Atmospheric Ammonia Research Articles

Isotopic characteristics and source analysis of atmospheric ammonia during agricultural periods in the Xichuan area of the Danjiangkou Reservoir

Nitrogen deposition is an important means of exogenous nitrogen input in reservoir water. Agricultural activities around the reservoir lead to a sharp increase in the concentration of ammonia in the atmosphere, which poses a threat to the reservoir water body. Clarifying the contribution of agricultural ammonia release to atmospheric NHx (gaseous NH3 and particulate NH4+), in the reservoir area can provide a theoretical foundation for local reactive nitrogen control. We collected atmospheric NH3 and NH4+ samples during the agricultural periods and analyzed the isotopic characteristics of atmospheric NHx and the contribution rates of different ammonia sources in the Xichuan area of the Danjiangkou Reservoir. The results showed that the initial δ15N values of NH3 (–30.0‰ to –7.2‰) and particulate NH4+(–33‰ to +4.9‰ for finer and coarser particles, respectively) are different, and their contribution ratios from dissimilar ammonia sources are also different, among which NH4+ is more susceptible to meteorological factors. However, since the atmospheric NHx in the Xichuan area is mainly gaseous NH3, the final sources of atmospheric ammonia nitrogen source depend on gaseous NH3. Agricultural sources (59%-74%) were the main NH3 sources in this area. Among them, the fertilizer use emission was dominant; it had the highest contribution rate in summer during the agricultural period and a more prominent impact in areas with less human interference. Reasonable regulation of the application of high-ammonia releasing fertilizer, especially during the agricultural period in summer, is an effective way to reduce the threat of atmospheric ammonia to water health.

Measurement of methane, nitrous oxide and ammonia in atmosphere with a compact quartz-enhanced photoacoustic sensor

We demonstrated a 19-inches 6U-rack sensing system based on quartz-enhanced photoacoustic spectroscopy for simultaneous detection of methane, nitrous oxide, and ammonia in atmosphere. The system embeds two detection modules, each one equipped with a quantum cascade laser as light source and a spectrophone composed of a T-shaped quartz tuning fork coupled with acoustic resonator tubes. The sensing system results compact, lightweight, and portable, with a computer interface for an easy end-user operation. The calibration was performed in laboratory environment with certified concentrations. Because of the NH3 large and permanent dipole moment, ammonia QEPAS signal was used to model and characterize adsorption/desorption processes, for an accurate and reliable sensor calibration. At 0.1 s signal integration time, detection limits of 28 ppb, 9 ppb, and 6 ppb were obtained for CH4, N2O, and NH3, respectively. Since these detection limits were well below the natural abundance of the three analytes in atmosphere, the sensor was employed to monitor CH4, N2O, and NH3 concentrations in laboratory air.

Biomass coffee grounds derived nitrogen-doped ultrafine carbon nanoparticles as an efficient electrocatalyst to oxygen reduction reaction

A nitrogen-doped carbon-based catalyst (Fe-C-CG) to oxygen reduction reaction (ORR) is synthesized by pyrolyzing a precursor from coffee grounds, iron chloride and commercial carbon black in ammonia atmosphere. The coffee grounds are pyrolyzed to carbon particles with diameters about 20 nm with the facilitation of carbon black. The carbon nanoparticles show higher reactive activity with ammonia to achieve the doping of nitrogen atoms to carbon with 3.33 at% of content in Fe-C-CG, which is greater than 0.47 at% in the product from commercial carbon black (Fe-C). Resultantly, the Fe-C-CG exhibits high ORR activity with 0.87 V of half wave potential and 5.48 mA cm−2 of limited diffusion current, which highly surpass the 0.71 V, 4.19 mA cm−2 for Fe-C, and are comparable with 0.86 V and 4.52 mA cm−2 for Pt/C catalyst, respectively. The Zn-air battery assembled with Fe-C-CG delivers 142 mW cm−2 of maximum power density and 774 mAh g−1Zn of specific capacity, and can stably work at 1.212–1.257 V of discharge voltage at 10 mA cm−2. This work provides a strategy to prepare a nonprecious metal and nitrogen doped carbon catalyst to ORR by using biomass as the basic material.

