Uptake Of NH4 Research Articles

Chemical Storage of Ammonia through Dynamic Structural Transformation of a Hybrid Perovskite Compound.

Toward renewable energy for global leveling, compounds that can store ammonia (NH3), a carbon-free energy carrier of hydrogen, will be of great value. Here, we report an organic-inorganic halide perovskite compound that can chemically store NH3 through dynamic structural transformation. Upon NH3 uptake, a chemical structure change occurs from a one-dimensional columnar structure to a two-dimensional layered structure by addition reaction. NH3 uptake is estimated to be 10.2 mmol g-1 at 1 bar and 25 °C. In addition, NH3 extraction can be performed by a condensation reaction at 50 °C under vacuum. X-ray diffraction analysis reveals that reversible NH3 uptake/extraction originates from a cation/anion exchange reaction. This structural transformation shows the potential to integrate efficient uptake and extraction in a hybrid perovskite compound through chemical reaction. These findings will pave the way for further exploration of dynamic, reversible, and functionally useful compounds for chemical storage of NH3.

Biochar-extracted liquor stimulates nitrogen related gene expression on improving nitrogen utilization in rice seedling.

Biochar has been shown to be an effective soil amendment for promoting plant growth and improving nitrogen (N) utilization. However, the physiological and molecular mechanisms behind such stimulation remain unclear. In this study, we investigated whether biochar-extracted liquor including 21 organic molecules enhance the nitrogen use efficiency (NUE) of rice plants using two N forms (NH4 +-N and NO3 --N). A hydroponic experiment was conducted, and biochar-extracted liquor (between 1 and 3% by weight) was applied to rice seedlings. The results showed that biochar-extracted liquor significantly improved phenotypic and physiological traits of rice seedlings. Biochar-extracted liquor dramatically upregulated the expression of rice N metabolism-related genes such as OsAMT1.1, OsGS1.1, and OsGS2. Rice seedlings preferentially absorbed NH4 +-N than NO3 --N (p < 0.05), and the uptake of NH4 +-N by rice seedlings was significantly increased by 33.60% under the treatment of biochar-extracted liquor. The results from molecular docking showed that OsAMT1.1protein can theoretically interact with 2-Acetyl-5-methylfuran, trans-2,4-Dimethylthiane, S, S-dioxide, 2,2-Diethylacetamide, and 1,2-Dimethylaziridine in the biochar-extracted liquor. These four organic compounds have similar biological function as the OsAMT1.1 protein ligand in driving NH4 +-N uptakes by rice plants. This study highlights the importance of biochar-extracted liquor in promoting plant growth and NUE. The use of low doses of biochar-extracted liquor could be an important way to reduce N input in order to achieve the purpose of reducing fertilizer use and increasing efficiency in agricultural production.

Efficient cavity-enhanced adsorption and recovery of low-concentration ammonia on pillar[5]arenes

Ammonia (NH3) capture has great implications for environmental protection and resource recovery. Developing effective and recyclable adsorbent materials to remove low-concentration NH3 in industrial waste gas is critical. Here, solid adsorbents per-hydroxylated pillar[5]arene (OHP[5]) and pillar[5]quinone (P[5]Q) with well-designed functional groups were synthesized and evaluated for NH3 adsorption. The results showed that both materials have high NH3 uptake capacity and excellent cycle stability. P[5]Q showed higher NH3 capacity (15.4 mmol/g) than OHP[5] (11.5 mmol/g) at ambient conditions (293.2 K and 1.0 bar). Dynamic breakthrough experiments showed that P[5]Q had good separation performance on low concentration NH3. Characterizations (including FTIR, SEM, and XPS) and density functional theory (DFT) studies revealed that the adsorption strength for NH3 on P[5]Q possessing CO groups was stronger than OHP[5] composed of phenolic hydroxyls. Also, the electron-accepting CO groups on P[5]Q could change the intramolecular charge distribution, in which an amount of NH3 enters and stores in the electron-deficient internal cavity of P[5]Q. It is demonstrated that P[5]Q with the suitable cavity has good potential for separating low concentration NH3 from industrial waste gas.

