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[Display omitted] • An aerobic-heterotrophic nitrogen removal strain was isolated from saltern sediment. • The strain removed nitrogen from high-salinity (2–10% (w/v) NaCl) wastewater. • Nitrogen removal occurred via ammonium assimilation and HN-AD processes. • The complete genome of the strain was sequenced. • A complex nitrogen metabolism network was proposed. Nitrogen (N) removal from high-salinity wastewater is a major challenge. The aerobic-heterotrophic nitrogen removal (AHNR) process has been demonstrated to be feasible for treating hypersaline wastewater. In this study, Halomonas venusta SND-01, a halophilic strain capable of performing AHNR, was isolated from saltern sediment. The strain achieved ammonium, nitrite, and nitrate removal efficiencies of 98%, 81%, and 100%, respectively. The N balance experiment suggests that this isolate removes N mainly via assimilation. Various functional genes related to N metabolism were found in the genome of the strain, establishing a complex AHNR pathway that includes ammonium assimilation, heterotrophic nitrification-aerobic denitrification, and assimilatory nitrate reduction. Four key enzymes in the N removal process were successfully expressed. The strain exhibited high-adaptability under C/N ratios of 5–15, salinities of 2%−10% (m/v), and pH of 6.5–9.5. Therefore, the strain shows high potential for treating saline wastewater with different inorganic N compositions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Subtropical Dolichospermum were better adapted to heat waves than subpolar isolates. • Nitrogen loading significantly increased cyanobacterial growth rates. • Heat waves significantly increases cyanobacterial growth rates. • Rising temperatures representing heat waves significantly suppress N 2 fixation. • Heat wave induced suppression of diazotrophy could exacerbate N limitation in lakes. The intensity and duration of heat waves are expected to increase this century, occurrences considered favorable for harmful, bloom-forming freshwater cyanobacteria. Dinitrogen (N 2) fixation is a major component of nitrogen cycling in freshwater systems, yet little is known with respect to how diazotrophic (N 2 fixing) cyanobacteria respond to heat waves. Here, we quantified the effects of elevated temperature and fixed N enrichment on the growth and N 2 fixation rates of Dolichospermum isolates from differing latitudes and cyanobacterial communities in four lakes across New York state, USA, during the summer and early fall. In culture experiments, temperatures ≥ 26℃ significantly reduced maximum growth rates of the sub-polar Dolichospermum strains from Finland relative to those grown at 20 − 25℃, while a strain of Dolichospermum isolated from subtropical Australia grew significantly faster at 20 − 30℃ compared to cooler temperatures. All strains, however, exhibited significantly lower N 2 fixation rates at higher temperatures (29 − 30℃) relative to lower temperatures (13-26℃). During ecosystem-based experiments with cyanobacterial communities comprised of Nostocales and other diazotrophic cyanobacteria, short-term (3–4 day) exposures to elevated temperatures mimicking heat waves (+3-6℃; 27-31℃) and/or N (NH 4 +) enrichment caused a significant increase in cyanobacterial net growth rates but also caused a significant decline in N 2 fixation rates. Collectively, results indicate that while heat waves and fixed N loading can promote cyanobacterial communities, they also suppress diazotrophy, which is generally regarded as a significant component of nitrogen cycling in eutrophic freshwater systems. Such reductions in N 2 fixation would promote or intensify N limitation of primary production in lakes during the summer, an outcome that would be exacerbated under future warming scenarios. [ABSTRACT FROM AUTHOR]

Ammonium and nitrate are the primary nitrogen sources in natural environments, and are essential for growth and development in photosynthetic eukaryotes. In this study, we report on the isolation and characterization of an ammonium transporter gene ( PyAMT1 ) which performs a key function in nitrogen (N) metabolism of Pyropia yezoensis thalli. The predicted length of PyAMT1 was 483 amino acids (AAs). The AA sequence included 11 putative transmembrane domains and showed approximately 33–44% identity to algal and plant AMT1 AA sequences. Functional complementation in an AMT -defective yeast mutant indicated that PyAMT1 mediated ammonium transport across the plasma membrane. Expression analysis showed that the PyAMT1 mRNA level was strongly induced by N-deficiency, and was more highly suppressed by resupply of inorganic-N than organic-N. These results suggest that PyAMT1 plays important roles in the ammonium transport system, and is highly regulated in response to external/internal N-status. [ABSTRACT FROM AUTHOR]

This study firstly achieved effectively simultaneous recovery of nitrogen and phosphorus sources from fermentation liquid using natural zeolites, and the optimization and mechanisms were studied. Results showed that adding zeolites to fermentation liquid could result in three major processes at the same time: (1) substantially recovering nitrogen and phosphorus, (2) obviously removing protein and polysaccharide, (3) distinctive maintenance of short chain volatile fatty acids (SVFA), indicating practical potential of fermentation reutilization. The ammonium was adsorbed on zeolites and then released calcium ions, which further precipitated with phosphate. The operational factors were evaluated using response surface methodology, and fitted model predicted that maximum simultaneous recovery rate of ammonium and phosphate could reach 94.06% and 98.28%. Furthermore, zeolite adsorption technology had promising temperature stability in range of 15–35 °C. Taken together, zeolite adsorption could serve as an alternative for recovering nitrogen and phosphorus resources from fermentation liquid. [ABSTRACT FROM AUTHOR]

An automated sample preparation unit for inorganic nitrogen (SPIN) coupled to a membrane inlet quadrupole mass spectrometer (MIMS) was developed for automated and sensitive determination of the 15N abundances and concentrations of nitrate, nitrite, and ammonium in aqueous solutions without any sample preparation. The minimum N concentration for an accurate determination of the 15N abundance is 7 µmol/L for nitrite and nitrate, with a relative standard deviation (RSD) of repeated measurements of <1%, and 70 µmol/L with an RSD < 0.4% in the case of ammonium. The SPIN--MIMS system provides a wide dynamic range (up to 3500 µmol/L) for all three N species for both isotope abundance and concentration measurements. The comparison of parallel measurements of 15N-labeled NH4+ and NO3- from soil extracts with the denitrifier method and the SPIN--MIMS system shows a good agreement between both methods. [ABSTRACT FROM AUTHOR]

Ammonium can enter stormwater control measures (SCMs) with the influent, but is also the intermediate product between organic nitrogen and nitrate, and it is important to retain and treat ammonium within the SCM. In this study the use of aluminosilicate aggregates (CA) and clinoptilolite zeolite (ZT) was investigated under SCM (column) conditions. ZT was found to have the highest capacity (0.45 mg NH4+-N/g ZT vis-à-vis 0.33 mg NH4+ CA) at 2.5 mg NH4-N/L. The presence of Ca2+ and K+ was found to reduce the capacity of the media significantly. Increasing the contact time from 10 minutes to 47 minutes enhanced the removal efficiency of the system by 70% for CA and 23% for ZT, respectively. Finally, changes in the influent ammonium concentration resulted in successful removal during concentration increases, but desorption of ammonium for sudden concentration reduction. The use of ZT in media-based SCMs is recommended for ammonium removal. [ABSTRACT FROM AUTHOR]

Application of chemical fertilizers, especially nitrogen (N), to crops has increased dramatically in the last half century and therefore developing crop varieties with improved N use efficiency (NUE) is urgent for sustainable agriculture. N utilization procedures generally can be divided into uptake, transport, and assimilation. Transporters for nitrate or ammonium acquisition and enzymes for assimilation are among the essential components determining NUE, and many transcription factors also play a pivotal role in regulating N use-associated genes, thereby contributing to NUE. Although some efforts in improving NUE have been made in various plants, the regulatory mechanisms underlying NUE are still elusive, and NUE improvement in crop breeding is very limited. In this review, the crucial components involved in N utilization and the candidates with the potential for NUE improvement in dicot Arabidopsis and monocot rice are summarized. In addition, strategies based on new techniques which can be used for dissecting regulatory mechanisms of NUE and also the possible ways in which NUE can be improved in crops are discussed. [ABSTRACT FROM AUTHOR]