Robust Porous TiN Layer for Improved Oxygen Evolution Reaction Performance.

The poor reversibility and slow reaction kinetics of catalytic materials seriously hinder the industrialization process of proton exchange membrane (PEM) water electrolysis. It is necessary to develop high-performance and low-cost electrocatalysts to reduce the loss of reaction kinetics. In this study, a novel catalyst support featured with porous surface structure and good electronic conductivity was successfully prepared by surface modification via a thermal nitriding method under ammonia atmosphere. The morphology and composition characterization-confirmed that a TiN layer with granular porous structure and internal pore-like defects was established on the Ti sheet. Meanwhile, the conductivity measurements showed that the in-plane electronic conductivity of the as-developed material increased significantly to 120.8 S cm−1. After IrOx was loaded on the prepared TiN-Ti support, better dispersion of the active phase IrOx, lower ohmic resistance, and faster charge transfer resistance were verified, and accordingly, more accessible catalytic active sites on the catalytic interface were developed as revealed by the electrochemical characterizations. Compared with the IrOx/Ti, the as-obtained IrOx/TiN-Ti catalyst demonstrated remarkable electrocatalytic activity (η10 mA cm−2 = 302 mV) and superior stability (overpotential degradation rate: 0.067 mV h−1) probably due to the enhanced mass adsorption and transport, good dispersion of the supported active phase IrOx, increased electronic conductivity and improved corrosion resistance provided by the TiN-Ti support.

A comparative study of real-time monitoring detection and active sampling measurements in evaluating exposure levels to ammonia.

Occupational exposure to ammonia is an important issue in the waste management sector, especially in composting and anaerobic digestion plants. In this sector, operators can be exposed to high contents of ammonia which is important to assess. The aim of this work was to provide a comparative study of two ammonia measurement techniques in the workplace air. The first one is an offline active collection of air samples that are then brought to laboratory for analysis and whose results are comparable to OELs. The second one involves real-time monitoring which is easy to deploy, allows for data to be processed both quickly and directly and to explain exposure peaks relative to workers’ activity. These two techniques were simultaneously deployed in several anaerobic digestion-composting plants to assess operators’ potential exposure to ammonia, and data were compared. Results show that there are linear correlations between concentrations obtained from both methods, with a trend to overestimate real concentrations in ammonia for several real-time detectors. This trend could however be explained by the time needed for exposure peaks to decrease. Real-time gas detectors, if cautiously used, are good investigation tools to quickly confirm or invalidate the presence of ammonia in the workplace atmosphere, and for both studying and optimising the workplace. The combination of both online and offline methods facilitates the analysis of a work area or station in order to improve the efficiency of prevention measures and to provide an accurate quantification of operators’ exposure for compliance checking of OELs.

Quantifying the importance of vehicle ammonia emissions in an urban area of northeastern USA utilizing nitrogen isotopes

Abstract. Atmospheric ammonia (NH3) is a critical component of our atmosphere that contributes to air quality degradation and reactive nitrogen deposition; however, our knowledge of NH3 in urban environments remains limited. Year-long ambient NH3 and related species were measured for concentrations and the nitrogen isotopic compositions (δ15N) of NH3 and particulate ammonium (pNH4+) were measured to understand the temporal sources and chemistry of NH3 in a northeastern US urban environment. We found that urban NH3 and pNH4+ concentrations were elevated compared to regional rural background monitoring stations, with seasonally significant variations. Local and transported sources of NHx (NH3+ pNH4+) were identified using polar bivariate and statistical back trajectory analysis, which suggested the importance of vehicles, volatilization, industry, and stationary fuel combustion emissions. Utilizing a uniquely positive δ15N(NH3) emission source signature from vehicles, a Bayesian stable isotope mixing model (SIMMR) indicates that vehicles contribute 46.8±3.5 % (mean ±1σ) to the annual background level of urban NHx, with a strong seasonal pattern with higher relative contribution during winter (56.4±7.6 %) compared to summer (34.1±5.5 %). The decrease in the relative importance of vehicle emissions during the summer was suggested to be driven by temperature-dependent NH3 emissions from volatilization sources, seasonal fuel-combustion emissions related to energy generation, and change in seasonal transport patterns based on wind direction, back trajectory, and NH3 emission inventory analysis. This work highlights that reducing vehicle NH3 emissions should be considered to improve wintertime air quality in this region.

