Low NH3 Research Articles

Optimization control strategy for diesel urea-selective catalytic reduction (SCR) urea injection based on the interior point method (IP) + higher order SCR model

In order to ensure that the NOx and NH3 emissions of diesel engines comply with the Euro VII emission standards, this paper optimizes the urea injection using a SCR model combined with the interior point method. First, the equations of the higher-order SCR model were simplified by the variable substitution method and the line method and solved by the backward difference formula to improve computational accuracy. The Levenberg-Marquardt algorithm was used to calibrate the chemical reaction rate parameters to optimize model performance. Second, an optimization cost function was designed to optimize the upstream NH3 concentration in combination with the interior point method and the higher-order SCR model to meet the requirements of Euro VII emission standards. Third, the model effect was verified by performing WHTC hot-start testing on an engine complying with the National VI emission standard. The results show that the average error between the measured NOx concentration and the calculated is 1.49 ppm, which verifies the high accuracy of the model. Finally, the effects of the interior point method, NSGA-II, and MOPSO algorithms in optimizing the upstream NH3 concentration were compared. The results showed that the interior point method outperformed the other algorithms in terms of optimization time and effect, with an optimization time of 149 s, a NOx conversion rate of 97.36 %, and an average downstream NH3 concentration of 4.65 ppm. This achieved a high NOx conversion rate and low NH3 slip in accordance with the requirements of the Euro VII regulation.

Effect of bedding application and air change rates on environmental ammonia concentrations for intensively housed beef cattle

Context Manure deposition during livestock export voyages contributes to air ammonia levels, potentially affecting human and animal health if not managed. Mitigation strategies may include increased air change rates and application of bedding. Aim This study examined the effect of bedding application rate (BAR) and air change rate (ACH) on air ammonia (NH3) concentrations and pad properties, including pad surface condition, pH, moisture, and pad ammonium (NH4+) concentrations, for intensively housed beef cattle. Methods Six 7-day runs were conducted with 72 Bos indicus cross steers (mean liveweight ± s.d. = 338 ± 32 kg) housed in respiration chambers by using a 3 × 3 factorial design. The BARs were set to 0%, 50%, and 100% of the Australian Standards for the Export of Livestock (ASEL), and ACH were varied at 20, 35, and 52. Air NH3 was measured twice daily at three heights. Pad surface condition was collected with the first air NH3 measurement. Video footage captured standing and lying behaviours for each steer. Pad samples were collected on the final day for pad chemical analysis. Key results The ACH of 20 changes per hour resulted in higher air NH3 concentration than ACH of 35 and 52. Higher BAR led to lower pad pH and moisture, with slightly lower pad NH4+ concentration in 100% and 50% BAR than 0% BAR. Although air NH3 concentration on Day 7 was positively correlated with pad NH4+ concentration, BAR had no marked effect on air NH3 concentration (within the temperature range of this experiment). Drier and firmer pad surfaces were associated with each high BAR and high ACH. Moreover, high BAR increased the frequency of lying behaviour in steers. Conclusions These findings indicated that NH3 can be mitigated by optimising air changes to minimise air NH3 concentration and utilising bedding to minimise pad NH4+. This offers practical solutions for intensively housed beef cattle, such as livestock export voyages to improve human and animal welfare onboard. Implications The study results emphasised the importance of optimising ACH to maintain low air NH3 concentrations in livestock export conditions. Although there was no evidence that BAR affects air NH3 directly, it reduced pad NH4+ and improved pad conditions for overall animal comfort and environmental quality in confined housing with sufficient air changes.