Forms of nitrogen inputs regulate the intensity of soil acidification.

Soil acidification induced by reactive nitrogen (N) inputs can alter the structure and function of terrestrial ecosystems. Because different N-transformation processes contribute to the production and consumption of H+ , the magnitude of acidification likely depends on the relative amounts of organic N (ON) and inorganic N (IN) inputs. However, few studies have explicitly measured the effects of N composition on soil acidification. In this study, we first conducted a meta-analysis to test the effects of ON or IN inputs on soil acidification across 53 studies in grasslands. We then compared soil acidification across five different ON:IN ratios and two input rates based on long-term field N addition experiments. The meta-analysis showed that ON had weaker effects on soil acidification than IN when the N addition rate was above 20 g N m-2 year-1 . The field experiment confirmed the findings from meta-analysis: N addition with proportions of ON ≥ 20% caused less soil acidification, especially at a high input rate (30 g N m-2 year-1 ). Structural equation model analysis showed that this result was largely due to a relatively low rate of H+ production from ON as NH3 volatilization and uptake of ON and NH4 + by the dominant grass species Leymus chinensis (which are both lower net contributors to H+ production) result in less NH4 + available for nitrification (which is a higher net contributor to H+ production). These results indicate that the evaluation of soil acidification induced by N inputs should consider N forms, and manipulations of relative composition of N inputs may provide an effective approach to alleviate the N-induced soil acidification.

Protic amino-2-propanol hydrochloride-based deep eutectic solvents with multiple hydrogen bond sites for efficient capture of NH3

The ammonia (NH3) emitting into the atmosphere during the industrial process of synthesizing ammonia not only constitutes serious air pollution, but also causes a waste of ammonia resources. Therefore, there is an urgent need to develop efficient ammonia capture technology. In this work, we report an efficient capture of NH3 by protic amino-2-propanol hydrochloride-based deep eutectic solvents (DESs). These DESs with multiple hydrogen bond sites exhibit remarkable NH3 uptake with up to 0.244 g NH3 per g DES at 293 K and 1 bar and good recyclability. Further mechanism study suggested that the introduction of hydrogen bond donors with rich hydroxyl groups provides a large number of hydrogen bond sites to achieve efficient absorption of NH3 through the intermolecular hydrogen bonds interaction. This research has obtained an alternative absorber for the capture of NH3, and it also provides ideas for the design of high-efficiency NH3 deep eutectic solvents absorbent.

Ionic liquid hybrid metal–organic frameworks for efficient adsorption and selective separation of ammonia at high temperature

Efficient adsorption and selective separation of ammonia at high temperature is a crucial and challenging issue. In this work, a series of stable ionic liquid hybrid materials have been developed by simple impregnation of ionic liquids into stable metal–organic framework Al-fum with 1D pores. The hybrid material [C2N][Zn3Cl7]@Al-fum-60% exhibited an exceptionally high uptake (9.9 mmol/g at 80 °C, 8.8 mmol/g at 100 °C) at high temperature, excellent uptake (9.8 mmol/g at 25.0 °C) at low ammonia concentration (100,000 ppm), and remarkable selective separation performance (selectivity factor is 25.1) of NH3 from NH3/CO2 mixture at high temperature. The NH3 uptake of [C2N][Zn3Cl7]@Al-fum-60% at 100 °C was higher than the capacity of most of typical porous NH3 adsorbents at room temperature. It is revealed that such superior NH3 capacity and selective separation performance are mainly attributed to coordination interactions of NH3 to Zn centre of the ionic liquids and the hydrogen bonding interactions of NH3 with Cl of the ionic liquids and NH3 with μ-OH of Al-fum.

