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Nighttime NO3-initiated oxidation of biogenic volatile organic compounds (BVOCs) such as monoterpenes is important for the atmospheric formation and growth of secondary organic aerosol (SOA), which has significant impact on climate, air quality, and human health. In such SOA formation and growth, highly oxygenated organic molecules (HOM) may be crucial, but their formation pathways and role in aerosol formation have yet to be clarified. Among monoterpenes, limonene is of particular interest for its high emission globally and high SOA yield. In this work, HOM formation in the reaction of limonene with nitrate radical (NO3) was investigated in the SAPHIR chamber (Simulation of Atmospheric PHotochemistry In a large Reaction chamber). About 280 HOM products were identified, grouped into 19 monomer families, 11 dimer families, and 3 trimer families. Both closed-shell products and open-shell peroxy radicals (RO2⚫) were observed, and many of them have not been reported previously. Monomers and dimers accounted for 47 % and 47 % of HOM concentrations, respectively, with trimers making up the remaining 6 %. In the most abundant monomer families, C10H15−17NO6−14, carbonyl products outnumbered hydroxyl products, indicating the importance of RO2⚫ termination by unimolecular dissociation. Both RO2⚫ autoxidation and alkoxy–peroxy pathways were found to be important processes leading to HOM. Time-dependent concentration profiles of monomer products containing nitrogen showed mainly second-generation formation patterns. Dimers were likely formed via the accretion reaction of two monomer RO2⚫, and HOM-trimers via the accretion reaction between monomer RO2⚫ and dimer RO2⚫. Trimers are suggested to play an important role in new particle formation (NPF) observed in our experiment. A HOM yield of 1.5%-0.7%+1.7% was estimated considering only first-generation products. SOA mass growth could be reasonably explained by HOM condensation on particles assuming irreversible uptake of ultra-low volatility organic compounds (ULVOCs), extremely low volatility organic compounds (ELVOCs), and low volatility organic compounds (LVOCs). This work provides evidence for the important role of HOM formed via the limonene +NO3 reaction in NPF and growth of SOA particles.

Anthropogenic nitrogen oxides may influence the cloud condensation nuclei (CCN) activity of biogenic secondary organic aerosols (SOA) in both daytime photooxidation and nighttime NO3 oxidation, which has significant implications for the climatic impact of SOA. We investigated the influence of NOx on the CCN activity of monoterpene‐derived SOA in OH oxidation and in NO3 oxidation. In OH oxidation, NOx had little influence on the hygroscopic parameter κ of organic aerosol (κOrg), which was attributed to the minor fraction of organic nitrates (ON) in SOA (<24%), resulted from the low branching ratio of RO2 + NO to form ON. In contrast, in NO3 oxidation κOrg was much reduced compared to OH/O3 oxidation due to a dominant fraction of ON. We report κ of MT‐derived ON formed in photo‐oxidation and NO3 oxidation (0.029–0.052) for the first time to our knowledge, which may be used to improve model simulations of CCN concentrations. Plain Language Summary Anthropogenic nitrogen oxides may influence the cloud formation ability of biogenic secondary organic aerosols (SOA) in both daytime and nighttime, which has implications to understand the climatic impact of SOA. However, the influence remains unclear. We found that for monoterpenes, a major class of precursors of biogenic SOA, NOx had little influence on the cloud formation ability of SOA in the daytime oxidation. In contrast, in the nighttime oxidation of monoterpenes by NO3, an important oxidant formed from NOx at night‐time, SOA had much lower cloud formation ability than that in the photo‐oxidation. The difference was attributed to the different fractions of organic nitrates (ON) in SOA. We also determined the κ of monoterpene‐derived ON for the first time to our knowledge. Key Points In daytime OH oxidation NOx had little influences on the cloud condensation nuclei (CCN) activity of MT‐SOA In nighttime NO3 oxidation MT‐SOA had much lower CCN activity compared with those formed via OH or O3 oxidation We report the κ of monoterpene‐derived organic nitrates (0.029–0.052) for the first time to our knowledge

The explicit reaction mechanism and dynamics of acrolein (CH 2  = CHCHO) with NO 3 were studied using quantum chemistry methods. We examined the potential energy surface (PES) for H-abstraction reactions by NO 3 and NO 3 addition to the unsaturated carbon atoms in the CH 2  = CHCHO molecule. The PES analysis and thermochemical calculations reveal that NO 3 -addition reactions and H-abstraction reactions are in competition with each other. The subsequent reactions of IM1 (CH 2 ONO 2 CHCHO), IM2 (CH 2 CHONO 2 CHO) and h-P3 were detailed investigated. The computed total rate constant increase with the temperature raising from 200 to 3000 K, and the rate constant is 1.43 × 10 − 15  cm 3 molecule − 1 s − 1 at 298 K, which is consistent with the experimental values. The lifetime of Acrolein oxidized by NO 3 radicals is estimated to be 14.20 days. Our theoretical investigations are of significant in understanding the oxidation process of unsaturated aldehyde by NO 3 .