Fe(OH)3/Ti3C2Tx nanocomposites for enhanced ammonia gas sensor at room temperature

Two-dimensional material (2D material) MXene has great application potential in gas sensors because of its excellent controllable performance and vast specific surface area. In this study, we used a straightforward in-situ electrostatic self-assembly technique to create Fe(OH)3/Ti3C2Tx nanocomposites, which were then used to fabricate gas sensors for ammonia detection at room temperature (25 ℃). Several characterization methods were performed aimed at determining the surface appearance and construction of the nanocomposites, and the sensing characteristics and mechanism were also systematically examined. The findings demonstrate the effective incorporation of amorphous Fe(OH)3 nanoparticles on the surface of Ti3C2Tx. Additionally the nanocomposites of Fe(OH)3/Ti3C2Tx have considerably higher specific surface area than pure Ti3C2Tx, hence offering more active NH3 adsorption sites. The response of the sensor to 100 ppm NH3 was 48.6% at room temperature, which was 9.3 times more higher than that of pure Ti3C2Tx. The sensors also have the advantages of long-term stability (33 days), low NH3 detection limit (500 ppb), and rapid recovery time (85 s) and response times (78 s). It is anticipated that this work will be helpful for developing the new generation of wearable ammonia sensors at room temperature.

Fat Distribution and Urolithiasis Risk Parameters in Uric Acid Stone Formers and Patients with Type 2 Diabetes Mellitus

Background: Uric acid (UA) nephrolithiasis affects approximately 10% of kidney stones, with a greater preponderance among patients with obesity and diabetes mellitus. UA lithogenicity is driven by abnormally acidic urine pH. Distinguishing the contribution of intrinsic (e.g., body adiposity) versus external (e.g., dietary) factors to UA stone propensity is challenging due to uncontrolled diets in outpatients in previously published studies. Methods: This compilation of metabolic studies with body composition examined by dual-energy X-ray absorptiometry (DXA) scan, and blood and urine biochemistry collected under a controlled metabolic diet was conducted across three distinct populations: 74 UA stone formers (UASF group), 13 patients with type 2 diabetes mellitus without kidney stones (DM group), and 51 healthy volunteers (HV group). Results: Compared to HV, both UASF and DM exhibited higher levels of net acid excretion (NAE), and significantly lower urine pH and lower proportion of NAE excreted as ammonium (NH4 +/NAE), all under controlled diets. UASF exhibited significantly lower NH4 +/NAE compared with DM. UASFs also showed higher total body and truncal fat compared to controls. Among the HV, lower NH4 +/NAE ratio correlated with higher truncal and total fat. However, this association was abolished in the UASF and DM groups who exhibit a fixed low NH4 +/NAE ratio across a range of body and truncal fat. Conclusion: The findings suggest a dual defect of diet-independent increase in acid production and impaired kidney NH4 + excretion as major contributors to the risk for uric acid stone formation. There is an inverse physiologic association between body fat content and NH4 +/NAE in HV while NH4 +/NAE is persistently low in UASF and DM regardless of body fat representing pathophysiology.

Low Strength Wastewater Treatment Using a Combined Biological Aerated Filter/Anammox Process

To achieve the in situ capacity expansion of the post-denitrification biological aerated filter (BAF-DN), the integration of BAF with the anammox process (BAF/AX) was proposed. With the objective of maximizing retaining ammonia nitrogen, the operational optimization of BAF was achieved by two distinct strategies. The treatment performance of BAF demonstrated that the removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) was 66.3~67.3% and 4~12%, respectively, under conditions of low aeration intensity (0.4 m3·m−2·h−1) or a shortened empty bed residence time (EBRT) of 30 min. Residual NH4+-N in the BAF effluent served as the ammonia substrate for the subsequent anammox process, which was successfully launched by using ceramic particles and sponges as carriers. Notably, the sponge carrier facilitated a shorter start-up period of 41 to 44 days. Furthermore, the sponge-based anammox reactor exhibited a superior NH4+-N removal capacity (≥85.7%), under operations of a shorter EBRT of 40 min, low influent NH4+-N concentrations (≤30 mg/L), and COD levels of ≤67 mg/L. In addition, a comprehensive evaluation of the BAF/AX process was conducted, which considered performance, cost-effectiveness, and engineering feasibility. The performance results illustrated that the effluent quality met the standard well (with a COD level of ≤ 50 mg/L, and a TN of ≤3.1~10.5 mg/L). Following a comparison against the low aeration intensity operation, it was recommended to operate BAF at a low EBRT within the BAF/AX process. Consequently, the treated volume was double the volume of the standalone BAF-DN, synchronously achieving low costs (0.413 yuan/m3).

