplastic polyurethane (TPU) conductive nanocomposites were fabricated by using TPU as a matrix and polypyrrole (PPy) coating multi-walled carbon nanotubes (MWCNTs) as conductive filler. The microstructure and gas-sensitive response properties of the nanocomposites to volatile organic vapors (VOCs) were systematically investigated. FTIR and HRTEM verified that PPy was successfully encapsulated on the surface of MWCNTs. FESEM showed that homogeneous dispersion of MWCNTs-g-PPy conductive nanofillers contributed to the formation of continuous conductive networks. The obtained TPU/MWCNTs-g-PPy nanocomposites possessed certain gas-sensitive response selectivity, especially for ammonia gas when compared with other target VOCs. The gas-sensitive response values were in the range of 90–100% with a response time of 40–50 s. An excellent recovery performance at 500 ppm ammonia atmosphere was also achieved. Moreover, the gas-sensitive response values to ammonia showed a good linear relationship with the concentration of ammonia gas. The nanocomposites showed excellent stability in both ammonia and dry-air cycle detection.

Construction of recombinant Pichia pastoris strains for ammonia reduction by the gdhA and glnA regulatory genes in laying hens

Ammonia emissions have become an important environmental challenge for the livestock industry. Probiotics are often used as additives to reduce ammonia, and the ammonia reduction efficiency of common probiotics is approximately 20–40%. In this study, we constructed a gdhA recombinant Pichia pastoris strain, glnA recombinant Pichia pastoris strain and gdhA-glnA Pichia pastoris recombinant strain using the gdhA and glnA genes, which have the potential function of reducing ammonia emissions. The results of in vitro fermentation showed that compared with the control, wild-type Pichia pastoris and pPICZA strains, the gdhA, glnA and gdhA-glnA recombinant strains significantly reduced ammonia emissions in laying hens (P < 0.05), with emission reduction efficiencies of 63.95%, 65.68% and 74.04%, respectively. The reason may be that the recombinant Pichia pastoris strains can convert ammonium nitrogen into amino acids for self-growth through ammonia assimilation, and reduce the pH, uric acid and urea content in the intestinal tract of livestock and poultry, and urease activity. Therefore, the construction of recombinant strains can provide technical support for reducing ammonia pollution in the livestock industry.

The depth of the diffusion of nitrogen in 16MnCr5 steel after gas nitriding

This research aims to determine the depth of diffusion of nitrogen in steel 16MnCr5 after gas nitriding. Nitriding was performed in the ammonia atmosphere at three temperatures (510, 550 and 590°C), with four different durations for each temperature. The research techniques were metallographic and electron probe micro-analysis (EPMA). According to the first method, with the optical microscope Neophot 30 of the firm Carl Zeiss Jena, the surfaces of all samples were observed. The nitriding layers were photographed with the help of a microscope, from which the depths of nitrogen diffusion were determined. The hardness-depth profiles of nitride specimens were determined with a Vickers automatic micro-hardness tester from LECO, and the distance between two consecutive points was 50 μm. The depth of nitrogen diffusion into the nitride samples was determined from the hardness curves. The nitrogen concentration-depth profiles of the nitrided specimens were determined with EPMA using a Joel JXA-8900RL microanalyser operated at 20 kV. A comparison of the results of the different experimental methods was made, which allowed conclusions to be made as regards the depth of nitrogen diffusion in 16MnCr5 steel.

Odor emissions: A public health concern for health risk perception.

The olfactory nuisance, due to the emissions of active molecules, is mainly associated with unproperly managed waste disposal and animal farming. Volatile compounds e.g., aromatics, organic and inorganic sulfide compounds, as well as nitrogen and halogenated compounds are the major contributor to odor pollution generated by waste management plants; the most important source of atmospheric ammonia is produced by livestock farming. Although an odorous compound may represent a nuisance rather than a health risk, long-term exposure to a mixture of volatile compounds may represent a risk for different diseases, including asthma, atopic dermatitis, and neurologic damage. Workers and communities living close to odor-producing facilities result directly exposed to irritant air pollutants through inhalation and for this reason the cumulative health risk assessment is recommended. Health effects are related to the concentration and exposure duration to the odorants, as well as to their irritant potency and/or biotransformation in hazardous metabolites. The health effects of a single chemical are well known, while the interactions between molecules with different functional groups have still to be extensively studied. Odor emissions are often due to airborne pollutants at levels below the established toxicity thresholds. The relationship between odor and toxicity does not always occurs but depends on the specific kind of pollutant involved. Indeed, some toxic agents does not induce odor nuisance while untoxic agents do. Accordingly, the relationship between toxicity and odor nuisance should be always analyzed in detail evaluating on the characteristics of the airborne mixture and the type of the source involved.