Functional Characterization of Ammonium Transporter MhAMT1;2 in Malus hupehensis

The absorption and utilization of NH4+ and NO3− by plant roots is closely related to soil moisture. In this study, we investigated the effect of short-time drought and rewatering on uptake and assimilation of NH4+ and NO3− in 1-year-old Malus hupehensis plants, as well as transcription changes of ammonium transporters (AMTs) and nitrate transporters (NRTs). In roots, the NH4+ and NO3− content and nitrate reductase activity decreased under drought and to some extent was restored after rewatering. Expression analysis indicated that most investigated AMTs and NRTs were down-regulated while MhAMT1;2 was significantly up-regulated in drought-stressed roots. Therefore, the function of MhAMT1;2 was further studied through bioinformatics analysis, tissue-specific expression, subcellular localization, and functional complementation in NH4+ uptake-defective yeast and Arabidopsis mutants. Results showed that MhAMT1;2 was mainly expressed in roots and localized to the cell membrane. Moreover, MhAMT1;2 can mediate NH4+ uptake in both yeast and Arabidopsis mutants, and the transport process was affected by external proton concentrations and ATP. The present study will create a basis for exploring the functional roles of plant AMT members and improving N uptake and use efficiency under drought condition in fruit trees.

Mesoporous Multiproton Ionic Liquid Hybrid Adsorbents for Facilitating NH3 Separation

Ionic liquids (ILs), as promising candidates for ammonia (NH3) separation and recovery, have attracted extensive attention due to their extremely low pressures, high gas affinity, and adjustable structures. However, the development of new absorbents or adsorbents for highly efficient, fast, and reversible separation is still a great challenge. In this work, multiproton ILs (MPILs) by simultaneously introducing two or more −H, −OH, or −SO3H sites into the cations were designed to enhance NH3 uptake, and the MPIL N,N,N′,N′-tetrakis (2-hydroxyethyl)ethylenediamine trifluoromethane sulfonate ([EdteH6][TfO]2) with four −OH and two −H sites exhibited a superhigh capacity of 5.08 mol NH3·(mol IL)−1 at 40 °C and 1 bar. To solve the slow gas–liquid mass transfer due to the high viscosity of MPILs, the designed MPILs were highly dispersed onto the molecular sieve HZSM-5 with abundant pore structures to prepare a series of porous MPIL-based hybrid adsorbents for NH3 adsorption. The highest capacity of 140.42 mg NH3·(g adsorbent)−1 at 30 °C and 1 bar was achieved by 60 wt % [EdteH6][TfO]2@HZSM-5-60 (HZ60) due to multiple hydrogen bonding and mesopore effects, which is superior to all of the nonmetal IL-based adsorbents reported to date. Meanwhile, the 60 wt % [EdteH6][TfO]2@HZ60 also exhibited high NH3/CO2 and NH3/N2 selectivities, which are almost 16 and 14 times greater than that of pure HZ60, respectively, along with excellent reversibility. This work provides a feasible way to design novel porous IL-based adsorbents for gas separation and recovery.

Ammonia Capture in Rhodium(II)-Based Metal-Organic Polyhedra via Synergistic Coordinative and H-Bonding Interactions.

Ammonia (NH3) is among the world's most widely produced bulk chemicals, given its extensive use in diverse sectors such as agriculture; however, it poses environmental and health risks at low concentrations. Therefore, there is a need for developing new technologies and materials to capture and store ammonia safely. Herein, we report for the first time the use of metal-organic polyhedra (MOPs) as ammonia adsorbents. We evaluated three different rhodium-based MOPs: [Rh2(bdc)2]12 (where bdc is 1,3-benzene dicarboxylate); one functionalized with hydroxyl groups at its outer surface [Rh2(OH-bdc)2]12 (where OH-bdc is 5-hydroxy-1,3-benzene dicarboxylate); and one decorated with aliphatic alkoxide chains at its outer surface [Rh2(C12O-bdc)2]12 (where C12O-bdc is 5-dodecoxybenzene-1,3-benzene dicarboxylate). Ammonia-adsorption experiments revealed that all three Rh-MOPs strongly interact with ammonia, with uptake capacities exceeding 10 mmol/gMOP. Furthermore, computational and experimental data showed that the mechanism of the interaction between Rh-MOPs and ammonia proceeds through a first step of coordination of NH3 to the axial site of the Rh(II) paddlewheel cluster, which triggers the adsorption of additional NH3 molecules through H-bonding interaction. This unique mechanism creates H-bonded clusters of NH3 on each Rh(II) axial site, which accounts for the high NH3 uptake capacity of Rh-MOPs. Rh-MOPs can be regenerated through their immersion in acidic water, and upon activation, their ammonia uptake can be recovered for at least three cycles. Our findings demonstrate that MOPs can be used as porous hosts to capture corrosive molecules like ammonia, and that their surface functionalization can enhance the ammonia uptake performance.