Bimetallic Cu11Ag3 Nanotips for Ultrahigh Yield Rate of Nitrate-to-Ammonium.

Electrochemical reduction of nitrate to ammonia (NRA) offers a sustainable approach for NH3 production and NO3- removal but suffers from low NH3 yield rate (<1.20 mmol h-1 cm-2). We present bimetallic Cu11Ag3 nanotips with tailored local environment and tip-enhanced effects, which achieve an ultrahigh NH3 yield rate of 2.36 mmol h-1 cm-2 at a low applied potential of -0.33 V vs. RHE, a high Faradic efficiency (FE) of 98.8%, and long-term operation stability at 1800 mg-N L-1 NO3-, outperforming most of the recently reported catalysts. At a NO3- concentration as low as 15 mg-N L-1, it still delivers a high FE of 86.9% and an NH3 selectivity of 93.8%. Operando ATR-FTIR spectra, finite-element method, and DFT calculations reveal that the Cu11Ag3 exhibits reduced adsorption energy barrier of *N intermediates, favorable water dissociation for *H generation and high energy barrier for H2 formation, while its tip-enhanced enrichment promoting NO3- accumulation.

Bimetallic Cu11Ag3 Nanotips for Ultrahigh Yield Rate of Nitrate‐to‐Ammonium

Electrochemical reduction of nitrate to ammonia (NRA) offers a sustainable approach for NH3 production and NO3‐ removal but suffers from low NH3 yield rate (&lt;1.20 mmol h‐1 cm‐2). We present bimetallic Cu11Ag3 nanotips with tailored local environment and tip‐enhanced effects, which achieve an ultrahigh NH3 yield rate of 2.36 mmol h‐1 cm‐2 at a low applied potential of ‐0.33 V vs. RHE, a high Faradic efficiency (FE) of 98.8%, and long‐term operation stability at 1800 mg‐N L‐1 NO3‐, outperforming most of the recently reported catalysts. At a NO3‐ concentration as low as 15 mg‐N L‐1, it still delivers a high FE of 86.9% and an NH3 selectivity of 93.8%. Operando ATR‐FTIR spectra, finite‐element method, and DFT calculations reveal that the Cu11Ag3 exhibits reduced adsorption energy barrier of *N intermediates, favorable water dissociation for *H generation and high energy barrier for H2 formation, while its tip‐enhanced enrichment promoting NO3‐ accumulation.

Bio-refinery of organic pollutants for wastewater reclamation

With rapid development of global climate change and resource scarcity, the demand for sustainable wastewater reclamation technologies is growing rapidly. Alginate like exopolymers (ALE) are value-added biopolymers that can be recovered from excess biomass. In this study, a novel biopolymer value-driven moving bed biofilm reactor (bMBBR) was constructed to achieve high-efficiency conversion of organics to Alginate like exopolymers (ALE). The results revealed that excellent COD and low NH4+-N reduction could be achieved, with the reduction efficiencies of 87.7 ± 0.6 % and 12.6 ± 0.8 %, respectively. It is indicated that high-rate organics conversion and blockage of nitrification activity for energy saving could be simultaneous achieved in this process. Additionally, the superior settleability (SVI30 < 80 mL/g) and functional genera related to extracellular polymeric substances (EPS) secretion were observed, making it promising for ALE recovery from residual biomass. The yields of ALE extraction from biofilm and suspended biomass ranged of 232.9–381.5 mg/g VSS. The property analyses demonstrated that the biopolymer had a similarity functional group between two samples and commercial alginate. Meanwhile, the profit evaluation results suggested that the net profit could be reached of 0.54 CNY/kg SS in the present study, which was higher than that of conventional waste activated sludge (−1.92 CNY/kg SS). Moreover, the economic value of ALE (0.38 CNY/m3 wastewater treated) was also 2.93 times of that obtained from CH4 (0.13 CNY/m3 wastewater treated). In general, the present study provides a prove of concept that bio-refinery of organics into value-added biopolymers could offer a promising direction towards next generation of sustainable wastewater treatment plants.