Selenium Mitigates Ammonia-Induced Neurotoxicity by Suppressing Apoptosis, Immune Imbalance, and Gut Microbiota-Driven Metabolic Disturbance in Fattening Pigs.

Ammonia could be regarded as one detrimental pollutant with an acrid smell in livestock sheds. So far, the pig breeding industry became the main source of atmospheric ammonia. Previous literature demonstrated that excessive ammonia inhalation might cause a series of physiological damage to multiple organs. Unfortunately, the toxicity mechanisms of gaseous ammonia to the porcine nervous system need further research to elucidate. Selenium (Se) involves in many essential physiological processes and has a mitigative effect on the exogenous toxicant. There were scant references that corroborated whether organic Se could intervene in the underlying toxicity of ammonia to the hypothalamus. In the present study, multi-omics tools, ethology, and molecular biological techniques were performed to clarify the detailed mechanisms of relaxation effects of L-selenomethionine on ammonia poisoning. Our results showed that ammonia inhalation caused the clinical symptoms and the increment of positive apoptosis rate in the hypothalamus with the dysfunction of mitochondrial dynamics factors, while obvious mitochondria structure defects were observed. In parallel, the inflammation medium levels and gut microbes-driven metabolism function were altered to mediate the neurotoxicity in fattening pigs through the initiation of inflammation development. Interestingly, L-selenomethionine could attenuate ammonia toxicity by activating the PI3K/Akt/PPAR-γ pathway to inhibit the mitochondria-mediated apoptosis process, blocking the abnormal immune response and the accumulation of reactive oxygen species in the nucleus. Meanwhile, Se could enhance the production performance of fattening sows. Taken together, our study verified the novel hypothesis for the toxicity identification of aerial ammonia and provided a therapeutic strategy for the treatment of occupational poisoning.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12011-022-03434-w.

(Invited, Digital Presentation) Eco-Friendly and Sustainable Ammonia Production with Atmospheric Pressure Rotating Gliding Arc Discharge

Increasing fossil-free global energy demands have motivated the scientific community to investigate new clean and sustainable techniques that can meet global energy demands. The production of green and sustainable fuel, such as ammonia, from base molecules like water and nitrogen using electricity from renewable sources shows great potential to solve energy issues. Non-thermal atmospheric pressure plasma-based ammonia synthesis has great potential for carbon-free fertilizer production powered by renewable electricity. We developed an atmospheric pressure rotating gliding arc discharge reactor coupled with a catalyst for a higher ammonia production rate. Here we reported two-step ammonia production, including 1) facile production of NOx and hydrogen from nitrogen discharge in water, and 2) highly selective catalytic reduction of NOx to ammonia in the presence of hydrogen. The studied plasma technique offers ~0.84 % ammonia concentration with ~95 % selectivity and a 120 µmol/s production rate by integrating a catalytic reduction system with plasma. Compared with previous studies on ammonia synthesis from nitrogen, the remarkable ammonia yield (300–400-fold higher). These promising results provide a breakthrough in the transition toward sustainable and environmentally friendly ammonia production.