Nitrogen (N) availability influences the productivity and distribution of plants in tropical montane forests. Strategies to acquire soil N, such as direct uptake of organic compounds or associations with root symbionts to enhance N acquisition in exchange for carbon (C), may facilitate plant species coexistence and ecosystem N retention. Alternatively, rapid microbial turnover of soil N forms in tropical soils might promote flexible plant N-uptake strategies and mediate species coexistence. We tested whether sympatric plant species with different root symbiont associations, and therefore potentially different nutrient acquisition strategies, partition chemical forms of N or show plasticity in N uptake in a tropical pre-montane forest in Panama. We traced the movement of three 15N forms into soil pools, microbes, and seedlings of eleven species differing in root traits. Seedlings were grown in a split-plot field transplant experiment, with plots receiving equimolar mixtures of ammonium, nitrate, and glycine, with one form isotopically labeled in each block. After 48 h, more 15N was recovered in microbes than in plants, while all pools (extractable organic and inorganic N, microbial biomass, and leaves) contained greater amounts of 15N from nitrate than from ammonium or glycine. Furthermore, 13C from dual-labeled glycine was not recovered in the leaves of any seedling, suggesting the studied species do not directly take up organic N or transform organic N prior to translocation to leaves. Nitrogen uptake differed by root symbiont group only for nitrate, with greater 15N recovery in plants with arbuscular mycorrhizal (AM) associations or proteoid roots compared to orchids. Some root trait groups differed in 15N recovery among N forms, with greater nitrate uptake than ammonium or glycine by AM-associated and N2-fixing plants. However, only five of eleven species showed differences in uptake among N forms. These results indicate flexibility in uptake of N forms in tropical plants across root trait groups, with only a few species displaying weak preferences for a specific N form. [ABSTRACT FROM AUTHOR]

A greenhouse experiment was conducted, in order to study the effect of nitrogen (N) form (NO 3 − , NH 4 + , urea, NH 4 + + NO 3 − ) and concentration (1, 8 and 16 mM) on growth, mineral nutrition and photosynthetic performance of olive plants ( Olea europaea L., cv. ‘Kalamon’). Our data indicate that when plants at high supply (16 mM) received urea as N source better growth performance was recorded, compared to the cases olive plants received other N forms; however, at low to medium N supply (1 or 8 mM) better plant growth performance observed when they were fertilized with NO 3 − –N. Total N uptake at 16 mM was significantly lower when plants received NO 3 − –N, in comparison to the other N forms. NO 3 − form at 16 mM resulted in lower total uptake of P, Fe, Mn and Zn, compared to the other treatments. On the other hand, NH 4 + -N at high N supply (16 mM) resulted in lower total uptake of Ca and Mg. However, significantly higher K uptake was found when plants were treated with NH 4 + , at high N rate (16 mM). High N supply in the form of NH 4 + -N significantly inhibited net photosynthetic rate (A), although the chlorophyll fluorescence (as an indicator of the function of PSII) did not significantly differ among the N treatments. In conclusion, urea-N proved to be the most appropriate N form for the mineral nutrition of the olive cultivar ‘Kalamon’; thus, it should be preferred as a source of N in olive groves receiving high N fertilizations. [ABSTRACT FROM AUTHOR]

Mechanisms through which microorganisms are impacted by surface application of ground cover and nutrient source in organic orchard management are not fully understood. Twelve ground cover (compost, wood chips, paper mulch, or mow-and-blow) by fertilizer (poultry litter, organic commercial, or a no-fertilizer control) treatment combinations were applied annually in April beginning in 2006, with soil collected in March 2007 and 2013 to determine the 1-year and 7-year effects of treatments on soil chemical and biological properties. Organic matter (OM) increased through time regardless of ground cover treatment averaged across fertilizers, with the greatest increase occurring with compost addition. Soil water content, microbial biomass N, ammonium-N, and nitrate-N were greater in 2013 than in 2007 at the 0–10 cm depth. Denaturing gradient gel electrophoresis analysis of denitrifying ( nirK) communities revealed that fertilizers did not have a significant main effect or interaction with ground covers. Greater nirK richness and diversity coincided with clustering of the nirK community composition within compost treatments, and greater dissolved organic carbon concentrations with compost compared to wood chip or mow-and-blow treatments in 2007. By 2013 nirK communities in wood chip and compost ground covers tended to cluster together. Furthermore, soil nirK richness increased significantly from 2007 to 2013 in compost and wood chip treatments and was greatest in 2013 under those two ground covers. Diversity with wood chip addition increased from among the least in 2007 to among the greatest in 2013. Greater richness and diversity and community composition in the nirK community within a year of compost additions and gradually over time with wood chip addition indicate potential for enhanced denitrification in low OM, organic apple orchard soil receiving compost and wood chips mulches. [ABSTRACT FROM AUTHOR]

Ammonium (NH 4 + ) is not only nitrogen source that can support methanotrophic growth, but also it can inhibit methane (CH 4 ) oxidation by competing with CH 4 for the active site of methane monooxygenase. NH 4 + conversion and its feedback effect on the growth and activity of methanotrophs were evaluated with Methylosinus sporium used as a model methanotroph. Nitrogen sources could affect the CH 4 -derived carbon distribution, which varied with incubation time and nitrogen concentrations. More CH 4 -derived carbon was incorporated into biomass in the media with NH 4 + –N, compared to nitrate–nitrogen (NO 3 − –N), as sole nitrogen source at the nitrogen concentrations of 10–18 mmol L −1 . Although ammonia (NH 3 ) oxidation activity of methanotrophs was considerably lower, only accounting for 0.01–0.06% of CH 4 oxidation activity in the experimental cultures, NH 4 + conversion could lead to the pH decrease and toxic intermediates accumulation in the their habits. Compared with NH 4 + , nitrite (NO 2 − ) accumulation in the NH 4 + conversion of methanotroph had stronger inhibition on its activity, especially the joint inhibition of NO 2 − accumulation and the pH decrease during the NH 4 + –N conversion. These results suggested that more attention should be paid to the feedback effects of NH 4 + conversion by methanotrophs to understand effects of NH 4 + on CH 4 oxidation in the environments. [ABSTRACT FROM AUTHOR]

This study was done to evaluate the growth responses of tomato plants (Lycopersicon esculentumMill.) to foliar application of ammonium sulfate in different concentrations of 0, 50, 100, or 200 mM once per week, as well as 50 mM in every other day under greenhouse and hydroponic culture system. The results showed that foliar application of ammonium restricted the plant height, yield, and vitamin C content of fruits, but it increased the chlorophyll content in treated plants. The highest and the lowest yield were obtained from zero (control) and 200 mM treated plants, respectively. Fruit hardness was not affected by treatments, while blossom end rot disorder was increased by higher concentrations of ammonium sulfate. In general, the result indicated that tomato plant is rather sensitive to foliar application of ammonium sulfate particularly to higher concentrations and application numbers. [ABSTRACT FROM PUBLISHER]

Salinity intrusion caused by land subsidence resulting from increasing groundwater abstraction, decreasing river sediment loads and increasing sea level because of climate change has caused widespread soil salinization in coastal ecosystems. Soil salinization may greatly alter nitrogen (N) cycling in coastal ecosystems. However, a comprehensive understanding of the effects of soil salinization on ecosystem N pools, cycling processes and fluxes is not available for coastal ecosystems. Therefore, we compiled data from 551 observations from 21 peer-reviewed papers and conducted a meta-analysis of experimental soil salinization effects on 19 variables related to N pools, cycling processes and fluxes in coastal ecosystems. Our results showed that the effects of soil salinization varied across different ecosystem types and salinity levels. Soil salinization increased plant N content (18%), soil NH4+ (12%) and soil total N (210%), although it decreased soil NO3− (2%) and soil microbial biomass N (74%). Increasing soil salinity stimulated soil N2O fluxes as well as hydrological NH4+ and NO2− fluxes more than threefold, although it decreased the hydrological dissolved organic nitrogen ( DON) flux (59%). Soil salinization also increased the net N mineralization by 70%, although salinization effects were not observed on the net nitrification, denitrification and dissimilatory nitrate reduction to ammonium in this meta-analysis. Overall, this meta-analysis improves our understanding of the responses of ecosystem N cycling to soil salinization, identifies knowledge gaps and highlights the urgent need for studies on the effects of soil salinization on coastal agro-ecosystem and microbial N immobilization. Additional increases in knowledge are critical for designing sustainable adaptation measures to the predicted intrusion of salinity intrusion so that the productivity of coastal agro-ecosystems can be maintained or improved and the N losses and pollution of the natural environment can be minimized. [ABSTRACT FROM AUTHOR]