Tempo-spatial Variations in Nitrogen and Phosphorus Loads in Jianli-Hankou Reach of the Middle Yangtze River During the Past 20 Years

Ammonia nitrogen （NH4+-N） and total phosphorus （TP） were the major control pollutants in the Yangtze River Basin. Based on measured data from 2003 to 2020, the temporal and spatial variations in concentrations and fluxes of NH4+-N and TP in the Jianli to Hankou （JL-HK） reach of the Middle Yangtze River were studied, and the impacts of flow-sediment factors, tributary inflows, and others on variations in NH4+-N and TP fluxes were discussed. The results showed that： ① In recent years, NH4+-N and TP concentrations in the mainstream have declined significantly, with annual NH4+-N and TP concentrations at each monitoring station in 2020 averagely decreasing by 41% and 34% compared to those in 2003, respectively. Spatially, NH4+-N and TP concentrations decreased and then increased along the mainstream. NH4+-N and TP concentrations of tributary inflows, which include the Dongting Lake and Han River, were generally lower than that of the mainstream. The multi-year average values of NH4+-N and TP concentrations were both averaged at 0.12 mg·L-1 in the mainstream and were averaged at 0.11 mg·L-1 and 0.09 mg·L-1 in the tributary inflows. ② The flux differences between the upper and lower sections net of tributary confluences showed that NH4+-N and TP fluxes were lost in the Jianli to Luoshan （JL-LS） sub-reach and increased in the Luoshan to Hankou （LS-HK） sub-reach in most years. NH4+-N and TP fluxes decreased in the JL-LS sub-reach, which was related to the lower NH4+-N and TP concentrations in lateral inflows, such as Dongting Lake, and thus lowered the NH4+-N and TP concentrations in the mainstream. The LS-HK sub-reach showed the opposite trends, and the water and sediment loads increased in this sub-reach. Across the whole JL-HK reach, TP flux as well as water and sediment loads were recharged along the reach, whereas NH4+-N flux was reduced greatly, which could be attributed to the pollution abatement conducted in the Yangtze River Basin, which mainly focused on NH4+-N. ③ The correlation analysis results showed that NH4+-N fluxes had the strongest correlation with NH4+-N concentrations but not significantly correlated with discharges and sediment transport rates, indicating that NH4+-N was mainly controlled by point source pollution in the study reach. TP fluxes had higher correlations with discharges and sediment transport rates in high flow level periods, and the correlations between TP fluxes and TP concentrations were better in low flow level periods, reflecting that point source pollution contributed more to TP in dry seasons compared to flood seasons.

Tracking control of dynamic ammonia coverage ratio references based on DC-SMC under a novel SCR-DeNOX structure

In response to the growing challenges of nitrogen oxides (NOX) emission control, NH3-based selective catalytic reduction (SCR) technology has been widely adopted to reduce NOX emission from marine diesel engine exhaust. In this study, the SCR mechanism model is based on a refined eight-state model. A novel structure of SCR-DeNOX system is established, which incorporates a by-pass valve and pipe. Unlike existing parallel and series SCR-DeNOX platforms, the novel structure shows a certain advantage in reducing NH3 and maintains a relatively high NOX conversion efficiency. Adaptive sliding mode observers (ASMO) are designed to generate dynamic ammonia coverage ratio references, replacing traditional fixed references. In addition, they also address the variations in the SCR-DeNOX model. The sliding mode control (SMC) is used to track the ammonia coverage ratio reference in upper cell by controlling ammonia injection. The decoupling with SMC (DC-SMC) is proposed to track the ammonia coverage ratio reference in the lower cell by controlling split ratio. The simulation results show the system with DC-SMC shows a 15.46% improvement in NOX conversion efficiency compared to that with SMC. Additionally, it shows a lower NH3 cost.