Effects of Rhus typhina Invasion on Soil Physicochemical Properties and Carbon Emissions in Urban Green Spaces

Alien plants invasion have become a hot issue in the field of ecology. The invasion of alien plants is usually accompanied by changes in the physical and chemical properties of the soil, the ensuing negative feedback creates a favorable environment for its own growth and expansion. Invasive plans have a strong ability to sequester carbon, which can greatly affect the original local ecological environment. In this study, we selected Rhus typhina, an invasive plant widely used for greening, as the experimental subject and natural growing grassland as the control. The aims were to investigate the effects of different degrees of invasion of R. typhina on soil physicochemical properties and carbon emissions, and to explore the influential factors on carbon emission. The results showed that R. typhina invasion significantly increased soil pH, total nitrogen content, easy extraction of glomalin-related soil protein (EEG) and cumulative CO2 emissions (CEM). It is worth noting that the CEM increased significantly during the severe invasion by R. typhina. The significant increase in soil NH4+-N content and the decrease in soil NO3−-N content indicate that the soil after the invasion of R. typhina has better uptake of NH4+-N. Temperature and soil moisture content had significant direct effects on CEM, while NH4+-N, NO3−-N, EEG and temperature sensitivity of soil organic carbon mineralization Q10 (30 °C/20 °C) had a direct but non-significant effect on CEM. The above findings suggest that R. typhina can generate positive feedback by influencing the physicochemical properties and CEM of the soil, opening the way for its own expansion, which can be targeted to prevent the destruction of local ecosystems during the introduction of cultivation and subsequent management.

Incorporating concepts of biodiversity into modern aquaculture: macroalgal species richness enhances bioremediation efficiency in a lumpfish hatchery

Aquaculture is one of the fastest growing food producing sectors; however, intensive farming techniques of finfish have raised environmental concerns, especially through the release of excessive nutrients into surrounding waters. Biodiversity has been widely shown to enhance ecosystem functions and services, but there has been limited testing or application of this key ecological relationship in aquaculture. This study tested the applicability of the biodiversity-function relationship to integrated multi-trophic aquaculture (IMTA), asking whether species richness can enhance the efficiency of macroalgal bioremediation of wastewater from finfish aquaculture. Five macroalgal species (Chondrus crispus, Fucus serratus, Palmaria palmata, Porphyra dioica, and Ulva sp.) were cultivated in mono- and polyculture in water originating from a lumpfish (Cyclopterus lumpus) hatchery. Total seaweed biomass production, specific growth rates (SGR), and the removal of ammonium (NH&lt;sub&gt;4&lt;/sub&gt; &lt;sup&gt;+&lt;/sup&gt;), total oxidised nitrogen (TON), and phosphate (PO&lt;sub&gt;4&lt;/sub&gt; &lt;sup&gt;3-&lt;/sup&gt;) from the wastewater were measured. Species richness increased total seaweed biomass production by 11% above the average component monoculture, driven by an increase in up to 5% in SGR of fast-growing macroalgal species in polycultures. Macroalgal species richness further enhanced ammonium uptake by 25%, and TON uptake by nearly 10%. Phosphate uptake was not improved by increased species richness. The increased uptake of NH&lt;sub&gt;4&lt;/sub&gt; &lt;sup&gt;+&lt;/sup&gt; and TON with increased macroalgal species richness suggests the complementary use of different nitrogen forms (NH&lt;sub&gt;4&lt;/sub&gt; &lt;sup&gt;+&lt;/sup&gt; vs. TON) in macroalgal polycultures. The results demonstrate enhanced bioremediation efficiency by increased macroalgal species richness and show the potential of integrating biodiversity- function research to improve aquaculture sustainability.

