Excess Ammonium Research Articles

Recovery of Phosphate and Ammonium from Dairy Cow Urine by Struvite Crystallization with Vertical Reactor

Excess phosphate (PO43-) and ammonium (NH4+) in wastewater can cause environmental damages, such as pollutants and eutrophication in water. Dairy cow urine is a dangerous liquid waste that contains high amounts of phosphate and ammonium. The removal of PO4 and NH4 components can be done by crystallizing them into struvite fertilizers. Struvite (MgNH4PO4.6H2O) is a mineral formed from magnesium, ammonium, and phosphate with the equimolar ratio. The crystallization process of struvite is carried out using a vertical reactor. MAP solution (magnesium ammonium phosphate) is prepared by reacting MgCl2, H3PO4, and dairy cow urine with MAP molar ratio of 1 : 1 : 1 and KOH 1N. The study run in pH 8; 8.5; 9; 9.5; 10 and temperature variations of 25, 30, 35, 40, 45˚C in vertical reactor continuously. The struvite precipitate was filtered and dried, it is analyzed by XRF to determine the struvite composition and SEM to determine the morphology of the struvite. The results showed that the best percentage of phosphate and ammonium was at 45˚C and pH 9.5, it was 33.2% and 27.9%.

S2532 Hyperammonemia Over 500 µmol/L as a Cause of the Seizure

INTRODUCTION: Hyperammonemia is a dangerous metabolic disturbance characterized by an excess of ammonia in the blood that may lead to cerebral edema, brain injury, and death. It is commonly secondary to acute or chronic liver failure, inborn errors of metabolism, upper gastrointestinal bleeding, medication-induced, chemotherapy, and non-hepatic causes such as ureterosigmoidostomy, and infections. Hyperammonemia is a life-threatening condition that can affect patients of any age. Elevations of ammonia in plasma could be either from increased production or decreased detoxification. The hepatic urea cycle is the main pathway to detoxify ammonia. It can become defective due to an inherited enzyme deficiency or secondary to accumulated toxic metabolites. CASE DESCRIPTION/METHODS: An 83-Year-old female with history of chronic kidney disease presented with acute loss of motor function in the bilateral lower extremities and areflexia. The initial working diagnosis was cord infarct or cord related to lower motor neuron disease. Lumbar puncture and spinal cord MRI were unrevealing. Ammonia level was 595µmol/L. The patient was transferred to ICU where she started to have seizures. She was started on lactulose and Keppra. CTA of the abdomen showed extensive atherosclerotic changes in her mesenteric vessels. She was started on continuous dialysis, but became hypotensive requiring inotropes and later expired. DISCUSSION: There is a poor correlation between plasma ammonia levels and patients' mental status. However, studies have shown that sustained ammonia levels above 150 to 200 µmol/L greatly increase intraneuronal osmolality and increase the risk for intracranial hypertension leading to encephalopathy. An absolute ammonia level above which dialysis is recommended in adults is not well defined and relies heavily on clinical evaluation. Monitoring ammonia levels, neurologic status, arterial or venous pH, and hemodynamic parameters in hyperammonemia patients could prompt for acute dialysis. Dialysis can be discontinued once the mental status is restored to the baseline and ammonia levels have declined or stabilized. Hyperammonemia must be excluded in patients with an unexplained change in consciousness or encephalopathy. Early detection and treatment of hyperammonemia with medical and supportive management is crucial. Ammonia is a dialyzable agent and can be easily removed via renal replacement therapy.

Chemocline collapse in Lake Kivu as an analogue for nitrogen cycling during Oceanic Anoxic Events

One of the outstanding issues in the study of nutrient dynamics during Oceanic Anoxic Events (OAEs) is the preservation of 15N-depleted nitrogen isotope signals, which are not observed in analogous modern environments. The favored mechanism for δ15N values below 0‰ is utilization of excess ammonium derived from underlying anoxic waters by primary producers. However, there are few modern examples available for testing this hypothesis, due to the overall well-oxygenated state of modern oceans. Here, we present sedimentary δ13Corg and δ15Nbulk data, as well as pigment biomarker ratios, from the sediments of Lake Kivu, a meromictic lake in East Africa. This system serves as a potential analogue for the development of strongly depleted δ15Nbulk in OAE black shales. We focus on intervals of organic carbon enrichment (sapropels) that are interpreted to have been the result of lake water column mixing events. Sediment δ13Corg and δ15Nbulk decrease by up to 6 and 4‰ respectively near the base of sapropel layers. These negative excursions provide evidence for the mixing of 13C-depleted dissolved inorganic carbon and ammonium in excess of photosynthetic need, derived from the deeper anoxic basin of the lake. Support of this model is also provided by photosynthetic pigment biomarkers which show significant fluctuations in phototrophic ecology consistent with water column mixing and changes in nutrient status. Further evidence for the shallowing of the chemocline during sapropel deposition is found in the presence of bacteriochlorophyll derivatives produced by phototrophic sulfide oxidizers.