Combustion characteristics on ammonia injection velocity and positions for ammonia co-firing with coal in a pilot-scale circulating fluidized bed combustor

Ammonia (NH3) co-firing with coal in thermal power plant offers a viable solution for reducing CO2 emissions. Optimizing the NH3 injection method is crucial to achieving comparable performance and pollutant emissions in NH3–coal co-firing compared to coal only combustion in a circulating fluidized bed combustion system. The impact of NH3 co-firing with coal on the injection velocity and location in related to the NH3 supply method was evaluated. Injection velocity was controlled by varying the number of ammonia supply ports and their heights (0.2 m and 1.8 m from the distributor). Injecting NH3 through one port at a high velocity of 2.4 m/s increases CO emissions while decreasing NO emissions due to the formation of a reducing environment. Conversely, utilizing two ports with low NH3 injection velocity of 1.2 m/s exhibited the opposite trend in CO and NO emissions, achieving the highest combustion efficiency without the formation of N-containing components. This injection velocity promotes better mixing of gases (air and NH3) and solids (bed materials and coal) without hindering coal combustion. Regarding greenhouse gases emissions, the part of CO2 emissions decreased by considering CO2 concentration and flue gas flow rate, while the part of N2O emissions significantly increased due to N-chemistry by > 5 times.

Effect of electrooxidation pretreatment on treatment efficiency, membrane fouling and microbial community of a membrane bioreactor treating sludge dewatering wastewater

This study investigated electrooxidation (EO) pretreatment for sludge dewatering wastewater and condensate generated during the process, aiming to enhance its treatment via a membrane bioreactor (MBR) and prevent membrane fouling. EO treatment could achieve a complete suspended solids (SS) removal along with 97.4 % EPS and 90.1 % colour removal under the optimum conditions. However, the NH4+-N and total organic carbon (TOC) concentration in wastewater increased (16 % and 72.8 %, respectively) due to break down of the complex organic substances present in the wastewater. MBR treating EO pretreated wastewater showed significant improvement against membrane fouling, as shown by reduction in transmembrane pressure (TMP) from 15 kPa in control to 0 kPa in the experimental reactor. The MBR operated with EO-treated wastewater and a 16-day HRT resulted in a low effluent NH4+-N concentrations of 469.3 mg/L (74.9 % removal) along with a very low TOC concentration of 24.3 mg/L (98.7 % removal). The microbial community analysis revealed that enrichment of selected organic carbon degraders (Defluviitoga, Pedobacter, and Flavobacteriaceae) and nitrogen cycle bacteria (Dechloromonas, Comamonas, Arenibacter, Brevundimonas, Thauera, and Aequorivita), including some aerobic denitrifiers (Aquamicrobium and Chryseobacterium) in the experimental reactor treating EO-pretreated wastewater is responsible for enhancing microbial degradation and its overall performance.

Parasitism by Cuscuta gronovii mediated soil legacy effects and the competitive ability of invasive and native plant species by changing soil abiotic and biotic properties