Wearable Conductive Polymer Matrix Composites for Breath Monitoring with Ammonia Detection

Conductive polymers, such as polyaniline (PANI), Polythiophene (PTh), polypyrrole (PPy), etc., are widely used for gas sensors due to their excellent electrical conductivity and low cost to manufacture [1]. In particular, PANI has attracted more attention due to its ease of synthesis, high environmental stability, and high reactivity with ammonia gas. In addition, the selection of acid-base dopant during the preparation process of polyaniline can adjust carrier concentrations for the change in electrical conduction or resistance to improve sensing properties. There have been many reports on the fabrication of flexible gas sensors using PANI [2-4]. Bandgar et al. [5] synthesized a low-temperature flexible polyaniline gas sensor by in-situ chemical oxidation polymerization of aniline on a polyethylene terephthalate (PET) substrate, showing 99% reproducibility, rapid response and recovery. Still, the response value was only 26% in 100 ppm ammonia atmosphere. Qi et al. [6] prepared a gas sensor by in-situ polymerization of aniline on non-woven fabric. The high air permeability of the fabric effectively improved the performance of the polyaniline-based gas sensor. Due to the outbreak of the COVID-19 pandemic, the use of face masks in public has become essential to reduce the spread of the virus. Some reports claim that the increased carbon dioxide in the mask over time may cause medical issues related to the respiratory system. Therefore, monitoring breathing air quality can help detect the wearer's vital conditions.In this study, we used a disposable mask as a flexible substrate to prepare polypropylene/carbon nanotube/polyaniline composite film through a layer-by-layer method. The polypropylene/carbon nanotube composite films were prepared by applying the carbon nanotube aqueous solution with surfactants evenly on the surface of a mask filter layer by a drop-coating method. Then, the in-situ polyaniline polymerization was performed on the surface of the polypropylene/carbon nanotube composite film through ammonium sulfate. The polypropylene/carbon nanotube /polyaniline composite film exhibits high sensitivity, fast sensing response/recovery time, room temperature operation, reliable flexibility, and cycle stability. The synthesized and wearable masks have demonstrated real-time detection respiratory rate and other breathing conditions such as CO2 and humidity. The ammonia gas sensing can also be used as a potential biomarker for health screening. The design and integration of multiple gas sensing materials in masks will help wearers better understand their own body conditions.

Regulating nitrogen vacancies within graphitic carbon nitride to boost photocatalytic hydrogen peroxide production

AbstractIntroducing nitrogen vacancies is an effective method to improve the catalytic performance of g‐C3N4‐based photocatalysts, whereas understanding how nitrogen vacancies types affect the catalytic performance remains unclear. Herein, two different types of nitrogen vacancies were successfully introduced into g‐C3N4 by pyrolysis of melamine under argon and ammonia atmosphere with subsequent HNO3 oxidation. The pyrolysis atmosphere is found to have a significant influence on the introduced nitrogen vacancies type, where tertiary nitrogen groups (N3C) and sp2‐hybridized nitrogen atoms (N2C) were the preferred sites for the formation of nitrogen vacancies under ammonia and argon pyrolysis, respectively. Moreover, nitrogen vacancies from N3C are experimentally and theoretically demonstrated to facilitate the narrowed band gap and the improved oxygen absorption capability. As expected, the optimal catalyst exhibits high H2O2 yield of 451.8 µM, which is 3.8 times higher than the pristine g‐C3N4 (119.0 µM) after 4 h and good stability after10 photocatalytic runs.

Sublethal ammonia induces alterations of emotions, cognition, and social behaviors in zebrafish (Danio rerio).

Ammonia pollutants were usually found in aquatic environments is due to urban sewage, industrial wastewater discharge, and agricultural runoff and concentrations as high as 180mg/L (NH4+) have been reported in rivers. High ammonia levels are known to impair multiple tissue and cell functions and cause fish death. Although ammonia is a potent neurotoxin, how sublethal concentrations of ammonia influence the central nervous system (CNS) and the complex behaviors of fish is still unclear. In the present study, we demonstrated that acute sublethal ammonia exposure can change social behavior of adult zebrafish. The exposure to 90mg /L of (NH4+) for 4h induced a strong fear response and lower shoaling cohesion; exposure to 180mg /L of (NH4+) for 4h reduced the aggressiveness, and social recognition, while the anxiety, social preference, learning, and short-term memory were not affected. Messenger RNA expressions of glutaminase and glutamate dehydrogenase in the brain were induced, suggesting that ammonia exposure altered glutamate neurotransmitters in the CNS. Our findings in zebrafish provided delicate information of ammonia neurotoxicity in complex higher-order social behaviors, which has not been revealed previously. In conclusion, sublethal and acute ammonia exposure can change specific behaviors of fish, which might lead to reductions in individual and population fitness levels.