Nitrogen-Doped Nanoporous Anodic Stainless Steel Foils towards Flexible Supercapacitors.

In this work, we report the fabrication and enhanced supercapacitive performance of nitrogen-doped nanoporous stainless steel foils, which have been prepared by electrochemical anodization and subsequent thermal annealing in ammonia atmosphere. The nanoporous oxide layers are grown on type-304 stainless steel foil with optimal thickness ~11.9 μm. The N-doped sample exhibits high average areal capacitance of 321.3 mF·cm−2 at a current density of 1.0 mA·cm−2, 3.6 times of increment compared with untreated one. Structural and electrochemical characterizations indicate that the significant enhancement is correlated to the high charge transfer efficiency from nitriding nanosheet products Fe3N. Our report here may provide new insight on the development of high-performance, low-cost and binder-free supercapacitor electrodes for flexible and portable electronic device applications with multiple anions.

Air contamination of therapeutic drug monitoring assay reagents results in falsely high plasma ammonia levels.

Accumulating evidence shows that contamination of blood samples by atmospheric ammonia affects blood ammonia test levels; however, reports on the effect of ammonia contamination of assay reagents are limited. Here, we aimed to clarify the effect of ammonia contamination of assay reagents, particularly the therapeutic drug monitoring (TDM) reagents, on the detection levels of blood ammonia using enzymatic assays. Ammonia gas was measured in the refrigerator compartment of the automatic analyser and the reaction tank water, probe wash water and drain outlets connected to the automatic analyser. At different time points following the closure of the cold storage, ammonia levels in quality control plasma samples were measured using three commercial assay reagents to evaluate the effect of air contamination. The distribution of evaporated ammonia in the reagent was measured using the CicaLiquid NH3 assay kit containing the assay reagent most affected by air contamination. It was confirmed that ammonia gas was generated in the cold storage of the automatic analyser. More than half of the reagents detected >0.25 ppm ammonia, and the highest concentration was detected in the TDM reagent. The ammonia levels obtained using all three reagents increased significantly after 3h of air contamination. The effect was resolved by measuring a 'dummy' sample or mixing the reagents by inversion. We demonstrated that air contamination by TDM reagents placed in cold storage could result in significantly falsely high ammonia measurements. Preventing this effect would improve the accuracy of ammonia measurements.

Three-dimensional Ni-MoN nanorod array as active and non-precious metal electrocatalyst for methanol oxidation reaction

• Three-dimensional Ni-MoN nanorod array electrocatalyst is facilely designed and synthesized. • The nitridation process ensures the uniform distribution of active Ni sites across the robust MoN nanorods. • The constructed Ni-MoN nanorod array exhibits a promising electrocatalytic activity towards methanol oxidation reaction. The development of direct methanol fuel cells requires low-cost, non-noble-metal electrocatalysts. However, it has not been widely used because of its limited activity, poor durability, and slow kinetics. Herein, the 3D nanostructured arrays of Ni-MoN composite nanorods were facilely prepared on the nickel foam (Ni-MoN NR/NF), which involves the direct hydrothermal synthesis of NiMoO 4 on NF and further nitridation treatment in the atmosphere of ammonia. The nitridation ensures the uniform distribution of active Ni sites across the robust MoN nanorods. Owing to the collaborative effect of Ni and the specific 3D MoN nanorod structure, the Ni-MoN NR/NF exhibits a promising electrocatalytic activity towards methanol oxidation reaction (MOR), which shows excellent activity (374 mA cm −2 @0.8 V vs. Hg/HgO), fast kinetics (40 mV dec −1 for the Tafel slope) and good stability. This work has shed light on the design of high-performance non-noble-metal electrocatalysts for MOR.

Effect of electric potentials on high‐temperature plasma nitriding of 2Cr13 stainless steel with active screen assisted

AbstractThe influence of electric potentials on the characteristics of modified layers with plasma nitriding of 2Cr13 stainless steel at a high temperature was investigated. Three active screens were placed on the cathodic plate. Three groups of 2Cr13 stainless steel samples were set with cathodic, anodic, and floating potentials. Samples were nitrided at 500 °C for 5 h in an ammonia atmosphere. The treated samples were analyzed using x‐ray diffraction, scanning electron microscopy with energy dispersive x‐ray spectroscopy, surface roughness tester, and atomic force microscopy. It is proved that nitriding treatments can be suitably carried out at three electric potentials, but the corresponding modified layers take on different microstructure, morphology, and hardness behaviors. It found that the three nitrided samples are mainly composed of the ϵ−Fe2‐3N and γ’−Fe4N phases. The order of thicknesses of the nitrided layers is: floating &lt; anodic &lt; cathodic potential. The results also demonstrated that electric potentials play essential roles in the corrosion resistance and tribological properties in plasma nitriding treatment. Because there is no visible precipitation of chromium nitride in the modified layer, the corrosion resistance of the floating nitrided sample is better than that of the other two samples.