Parasitic plants can mediate soil conditioning by invasive and native host plant species, but how this may affect the competitive ability of these plants when they later grow in the conditioned soil has never been tested. This study tested whether soil conditioned by three invasive and three native plant species, either parasitized by a holoparasitic plant Cuscuta gronovii or non-parasitized, would differentially affect the competitive ability of those species. In the first phase, field soil was conditioned using individuals of the six host plant species, either parasitized or non-parasitized. The second phase tested the competitive ability of individuals of those invasive and native plants by growing them alone or in competition with Trifolium repens in either live or sterilized conditioned soil. In the soil conditioning phase, parasitism significantly increased soil NH4+-N concentration by 17 %, decreased soil organic carbon by 18 %, and marginally decreased microbial biomass carbon concentration by 21 %. In the soil feedback phase, native plant species generally had higher competitive ability in soil that was conditioned by parasitized plants than in soil that was conditioned by non-parasitized plants. In contrast, soil conditioned by parasitized plants had only a marginal effect on the competitve ability of invasive plants, compared to growth in soil conditioned by non-parasitized plants. Native plants had greater competitive ability in soil with lower soil organic carbon, while invasive plants had greater competitive ability in soil with higher microbial biomass carbon and lower NH4+-N. These findings demonstrate that parasitism by C. gronovii mediated different soil legacy effects of invasive and native plant species through changes in soil organic carbon, soil NH4+-N, and microbial biomass carbon levels. Broadly, these results suggest that parasitic plants may limit invasions by alien plant species and promote the co-existence of the invaders with native plant species through soil-mediated legacy effects.

Self-regenerable oxygen system using microalgae-bacterial consortium for ammonium removal from wastewater

This study investigated self-regenerable oxygen system using microalagae-bacterial consortium for ammonium removal from wastewater and its kinetic modeling based on a combined mechanistic and empirical approach. By mechanistic modeling using a simple microalgal-bacterial Monod model, based on algal growth due to NH4+, NO3− and NO2−, the nitrogen and DO profiles were accurately predicted under different nitrogen conditions (low, medium, and high NH4+ concentrations). The mathematical modeling results showed that sufficient oxygen was available for nitrification at low initial NH4+ ammonium concentration levels, even when dual nitrogen substrate (NH4+–NO2−, NH4+–NO3− or NO2−–NO3−) or all three in combination (NH4+–NO2−–NO3−) were used, compared with high initial ammonium concentration levels. The DO profile was successfully used to monitor N transformation and N uptake in the PSBR based on net O2 uptake rate, O2 production rate, and O2 saturation profile. By empirical modeling of the data obtained, the actual O2 produced by microalgae with the different N species was calculated based on N mass balance and empirical equations. The empirical model further revealed that low NH4+ concentration levels (up to 82.5 mg N/L) favored successful nitrification due to the sufficient production of O2 in the system. However, NH4+ concentration in the range 82.5–132.5 mg N/L affected the nitrification efficiency due to insufficient O2 produced in the system, whereas high ammonium concentration results in nitritation/partial nitrification due to the high demand of O2 by AOB and inhibition in the growth of NOB.

Analyzing performance and microbial mechanisms in an incineration leachate treatment after waste separation: Integrated metagenomic and metaproteomic analyses

The absence of food waste after separation poses a significant challenge to incineration leachate treatment, as it decreases the C/N ratio and COD of leachate, greatly impacting the biological treatment process. A one-year in-situ study was systematically conducted in an incineration leachate treatment plant that experienced waste separation, focusing on the variations in carbon and nitrogen removal performance as well as the involved microbial mechanism of the “anaerobic digestion (AD) + two-stage A/O” process. Results indicated that the biodegradability of leachate significantly decreased over time, with COD concentration decreasing by 10 times and the average C/N ratio decreasing from 12.3 to 1.4. The AD process was maintained stable, achieving a COD removal efficiency exceeding 92 %. The nitrification process also remained stable; while the denitrification process was significantly affected, and a nine-fold increase in external glucose addition was required to achieve a nitrogen removal efficiency of 85 %. Metagenomic analysis indicated that comammox Nitrospira (contributing 90 % to ammonia monooxygenase) occupied the dominant position over Nitrosomonas for nitrification due to the low NH4+-N concentration in A/O tanks (<35 mg/L), and Methanothrix was substituted by Methanosarcina for methanogenesis in AD unit. Metaproteomic results further elucidated that the expression of enzymes responsible for denitrification process, i.e., Nir, Nor, Nos (convert NO2− to N2), was decreased significantly, although the expression of enzymes related to glycolysis and TCA cycle were stimulated by glucose addition. The expression of Nar (convert NO3−-N to NO2−-N) remained stable, while the imbalance expression within denitrifying enzymes might have facilitated occurrence of partial denitrification, attributed to the low C/N ratio. The results prove that the function robustness and metabolic versatility were achieved in leachate treatment plant after waste separation but at the cost of the high external carbon resource addition, highlighting the urgent requirement for low-carbon nitrogen removal technologies.