Defects in a Metal–Organic Framework Fabricated by Carboxy-Functionalized Ionic Liquids for Enhancing NH3 Uptake

Ammonia (NH3) is a promising clean energy because of its high hydrogen density and carbon-free nature. Therefore, the capture, storage, and desorption of NH3 have received widespread attention in recent years. However, achieving highly efficient capture and release of NH3 remains a challenge. Herein, an efficient strategy is proposed to fabricate defects in a metal–organic framework (UiO-66) by using ionic liquid as a modulator for the first time. It is found that the NH3 adsorption capacity of the optimal defective UiO-66 is up to 1.60 times that of the pristine UiO-66 because of 16.8% of the linker missing. It is noteworthy that the adsorption of NH3 in the defective UiO-66 is completely reversible under conventional pressure-swing conditions, and more than 95% of the NH3 uptake capacity can be maintained after 30 adsorption–desorption cycles. It is revealed that the enhanced coordinating interaction of NH3 to Zr4+ and hydrogen bonding interactions between NH3 and oxygen-containing groups in the framework are the main driving forces for the substantially increased NH3 uptake. In addition, the strategy developed here is green and simple for manufacturing defects, which opens up a new pathway to the preparation of a wide range of solid adsorbents and catalysts.

Surface modification of coal tailings by thermal air oxidation for ammonia capture

Utilization of coal tailings (CTs) to enable ammonia (NH 3 ) capture is of interest from pollution control and waste management perspectives. In this work, CTs were surface modified by air oxidation at different temperatures and varying duration to increase the uptake of NH 3 . The CTs treated at 300 and 250 °C for 5 h achieved an NH 3 uptake of 52.5 and 45.3 mg g −1 , respectively, which was significantly higher than that of the untreated CT (2.1 mg g −1 ). A linear relationship between NH 3 uptake and concentration of acidic surface functional groups was found (R 2 = 0.99). Spectroscopic analysis showed that NH 3 can be retained on the oxidized CT through chemisorption involving carboxylic groups, leading to the formation of amides. Kinetic studies in the temperature range of 200–300 °C revealed an activation energy of 50.2 kJ mol −1 for the formation of acidic surface functional groups on CTs. These comparably mild conditions for the oxidative surface modification make CTs versatile and readily available materials for reducing agricultural NH 3 emissions.

Heteroatom-Doped Porous Carbons as Effective Adsorbers for Toxic Industrial Gasses.

Ammonia (NH3), often stored in large quantities before being used in the production of fertilizer, and sulfur dioxide (SO2), a byproduct of fossil fuel consumption, particularly the burning of coal, are highly toxic and corrosive gases that pose a significant danger to humans if accidentally released. Therefore, developing advanced materials to enable their effective capture and safe storage is highly desired. Herein, advanced benzimidazole-derived carbons (BIDCs) with an exceptional capacity for NH3 and SO2 have been designed and tested. These heteroatom-doped porous carbon adsorbents were synthesized by thermolysis of imidazolate-potassium salts affording high surface area and controlled heteroatom content to optimize for rapid NH3 and SO2 gas uptake and release under practical conditions. According to gas uptake measurements, these nitrogen-doped carbons exhibit exceptional gas adsorption capacity, with BIDC-3-800 adsorbing 21.42 mmol/g SO2 at 298 K and 1 bar, exceeding most reported porous materials and BIDC-2-700 adsorbing 14.26 mmol/g NH3 under the same conditions. The NH3 uptake of BIDC-2-700 surpassed reported activated carbons and is among the best adsorbents including metal organic frameworks (MOFs). Our synthetic method allows for control over both textural and chemical properties of the carbon and enables heteroatom functionality to be incorporated directly into the carbon framework without the need for postsynthetic modification. These materials were also tested for recyclability; all adsorbents showed almost complete retention of their initial gas uptake capacity during recyclability studies and maintained their structural integrity and their previous adsorption capacity of both NH3 and SO2, highlighting their potential for practical application.