The oxidation reactions of organic functional groups are one of the important processes in synthesis and chemical industries and have wide applications. Therefore, it is very important to use suitable, cheap, biocompatible, non-toxic catalysts as well as oxidants that do not produce by-products or non-toxic by-products. In the upcoming project, we are trying to use deep eutectic solvents (DESs) containing tempo unit as an active oxidizing catalyst in alcohol oxidation. Numerous catalytic systems have been developed for the aerobic oxidation of alcohols, with TEMPO-based systems utilizing metal co-catalysts being the most extensively studied. This study introduces a novel catalytic system, namely a TEMPO-supported DES (TEMPO-DES) and Fe(NO 3 ) 3 ·9H 2 O for the oxidation of alcohols using molecular oxygen as the terminal oxidant. The TEMPO-DES was prepared by combining salt ([Quaternium-TEMPO] + Cl − ) with glycine. The TEMPO-DES/Fe(NO 3 ) 3 system demonstrated excellent performance in selectively oxidizing various alcohols to their corresponding aldehydes and ketones under mild and solvent-free conditions. Furthermore, the DES could be easily recovered without experiencing significant loss of catalytic activity.

The interaction of nitrate radicals (NO3) with the air–water interface is a critical aspect of atmospheric chemistry, influencing processes such as secondary organic aerosol (SOA) formation, pollutant transformation, and nighttime oxidation. This study investigates the behavior of NO3 radicals at the air–water interface and in bulk water environments through ab initio molecular dynamics simulations, directly comparing them with Cl and ClO radicals. Three distinct configurations of NO3 in water droplets were analyzed: surface-parallel, surface-perpendicular, and bulk-phase. The results reveal environment-dependent dynamics, with surface-localized NO3 radicals exhibiting fewer but more flexible hydrogen bonds compared to bulk-solvated radicals. Analysis of radial distribution functions, coordination numbers, and population distributions demonstrates that NO3 radicals maintain distinct interfacial and bulk-phase preferences, with rapid equilibration in both environments. Electronic structure analysis shows significant modulation of spin density and molecular orbital distributions between surface and bulk environments. The comparative analysis with Cl and ClO radicals highlights how the unique planar geometry and delocalized π-system of NO3 influence its hydration patterns and interfacial activity. These results offer fundamental molecular-level insights into NO3 radical behavior at the air–water interface and in aqueous environments, enhancing our understanding of their role in heterogeneous atmospheric processes and nocturnal chemistry.

Coatings with developed surface stereometry, being based on a porous system, may be obtained by plasma electrolytic oxidation, PEO (micro arc oxidation, MAO). In this paper, we present novel porous coatings, which may be used, e.g., in micromachine’s biocompatible sensors’ housing, obtained in electrolytes containing magnesium nitrate hexahydrate Mg(NO3)2·6H2O and/or zinc nitrate hexahydrate Zn(NO3)2·6H2O in concentrated phosphoric acid H3PO4 (85% w/w). Complementary techniques are used for coatings’ surface characterization, such as scanning electron microscopy (SEM), for surface imaging as well as for chemical semi-quantitative analysis via energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), glow discharge optical emission spectroscopy (GDOES), and X-ray powder diffraction (XRD). The results have shown that increasing contents of salts (here, 250 g/L Mg(NO3)2·6H2O and 250 g/L Zn(NO3)2·6H2O) in electrolyte result in increasing of Mg/P and Zn/P ratios, as well as coating thickness. It was also found that by increasing the PEO voltage, the Zn/P and Mg/P ratios increase as well. In addition, the analysis of XPS spectra revealed the existence in 10 nm top of coating magnesium (Mg2+), zinc (Zn2+), titanium (Ti4+), and phosphorus compounds (PO43−, or HPO42−, or H2PO4−, or P2O74−).

Nitritation-anammox treatment can be a potentially energy-and resource-efficient technology for treating mainstream wastewater. However, the issue of nitrate residue from anammox treatment remains to be addressed. Herein, external recirculation of the anammox effluent to a hybrid anaerobic reactor (HAR), which was also to provide a continuous flow with low COD/N for the nitritation-anammox reactor, was employed to decrease the residue compounds. The recirculation ratio of 50% was observed to be the optimal to achieve the best overall performance with potential savings in energy demand. Specifically, in the operation scenario of R = 50%, the highest COD removal of ~90% by the HAR was achieved. Meanwhile, the lowest COD/NH₄⁺-N ratio of ~2.0 in the HAR effluent ensured the lowest observed NO₃⁻-N/ NH₄⁺-N ratio of ~14% in the nitritation-anammox reactor. These results have demonstrated the feasibility of applying external recirculation for nitrate residue removal via denitrification in the anaerobic pretreatment stage.