The poultry industry produces abundant quantities of nutrient-rich litter, much of which is composted before use as a soil amendment. However, a large proportion of nitrogen (N) in poultry litter is lost via volatilisation during composting, with negative environmental and economic consequences. This study examined the effect of incorporating biochar during composting of poultry litter on ammonia (NH 3 ) volatilisation and N retention. Biochars produced at 550 °C from greenwaste (GWB) and poultry litter (PLB) feedstocks were co-composted with a mixture of raw poultry litter and sugarcane straw [carbon (C):N ratio 10:1] in compost bins. Ammonia emissions accounted for 17% of the total N (TN) lost from the control and 12–14% from the biochar-amended compost. The TN emitted as NH 3 , as a percentage of initial TN, was significantly lower ( P < 0.05) i.e. by 60% and 55% in the compost amended with GWB and PLB, respectively, relative to the control. The proportion of N retained in the finished compost, as a percentage of initial TN, was 84%, 78% and 67% for the GWB, PLB and nil biochar control, respectively. Lower concentration of dissolved organic C (DOC) together with higher activity of beta-glucosidase and leucine-aminopeptidase were found in the GWB-amended compost ( cf. control). It is hypothesized that lower NH 3 emission in the GWB-amended compost was caused not just by the higher surface area of this biochar but could also be related to greater incorporation of ammonium (NH 4 + ) in organic compounds during microbial utilisation of DOC. Furthermore, the GWB-amended compost retained more NH 4 + at the end of composting than the PLB-amended compost. Results showed that addition of biochar, especially GWB, generated multiple benefits in composting of poultry litter: decrease of NH 3 volatilisation, decrease in NH 3 toxicity towards microorganisms, and improved N retention, thus enhancing the fertiliser value of the composted litter. It is suggested that the latter benefit is linked to a beneficial modification of the microbial environment. [ABSTRACT FROM AUTHOR]

Bemisia tabaci is one of the most damaging pests in tomato greenhouse production. The resistance of B. tabaci to insecticides requires a new approach with respect to the integrated management of this pest., The effect of grafting (nongrafted and tomato grafted on the rootstock Arnold) and nitrogen ( N) rates (75, 140 and 205 mg/ L) on the density of B. tabaci large nymphs (fourth instar to pupae) was studied in 2012. In 2013, large nymphs density was examined in relation to grafting treatments (nongrafted, self-grafted and tomatoes grafted onto the rootstocks Arnold and He- Man) and NO3− : NH4+ ratios (92 : 8, 85 : 15 and 70 : 30)., A reduction of B. tabaci population density was found for rootstock Arnold grown at 140 and 205 mg/ L N in the nutrient solution. Pupal size decreased with decreasing N fertilization. In the second experiment, rootstocks contributed to a reduction of B. tabaci density at different NO3− : NH4+ ratios. The lowest B. tabaci population density was found on plants grafted onto He- Man rootstock supplied with an 85 : 15 and 70 : 30 NO3− : NH4+ ratio in nutrient solutions. The increased proportion of NH4+ in the 85 : 15 NO3− : NH4+ ratio generally reduced the B. tabaci pupal size for all rootstocks., Grafting and N adjustment could represent useful tools for integrated greenhouse pest management. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3 ) emissions and ammonium (NH 4 + ) deposition can have harmful effects on the environment and human health but remain generally unregulated in the U.S. PM 2.5 regulations require that an area not exceed an annual average PM 2.5 value of 12 μg/m 3 (averaged over three years), and since NH 3 is a significant precursor to PM 2.5 formation these are the closest indirect regulations of NH 3 emissions in the U.S. If the U.S. elects to adopt NH 3 emission regulations similar to those applied by the European Union, it will be imperative to first adequately quantify NH 3 emission sources and transport, and also understand the factors causing varying emissions from each source. To further investigate NH 3 emission sources and transport at a regional scale, NH 3 was sampled monthly at a subset of nine Ammonia Monitoring Network (AMoN) sites and analyzed for nitrogen isotopic composition of NH 3 (δ 15 N-NH 3 ). The observed δ 15 N-NH 3 values ranged from −42.4 to +7.1‰ with an average of −15.1 ± 9.7. The observed δ 15 N-NH 3 values reported here provide insight into the spatial and temporal trends of the NH 3 sources that contribute to ambient [NH 3 ] in the U.S. In regions where agriculture is prevalent (i.e., U.S. Midwest), low and seasonally variable δ 15 N-NH 3 values are observed and are associated with varying agricultural sources. In comparison, rural nonagricultural areas have higher and more seasonally consistent δ 15 N-NH 3 values associated with a constant “natural” (e.g. soil, vegetation, bi-directional flux, ocean) NH 3 source. With regards to temporal variation, the peak in U.S. spring agricultural activity (e.g. fertilizer application, livestock waste volatilization) is accompanied by a decrease in δ 15 N-NH 3 values at a majority of the sites, whereas higher δ 15 N-NH 3 values in other seasons could be due to shifting sources (e.g. coal-fired power plants) and/or fractionation scenarios. Fractionation processes that may mask NH 3 source signatures are discussed and require further investigation to optimize the utility of the nitrogen isotopic composition to determine NH 3 sources and dynamics. [ABSTRACT FROM AUTHOR]

Glutamine synthetase (GS) catalyzes a reaction that incorporates ammonium into glutamate and yields glutamine in the cytosol and chloroplasts. Although the enzymatic characteristics of the GS1 isozymes are well known, their physiological functions in ammonium assimilation and regulation in roots remain unclear. In this study we show evidence that two cytosolic GS1 isozymes (GLN1;2 and GLN1;3) contribute to ammonium assimilation in Arabidopsis roots. Arabidopsis T-DNA insertion lines for GLN1;2 and GLN1;3 (i.e. gln1;2 and gln1;3 single-mutants), the gln1;2:gln1;3 double-mutant, and the wild-type accession (Col-0) were grown in hydroponic culture with variable concentrations of ammonium to compare their growth, and their content of nitrogen, carbon, ammonium, and amino acids. GLN1;2 and GLN1;3 promoter-dependent green fluorescent protein was observed under conditions with or without ammonium supply. Loss of GLN1;2 caused significant suppression of plant growth and glutamine biosynthesis under ammonium- replete conditions. In contrast, loss of GLN1;3 caused slight defects in growth and Gln biosynthesis that were only visible based on a comparison of the gln1;2 single- and gln1;2:gln1;3 double-mutants. GLN1;2, being the most abundantly expressed GS1 isozyme, markedly increased following ammonium supply and its promoter activity was localized at the cortex and epidermis, while GLN1;3 showed only low expression at the pericycle, suggesting their different physiological contributions to ammonium assimilation in roots. The GLN1;2 promoter-deletion analysis identified regulatory sequences required for controlling ammonium-responsive gene expression of GLN1;2 in Arabidopsis roots. These results shed light on GLN1 isozyme-specific regulatory mechanisms in Arabidopsis that allow adaptation to an ammonium-replete environment. [ABSTRACT FROM AUTHOR]

Removal of biologically available nitrogen (N) by the microbially mediated processes denitrification and anaerobic ammonium oxidation (anammox) affects ecosystem N availability. Although few studies have examined temperature responses of denitrification and anammox, previous work suggests that denitrification could become more important than anammox in response to climate warming. To test this hypothesis, we determined whether temperature responses of denitrification and anammox differed in shelf and estuarine sediments from coastal Rhode Island over a seasonal cycle. The influence of temperature and organic C availability was further assessed in a 12-week laboratory microcosm experiment. Temperature responses, as characterized by thermal optima ( Topt) and apparent activation energy ( Ea), were determined by measuring potential rates of denitrification and anammox at 31 discrete temperatures ranging from 3 to 59 °C. With a few exceptions, Topt and Ea of denitrification and anammox did not differ in Rhode Island sediments over the seasonal cycle. In microcosm sediments, Ea was somewhat lower for anammox compared to denitrification across all treatments. However, Topt did not differ between processes, and neither Ea nor Topt changed with warming or carbon addition. Thus, the two processes behaved similarly in terms of temperature responses, and these responses were not influenced by warming. This led us to reject the hypothesis that anammox is more cold-adapted than denitrification in our study system. Overall, our study suggests that temperature responses of both processes can be accurately modeled for temperate regions in the future using a single set of parameters, which are likely not to change over the next century as a result of predicted climate warming. We further conclude that climate warming will not directly alter the partitioning of N flow through anammox and denitrification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Upgrading nitrogen removal performances in wastewater treatment plants by BES. • Enhancing the polishing action of secondary treatments to avoid tertiary treatments. • Nitrate and ammonium removal without nitrous oxide accumulation. • Disinfection of wastewater via electrochemical anodic oxidation. Economic options to retrofit wastewater treatment plants (WWTPs) without tertiary treatments need to be explored. In this regard, bioelectrochemical systems (BES) can be hybridized with existing technologies, upgrading the removal performance of original techniques while avoiding replacement costs. Yet, few demonstrations of merged systems have been given. For the first time, in this work it was built a lab-scale model of a BES merged with a secondary settler, namely e-settler, to enhance the polishing performance of already existing WWTPs. In particular, to concomitantly increase nitrogen removal and perform wastewater (WW) disinfection, avoiding further tertiary treatments. In the e-settlers, nitrogen removal was increased through bioelectrochemical stimulation. Concomitant ammonium and nitrate removal without nitrite accumulation and a negligible amount of nitrous oxide emissions were observed. Ti-MMO as anode material showed a high disinfectant action. In conclusion, it was demonstrated how a simple bioelectrochemical set-up can upgrade existing WWTPs. The following step requires the study at a larger scale, identifying optimal operational and structural parameters for the in-situ application. The main limitations of the e-settlers were discussed, linking them to possible solutions that need to be deepened in a lab-scale model of conventional secondary treatments (activated sludge followed by secondary settler). [ABSTRACT FROM AUTHOR]

