Nitrogen-containing Organic Compounds Research Articles

Catalysts for C-N coupling in urea electrosynthesis under ambient conditions from carbon dioxide and nitrogenous species.

Urea is an indispensable nitrogen-containing organic compound in modern human life. However, the current industrial synthesis of urea involves ammonia, which is produced through the Haber-Bosch process under harsh reaction conditions, causing huge energy consumption and heavy environmental pollution. Electrochemical reduction of carbon dioxide (CO2) and nitrogenous species (N2, NOx- and NO) have achieved significant progress, offering a promising approach for the electrochemical C-N coupling to produce urea under ambient conditions. Urea synthesis driven by renewable electricity represents a suitable alternative to the traditional process, contributing to the goal of carbon neutrality and nitrogen cycles. However, challenges such as low yield rate, poor selectivity and unveiled reaction mechanisms still need to be addressed. This review provides a summary of the latest catalysts utilized in urea electrosynthesis, aiming to provide guidance and prospects for the development of high-performance catalysts.

The effect of non-Saccharomyces yeasts on biogenic amines in Sauvignon Blanc wine and Gewürztraminer wine

Biogenic amine (BA) is a class of nitrogen-containing small molecular organic compounds with biological activity. Excessive BAs in wine affect flavor and quality of wine and are hazardous to human health. However, little attention has been paid to the effect of non-Saccharomyces yeasts and Saccharomyces cerevisiae mixed fermentation on BAs in white wine. The effect of mixed fermentation on BAs and amino acids in wine was investigated using two white grapes of Sauvignon Blanc and Gewürztraminer. Higher levels of total amino acids and BAs in Gewürztraminer wine compared to Sauvignon Blanc wine may be due to different grape varieties. Mixed fermentation did not influence BA profiles in Sauvignon Blanc wine, while it increased total BAs content. VL3 (VL) fermented wine has 33.7% less BAs content than EC1118 (EC) single-strain fermented wine. Similar phenomenon was found in Gewürztraminer wine produced by different fermentation combinations except that cadaverine was only detected in wine produced by Hanseniaspora uvarum participated in mixed fermentations. Principal coordinate analysis (PCoA) and permutational multivariate analysis of variance (PERMANOVA) revealed that the effects on BAs were related to grape varieties and yeast species in white wine. Ethanolamine, tryptamine, isoamylamine and histamine content in wine were related to grape varieties. Collectively, mixed fermentation increased BAs content in Sauvignon Blanc and Gewürztraminer wine. The content of BAs in wine fermented by VL single-strain fermentation was lower than that fermented by EC single-strain fermentation, which is more suitable for the winemaking of white wine.

Measurement report: Characteristics of nitrogen-containing organics in PM2.5 in Ürümqi, northwestern China – differential impacts of combustion of fresh and aged biomass materials

Abstract. Nitrogen-containing organic compounds (NOCs) are abundant and important aerosol components deeply involved in the global nitrogen cycle. However, the sources and formation processes of NOCs remain largely unknown, particularly in the city (Ürümqi, China) farthest from the ocean worldwide. Here, NOCs in PM2.5 collected in Ürümqi over a 1-year period were characterized by ultra-high-resolution mass spectrometry. The abundance of CHON compounds (mainly oxygen-poor unsaturated aliphatic-like species) in the positive ion mode was higher in the warm period than in the cold period, which was largely attributed to the contribution of fresh biomass material combustion (e.g., forest fires) associated with amidation of unsaturated fatty acids in the warm period, rather than the oxidation processes. However, CHON compounds (mainly nitro-aromatic species) in the negative ion mode increased significantly in the cold period, which was tightly related to aged biomass combustion (e.g., dry straws) in wintertime Ürümqi. For CHN compounds, alkyl nitriles and aromatic species showed higher abundance in the warm and cold periods, respectively. Alkyl nitriles can be derived from fresh biomass material combustion associated with the dehydration of amides (the main CHON compounds in the warm period). In contrast, aromatic species were tightly related to aged biomass burning. These findings further suggested different impacts of the combustion of fresh and aged biomass materials on NOC compositions in different seasons. The overall results shed light on the mechanisms by which fresh and aged biomass materials release different NOCs during combustion.