Enrichment of Comammox and Nitrite-Oxidizing Nitrospira From Acidic Soils.

In agricultural soils fertilized with a high amount of ammonium nitrogen, the pH decreases because of the oxidation of ammonia by nitrifiers. Molecular-based analyses have revealed that members of the genus Nitrospira dominate over other nitrifiers in some acidic soils. However, terrestrial Nitrospira are rarely cultivated and little is known about their ecophysiology. In addition, recent studies discovered a single microbe with the potential to oxidize both ammonia and nitrite (complete ammonia oxidizer; comammox) within Nitrospira, which had been previously recognized as a nitrite oxidizer. Despite their broad distribution, there are no enrichment samples of comammox from terrestrial or acidic environments. Here, we report the selective enrichment of both comammox and nitrite-oxidizing Nitrospira from the acidic soil of a heavily fertilized tea field. Long-term enrichment was performed with two individual continuous-feeding bioreactors capable of controlling ammonia or nitrite concentration and pH. We found that excessive ammonium supply was a key factor to enhance the growth of comammox Nitrospira under acidic conditions. Additionally, a low concentration of nitrite was fed to prevent the accumulation of free nitrous acid and inhibition of cell growth under low pH, resulting in the selective enrichment of nitrite-oxidizing Nitrospira. Based on 16S rRNA gene analysis, Nitrospira accounting for only 1.2% in an initial soil increased to approximately 80% of the total microorganisms in both ammonia- and nitrite-fed bioreactors. Furthermore, amoA amplicon sequencing revealed that two phylotypes belonging to comammox clade A were enriched in an ammonia-fed bioreactor. One group was closely related to previously cultivated strains, and the other was classified into a different cluster consisting of only uncultivated representatives. These two groups coexisted in the bioreactor controlled at pH 6.0, but the latter became dominant after the pH decreased to 5.5. Additionally, a physiological experiment revealed that the enrichment sample oxidizes ammonia at pH <4, which is in accordance with the strongly acidic tea field soil; this value is lower than the active pH range of isolated acid-adapted nitrifiers. In conclusion, we successfully enriched multiple phylotypes of comammox and nitrite-oxidizing Nitrospira and revealed that the pH and concentrations of protonated N-compounds were potential niche determinants.

Simultaneous Low-Order Phase Suppression and Defect Passivation for Efficient and Stable Blue Light-Emitting Diodes

Quasi-two-dimensional (quasi-2D) perovskite is rising as a promising luminescent material for blue perovskite light-emitting diodes (PeLEDs). However, typical quasi-2D perovskites show a wide distribution of low-order phases and low efficiency owing to the inefficient energy transfer. Meanwhile, the defects and traps generated during the perovskite crystallization increase nonradiative recombination, further aggravating the external quantum efficiency (EQE). Herein, we demonstrate a unique quasi-2D perovskite with low-order phase suppression and defect passivation for efficient energy transfer and light emission by incorporating a 2D perovskite and an excess ammonium salt into the quasi-2D perovskite solution. By optimizing the new class of quasi-2D perovskite, we achieve blue PeLEDs with the brightness of 1765 cd m–2, EQE of 7.51%, low turn-on voltage of 3.07 V, and long operation lifetime of 3961 s under constant driving current without any shift of the electroluminescence spectra. The work contributes to promoting efficient and stable blue PeLEDs.