Preparation and characterisation of NH3 gas sensor based on PANI/Fe-doped CeO2 nanocomposite

PANI/Fe-doped CeO2nanocomposite was synthesised by the in-situ process. The produced powders were characterised by XRD, XPS, FT-IR, Raman, HRTEM and SEM-EDS tests. The sensors' function was based on PANI/Fe-doped CeO2nanocomposite with thin film deposited on top of interdigitated electrodes (IDT). NH3 detection with PANI/Fe-doped CeO2 nanocomposite sensor could be successfully performed even at room temperature (RT) and relative humidity of 45 %. Results demonstrated that PANI/Fe-doped CeO2 might be promising sensing materials for detecting the low NH3 concentration (ppm). In addition, the sensor is selective to the interfering gases, including CO, CO2 and NO2. This sensor displays acceptable repeatability and stability over time.

A Urine pH-Ammonium Acid/Base Score and CKD Progression.

Acidosis is associated with exacerbated loss of kidney function in chronic kidney disease (CKD). Currently, acid/base status is assessed by plasma measures, although organ-damaging covert acidosis, subclinical acidosis, may be present before reflected in plasma. Low urine NH4+ excretion associates with poor kidney outcomes in CKD and is proposed as a marker for subclinical acidosis. However, low NH4+ excretion could result from either a low capacity or a low demand for acid excretion. We hypothesized that a urine acid/base-score reflecting both the demand and capacity for acid excretion would better predict CKD progression. 24-hour urine collections were included from three clinical studies of patients with CKD stage 3 and 4: A development cohort (n=82), a variation cohort (n=58), and a validation cohort (n=73). A urine acid/base-score was derived and calculated from urinary pH and [NH4+]. Subclinical acidosis was defined as an acid/base-score below the lower limit of the 95% prediction interval of healthy controls. Main outcomes were change in measured GFR after 18 months and CKD progression (defined as ≥50% decline in eGFR, initiation of long-term dialysis or kidney transplantation) during up to 10 years of follow-up. Subclinical acidosis was prevalent in all cohorts (n=54/82, 48/73, and 40/58, ∼67%). Subclinical acidosis was associated with an 18% (95% CI: 2-32) larger decrease of measured GFR after 18 months. During a median follow-up of 6 years, subclinical acidosis was associated with a markedly higher risk for CKD progression. Adjusted hazard ratios were 9.88 (95% CI 1.27-76.7) in the development cohort and 11.1 in the validation cohort (95% CI: 2.88-42.5). The acid/base-score had a higher predictive value for CKD progression than NH4+ excretion alone. Subclinical acidosis, defined by a new urine acid/base-score, was associated with a higher risk of CKD progression in patients with CKD stage 3 and 4.