The synergistic effect of NOx and SO2 on the formation and light absorption of secondary organic aerosols from ο-xylene photooxidation

Both NOx and SO2 are important anthropogenic air pollutants that significantly affect secondary organic aerosols (SOA) formation. However, our understanding of the combined effects of NOx and SO2 on SOA formation is still insufficient. The concentrations, optical properties, and chemical compositions of SOA formed through ο-xylene photooxidation under various NOx concentrations were investigated with or without SO2 in the chamber. It was found that SOA mass concentration increased from 60 to 129 μg m−3 when the initial NOx concentration was increased from 0 to 900 ppb. The presence of 50 ppb SO2 not only enhanced ο-xylene SOA formation by 1.6–2.9 times, but also changed the evolution of SOA with NOx. The enhancement of ο-xylene SOA formation was primarily attributed to acid-catalyzed heterogeneous reactions initiated by nitric acid and sulfuric acid. However, SOA concentration decreased under 900 ppb NOx when SO2 was present, likely due to the decrease in sulfate production because of the competition between NOx and SO2 for ·OH. In addition, nitrogen-containing organic compounds (NOCs) concentrations and mass absorption coefficients (MACλ=365 nm) were promoted by both NOx and SO2. Our research indicates that the promotion of both NOCs formation by NOx, and oligomer formation by SO2 were the main reasons for the enhanced SOA light absorption. The present research provides a scientific basis for understanding the combined effects of both NOx and SO2 on ο-xylene SOA formation, and illustrates that the imbalanced reduction of anthropogenic air pollutants would lead to new characteristics in SOA pollution.

Unveiling the Molecular Characteristics, Origins, and Formation Mechanism of Reduced Nitrogen Organic Compounds in the Urban Atmosphere of Shanghai Using a Versatile Aerosol Concentration Enrichment System.

Reduced nitrogen-containing organic compounds (NOCs) in aerosols play a crucial role in altering their light-absorption properties, thereby impacting regional haze and climate. Due to the low concentration levels of individual NOCs in the air, the utilization of accurate detection and quantification technologies becomes essential. For the first time, this study investigated the diurnal variation, chemical characteristics, and potential formation pathways of NOCs in urban ambient aerosols in Shanghai using a versatile aerosol concentration enrichment system (VACES) coupled with HPLC-Q-TOF-MS. The results showed that NOCs accounted over 60% of identified components of urban organic aerosols, with O/N < 3 compounds being the major contributors (>70%). The predominance of the positive ionization mode suggested the prevalence of reduced NOCs. Higher relative intensities and number fractions of NOCs were observed during nighttime, while CHO compounds showed an opposite trend. Notably, a positive correlation between the intensity of NOCs and ammonium during the nighttime was observed, suggesting that the reaction of ammonium to form imines may be a potential pathway for the formation of reduced NOCs during the nighttime. Seven prevalent types of reduced NOCs in autumn and winter were identified and characterized by an enrichment of CH2 long-chain homologues. These NOCs included alkyl, cyclic, and aromatic amides in CHON compounds, as well as heterocyclic or cyclic amines and aniline homologue series in CHN compounds, which were associated with anthropogenic activities and may be capable of forming light-absorbing chromophores or posing harm to human health. The findings highlight the significant contributions of both primary emissions and ammonium chemistry, particularly amination processes, to the pollution of reduced NOCs in Shanghai's atmosphere.