Multi-Step Synthesis of Biologically Active Novel N-Benzyl-3,5-Bis(Arylidene)-Piperidin-4-Ones and Some Derived Bicyclic and Tricyclic Ring Systems as Macromolecules

This study reports the synthesis of some new bicyclic and tricyclic heterocyclic macromolecules incorporated pyrano[3,2-c]pyridine, 1,6-naphthyridine, and pyrimidonaphthyridine rings starting from new dienones, N-benzyl-3,5-bis(arylidene)-piperidin-4-ones. The chemistry involved the cyclocondensation of dienones with malononitrile in the presence of piperidine yielded the target 2-aminopyranopyridine-3-carbonitriles. The reaction of dienones with malononitrile or ethyl cyanoacetate in the presence of excess ammonium acetate afforded the corresponding 2-aminonaphthyridines and/or 2-oxonaphthyridine derivatives, respectively, in good yields. The 2,4-disubstituted pyrimido[4,5-b][1,6]naphthyridines were successfully achieved from the reaction of the 2-aminonaphthyridine derivatives with the appropriate reagents. The structures of the isolated products were determined by elemental analysis and spectral methods (FT-IR, 1H-NMR, and 13C-NMR). The cytotoxicity of some of the prepared derivatives was also investigated.

Hydrogeological controls on ammonium enrichment in shallow groundwater in the central Yangtze River Basin

The controlling processes of excessive ammonium in surface water and groundwater in the central Yangtze River Basin remain unclear. In this study, monitoring of water levels and temporal-spatial distributions of major N compounds were implemented at the large Jiangshan plain and at the local site scale in the central Yangtze River Basin. The results indicate that the recharge, movement and transformation of ammonium were controlled by hydrogeological conditions. Manure and sewage from anthropogenic activities were identified as the main source of nitrogen compounds. The nitrogen loading into aquifers were governed by water table and groundwater flow. After entering subsurface soils, nitrification and dissimilatory nitrate reduction to ammonium (DNRA) were proposed as the ammonium consumption and production mechanisms, respectively, by combining the concentrations of ammonium‑nitrogen and nitrate‑nitrogen with the corresponding isotopic compositions. These microbially mediated processes controlling transport and transformation of nitrogen compounds were influenced by the seasonally varying groundwater flow regime that changed the redox conditions in the aquifers. In the subsurface environments, ammonium was converted to nitrate when sufficient oxygen supply was available, and this process was reversed under anoxic conditions along the groundwater flow path. A conceptual model for the reactive transport of nitrogen compounds jointly controlled by the vertical groundwater flows and biogeochemical processes was proposed, which provides new insights into the genesis of high ammonium groundwater.

Glutamate over-accumulation may serve as an endogenous indicator of tricarboxylic acid (TCA) cycle suppression under NH4+ nutrition in wheat (Triticum aestivum L.) seedlings

Soil excess ammonium (NH4+) has serious negative effects on crop growth and yield formation. Most studies of NH4+ stress have addressed only the effects of free NH4+, failing to recognize changes in nitrogen (N) assimilation products. Hydroponic experiments were conducted using 5 mM NH4+ or nitrate (NO3−) forms of N in two wheat cultivars that differed in NH4+ tolerance (NH4+-sensitive AK58 and NH4+-tolerant XM25). To evaluate the effects of NH4+ assimilation products on plant growth, 1 μM l-methionine sulfoximine (MSO, an inhibitor of glutamine synthetase) and 1 mM glutamate (a primary N assimilation product) were added to the N source solutions. NH4+ treatments significantly reduced plant biomass in both cultivars, but to a greater extent in AK58. These inhibition effects were alleviated by MSO and strengthened by the application of glutamate. The free NH4+ concentration was increased under NH4+ conditions and was enhanced by the application of MSO. Amino acids levels were significantly greater in both cultivars; however, XM25 showed a lower glutamate concentration and a lower ratio of (glutamate + glutamine) to (aspartic acid + asparagine) than AK58. Under NH4+ conditions, levels of tricarboxylic acid (TCA) cycle intermediates and adenosine triphosphate were decreased due to inhibited pyruvate kinase activity; this inhibition was enhanced by the application of glutamate, but relieved by MSO. These results show that, aside from the large amounts of free NH4+ in wheat tissues, as a primary N assimilation product, the over-accumulated glutamate is also involved in interrupting TCA cycle metabolism under NH4+ stress, leading to reduced plant growth.

Function and Regulation of Ammonium Transporters in Plants.