Climate and air quality impact of using ammonia as an alternative shipping fuel

As carbon-free fuel, ammonia has been proposed as an alternative fuel to facilitate maritime decarbonization. Deployment of ammonia-powered ships is proposed as soon as 2024. However, NO x , NH3 and N2O from ammonia combustion could impact air quality and climate. In this study, we assess whether and under what conditions switching to ammonia fuel might affect climate and air quality. We use a bottom–up approach combining ammonia engine experiment results and ship track data to estimate global tailpipe NO x , NH3 and N2O emissions from ammonia-powered ships with two possible engine technologies (NH3–H2 (high NO x , low NH3 emissions) vs pure NH3 (low NO x , very high NH3 emissions) combustion) under three emission regulation scenarios (with corresponding assumptions in emission control technologies), and simulate their air quality impacts using GEOS–Chem high performance global chemical transport model. We find that the tailpipe N2O emissions from ammonia-powered ships have climate impacts equivalent to 5.8% of current shipping CO2 emissions. Globally, switching to NH3–H2 engines avoids 16 900 mortalities from PM2.5 and 16 200 mortalities from O3 annually, while the unburnt NH3 emissions (82.0 Tg NH3 yr−1) from pure NH3 engines could lead to 668 100 additional mortalities from PM2.5 annually under current legislation. Requiring NH3 scrubbing within current emission control areas leads to smaller improvements in PM2.5-related mortalities (22 100 avoided mortalities for NH3–H2 and 623 900 additional mortalities for pure NH3 annually), while extending both Tier III NO x standard and NH3 scrubbing requirements globally leads to larger improvement in PM2.5-related mortalities associated with a switch to ammonia-powered ships (66 500 avoided mortalities for NH3–H2 and 1200 additional mortalities for pure NH3 annually). Our findings suggest that while switching to ammonia fuel would reduce tailpipe greenhouse gas emissions from shipping, stringent ammonia emission control is required to mitigate the potential adverse effects on air quality.

Optimized electrochemical ammonia production: From metal-N2/NOx batteries to aqueous metal-NOx– batteries

Ammonia plays a crucial role in contemporary society, impacting medicine, agriculture, and the chemical industry. The conventional industrial synthesis of NH3 through the Haber-Bosch technique, carried out under severe reaction conditions, leads to substantial energy consumption and environmental pollution. It is thus imperative for NH3 synthesis methods to be investigated under more favorable conditions. Synthesis of ammonia by electrocatalysis can effectively reduce the environmental damage and other urgent problems, which is a promising solution. Metal-nitrogen series batteries (M−N batteries), such as metal-nitrogen gas batteries, metal-nitrogen oxide batteries and metal-oxynitride batteries have been regarded recently as an exemplar of concurrent NH3 synthesis and energy production.Nonetheless, the large-scale application of these batteries is still limited by numerous challenges are currently existing in building high-efficiency M−N batteries, including poor Faradic efficiency and low NH3 yield. Therefore, a comprehensive overview of M−N batteries is offered, specifically focusing on advanced strategies for designing highly efficient cathode catalysts in anticipation of future developments. The metal anodes, cathodic electro-reduction reactions, and design principles are encompassed in the discussion, offering detailed insights to enhance understanding. Mechanisms, feasibility analyses, technoeconomic assessments, device combinations, and comparative evaluations are delved into in the review, contributing to a thorough comprehension of diverse systems and their application potential. Perspectives and opportunities for future research directions are also delineated.

Chronoamperometric Ammonium Ion Detection in Water via Conductive Polymers and Gold Nanoparticles.

Monitoring of ammonium ion levels in water is essential due to its significant impact on environmental and human health. This work aims to fabricate and characterize sensitive, real-time, low-cost, and portable amperometric sensors for low NH4+ concentrations in water. Two strategies were conducted by cyclic voltammetry (CV): electrodeposition of Au nanoparticles on a commercial polyaniline/C electrode (Au/PANI/C), and CV of electropolymerized polyaniline on a commercial carbon electrode (Au/PANIep/C). Au NPs increase the electrical conductivity of PANI and its ability to transfer charges during electrochemical reactions. The electrode performances were tested in a concentration range from 0.35 µM to 7 µM in NH4+ solution. The results show that the Au/PANI/C electrode performs well for high NH4+ concentrations (0.34 µM LoD) and worsens for low NH4+ concentrations (0.01 µM LoD). A reverse performance occurs for the electrode Au/PANIep/C, with a 0.03 µM LoD at low NH4+ concentration and 0.07 µM LoD at high NH4+ concentration. The electrodes exhibit a good reproducibility, with a maximum RSD of 3.68% for Au/PANI/C and 5.94% for Au/PANIep/C. In addition, the results of the repeatability tests show that the electrochemical reaction of sensing is fully reversible, leaving the electrode ready for a new detection event.