The biosynthesis of amino acids (AAs) in plants is affected by different nitrogen (N) sources. The effects of exogenous cyanide (KCN) on the concentrations and profiles of AAs in rice seedlings were carried out in the presence of nitrate (+NO 3 −)/ammonium (+NH 4 +) or N deficiency (-N). Targeted metabolomics analysis indicated that the highest accumulation of AAs in CN−-treated rice seedlings was detected in the "CN−+NH 4 +" treatments than in other treatments, wherein the doses of exogenous KCN did not significantly affect the total amount of AAs in rice seedlings at the same N fertilized condition. The total content of AAs in rice shoots under "CN−+NH 4 +" treatments was higher than other treatments, while the total content of AAs in rice roots under "CN−+NO 3 −" treatments was higher than other treatments. Also, the profiles of 21 AAs in CN−-treated rice seedlings showed tissue-specific under different N fertilization. The relative importance index (RII) of AA was used to evaluate the importance of AAs in CN−-treated rice seedlings under different N fertilization. The common AAs with higher RII values were compared between three different treatments of KCN (e.g., 0, 1, and 2 mg CN/L). Under "CN−+(-N)" treatments, Ala, Asp, Glu, Val, and Gly (Ala, Gly, Val, and Lys) were the common AAs in rice roots (shoots). Under "CN−+NO 3 −" treatments, Ala, Glu, Asp, Ser, and Thr (Asp, Ala, Thr, Ser, and Asn) were the common AAs with higher RII values in rice roots (shoots) between all CN− treatments. Under "CN−+NH 4 +" treatments, Asp, Gln, Asn, and Ala (Asp, Glu, and Thr) were the common AAs with higher RII values in rice roots (shoots) between all CN− treatments. These results suggested that using the RII to describe the change and fluctuation of AAs in rice plants may reflect the different N utilization strategies in response to exogenous CN− exposure. [Display omitted] • The profiles of AAs in CN−-treated rice in the presence of NO 3 −/NH 4 + or N deficiency were investigated. • NH 4 + showed a positive effect on biomass of CN−-treated rice than other N conditions. • More accumulation of AAs in CN−-treated rice was detected in the "CN−+NH 4 +" treatments than others. • The RII index was used to evaluate the importance of AAs in CN−-treated rice under different N conditions. • Glu, Asn, Asp and Ala carried more weight than others in CN−-treated rice under different N conditions. [ABSTRACT FROM AUTHOR]

High organic loadings to constructed wetlands can result in water quality issues such as low dissolved oxygen and high ammonium concentrations, with artificial aeration a potential mitigation option. This study compared baseline (no aeration – NA), continuous aeration (CA), and intermittent aeration (IA) conditions to improve water quality in a tertiary treatment free water surface constructed wetland (FWS CW) with night time hypoxia/anoxia, and high nutrient concentrations. The response variables included dissolved oxygen (DO), total nitrogen (TN), ammonium nitrogen (NH 4 +-N), nitrate nitrogen (NO 3 −-N), total phosphorus (TP), phosphate (PO 4 3–-P), and dissolved organic carbon (DOC). In situ aeration and monitoring was performed from April to June 2021 in a large, field-scale FWS CW, the Laratinga wetlands Mount Barker, South Australia. The results demonstrated that DO increased by an average 2.11 mg L−1 from NA to CA during the night and 1.26 mg L−1 and 1.84 mg L−1 from NA to IA during the night and day respectively when averaging over the basins. The C/N ratio was very low and there was no significant influence of DO on DOC concentrations. There was no significant difference in TN concentrations with the application of aeration aside from a decrease in the channel at night from NA to IA, and an increase in NH 4 +-N resulted under IA compared with NA in Basin 1 and 2 during the day. This implies that the N loadings exceeded the wetland's ability to complete nutrient conversions at a rate that aligns with input rate. The concentrations of NO 3 −-N increased at night under CA and IA treatments suggesting that some nitrification was promoted, or there was inhibition of dissimilatory nitrate reduction to ammonium. The concentrations of TP and PO 4 3–-P significantly increased with the aeration compared with no aeration, however there was no difference between the aeration treatments. This suggested that increased sediment resuspension during aeration increased P in the water. There was no change in DOC with the application of aeration. Overall, the DO increased with aeration application and may be able to better support the wetland ecology; however, the Laratinga wetland is overloaded and the capacity of the wetland to effectively transform and remove nutrients is inhibited, even with the application of artificial aeration. • Dissolved oxygen increased with the application of continuous and intermittent aeration. • There was no change in total nitrogen with aeration and ammonium levels remained high. • There was a small increase in nitrate, and total and soluble phosphorus with aeration. • Despite near-neutral pH values, unionised ammonia was calculated to be at toxic levels. • Using aeration to manage systems with high nutrient loadings is challenging. [ABSTRACT FROM AUTHOR]

Ammonium (NH 4 +) enrichment of riverbank filtration (RBF) systems is gaining popularity. However, most previous research has concentrated on NO 3 − removal efficiencies, while the mechanisms of NH 4 + enrichment remain unknown. A nitrogen biogeochemical process model was developed for the quantitative analysis of NH 4 + enrichment in the Kaladian well field in northwest Songyuan City, NE China. Data from laboratory experiments and in-situ monitoring were used to determine initial values and calibrate the thermodynamic/kinetic parameters representing nitrogen (N) biogeochemical reactions. (1) The NO 3 − from river was subjected to denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) within 10–14 m of the shore, whereas the NH 4 + in groundwater was caused by DNRA, organic nitrogen mineralization (MIN), and mixing with laterally recharged high NH 4 + groundwater. (2) DNF and DNRA were regulated by hydrodynamic processes, with the ranges of these processes being more significant in the wet season due to a higher hydraulic gradient. MIN occurred widely throughout the water flow path, with temperature primarily controlling the rates of the three reactions. (3) DNRA activity was relatively higher in the wet season when the water temperature was higher within 10–14 m of the shore. In the wet season, DNRA contributed 25%–30% to NO 3 − reduction, which was higher than in the dry season (5%–10%). DNRA contributed at least 40% and 15% to NH 4 + enrichment in the wet and dry seasons, respectively. (4). Organic N in media gradually released NH 4 + into groundwater via MIN and desorption across the entire flow path, with contributions to NH 4 + enrichment reaching 75% and 85%, respectively, in the wet and dry seasons. • Spatiotemporal variations of N biogeochemical reactions in RBF were identified. • Conditions for denitrification, DNRA, and mineralization in RBF were identified. • Simulation parameters were refined through multi-environmental N experiments. • Contributions of DNRA to NO 3 − reduction and NH 4 + enrichment were quantified. • Introduction. [ABSTRACT FROM AUTHOR]

Photosynthetic bacteria can utilize organic matter from wastewater to produce hydrogen gas, and the application of this process is an environment-friendly approach to produce energy. However, photo-fermentative hydrogen production can be inhibited by ammonium, which exerts an inhibitory role on the expression and activity of nitrogenase, the pivotal enzyme in hydrogen production. In this study, we constructed mutant strains of Rhodopseudomonas palustris by manipulating of nitrogen-regulatory genes. Photo-fermentative hydrogen production assay showed the ammonium concentration that nifA draT2 and nifA glnK2 double mutant strains can tolerate increased by 25 and 10 folds, respectively, compared with wild-type strain, though hydrogen yield decreased with the increase of ammonium concentration. Results indicate that manipulation of nitrogen-regulatory genes is an effective way to enhance the ammonium tolerance of photosynthetic bacteria and improve their hydrogen production. [ABSTRACT FROM AUTHOR]