Ammonium transporter (AMT)-mediated acquisition of ammonium nitrogen from soils is essential for the nitrogen demand of plants, especially for those plants growing in flooded or acidic soils where ammonium is dominant. Recent advances show that AMTs additionally participate in many other physiological processes such as transporting ammonium from symbiotic fungi to plants, transporting ammonium from roots to shoots, transferring ammonium in leaves and reproductive organs, or facilitating resistance to plant diseases via ammonium transport. Besides being a transporter, several AMTs are required for the root development upon ammonium exposure. To avoid the adverse effects of inadequate or excessive intake of ammonium nitrogen on plant growth and development, activities of AMTs are fine-tuned not only at the transcriptional level by the participation of at least four transcription factors, but also at protein level by phosphorylation, pH, endocytosis, and heterotrimerization. Despite these progresses, it is worth noting that stronger growth inhibition, not facilitation, unfortunately occurs when AMT overexpression lines are exposed to optimal or slightly excessive ammonium. This implies that a long road remains towards overcoming potential limiting factors and achieving AMT-facilitated yield increase to accomplish the goal of persistent yield increase under the present high nitrogen input mode in agriculture.

Genome-wide identification of the amino acid permease genes and molecular characterization of their transcriptional responses to various nutrient stresses in allotetraploid rapeseed

BackgroundNitrogen (N), referred to as a “life element”, is a macronutrient essential for optimal plant growth and yield production. Amino acid (AA) permease (AAP) genes play pivotal roles in root import, long-distance translocation, remobilization of organic amide-N from source organs to sinks, and other environmental stress responses. However, few systematic analyses of AAPs have been reported in Brassica napus so far.ResultsIn this study, we identified a total of 34 full-length AAP genes representing eight subgroups (AAP1–8) from the allotetraploid rapeseed genome (AnAnCnCn, 2n = 4x = 38). Great differences in the homolog number among the BnaAAP subgroups might indicate their significant differential roles in the growth and development of rapeseed plants. The BnaAAPs were phylogenetically divided into three evolutionary clades, and the members in the same subgroups had similar physiochemical characteristics, gene/protein structures, and conserved AA transport motifs. Darwin’s evolutionary analysis suggested that BnaAAPs were subjected to strong purifying selection pressure. Cis-element analysis showed potential differential transcriptional regulation of AAPs between the model Arabidopsis and B. napus. Differential expression of BnaAAPs under nitrate limitation, ammonium excess, phosphate shortage, boron deficiency, cadmium toxicity, and salt stress conditions indicated their potential involvement in diverse nutrient stress responses.ConclusionsThe genome-wide identification of BnaAAPs will provide a comprehensive insight into their family evolution and AAP-mediated AA transport under diverse abiotic stresses. The molecular characterization of core AAPs can provide elite gene resources and contribute to the genetic improvement of crop stress resistance through the modulation of AA transport.

Internal ammonium excess induces ROS-mediated reactions and causes carbon scarcity in rice

BackgroundOveruse of nitrogen fertilizers is often a major practice to ensure sufficient nitrogen demand of high–yielding rice, leading to persistent NH4+ excess in the plant. However, this excessive portion of nitrogen nutrient does not correspond to further increase in grain yields. For finding out the main constraints related to this phenomenon, the performance of NH4+ excess in rice plant needs to be clearly addressed beyond the well-defined root growth adjustment. The present work isolates an acute NH4+ excess condition in rice plant from causing any measurable growth change and analyses the initial performance of such internal NH4+ excess.ResultsWe demonstrate that the acute internal NH4+ excess in rice plant accompanies readily with a burst of reactive oxygen species (ROS) and initiates the downstream reactions. At the headstream of carbon production, photon caption genes and the activity of primary CO2 fixation enzymes (Rubisco) are evidently suppressed, indicating a reduction in photosynthetic carbon income. Next, the vigorous induction of glutathione transferase (GST) genes and enzyme activities along with the rise of glutathione (GSH) production suggest the activation of GSH cycling for ROS cleavage. Third, as indicated by strong induction of glycolysis / glycogen breakdown related genes in shoots, carbohydrate metabolisms are redirected to enhance the production of energy and carbon skeletons for the cost of ROS scavenging. As the result of the development of these defensive reactions, a carbon scarcity would accumulatively occur and lead to a growth inhibition. Finally, a sucrose feeding cancels the ROS burst, restores the activity of Rubisco and alleviates the demand for the activation of GSH cycling.ConclusionOur results demonstrate that acute NH4+ excess accompanies with a spontaneous ROS burst and causes carbon scarcity in rice plant. Therefore, under overuse of N fertilizers carbon scarcity is probably a major constraint in rice plant that limits the performance of nitrogen.