A composite consisting of intermetallic Ni3Fe and nitrogen-doped carbon for electrocatalytic water oxidation: The effect of increased pyridinic nitrogen dopant

Nitrogen-doped carbon (NC) has been studied as electrocatalysts or electrocatalyst support and the nitrogen content in carbon matrix is mainly dependent on the nitrogen-rich precursors. In this study, we prepare a composite consisting of intermetallic Ni3Fe and NC ([email protected]) via simply heating under ammonia and argon mixed gas atmosphere (Ar/NH3), aiming to further increase the nitrogen content. Compared to [email protected], the NH3-derived electrocatalyst has more N atoms which are in the form of pyridinic N in carbon structure, significantly improving the electron transport efficiency and reaction kinetics, and thereby further boosting the electrocatalytic activity. This work demonstrates that the introduction of ammonia gas flow during calcination is a simple and effective strategy to increase the nitrogen content for engineering NC-based electrocatalysts toward high-performance water splitting.

Mapping gaseous dimethylamine, trimethylamine, ammonia, and their particulate counterparts in marine atmospheres of China’s marginal seas – Part 2: Spatiotemporal heterogeneity, causes, and hypothesis

Abstract. Spatiotemporal heterogeneities in the concentrations of alkaline gases and their particulate counterparts in the marine atmosphere over China's marginal seas were investigated in terms of causes and chemical conversion during two winter cruise campaigns, using semi-continuous measurements made by an onboard URG-9000D Ambient Ion Monitor-Ion Chromatograph (AIM-IC, Thermo Fisher). During the cruise campaign over the East China Sea from 27 December 2019 to 6 January 2020, the concentrations of gas-phase atmospheric trimethylamine (TMAgas) varied by approximately 1 order of magnitude, with an average (± standard deviation) of 0.10±0.04 µg m−3 corresponding to a mixing ratio of 26±17 pptv. Corresponding mean values were 0.037±0.011 µg m−3 (14±5 pptv in mixing ratio) over the Yellow Sea during the period from 7 to 16 January 2020 and 0.031±0.009 µg m−3 (12±4 pptv in mixing ratio) over the Yellow Sea and Bohai Sea from 9 to 22 December 2019. By contrast, the simultaneously observed concentrations of TMA in PM2.5, detected as TMAH+, over the East China Sea were 0.098±0.069 µg m−3 and substantially smaller than the 0.28±0.18 µg m−3 observed over the Yellow Sea and Bohai Sea from 9 to 22 December 2019. A significant correlation between TMAgas and particulate TMAH+ was observed over the East China Sea, but no correlation was found over the Yellow Sea and Bohai Sea. Proportional or disproportional variations in concentrations of TMAgas with particulate TMAH+ over the sea zones were probably attributed to the difference in the enrichment of TMAH+ in the sea surface microlayer. In addition, spatiotemporal heterogeneities in concentrations of atmospheric ammonia (NH3gas), atmospheric dimethylamine (DMAgas), and DMA in PM2.5, detected as DMAH+, were investigated. Case analyses were performed to illustrate the formation and chemical conversion of particulate aminium ions in marine aerosols. Finally, we hypothesized the release of basic gases and particulate counterparts from the ocean to the atmosphere, together with the secondary formation of DMAH+ and chemical conversion of TMAH+, in the marine atmosphere.

Assessment of Ammonia as a Biosignature Gas in Exoplanet Atmospheres.