Standoff sub-ppb level measurement of atmospheric ammonia with calibration-free wavelength modulation spectroscopy

Ammonia (NH3) plays a significant role in the formation of atmospheric particulate matter, and influences on environmental and public health as well as climate change. Thus, it is important to sensitive measurement of atmospheric NH3. In the present work, a sub-ppb level standoff open-path NH3 sensor was developed for on line, sensitive measurement of atmospheric NH3. A 9.06 μm distributed feedback quantum cascade laser was employed to probe the ammonia absorption lines located on fundamental rotational-vibrational absorption band and calibration-free wavelength modulation spectroscopy technique was employed to retrieve NH3 concentration directly. The standoff open-path NH3 sensor performance was investigated in laboratory corridor with 80 m open path length (Hefei, China) and a minimum detection limit of 0.46 ppb (3σ) was obtained. Finally, field campaign measurement was carried out in a winter wheat farmland (Changshu, China). Field measurement shown that the concentration of NH3 varies from 7 ppb to 30 ppb with an average of 14 ppb. The developed standoff sensor has high potential to be a robust tool for monitoring atmospheric NH3 or study of regional ammonia emissions in farmland or feedlot scale.

Formation mechanism and control strategy for particulate nitrate in China

Over the past decade, fine particulate matter (PM) pollution in China has been abated significantly, benefiting from strict emission control measures, but particulate nitrate continues to rise. Here, we review the progress in particulate nitrate (pNO3−) pollution characterization, nitrate formation mechanisms, and the proposed control strategies in China. The spatial and temporal distributions of pNO3− are summarized. The current status of knowledge on the chemical mechanism is updated, and the significance of its formation pathways is assessed by various approaches such as field observation and modelling of nitrate production rate, as well as isotopic analysis. The factors impacting pNO3− formation and the corresponding pollution regulation strategies are discussed, in which the importance of atmospheric oxidation capacity and ammonia are addressed. Finally, the challenges and open questions in pNO3− pollution control in China are outlined.

Mo2N as a high-efficiency catalyst for transfer hydrogenation of nitrobenzene using stoichiometric hydrazine hydrate

A straightforward and commonly-used approach of direct pyrolysis for the preparation of molybdenum nitride (Mo2N) is conducted via reduction of MoO3 under ammonia atmosphere. The as-synthesized Mo2N catalyst demonstrated high activity for transfer hydrogenation of nitrobenzene, giving a 99% aniline yield at near-room temperature of 30 °C within only 50 min. More significantly, the amount of the hydrogen donor hydrazine monohydrate (N2H4·H2O) can be limited to stoichiometric molar ratio (-NO2: N2H4·H2O = 1: 1.5), preventing the possible generation of hazardous NH3, which is seldom reported in previous protocols. Through various characterizations and control experiments, conclusively, the remarkable catalytic performance of Mo2N catalyst should be credited to the large quantity of Lewis-acidic Mo sites. This research might provide a practical approach to aromatic amines production.