Composition, diversity, and activity of aerobic ammonia-oxidizing Bacteria and Archaea in the intertidal sands of a grand strand South Carolina beach.

Aerobic ammonia oxidation to nitrite has been established as an important ecosystem process in regulating the level of nitrogen in marine ecosystems. This process is carried out by ammonia‐oxidizing bacteria (AOB) within the classes Betaproteobacteria and Gammaproteobacteria and ammonia‐oxidizing Archaea (AOA) from the phylum Thaumarchaeota, and the latter of which has been established as more prevalent in marine systems. This study investigated the presence, abundance, and activity of these groups of microbes at a beach near Springmaid Pier in Myrtle Beach, South Carolina, through the implementation of next generation sequencing, quantitative PCR (qPCR), and microcosm experiments to monitor activity. Sequencing analysis revealed a diverse community of ammonia‐oxidizing microbes dominated by AOA classified within the family Nitrosopumilaceae, and qPCR revealed the abundance of AOA amoA genes over AOB by at least an order of magnitude in most samples. Microcosm studies indicate that the rates of potential ammonia oxidation in these communities satisfy Michaelis–Menten substrate kinetics and this process is more active at temperatures corresponding to summer months than winter. Potential rates in AOA medium were higher than that of AOB medium, indicating a potentially greater contribution of AOA to this process in this environment. In conclusion, this study provides further evidence of the dominance of AOA in these environments compared with AOB and highlights the overall efficiency of this process at turning over excess ammonium that may be present in these environments.

Silicon mitigates ammonium toxicity in plants

AbstractThe search for high yield has identified ammonium toxicity as a problem in arable soils world wide. Ammonia toxicity can be suppressed by the use of silicon, but this fact still needs to be elucidated. Therefore, this review aimed to highlight the harmful effects of ammonium toxicity on model plants, and to determine the effects of Si on the mitigation of abiotic stress. Some plant species are considered as tolerant, and others as sensitive to high N concentrations. In sensitive plants, high ammonium concentrations may hinder the plant's development and even lead to the plant's death due to biochemical, physiological, and nutritional changes. Studies have demonstrated that silicon can mitigate or alleviate the deleterious effects caused by the toxic effect of NH4+. These findings were attributed to improvements in the physiological and nutritional parameters of plants. Given the importance of ionic balance between N forms for the plant's development, further studies must be performed to detect mechanisms promoted by Si to decrease or mitigate the harmful effects caused by excess ammonium in plants.

Heterogeneous expression of the ammonium transporter AgAmt in chemosensory appendages of the malaria vector, Anopheles gambiae

Ammonia is one of the principal kairomones originating from human and other animal emanations and in that context, plays an essential role in the host-seeking behaviors of the malaria vector mosquito Anopheles gambiae. Nevertheless, despite its importance in directing host-seeking, the mechanisms underlying ammonia detection in the mosquito olfactory system remains largely unknown. In addition to ongoing efforts to identify and characterize the molecular receptors that underlie ammonia sensitivity, previous studies have revealed a prominent role for ammonium transporters (Amt) in modulating antennal and behavioral responses in Drosophila melanogaster and An. gambiae. In the former, localization of DmAmt in antennal sensilla to auxiliary cells surrounding the ammonia sensory neurons led to the hypothesis that its role was to clear excess ammonium ions in the sensillar lymph. In the latter, RT-PCR and heterologous expression have been used to examine the expression and functional characteristics of the An. gambiae ammonium transporter, AgAmt. We now employ advanced transgenic tools to comprehensively examine AgAmt spatial localization across the peripheral chemosensory appendages in larvae and adult female An. gambiae. In the larval antennae, AgAmt appears localized in both neuronal and auxiliary cells. In contrast to D. melanogaster, in the adult antennae, AgAmt-derived signals are observed in both non-neuronal auxiliary cells and in sensory neurons in ammonia-responsive basiconic and coeloconic sensilla. In the maxillary palps, labella, and tarsi, AgAmt appears restricted to sensory neurons. We have also characterized the responses to ammonia of adult antennal coeloconic sensilla and maxillary palp capitate pegs revealing a correlation between sensillar AgAmt expression and ammonia sensitivity. Taken together, these data suggest that AgAmt may play heterogeneous roles in the adult and larval chemosensory apparatus and potentially broad utility as a supra-receptor target in mosquito control.