Ammonia (NH3) in a terrestrial planet atmosphere is generally a good biosignature gas, primarily because terrestrial planets have no significant known abiotic NH3 source. The conditions required for NH3 to accumulate in the atmosphere are, however, stringent. NH3's high water solubility and high biousability likely prevent NH3 from accumulating in the atmosphere to detectable levels unless life is a net source of NH3 and produces enough NH3 to saturate the surface sinks. Only then can NH3 accumulate in the atmosphere with a reasonable surface production flux. For the highly favorable planetary scenario of terrestrial planets with hydrogen (H2)-dominated atmospheres orbiting M dwarf stars (M5V), we find that a minimum of about 5 ppm column-averaged mixing ratio is needed for NH3 to be detectable with JWST, considering a 10 ppm JWST systematic noise floor. When the surface is saturated with NH3 (i.e., there are no NH3-removal reactions on the surface), the required biological surface flux to reach 5 ppm is on the order of 1010 molecules/(cm2·s), comparable with the terrestrial biological production of methane (CH4). However, when the surface is unsaturated with NH3, due to additional sinks present on the surface, life would have to produce NH3 at surface flux levels on the order of 1015 molecules/(cm2·s) (∼4.5 × 106 Tg/year). This value is roughly 20,000 times greater than the biological production of NH3 on the Earth and about 10,000 times greater than Earth's CH4 biological production. Volatile amines have similar solubilities and reactivities to NH3 and hence share NH3's weaknesses and strengths as a biosignature. Finally, to establish NH3 as a biosignature gas, we must rule out mini-Neptunes with deep atmospheres, where temperatures and pressures are high enough for NH3's atmospheric production.

Oscillatory Mechanism of α-Fe(N) ↔ γ'-Fe4N Phase Transformations during Nanocrystalline Iron Nitriding.

The kinetics of nanocrystalline α-iron nitriding to γ’-iron nitride in an ammonia atmosphere was studied at 598–648 K and at atmospheric pressure. Oscillatory changes in nitriding reaction rates depending on nitrogen concentration in a solid sample were observed. This phenomenon was explained by a gradual change in the iron active surface coverage degree, with nitrogen resulting from a gradual change in the free enthalpy of nitrogen segregation. The α-Fe(N) nanocrystallites’ transformation into γ’-Fe4N went through six metastable FeNx states. The continuous function proposed by Fowler and Guggenheim was modified to a stepwise variable function.

Effects of Different Ammonia Concentrations on Pulmonary Microbial Flora, Lung Tissue Mucosal Morphology, Inflammatory Cytokines, and Neurotransmitters of Broilers.

Simple SummaryAmmonia is the dominant pollutant gas in poultry houses, and it is harmful to broilers, especially in the cold season. Exposure to ammonia leads to damage to the respiratory system of broilers, affects the health of broilers, and reduces production performance. To date, the relationship between lung flora and immune system and brain exposed to ammonia is unclear, and there have been numerous studies on the lung–brain axis in recent years. Therefore, the aim of this study is to explore the effects of ammonia on lung microflora, lung tissue mucosal morphology, inflammatory cytokines, and neurotransmitters. Moreover, exploring these mechanisms can help in the development of strategies that alleviate the negative effects of the performance of ammonia. Our study suggests that the damage caused by ammonia to broiler lungs may be mediated by the lung–brain axis.Atmospheric ammonia is one of the main environmental stressors affecting the performance of broilers. Previous studies demonstrated that high levels of ammonia altered pulmonary microbiota and induced inflammation. Research into the lung–brain axis has been increasing in recent years. However, the molecular mechanisms in pulmonary microbiota altered by ambient ammonia exposure on broilers and the relationship between microflora, inflammation, and neurotransmitters are still unknown. In this study, a total of 264 Arbor Acres commercial meal broilers (21 days old) were divided into 4 treatment groups (0, 15, 25, and 35 ppm group) with 6 replicates of 11 chickens for 21 days. At 7 and 21 D during the trial period, the lung tissue microflora was evaluated by 16S rDNA sequencing, and the content of cytokines (IL-1β, IL-6, and IL-10) and norepinephrine (NE), 5-hydroxytryptamine (5-HT) in lung tissue were measured. Correlation analysis was established among lung tissue microflora diversity, inflammatory cytokines, and neurotransmitters. Results showed that the broilers were not influenced after exposure to 15 ppm ammonia, while underexposure of 25 and 35 ppm ammonia resulted in significant effects on pulmonary microflora, inflammatory cytokines, and neurotransmitters. After exposure to ammonia for 7 and 21 days, both increased the proportion of Proteobacteria phylum and the contents of IL-1β and decreased the content of 5-HT. After exposure to ammonia for 7 days, the increase in Proteobacteria in lung tissue was accompanied by a decrease in 5-HT and an increase in IL-1β. In conclusion, the microflora disturbance caused by the increase in Proteobacteria in lung tissue may be the main cause of the changes in inflammatory cytokines (IL-1β) and neurotransmitters (5-HT), and the damage caused by ammonia to broiler lungs may be mediated by the lung–brain axis.