Extensive research on the anammox-based processes under mainstream conditions is currently in progress. Most studies have used a long acclimation period for the partial nitritation-anammox (PN-An) sludge at a low temperature and ammonium concentration. However, in this study, the results demonstrated that PN-An granular biomass produced under sidestream conditions (30 °C and 1000 mg NH 4 + -N/L) can operate at 15 °C and 50 mg NH 4 + -N/L without acclimation. The nitrogen removal efficiency was 70% and was stable for 60 days. The long-term operation of the system with progressive adaptation provided important information for process optimization. Control of the dissolved oxygen (DO) concentration was crucial to maintain the balance between ammonia oxidizing bacteria (AOB) and anammox bacteria activities. A calculation of the oxygen penetration depth inside the granules is proposed to estimate an adequate DO level, which allows for the definition of the aerobic and anoxic zones that depend on the temperature, the size distribution and the granule density. However, the development of NOB was difficult to avoid with DO control alone. The selective washing-out of the floccular biomass, which contains mainly NOB, is proposed, leaving the granular fraction with the AOB and anammox bacteria in the system. [ABSTRACT FROM AUTHOR]

Stream hydraulics control flux into and out of slow-moving water transient storage (WTS) zones and, thus, hydrologic retention in stream channels. In-stream nutrient uptake is thought to depend on hydrologic retention, so stream hydraulics could influence the extent to which in-stream nutrient biogeochemistry affects nutrient export downstream. Our goals were to: 1) characterize WTS with an emphasis on water residence time and 2) evaluate its influence on nutrient uptake. We analyzed data from 2 y of monthly solute-tracer injections with accompanying nutrient-uptake estimates in 2 hydrogeomorphically different streams. We fit the conservative tracer breakthrough curves to 2 hydrodynamic models: the one-dimensional transport with inflow and storage (OTIS) and the stochastic mobile-immobile model (SMIM), which allows for a wide distribution of water residence times. The 2 streams differed hydraulically, especially in water residence-time distributions in WTS zones. SMIM parameters depended less on discharge than did OTIS parameters, indicating that SMIM may be influenced more by local features of channel morphology than by hydrologic conditions. NH4+ uptake differed between streams, was correlated with all SMIM hydraulic parameters, and was weakly correlated with only 1 OTIS parameter. Based on SMIM correlations, the parameters related to the exchange of free-flowing water with water storage zones and the in-stream retention times explained 43 and 41%, respectively, of the variation in NH4+ uptake in the streams. Soluble reactive P (SRP) uptake was similar between streams and was not correlated with hydraulic parameters. These results indicate that hydraulics and residence time of water can be important regulators of WTS zones and nutrient uptake in headwater streams, but other environmental factors must be considered for complete understanding of in-stream nutrient processing capacity. [ABSTRACT FROM AUTHOR]

We tested the capability of plants to utilize protein as the exclusive source of nitrogen. The aim of this study was to find out how such a nutrition affected plantlet growth, photosynthetic performance, and N assimilation metabolism in tobacco ( Nicotiana tabacum L., cv. Petit Havana SR1) grown in vitro. Plantlets grown in a casein-supplemented (CA) medium were compared to plantlets grown in a complete Murashige-Skoog (MS) medium, plantlets grown in an ammonium-deficient medium (N1), or plantlets grown in a nitrate-reduced medium (N2). In addition, the plantlets were grown in the presence or absence of 1.5 % (m/v) saccharose as an additional carbon source. Casein, similarly as inorganic N limitation, reduced generally plantlet growth, whereas no significant effects were observed on photosynthetic parameters evaluated by chlorophyll a fluorescence. Although addition of saccharose stimulated the plantlet growth particularly in the MS, it showed a rather negative influence both on the growth and on the photochemical efficiency of photosystem II in the plantlets grown in the CA and N1. The activities of enzymes involved in N assimilation, such as nitrate reductase (NR) and glutamine synthetase (GS), were lower in the plantlets grown in the CA, N1, and N2, both in leaves and in roots. On the other hand, glutamate synthase and glutamate dehydrogenase were employed by the plantlets grown in the CA. The presence of saccharose in the growth medium stimulated mainly NR and GS activities in the MS grown plantlets, whereas enzyme activities of the plantlets grown on the N1, N2, and CA were not significantly influenced. We proved that the tobacco plantlets can utilize casein as the sole source of N particularly during their photoautotrophic cultivation. Contrary to positive effects of photomixotrophic nutrition for the MS grown plantlets, exogenous sugar seemed to diminish the ability of the casein-supplemented plantlets to utilize efficiently the additional C source. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the effect of increasing feedstock treatment rate on the performance of full-scale anaerobic digestion using laboratory-scale reactors with digestate and feedstock from full-scale digesters. The studied nitrogen-containing feedstocks were i) a mixture of industrial by-products and pig slurry, and ii) municipal sewage sludge, which digestion was studied at 41 and 52 °C, respectively. This study showed the successful reduction of hydraulic retention times from 25 and 20 days to around 15 days, which increased organic loading rates from 2 to 3.5 kg volatile solids (VS)/m 3 d and 4 to 6 kg VS/m 3 d. As a result, the optimum retention time in terms of methane production and VS removal was 10–15% lower than the initial in the full-scale digesters. Accumulation of acids during start-up of the co-digestion reactor was suggested to be connected to the high ammonium nitrogen concentration and intermediate temperature of 41 °C. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deposition levels and frequencies of extreme drought events are increasing globally. In efforts to improve understanding of plants' responses to associated stresses, we have investigated responses of mosses to drought under elevated nitrogen conditions. More specifically, we exposed Pogonatum cirratum subsp. fuscatum and Hypnum plumaeforme to various nitrate ( KNO3) or ammonium ( NH4Cl) treatments, with and without water deficit stress and monitored indices related to carbon (C) and N metabolism both immediately after the stress and after a short recovery period. The results show that N application stimulated both C and N assimilation activities, including ribulose-1,5-bisphosphate carboxylase, glutamine synthetase/glutamate synthase ( GS/ GOGAT), and glutamate dehydrogenase ( GDH) activities, while water deficit inhibited C and N assimilation. The mosses could resist stress caused by excess N and water deficit by increasing their photorespiration activity and proline (Pro) contents. However, N supply increased their sensitivity to water stress, causing sharper reductions in C and N assimilation rates, and further increases in photorespiration and Pro contents, indicating more serious oxidative or osmotic stress in the mosses. In addition, there were interspecific differences in N assimilation pathways, as the GS/ GOGAT and GDH pathways were the preferentially used ammonium assimilation pathways in P. cirratum and H. plumaeforme when stressed, respectively. After rehydration, both mosses exhibited overcompensation effects for most C and N assimilation activities, but when supplied with N, the activities were generally restored to previous levels (or less), indicating that N supply reduced their ability to recover from water deficit stress. In conclusion, mosses can tolerate a certain degree of water deficit stress and possess some resilience to environmental fluctuations, but elevated N deposition reduces their tolerance and ability to recover. [ABSTRACT FROM AUTHOR]

We present the development of a method for the simultaneous determination of inorganic nitrogen species in oxidized (NO2-, NO3-) and reduced (NH4+) forms using ion chromatography with diode-array detection (205, 208, and 425 nm, respectively). The oxidized forms were determined directly after the separation in the anion exchanger, while the reduced form was determined in the column hold-up time after derivatization with the Nessler reagent. The use of an appropriate modifier (Seignette reagent) and mobile phase (NaCl) enabled the determination of inorganic nitrogen species in highly salinated environmental samples (water, sediments). Moreover, low detection limits were obtained of 0.04 mg/L for NH4+ and 0.006 and 0.005 mg/L for NO2- and NO3-, respectively. The analysis of environmental samples indicated NH4+ contents of up to 1161 ± 47 mg/kg and NO3- of up to 148 ± 6 mg/kg for sediment samples, as well as the NH4+ concentrations of up to 0.98 ± 0.10 mg/L, NO2- of up to 24 ± 1 mg/L and NO3- of up to 20 ± 1 mg/L for water samples. [ABSTRACT FROM AUTHOR]