Restricted nitrous oxide emissions by ammonia oxidizers in two agricultural soils following excessive urea fertilization

Nitrogen (N) fertilizer placement in bands is a widely accepted agricultural practice to increase N use efficiency. An excessive ammonium concentration in a fertilizer band can increase osmotic stress on ammonia oxidizers and potentially affect nitrification and resultant nitrous oxide (N2O) emissions, which is of great significance for soil function and climate change. The objectivity of this study was to identify the effects of excessive ammonium concentration on N2O emissions and ammonia oxidizers in two agricultural soils. In this study, we established a 56-day soil microcosm receiving a series of high concentrations of urea at 600, 900, and 1200 mg N kg−1 (termed as N600, N900, and N1200, respectively), which simulated high ammonium levels in the center or proximity of a fertilizer band in two types of agricultural soils (fluvo-aquic soil and anthrosol). The mineral N concentrations, net nitrification rate, and N2O emissions were measured during the incubation. In addition, the abundances of bacterial and archaeal amoA were determined by using real-time quantitative PCR. Urea fertilization simultaneously increased the net nitrification rate and N2O emission at the early stage of incubation in both soils, suggesting N2O production was mainly from ammonia oxidation. Ammonia oxidizing bacteria (AOB) but not archaea (AOA) abundance was stimulated following urea fertilization and was positively correlated with N2O emission, indicating the dominant role of AOB in ammonia oxidation and N2O production in fertilized soils. The cumulative N2O emission was significantly higher in N1200 and N900 than N600 in both soils, but no further increase was observed in N1200 in the anthrosol. This implies restricted N2O production of ammonia oxidizers at excessive ammonium concentrations in the anthrosol. In the two soils treated with no N addition, the abundances of AOA amoA increased along the incubation time. The present study collectively suggested that excessive urea-N addition was more effective in inhibiting N2O emission in the anthrosol than in the fluvo-aquci soil. AOB rather than AOA dominated the soil nitrification and N2O emissions under high N addition in both soils. The band fertilization regime may reduce the loss of N fertilizer from nitrification without necessarily increasing N2O emissions.

Better understanding of the activated sludge process combining fluorescence-based methods and flow cytometry: A case study

This study aims to demonstrate the validity of fluorescence-based methods, together with flow cytometry, as a complementary tool to conventional physicochemical analyses carried out in wastewater treatment plants (WWTPs), for the control of the currently largely unknown activated sludge process. Staining with SYTO 9, propidium iodide and 5-(and 6)-carboxy-2′,7′-difluorodihydrofluorescein diacetate (carboxy-H2DFFDA) was used for cell viability and oxidative stress monitoring of the bacterial population forming the activated sludge of a WWTP. Throughout the period of research, several unstable periods were detected, where the non-viable bacteria exceeded the 75% of the total bacterial population in the activated sludge, but only in one case the cells with oxidative stress grew to 9%, exceeding the typical values of 2%–5% of this plant. These periods coincided in two cases with high values of total suspended solids (SST) and chemical oxygen demand (COD) in the effluent, and with an excess of ammonia in other case. A correlation between flow cytometric and physicochemical data was found, which enabled to clarify the possible origin of each case of instability in the biological system. This experience supports the application of bacterial fluorescence staining, together with flow cytometric analysis, as a simple, rapid and reliable tool for the control and better understanding of the bacteria dynamics in a biological wastewater treatment process.