Regional social-ecological system coupling process from a water flow perspective

The social-ecological system is receiving more and more attention, and water resources have been a focal point for linking social systems and ecosystems, but how to clarify the regional social-ecological system coupling process through the water flow perspective and how to make ecosystem services management decisions still needs further research. This study integrates water quantity and quality and proposes a water-related ecosystem services flow framework. This study applied the framework to the Wuding River watershed and simulated water quantity and quality by SWAT model. The results showed that: (1) there is significant spatial heterogeneity in ecosystem service provisioning and meaningful improvement in water quality under the function of human-made capital in the green phase of the ecosystem services flow; (2) in the red phase, beneficiaries use the water supply for their production and life and discharge >7400 tons pollution loads into the ecosystem; (3) in this process, human-made capital reduces about 35 % of the ammonia pollution, and meanwhile, the ecosystem relies on its environment to further clean up about 44 % of the load. The research framework is suitable for watershed social-ecological systems with simplistic interactions, guiding ecological compensation schemes and related management policies. Furthermore, providing a scientific basis for the sustainable use of regional water resources.

Cracking behavior of AISI 316L stainless steel powder by gas nitriding and its influence on spark plasma sintering

In this study, the effect of nitriding temperature on the deformation behavior of spherical AISI 316L powders was investigated. The results showed that the nitrogen content in powders was significantly increased by increasing the nitriding temperature under ammonia atmosphere. However, the resulted residual stress led to the deformation or even cracking in powders, the cause of drastic changes in the bulk density and fluidity of powders. Furthermore, the microstructure and properties of alloys synthesized by spark plasma sintering were also analyzed. The obtained results also indicate that the powder deformation has no influence on the consistency of sintered samples, but the nitriding temperature of AISI 316L powder obviously affects the morphology and performance of sintered samples. Nitrogen initially exists as interstitial atom in the steels till the nitriding temperature rises to 500 °C where nitrides begin to precipitate in the sample. Such morphological transition of nitrogen atoms has a significant impact on the mechanical properties of the alloys. The better corrosion resistance of the alloy prepared over 500 °C in 3.5 wt.% NaCl solution shows that the nitriding temperature also matters for corrosion performance.

Is fertilization the dominant source of ammonia in the urban atmosphere?

It was previously believed that ammonia (NH3) has a short residence time in the atmosphere and cannot be transported far from its sources. In late March, however, this study observed a severe NH3 episode in urban Beijing when fertilizer was intensively applied on the North China Plain, with the highest hourly concentrations of 66.9 μg m-3 throughout the year. The stable nitrogen isotopic composition of NH3 (δ15N-NH3) during this episode (-37.0 to -20.0‰) fell in the range of endmembers of fertilizer and livestock, suggesting the long-range transport of NH3 from agricultural to urban regions. Based on a Bayesian isotope mixing model, the contribution of agriculture (fertilization) to urban NH3 concentrations was apportioned as 43.5% (26.0%) on polluted days. However, these contributions were reduced to 29.1% (12.8%) when nitrogen isotope fractionation between NH3 and ammonium was considered. In contrast to the limited contribution of agricultural sources, we found that nonagricultural emissions, particularly vehicles, dominate the source of NH3 in urban Beijing, even during the fertilization period. This finding indicated that nonagricultural sources should be considered when designing a control strategy for NH3 to reduce haze pollution in the urban atmosphere.

Increasing the accuracy of atmospheric ammonia concentrations calculated from Open-Path Fourier transform infrared spectra using partial least squares model by scanning and removing interference spectral data

Monitoring atmospheric pollutants has raised worldwide concerns in last decades, due to deterioration of air quality. Multivariate regression methods have gained extensive applications in calculating and monitoring concentrations of air pollutants, for example ammonia (NH 3 ), using Open-Path Fourier Transform Infrared (OP/FT-IR) spectra data. However, the prediction accuracy of multivariate regression models is interfered heavily by the dominant and omnipresent absorption bands of atmospheric H 2 O vapor and CO 2 in OP/FT-IR spectra. Hence, a new method of variable selection, referred to as window of scanning and removing interference information (WSRII), is developed to remove interference data of OP/FT-IR spectra. The key of WSRII is to confirm informative variables according to the change of root mean square error of calibration in the partial least squares regression (PLSR) model after removing a spectral window. If the change is greater than 0, the spectral window is reserved as an informative information window. Then, the new matrixes of spectral data are reconstructed by using the informative information windows, which are selected by changing position of the spectral window in full wave number range. Based on this, a PLSR model is rebuilt to predict accurately NH 3 concentrations. The results showed that the proposed method was able to eliminate uninformative information and improved prediction accuracy of PLSR models. Moreover, this process of variable selection is significantly potential to improve prediction accuracy of PLSR model for monitoring atmospheric NH 3 concentrations in real time.