Anaerobic ammonium oxidation (anammox) as an important nitrogen removal pathway has been investigated in intertidal marshes. However, the rhizosphere-driven anammox process in these ecosystems is largely overlooked so far. In this study, the community dynamics and activities of anammox bacteria in the rhizosphere and non-rhizosphere sediments of salt-marsh grass Spartina alterniflora (a widely distributed plant in estuaries and intertidal ecosystems) were investigated using clone library analysis, quantitative PCR assay, and isotope-tracing technique. Phylogenetic analysis showed that anammox bacterial diversity was higher in the non-rhizosphere sediments ( Scalindua and Kuenenia) compared with the rhizosphere zone (only Scalindua genus). Higher abundance of anammox bacteria was detected in the rhizosphere (6.46 × 10-1.56 × 10 copies g), which was about 1.5-fold higher in comparison with that in the non-rhizosphere zone (4.22 × 10-1.12 × 10 copies g). Nitrogen isotope-tracing experiments indicated that the anammox process in the rhizosphere contributed to 12-14 % N generation with rates of 0.43-1.58 nmol N g h, while anammox activity in the non-rhizosphere zone contributed to only 4-7 % N production with significantly lower activities (0.28-0.83 nmol N g h). Overall, we propose that the rhizosphere microenvironment in intertidal marshes might provide a favorable niche for anammox bacteria and thus plays an important role in nitrogen cycling. [ABSTRACT FROM AUTHOR]

Based on the backbone of the nitrogen-rich triazole and tetrazole structure, their N-OH derivatives were designed to improve the properties of energetic materials. This work introduces five novel nitrogen-rich derivatives and their energetic salts as high-performance compounds. Reliable methods and correlations are used to predict the heat of formation, density, detonation, and combustion properties and explosive power. The predicted energetic properties are also compared with well-known explosives, TNT, TATB, RDX, and HMX, to evaluate the performance. A majority of the designed salts exhibited high positive heats of formation, good detonation properties, and high explosive power. Ammonium, hydrazinium, and hydroxylammonium salts ( 1- 3), which have relatively high densities (over 1.86 g/cm3), resulted in good detonation velocities (above 9.0 km/s) and pressures (above 35 GPa), making them competitive energetic materials. [ABSTRACT FROM AUTHOR]

In this study, the suitability of excess biofloc that was discarded as waste from Litopenaeus vannamei farm effluent was investigated for effectiveness as a dietary replacement in rearing L . vannamei postlarvae (PL). A commercial shrimp diet (control) was compared to four diets containing dried waste biofloc at 25%, 50%, 75% and 100% replacement levels and fed to shrimp PL to evaluate the survival rate, growth performance and nutritional composition. Total ammonium nitrogen and nitrite nitrogen were maintained in culture tanks with minimal water exchange throughout the experiment. Results showed that PLs fed with 50% biofloc feed (50% BF) had significantly higher (p < 0.05) specific growth rate compared to the other treatments. In addition, PLs fed with 50% and 75% BF had significantly higher survival rate (p < 0.05) compared to those fed with commercial feed only. However, protein content of PLs fed with 50% and 75% BF was comparable to those of 100% commercial feed. This study demonstrates that waste biofloc has potential to be used as a cost effective feed for rearing shrimp PLs. [ABSTRACT FROM AUTHOR]

The assimilation and availability of nitrogen in its different forms can significantly affect the response of primary productivity under the current atmospheric alteration and soil degradation. An elevated CO 2 concentration (e[CO 2 ]) triggers changes in the efficiency and efficacy of photosynthetic processes, water use and product yield, the plant response to stress being altered with respect to ambient CO 2 conditions (a[CO 2 ]). Additionally, NH 4 + has been related to improved plant responses to stress, considering both energy efficiency in N-assimilation and the overcoming of the inhibition of photorespiration at e[CO 2 ]. Therefore, the aim of this work was to determine the response of sweet pepper plants ( Capsicum annuum L.) receiving an additional supply of NH 4 + (90/10 NO 3 − /NH 4 + ) to salinity stress (60 mM NaCl) under a[CO 2 ] (400 μmol mol −1 ) or e[CO 2 ] (800 μmol mol −1 ). Salt-stressed plants grown at e[CO 2 ] showed DW accumulation similar to that of the non-stressed plants at a[CO 2 ]. The supply of NH 4 + reduced growth at e[CO 2 ] when salinity was imposed. Moreover, NH 4 + differentially affected the stomatal conductance and water use efficiency and the leaf Cl − , K + , and Na + concentrations, but the extent of the effects was influenced by the [CO 2 ]. An antioxidant-related response was prompted by salinity, the total phenolics and proline concentrations being reduced by NH 4 + at e[CO 2 ]. Our results show that the effect of NH 4 + on plant salinity tolerance should be globally re-evaluated as e[CO 2 ] can significantly alter the response, when compared with previous studies at a[CO 2 ]. [ABSTRACT FROM AUTHOR]

The brucellae are α-Proteobacteriacausing brucellosis, an important zoonosis. Although multiplying in endoplasmic reticulum-derived vacuoles, they cause no cell death, suggesting subtle but efficient use of host resources. Brucellae are amino-acid prototrophs able to grow with ammonium or use glutamate as the sole carbon–nitrogen sourcein vitro. They contain more than twice amino acid/peptide/polyamine uptake genes than the amino-acid auxotrophLegionella pneumophila, which multiplies in a similar vacuole, suggesting a different nutritional strategy. During these two last decades, many mutants of key actors in nitrogen metabolism (transporters, enzymes, regulators, etc.) have been described to be essential for full virulence of brucellae. Here, we review the genomic and experimental data onBrucellanitrogen metabolism and its connection with virulence. An analysis of various aspects of this metabolism (transport, assimilation, biosynthesis, catabolism, respiration and regulation) has highlighted differences and similarities in nitrogen metabolism with other α-Proteobacteria. Together, these data suggest that, during their intracellular life cycle, the brucellae use various nitrogen sources for biosynthesis, catabolism and respiration following a strategy that requires prototrophy and a tight regulation of nitrogen use. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ionic heavy metals led to greater decrease of SAA than nanoparticulate forms. • Universal ANN and Gaussian model were established to predict nitrogen removal. • HRGs increased with addition of heavy metals, but functional genes were opposite. • Nanoparticulate heavy metals promoted AOB, while Ni2+ and CuO NPs inhibited NOB. • Inhibition ratios of heavy metals on anammox process ranged from 5 to 98 %. As a promising process to remove nitrogen, anaerobic ammonium oxidation (anammox) is sensitive to environmental factors and toxic substances (antibiotics, heavy metals, sulfides, etc.). Especially, the nitrogen removal efficiency and biological activity of the anammox system were greatly inhibited by heavy metals. Few studies have been devoted to systematically investigating the effects and quantitatively deciphering the mechanism of different heavy metals on anammox-based systems. Based on the big data analysis of previous publications, the ionic heavy metals contributed to the greater decrease of specific anammox activity (SAA) than their nanoparticulate forms. Especially the inhibition ratio of SAA severely deteriorated under Cu2+ and CuO NPs, reaching 85 % and 81 %, respectively. This inhibition effect of heavy metals on nitrogen removal was also verified by the correlation analysis. Moreover, Logistic kinetic model was suitable to fit the inhibition periods of heavy metals, and Gaussian model could accurately predict nitrogen removal rate (R2 over 0.95) better than artificial neural network model. Based on quantitatively calculation of three independent nitrogen removal processes, nano heavy metals had a slight promotion effect on the ammonia oxidation process that proliferated amo A, while Ni2+ and CuO nanoparticulate inhibited nitrite oxidation process severely accompanying by the augmentation of resistance genes. Importantly, the anammox process was restrained by all heavy metals, verifying that anammox played a key role in the whole nitrogen removal process. This big data analysis provides a useful direction that it should give priority to ionic heavy metal and the copper element for anammox-based process under stress of heavy metals. [ABSTRACT FROM AUTHOR]