Polymer-encapsulated crystalline zirconium phosphates as NH4+ and K+ ion exchangers for application in sorbent dialysis cartridges

The ion exchange properties of crystalline ⍺- and γ-zirconium phosphates in the sodium and hydrogen forms were investigated. The zirconium phosphates were synthesized by a mechanochemistry-assisted protocol. Amongst the compounds, ⍺-Na2-zirconium phosphate and γ-H2-zirconium phosphate were found to be excellent ion exchangers for NH4+ and K+ ions, two key cations in renal sorbent dialysis systems. The maximum NH4+ uptake by ⍺-Na2-zirconium phosphate was 5.5 mmol/g, close to the theoretical limit of exchangeable sites. In multi-ion solutions, γ-H2-zirconium phosphate was a selective exchanger for K+ with total uptake capacity of 2.9 mmol/g. The as-synthesized microcrystalline zirconium phosphates were encapsulated by polyacrylonitrile to form spherical porous beads of tailorable sizes. Owing to the porosity, access to the ion exchange sites of the embedded zirconium phosphates particles was unaffected, enabling fast kinetics in the uptake of NH4+ and K+. In this form, the PAN/ZrP beads can be easily handled in sorbent cartridges. The activity of the PAN/ZrP beads could be fully restored by simple regeneration with the appropriate electrolyte.

Macromolecular-metal complexes induced by Co(II) with polymer and flexible ligands for ammonia uptake compared with MOFs

MOFs are considered as potential adsorbents for their outstanding properties, but it’s troublous for reversible ammonia adsorption or the collapse of MOFs’ framework. Macromolecular-metal complexes (MMCs) are proposed to efficient and reversible NH3 uptake at the first time with the consideration of the same coordinated unit to MOFs but with entropic advantage to assist the reversibility. In this work, the MMCs are developed with the construction of stable porous macromolecular-Co(II) networks and competitive flexible ligands to target the high capacity of 19.5 mmol/g under STP and reversibility of MMCs. The efficient NH3 uptake of MMCs was proposed to the coordination of NH3 with Co(II) along with the hydrogen bonding interaction with flexible ligand and the physical adsorption for the porosity of MMCs, meanwhile, the invariable macromolecular-Co(II) networks protect MMCs from collapse and comfine the flexible ligand. The comfined ligand would compete with NH3 to coordinate with Co(II), which promotes the release of NH3 and the reversibility of MMCs. The development of MMCs in this work provides a potential and competitive choice for NH3 storage as well as other special applications for the tunable structure trough regulating the macromolecule, metallic center, and ligand.

Direct Observation of Ammonia Storage in UiO-66 Incorporating Cu(II) Binding Sites.

The presence of active sites in metal–organic framework (MOF) materials can control and affect their performance significantly in adsorption and catalysis. However, revealing the interactions between the substrate and active sites in MOFs at atomic precision remains a challenging task. Here, we report the direct observation of binding of NH3 in a series of UiO-66 materials containing atomically dispersed defects and open Cu(I) and Cu(II) sites. While all MOFs in this series exhibit similar surface areas (1111–1135 m2 g–1), decoration of the −OH site in UiO-66-defect with Cu(II) results in a 43% enhancement of the isothermal uptake of NH3 at 273 K and 1.0 bar from 11.8 in UiO-66-defect to 16.9 mmol g–1 in UiO-66-CuII. A 100% enhancement of dynamic adsorption of NH3 at a concentration level of 630 ppm from 2.07 mmol g–1 in UiO-66-defect to 4.15 mmol g–1 in UiO-66-CuII at 298 K is observed. In situ neutron powder diffraction, inelastic neutron scattering, and electron paramagnetic resonance, solid-state nuclear magnetic resonance, and infrared spectroscopies, coupled with modeling reveal that the enhanced NH3 uptake in UiO-66-CuII originates from a {Cu(II)···NH3} interaction, with a reversible change in geometry at Cu(II) from near-linear to trigonal coordination. This work represents the first example of structural elucidation of NH3 binding in MOFs containing open metal sites and will inform the design of new efficient MOF sorbents by targeted control of active sites for NH3 capture and storage.