Effects of Feed-Through Sulfur on Growth Performance, Atmospheric Ammonia Levels, and Footpad Lesions in Broilers Raised Beginning with Built-Up Litter.

Simple SummaryDuring commercial farming of chickens, accumulation of feces and moisture in the litter on the floor of the chicken house can lead to ammonia production by natural bacteria in the litter that ingest the chicken feces. Excessive ammonia levels can lead to health problems for the chickens, which can inhibit their growth and cause sores on their breasts and paws. To mitigate this animal welfare issue, this experiment tested the use of sulfur as a feed additive (feed-through sulfur) to acidify chicken feces and prevent ammonia from being formed from bacterial action. In this experiment, feed-through sulfur was tested on three different flocks of chickens. The combination of feed-through sulfur with a traditional litter acidifier, sodium bisulfate, showed improved ammonia control over sodium bisulfate alone in one flock. For the other two flocks, ammonia control was similar between feed-through sulfur with sodium bisulfate and sodium bisulfate alone. In addition, litter acidification was best with the combination of feed-through sulfur and sodium bisulfate in 2 out of 3 flocks. These results indicate the possibility that adding sulfur to feed while also using sodium bisulfate litter treatment may work together to better control ammonia in the chicken house.To the poultry industry, ammonia accumulation within poultry houses can be a costly issue, as this can lead to problems with bird performance, damage to economically important parts such as paws, and customer disapproval due to animal welfare concerns. Common management practices for ammonia control can be quite effective; however, these methods are used variably from farm to farm, which necessitates ammonia control measures that poultry companies can more uniformly implement across all contract growers. One possible measure is ammonia control through feed additives, which would allow poultry companies more direct control over the treatment. This project explored the efficacy of elemental sulfur added directly to the feed (feed-through sulfur) in controlling litter ammonia levels, live performance, and paw quality of broilers raised on built-up litter over three successive flocks. Feed-through sulfur on its own showed inconsistent effects on performance or footpad lesions after 38 days of production compared to sodium bisulfate or control treatments. However, combination of feed-through sulfur and sodium bisulfate showed a potential synergistic effect on ammonia levels and litter pH, although there were few differences between treatments and controls; therefore, additional research must be explored to confirm these observations.

New insight into ammonium removal in riverbanks under the exposure of microplastics

Riverbanks play the key role in ammonium removal from runoff entering river. Currently, microplastics (MPs) are frequently detected in riverbanks receiving urban and agricultural runoff. Nevertheless, the effect of MPs accumulation on ammonium removal in riverbanks is still unknown. We utilized sediment flow-through reactors to investigate the impact and mechanism of MPs accumulation on ammonium removal in riverbanks. These results revealed that MPs accumulation decreased ammonium removal in sediment by 8.2 %−12.8 % resulting from the reduction in nitrifier abundance (Nitrososphaera and Nitrososphaeraceae) and genes encoding ammonium and hydroxylamine oxidation (amoA, amoB, amoC, and hao) by MPs accumulation. Furthermore, MPs accumulation decreased the substrate and gene abundance of hydroxylamine oxidation process to reduce N2O emission (16.3 %−34.3 %). Notably, mathematic model verified that sediment physical properties changed by MPs accumulation were direct factors affecting ammonium removal in riverbank. It was suggested that both the biotoxicity of MPs and sediment physical properties should be considered in the ammonium removal process. To summarize, this study for the first time comprehensively clarifies the impact of MPs on the ammonium removal capacity of riverbanks, and provides information for taking measures to protect the ecological function of the riverbank and river ecosystem from MPs and ammonium pollution.