[Display omitted] • The coupling of Feammox and NDFO is novel and cost-effective. • The comparison between this process and other denitrification technologies is summarized. • The main factors affecting the coupling process and the research of the process are analyzed. • The transformation forms of iron and nitrogen are two key issues in the coupling process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Significant difference in nitrogen conversion of different composting. • Functional keystone involved in the nitrogen conversion were identified. • Change in abundance of functional keystone was limited during composting. • Composting microenvironment drove functional keystone. In this study, nitrogen transformation of chicken manure (CM) and cattle dung (CD) during composting was analyzed and its related functional keystones were identified. The results showed that chicken manure showed more severe nitrogen conversion during composting. The main N conversion factors in cattle dung were nitrite nitrogen (NO 2 –-N) and ammonium nitrogen (NH 4 +-N), while the main N conversion factors in chicken manure were NH 4 +-N and nitrate nitrogen (NO 3 –-N). The nitrogen-transforming bacterial community in chicken manure was more diverse. Variations in functional keystone abundances in cattle dung tended to be confined to the cooling and maturation periods, whereas changes in chicken manure persisted throughout the composting process. Environmental factors affected the functional keystones of nitrogen transformation. This study may provide directions for regulating nitrogen conversion in animal manure composting. [ABSTRACT FROM AUTHOR]

Mires are among the ecosystems most affected by eutrophication caused by excessive nitrogen (N) inputs via N deposition of ammonium (NH4+), nitrate (NO 3 –), nitric acid (HNO 3), nitrogen dioxide (NO 2), and ammonia (NH 3). As NH 3 emissions are mostly generated by agriculture, a particular conflict of interest exists in areas where agricultural production systems are located nearby sensitive ecosystems, as often is the case in Switzerland. Therefore, this study aimed at quantifying and evaluating total N inputs to a mire in the Swiss Alpine foothills during 2007–2019, focusing on NH 3 dry deposition. Three surface–vegetation–atmosphere transfer models were used to estimate dry deposition of NH 3 based on micrometeorological data in combination with monthly passive sampler NH 3 concentration measurements. NH 3 -N dry deposition summed up to 1.5–5.2 kg N ha–1 a–1, while total N loads were 11.5–14.2 kg N ha–1 a–1, well beyond the critical N loads for raised bogs (5–10 kg N ha–1 a–1), and also higher than the lower limits for oligotrophic fens and mountain hay meadows (10 kg N ha–1 a–1). Hence, the mire studied is most likely negatively affected by eutrophication, which could ultimately lead to biodiversity loss and ecosystem instability. This is particularly remarkable as the monthly NH 3 concentrations at the study site (0.4–4.7 µg m–3) are comparatively low for Switzerland. • 14 years of monthly NH 3 deposition over a mountain mire landscape was quantified. • Full nitrogen deposition to mire was estimated as 11.5–14.2 kg N ha–1 a–1. • This N input exceeded the critical loads for nitrogen of raised bogs and fens. • Options to reduce local NH 3 emissions from farms are assessed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Elevated ammonium levels promote the formation of organic nitrogen. • High ammonium nitrogen reduces nitrogen losses during sludge composting. • Transformation of nitrogen fractions by the bacterial community was altered. • Core bacterial communities promoted the conversion of NH 4 +-N to AN and HUN. This study aimed to clarify the conversion relationship between organic and inorganic nitrogen. The NH 4 Cl was used to enhance the inorganic nitrogen content. The key role of bacterial conversion of ammonium to organic nitrogen under ammonium stress was explored. Studies had shown that ammonium stress increased the amide nitrogen and bioavailable nitrogen content by 36.95% and 32.25%, respectively. Network and regression analyses showed that the microbial community structure was restructured by high ammonium and more bacteria were involved in the conversion of inorganic nitrogen to organic nitrogen(i.e., amide nitrogen, unknown nitrogen). Variation partition analysis and structural equation model showed that the bacterial community was the main contributor to organic nitrogen production(up to 67.4%), which reduced the nitrogen loss by 6.03%. These findings shed light on the poorly understood interaction between inorganic and organic nitrogen by clarifying the role of core bacterial communities in nitrogen conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • The limited step for N removal depended on the presence of plants. • The plants and low water level improved NH 4 + - N rather than TN removal. • N genes and nitrifying populations were affected in later period by treatments. • Cooccurrence network and associated heatmap evidenced interaction of N removal. • The differences in six core pathways of N metabolism depended on CW type. With occurrence of emerging contaminants in wastewater, nitrogen metabolism in constructed wetlands (CWs) should be re-evaluated at different environmental variables to withstand adversely exogenous contaminants. This study investigated functional gene, key enzyme, and microbe regulating nitrogen metabolism in three different configuration design CWs (planted W1 and W3 with full and low water level, unplanted W2 with full water level) when exposed to graphene oxide, one of most popular carbon-based nanomaterials. It was found that nitrogen removal was achieved by classical nitrification and denitrification, which was limited by nitrification in W2 and denitrification in planted CWs, presenting optimal balance between nitrification and denitrification in W1. Compared to W2, ammonium removals increased by 48% and 107% in W1 and W3, conversely total nitrogen removals decreased by 6% and 14% due to nitrate accumulation. Ammonia monooxygenase was the most sensitive to variables among four key enzymes. Bacteria were more abundant than archaea in CWs, both of functional genes and nitrifying populations were obviously affected by plant and water level in later period. The dominant denitrification populations were class Gammaproteobacteria followed by Alphaproteobacteria with the highest abundance observed in W2. Their species richness at genus level was higher on day 30 in W2 than planted CWs, but similar on day 120 in three CWs. The cooccurrence network and associated heatmap evidenced complex interaction among key enzymes, functional genes, and functional genera for nitrogen removal. KEGG annotations revealed specific differences in six core pathways of nitrogen metabolism in three CWs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simultaneous V(V) and NH 4 +-N removals are achieved in a MBfR. • V(V) is reduced to insoluble V(IV) confirmed by SEM and XRD characterization. • Nitrification/denitrification bioprocesses achieve NH 4 +-N removal. • Pseudomonas cooperates with others for V(V) and NH 4 +-N removals. • The gene abundances increase with improved enzyme activities for nitrogen cycling. Ammonium (NH 4 +) is commonly used as either a precipitant or extractant in metallurgy of non-ferrous metal and rare earth ore (e.g., vanadium). This results in the coexistence of toxic metal and NH 4 +-N in the effluent. Despite its toxicity, there remains little in the way of biological treatments to synchronously eliminate vanadate [V(V)] and NH 4 +-N in vanadium smelting wastewater. In this study, simultaneous V(V) and NH 4 +-N removal was achieved using a membrane biofilm reactor (MBfR). The removal efficiencies for V(V) and NH 4 +-N reached 96.8 ± 0.8% and 75.4 ± 1.2%, respectively, with initial concentrations for both beginning at 10 mg/L along with a hydraulic retention time at 36 h. V(V) was mainly reduced to V(IV) precipitates. Complete nitrogen removal was achieved with negligible NO 3 –-N/NO 2 –-N accumulation. Pseudomonas was identified as the main contributor to V(V) reduction, nitrification, and denitrification. The identified V(V) reducers and nitrifying/denitrifying bacteria were positively related to the V(V) and NH 4 +-N removal capacity of MBfR. The increased gene abundance and improved enzymic activity for nitrogen cycling collectively evidenced that V(V) reduction was catalyzed by denitrification enzymes and NH 4 +-N was removed through nitrification/denitrification. Collectively, the results from this study offer a novel strategy for the treatment of vanadium-bearing smelting wastewater by eliminating V(V) and NH 4 +-N in a one-step bioprocess. [ABSTRACT FROM AUTHOR]

The negative impacts of herbivore consumption on plants are well known, but impacts on ecosystem processes are not. Herbivores can alter soil nutrient availability through herbivory and waste deposition. If predators significantly reduce herbivory, they may impact some soil ecosystem processes. Gray wolves may regulate white-tailed deer herbivory in Great Lakes forests, and this may impact soil nitrogen availability. Deer exclosure/control plots in high- and low-wolf use forest patches were employed to determine whether wolves and/or deer affect nitrogen availability. Despite evidence for deer affecting soil nitrogen availability in other forests and wolves affecting it in grasslands, we found no such effects in this forest. Given the context dependence of top-down impacts on nutrient dynamics, we encourage further inquiry. [ABSTRACT FROM AUTHOR]