Does quantification of [11C]meta-hydroxyephedrine and [13N]ammonia kinetics improve risk stratification in ischemic cardiomyopathy

BackgroundIn ischemic cardiomyopathy patients, cardiac sympathetic nervous system dysfunction is a predictor of sudden cardiac arrest (SCA). This study compared abnormal innervation and perfusion measured by [11C]meta-hydroxyephedrine (HED) vs [13N]ammonia (NH3), conventional uptake vs parametric tracer analysis, and their SCA risk discrimination. MethodsThis is a sub-study analysis of the prospective PAREPET trial, which followed ischemic cardiomyopathy patients with reduced left ventricular ejection fraction (LVEF ≤ 35%) for events of SCA. Using n = 174 paired dynamic HED and NH3 positron emission tomography (PET) scans, regional defect scores (%LV extent × severity) were calculated using HED and NH3 uptake, as well as HED distribution volume and NH3 myocardial blood flow by kinetic modeling. ResultsDuring 4.1 years follow-up, there were 27 SCA events. HED defects were larger than NH3, especially in the lowest tertile of perfusion abnormality (P < .001). Parametric defects were larger than their respective tracer uptake defects (P < .001). SCA risk discrimination was not significantly improved with parametric or uptake mismatch (AUC = 0.73 or 0.70) compared to HED uptake defect scores (AUC = 0.67). ConclusionQuantification of HED distribution volume and NH3 myocardial blood flow produced larger defects than their respective measures of tracer uptake, but did not lead to improved SCA risk stratification vs HED uptake alone.

Modeling Reactive Ammonia Uptake by Secondary Organic Aerosol in a Changing Climate: A WRF-CMAQ Evaluation

In addition to the well-constrained inorganic acid-base chemistry of ammonia resulting in fine particulate matter (PM2.5) formation, ammonia also reacts with certain organic compounds in secondary organic aerosol (SOA) to produce less basic nitrogen-containing organic compounds. In this study, the potential meteorology and air quality impacts of the heterogeneous uptake of NH3 by SOA are investigated using the WRF-CMAQ two-way coupled model, which calculates the two-way radiative forcing feedback caused by aerosol between meteorology and chemistry in a single simulation. Simulations with and without the NH3-SOA uptake are performed over the contiguous US for July 2014 and July 2050 under the RCP 8.5 IPCC scenario to study the potential impact of climate change. A comparison with multiple observation network data shows that the NH3-SOA uptake improves the model performance for PM2.5 prediction (bias reduced from −22% to −17%), especially the underestimation of organic carbon over the Southeastern US (bias reduced from −17% to −7%). Secondly, the addition of the NH3-SOA chemistry significantly impacts the concentration of NH3 and NH4+, thus affecting the modeled particle acidity. Including the NH3-SOA uptake also impacts the meteorological conditions through the WRF-CMAQ two-way feedback. Moreover, the impact on meteorological conditions results in different windspeed or dispersion conditions, thus affecting air quality predictions. Finally, simulations including the NH3-SOA uptake under the warmer climate conditions of 2050 show a smaller impact on air quality predictions than it does under current climate conditions. This study confirms the importance and necessity of including NH3-SOA chemistry in air quality predictions.

Ordinary heterotrophic organisms with aerobic storage capacity provide stable aerobic granular sludge for C and N removal

The study investigated the mechanisms and microbial communities underlying the long-term stability and removal performances shown by aerobic granular sludge (AGS) reactor involving polyhydroxyalkanoates (PHA) aerobic-storing bacteria. The characteristics of the sludge, removal performances and bacterial community structure were determined. The prevailing metabolic phenotype was similar in the parent conventional activated sludge (CAS) reactor and its upgraded AGS version, showing high COD and NH4 uptake, versus low P and N reduction. Polyphosphate and glycogen accumulating organisms, PAO and GAO, were not enriched in the reactors despite initial targeting of anaerobic-aerobic cycle. Instead, PHA-aerobic storing bacteria (Thauera and Paracoccus) were dominant, but revealing a stable AGS system for BOD and N removal. The PAO/GAO failed selection and Thauera overgrowth were analyzed for beneficial use in developing alternative AGS technology for BOD and N removal applications.