Plant–microbe interactions are key to nutrient-use efficiency. Root microbes are influenced by rhizosphere soil and plant cultivars. The impact of cultivar-by-nitrogen (N) interactions on the maize-root microbiome remains unclear, yet it is crucial for understanding N use efficiency in maize. This study evaluated the effects of maize cultivars and N forms, along with their interactions, on the diversity and composition of root bacteria and fungi. Additionally, we examined correlations between soil microbes and root metabolites. The maize cultivar Zhengdan 958 (ZD958) showed a positive response to the mixture of nitrate and ammonium N, resulting in increased in biomass, grain yield, shoot N content, grain N content, and root area. In contrast, the cultivar Denghai605 (DH605) did not exhibit a similar response. The diversity and composition of root bacteria and fungi differed between ZD958 and DH605. The N form primarily affected the community structure of rhizospheric fungi in ZD958 and rhizospheric bacteria in DH605, rather than endophytic microbes. A mixed N supply increased the relative abundance of Basidiomycota, which was positively correlated with ZD958 yield. For DH605, a mixed N treatment enhanced nitrification functions involving Bacteroidetes and Proteobacteria, while it reduced the effects of ammonium N supply. The dominant rhizospheric microbes in DH605 showed a stronger response to changes in root metabolites compared to those in ZD958. A mixed N supply increased the content of palmitoleic acid in ZD958 root exudates, facilitating the recruitment of beneficial rhizospheric microbes, which promotes maize growth. In DH605, a mixed N supply decreased the concentration of sphinganine, which is significantly correlated with Acidobacteria (negatively), Proteobacteria (negatively), Bacteroidetes (positively), and TM7 (positively). Our findings suggest that different maize cultivars respond differently to N forms, causing distinct rhizospheric microbial effects, and that root metabolites send metabolic signals to regulate and recruit key bacterial and fungal communities.

In a 28-day incubation study, ball milling technologies were applied to enhance the sorptive and functional properties of pristine biochar. The effect of ball-milled (BM) biochar, neem seed cake, and their co-amendment was evaluated on nitrification, ammonia (NH3) volatilization, and the abundance of nitrifying microbial communities in three contrasting tropical soils of different pH (acidic, neutral, and alkaline). The amendments were applied at 2% dry w/w to soils fertilized with ammonium chloride (NH4Cl). Results showed that in neutral and alkaline soils, the co-amendment led to a 40% and 64% increase in NH3 volatilization, respectively, compared to control due to significant ammonium (NH4+) retention and temporary nitrification inhibition. Conversely, in acidic soil, BM biochar and neem seed cake amplified nitrification by 23% and 62%, respectively, compared to sole amendments, while neem seed cake increased NH3 volatilization by 56% compared to BM biochar + neem seed cake due to NH4+ retention, altered soil pH, and changes in nitrifying microbial community. The abundance of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and complete ammonia oxidizers (Comammox) was altered by changes in soil pH and N availability modulated by BM biochar and neem seed cake. Correlation analysis revealed significant relationships between soil organic matter (SOM), NH4+, and NO3− on the abundance of nitrifying microorganisms. The study affirms the efficacy of BM biochar-neem seed cake co-amendment on nitrification inhibition but indicates potential N losses by NH3 volatilization depending on soil type, highlighting the need for soil type-specific management strategies to optimize N retention while minimizing environmental impacts.Article highlightsBall-milled biochar + neem cake inhibited nitrification but increased NH3 volatilization in neutral and alkaline soilsIn acidic soil, the co-amendment increased nitrification while reducing NH3 volatilization compared to neem cake aloneEffects on N cycling and microbial communities varied by soil pH, emphasizing need for soil-specific strategies

Structure–activity (SAR) methods are presented for estimating rate constants at 298 K and approximate temperature dependences for the reactions of organic compounds with OH, NO3, and Cl radicals and O3, and O(3P) in the lower atmosphere. These are needed for detailed mechanisms for the atmospheric reactions of organic compounds. Base rate constants are assigned for the various types of H-abstraction and addition reactions, with correction factors for substituents around the reaction site and in some cases for rings and molecule structure or size. Rate constant estimates are made for hydrocarbons and a wide variety of oxygenates, organic nitrates, amines, and monosubstituted halogen compounds. Rate constants for most hydrocarbons and monofunctional compounds can be estimated to within ±30%, though predictions are not as good for multifunctional compounds, and predictions for ~15% of the rate constants are off by more than a factor of 2. Estimates are more uncertain in the case of NO3 and O3 reactions. The results serve to demonstrate the capabilities and limitations of empirical methods for predicting rate constants for the full variety of organic compounds that may be of interest. Areas where future work is needed are discussed.