Highly time-resolved chemical characterization and implications of regional transport for submicron aerosols in the North China Plain

To investigate the regional transport and formation mechanisms of submicron aerosols in the North China Plan (NCP), for the first time, we conducted simultaneous combined observations of the non-refractory submicron aerosols (NR-PM1) chemical compositions using aerosol mass spectrometer at urban Beijing (BJ) and at regional background area of the NCP (XL), from November 2018 to January 2019. During the observation period, average mass concentrations of PM1 in BJ and XL were 26.6 ± 31.7 and 16.0 ± 18.7 μg m−3 respectively. The aerosol composition in XL showed a lower contribution of organic aerosol (33% vs. 43%) and higher fractions of nitrate (35% vs. 30%), ammonium (16% vs. 13%), and chlorine (2% vs. 1%) than in BJ. Additionally, a higher contribution of secondary organic aerosol (SOA) was also observed in XL, suggesting low primary emissions and highly oxidized OA in the background area. Nitrate displayed a significantly enhanced contribution with the aggravation of aerosol pollution in both BJ and XL, which was completely neutralized by excess ammonium at both sites, suggesting that the abundant ammonia emissions in the NCP favor nitrate formation on a regional scale. In addition, a higher proportion of nitrate in XL can be attributed to the more neutral and higher oxidation capacity of the background atmosphere. Heterogeneous aqueous reaction plays an important role in sulfate and SOA formation, and is more efficient in BJ which can be attributed to the higher aerosol surface areas at urban site. Regional transport from the southwestern regions of NCP showed a significant impact on the formation of haze episodes. Beside the invasion of transported pollutants, the abundant water vapor associated with the air mass to the downwind background area further enhanced local secondary transformation and expanded the regional scope of the haze pollution in the NCP.

Characteristics of Internal Ammonium Loading from Long-Term Polluted Sediments by Rural Domestic Wastewater.

Given long-term decentralized and centralized rural domestic wastewater (RDW) discharge, nitrogen is continuously depositing in sediments. RDW discharge is assumed to be an important source of ammonium in surface water; however, the effect of long-term RDW discharge on nitrogen pollution in sediments remains unknown. Batch incubations were conducted to investigate the characteristics of internal ammonium loading from long-term polluted sediments by RDW discharge. Four sediments were demonstrated to be heavily polluted by long-term RDW discharge, with total nitrogen (TN) values of 5350, 8080, 2730, and 2000 mg·kg−1, respectively. The internal ammonium release from sediment was a slow and long process, and the risk of ammonium release from sediment during the dry season was significantly greater than that during the wet season. Though all selected sediments were heavily polluted by long-term RDW discharge, the relative contribution of internal ammonium loading from sediments was generally lower than that of external pollution. Hence, dredging is not suggested for RDW-polluted sediments except in response to an emergency. The excessive ammonium in the selected catchment was mainly from untreated and centralized black water in RDW. Centralized black waters in rural communities are highlighted to be separately treated or reused to maintain ammonium content at a safe level.

Role of Excess FAI in Formation of High‐Efficiency FAPbI3‐Based Light‐Emitting Diodes

AbstractIntroducing extensively excess ammonium halides when forming perovskites has recently been demonstrated as an effective approach to improve the performance of perovskite light‐emitting diodes (PeLEDs). Here, Cs0.17FA0.83PbI2.5Br0.5 is used as a model system to elucidate the impact of introducing excess formamidinium iodide (FAI) on the crystallization process of the perovskite film and operation of the corresponding PeLED. The excess FAI ratio is varied from 0 to 120 mol% and the crystallization process of the perovskite through in situ absorbance, in situ photoluminescence, and ex situ X‐ray diffraction measurements is systematically monitored. The results suggest that excess FAI triggers formation of a compact wide‐bandgap intermediate phase in the as‐deposited film, which then transforms to isolated and highly crystalline perovskite grains upon annealing. Using excitation correlation photoluminescence spectroscopy it is found that excess FAI results in a lower density of deep trap states and therefore a reduction of nonradiative losses in the material. This leads to a greatly enhanced maximum external quantum efficiency (EQE) from 0.25% (stoichiometric) to 12.7% (90 mol% excess). Furthermore, the FAI‐excess perovskite film is optimized with Pb(SCN)2 and 5‐ammonium valeric acid iodide additives and achieve a record radiance of 965 W Sr−1 m−2 for near‐infrared PeLEDs and a high EQE of 17.4%.

Nanosecond, Time-Resolved Shift of the Photoluminescence Spectra of Organic, Lead-Halide Perovskites Reveals Structural Features Resulting from Excess Organic Ammonium Halide

The effort to drive solution-based perovskite solar cells toward higher efficiency has been considerable, reaching over 24%. Such progress has been made possible by the low-energy barrier to crysta...