A chemical-less process using vacuum-UV (VUV) as radiation source was used for direct oxidation of ammonium to N 2 from the contaminated water. The effect of water pH, aeration, initial ammonium concentration, reaction time, and water anions on ammonium oxidation was evaluated in batch experiments. The oxidation of ammonium improved with the increase in water pH and the highest oxidation level obtained at the pH 8. Although the aeration partly improved ammonium oxidation efficiency, it inhibited the selective oxidation of ammonium to N 2 . The complete oxidation of ammonium at concentrations of 25, 50, 75 and 100 mg NH 4 + /L was obtained at the reaction times of 5, 6, 7.5 and 10 h, respectively, following pseudo first-order kinetic model. In addition, the selectivity to nitrate and N 2 formation obtained in the range of 7.7–14.8% and 85.2–92.3%, respectively. In continuous flow experiments, the complete oxidation of 50 mg/L ammonium observed at HRT of 8 h with N 2 selectivity above 99%. Sulfate had the lowest and carbonate had the highest scavenging effect among the selected anions on radicals species generated in the VUV photoreactor. Accordingly, the VUV photoreactor is an efficient and promising chemical-less advanced process for selective oxidation of ammonium to N 2 . [ABSTRACT FROM AUTHOR]

The oxidation of ammonium (NH 4 + ) under iron reducing conditions, also referred to as Feammox, has been described in recent years by several investigators. The environmental characteristics in which the Feammox process occurs need to be understood in order to determine its contribution to the nitrogen cycle. In this study, through extensive field sampling at various locations in the US (mostly New Jersey) and South China, soil chemical analyses, serial incubation experiments, analysis of microbial communities, and using canonical correspondence analyses, it was determined that the soil pH, as well as its Fe(III) and NH 4 + concentration were the most important factors controlling the distribution of Acidimicrobiaceae , which have been linked to the Feammox reaction. Under the conditions that favored the presence of Feammox bacteria and their oxidation of NH 4 + under iron reducing conditions, denitrification bacteria were also abundant. However, the presence of known nitrous oxide (N 2 O) reducers was limited under these conditions, implying that at locations where the Feammox process is active, conditions might favor a higher N 2 O:N 2 ratio for the nitrogen (N) end products. To determine the effect of dissolved oxygen (DO) on NH 4 + oxidation under iron reducing conditions, incubations were conducted at two different DO levels. In incubations with DO < 0.02 mg/L, and when NH 4 + oxidation was noticeable, the proportion of Acidimicrobiaceae with respect to total bacteria increased, while the proportion of other known NH 4 + oxidizing bacteria (aerobic ammonia-oxidizing bacteria and anammox bacteria) decreased. In incubations of the same soil but with DO = 0.8–1.0 mg/L the opposite trend was observed, indicating that Feammox favored very low or no DO in these incubations. [ABSTRACT FROM AUTHOR]

Cellular pH homeostasis is fundamental for life, and all cells adapt to maintain this balance. In plants, the chemical form of nitrogen supply, nitrate and ammonium, is one of the cellular pH dominators. We report that the rice nitrate transporter OsNRT2.3 is transcribed into two spliced isoforms with a natural variation in expression ratio. One splice form, OsNRT2.3b is located on the plasma membrane, is expressed mainly in the phloem, and has a regulatory motif on the cytosolic side that acts to switch nitrate transport activity on or off by a pH-sensing mechanism. High OsNRT2.3b expression in rice enhances the pH-buffering capacity of the plant, increasing N, Fe, and P uptake. In field trials, increased expression of OsNRT2.3b improved grain yield and nitrogen use efficiency (NUE) by 40%. These results indicate that pH sensing by the rice nitrate transporter OsNRT2.3b is important for plant adaption to varied N supply forms and can provide a target for improving NUE. [ABSTRACT FROM AUTHOR]

Accessing different nitrogen (N) sources involves a profound adaptation of plant metabolism. In this study, a quantitative proteomic approach was used to further understand how the model plant Arabidopsis thaliana adjusts to different N sources when grown exclusively under nitrate or ammonium nutrition. Proteome data evidenced that glucosinolate metabolism was differentially regulated by the N source and that both TGG1 and TGG2 myrosinases were more abundant under ammonium nutrition, which is generally considered to be a stressful situation. Moreover, Arabidopsis plants displayed glucosinolate accumulation and induced myrosinase activity under ammonium nutrition. Interestingly, these results were also confirmed in the economically important crop broccoli (Brassica oleracea var. italica). Moreover, these metabolic changes were correlated in Arabidopsis with the differential expression of genes from the aliphatic glucosinolate metabolic pathway. This study underlines the importance of nitrogen nutrition and the potential of using ammonium as the N source in order to stimulate glucosinolate metabolism, which may have important applications not only in terms of reducing pesticide use, but also for increasing plants' nutritional value. [ABSTRACT FROM AUTHOR]

A novel nitrogen removal strategy, the combined photoelectrocatalytic oxidation and autotrophic biofilm denitrification, was developed to achieve simultaneous NH 4 + -N oxidation and NO 3 − -N reduction in a single reactor. AgI/TiO 2 -NTs and autotrophic denitrifying biofilm were used as anode and cathode, respectively. NH 4 + -N oxidation efficiency was enhanced by 3 times after the introduction of visible light. Moreover, NO 3 − -N and NO 2 − -N generated in the process of NH 4 + -N oxidation could be further removed by biocathode. Applied voltage and pH have significant effects on nitrogen removal. The NO 3 − -N and NH 4 + -N removal efficiencies gradually increased from 27.2% to 74.3% and 60.0% to 83.1%, respectively, when the voltage increased from 1.0 V to 3.0 V. Neutral or slightly alkaline condition was favorable on account of the autotrophic denitrifying biofilm. The optimum TN (TN NH 4 + -N + NO 3 − -N + NO 2 − -N) removal efficiency was up to 89.6% at pH 8 with 3.0 V voltage. [ABSTRACT FROM AUTHOR]

This study aimed to assess the impact of land use patterns on water quality and benthic diatom community structure and to test the applicability of diatom indices developed in other regions of the world to a small temperate southern African river system. Sampling was conducted at eight study sites along the length of the river on four separate occasions. Multivariate data analyses were performed on the diatom community dataset to specify the main gradients of floristic variation and to detect and visualize similarities in diatom samples in relation to land-use patterns within the catchment. One hundred and twelve (112) diatom species belonging to 36 genera were recorded during the study. Canonical correspondence analysis (CCA) demonstrated that variations in the benthic diatom community structure were best explained by ammonium, nitrate, conductivity, pH, temperature, resistivity and water flow. OMNIDIA was used for calculation of selected diatom water quality indices. A number of the indices, e.g., the trophic diatom index (TDI), eutrophication/pollution index and biological index of water quality (BIWQ), either under- or over-estimated the water quality of the system. With few exceptions, there were no significant correlations (p> 0.05) between the diatom indices' values and the nutrient variables. The absence of any significant correlations between the diatom indices' values and selected physico-chemical variables suggests that indices developed in other regions of the world may not be suitable for temperate southern African rivers. [ABSTRACT FROM AUTHOR]

Climate change is predicted to have widespread impacts on freshwater lake and reservoir nutrient budgets by altering both hypolimnetic hypoxia and runoff, which will in turn alter the magnitude of internal and external nutrient loads. To examine the effects of these potential climate scenarios on nitrogen (N) and phosphorus (P) budgets, we conducted a whole-catchment manipulation of hypolimnetic oxygen conditions and external loads to Falling Creek Reservoir (FCR), an old, eutrophic reservoir in a reforested catchment with a history of agricultural land use. Throughout 2 years of monitoring, internal N and P loading during hypoxic conditions dominated the hypolimnetic mass of nutrients in FCR, regardless of changes in external loading. FCR commonly functioned as a net sink of N and P, except during hypoxic conditions, when the reservoir was a net source of ammonium ( $$ {\text{NH}}_{4}^{ + } $$ ) to downstream. We observed extremely high nitrate-nitrite ( $$ {\text{NO}}_{3}^{ - } {-}{\text{NO}}_{2}^{ - } $$ ), soluble reactive P (SRP), total nitrogen (TN), and total phosphorus (TP) retention rates, indicating that the reservoir served as a sink for greater than 70% of $$ {\text{NO}}_{3}^{ - } {-}{\text{NO}}_{2}^{ - } $$ inputs and greater than 30% of SRP, TN, and TP inputs, on average. Our study is notable in the length of time since reforestation (>80 years) that a reservoir is still exhibiting high N and P internal loading during hypoxia, potentially as a result of the considerable store of accumulated nutrients in its sediment from historical agricultural runoff. Our whole-catchment manipulations highlight the importance of understanding how multiple aspects of global change, waterbody and catchment characteristics, and land use history will interact to alter nutrient budgets in the future. [ABSTRACT FROM AUTHOR]