Molecular analysis of secondary organic aerosol and brown carbon from the oxidation of indole

Abstract. Indole (ind) is a nitrogen-containing heterocyclic volatile organic compound commonly emitted from animal husbandry and from different plants like maize with global emissions of 0.1 Tg yr−1. The chemical composition and optical properties of indole secondary organic aerosol (SOA) and brown carbon (BrC) are still not well understood. To address this, environmental chamber experiments were conducted to investigate the oxidation of indole at atmospherically relevant concentrations of selected oxidants (OH radicals and O3) with or without NO2. In the presence of NO2, the SOA yields decreased by more than a factor of 2, but the mass absorption coefficient at 365 nm (MAC365) of ind-SOA was 4.3 ± 0.4 m2 g−1, which was 5 times higher than that in experiments without NO2. In the presence of NO2, C8H6N2O2 (identified as 3-nitroindole) contributed 76 % to all organic compounds detected by a chemical ionization mass spectrometer, contributing ∼ 50 % of the light absorption at 365 nm (Abs365). In the absence of NO2, the dominating chromophore was C8H7O3N, contributing to 20 %–30 % of Abs365. Indole contributes substantially to the formation of secondary BrC and its potential impact on the atmospheric radiative transfer is further enhanced in the presence of NO2, as it significantly increases the specific light absorption of ind-SOA by facilitating the formation of 3-nitroindole. This work provides new insights into an important process of brown carbon formation by interaction of two pollutants, NO2 and indole, mainly emitted by anthropogenic activities.

Characteristics and source apportionment of water-soluble organic nitrogen (WSON) in PM2.5 in Hong Kong: With focus on amines, urea, and nitroaromatic compounds

Water-soluble organic nitrogen (WSON) is ubiquitous in fine particulate matter (PM2.5) and poses health and environmental risks. However, there is limited knowledge regarding its comprehensive speciation and source-specific contributions. Here, we conducted chemical characterization and source apportionment of WSON in 65 PM2.5 samples collected in Hong Kong during a 1-yr period. Using various mass-spectrometry-based techniques, we quantified 22 nitrogen-containing organic compounds (NOCs), including 17 nitroaromatics (NACs), four amines, and urea. The most abundant amine and NACs were dimethylamine and 4-nitrocatechol, respectively. Two secondary (i.e., secondary formation and secondary nitrate) and five primary sources (i.e., sea salt, fugitive dust, marine vessels, vehicle exhaust, and biomass burning) of WSON and these three categories of NOCs were identified. Throughout the year, secondary sources dominated WSON formation (69.0%), while primary emissions had significant contributions to NACs (77.1%), amines (75.9%), and urea (83.7%). Fugitive dust was the leading source of amines and urea, while biomass burning was the main source of NACs. Our multi-linear regression analysis revealed the significant role of sulfate, NO3, nitrate, liquid water content, and particle pH on WSON formation, highlighting the importance of nighttime NO3 processing and heterogeneous and aqueous-phase formation of NOCs in the Hong Kong atmosphere.

An insight into recent updates on analytical techniques for bioactive alkaloids.

Alkaloids represent a wide class of naturally existing nitrogen-containing organic compounds having diverse biological activities. They are primary bioactive substances extracted from diverse plant parts. Due to their diverse biological activities, they are frequently used as medicines. The alkaloids have diverse pharmacological impacts on the human body; alkaloids are used for prevention, treatment, and reduction of discomfort associated with chronic illnesses. As most alkaloids exist in plants in complex form, combined with numerous other natural plant components, it is essential to recognize and characterize these molecules using different analytical techniques. We aimed to review the literature on the methods and protocols for the analysis of naturally occurring alkaloids. We carried out a literature survey using the PubMed, Scopus, and Google Scholar databases and other relevant published materials. The keywords used in the searches were "alkaloids," "analytical methods," "HPLC method," "GC method," "electrochemical methods," and "bioanalytical methods," in various combinations. In this article, several classes of alkaloids are presented, along with their biological activities. Moreover, it includes a thorough explanation of chromatographic techniques, hyphenated techniques, electrochemical techniques, and current trending analytical methods utilized for the isolation, identification, and comprehensive characterization of alkaloids. The various analytical techniques play an important role in the identification as well as the characterization of various alkaloids from plants, plasma samples, and urine samples. The hyphenation of various chromatographic techniques with mass spectrometry and NMR spectroscopy plays a crucial role in the characterization of unknown compounds.

Determination of nitrogen-containing organic compounds in commercially available recycled cardboards intended for food contact applications

In today’s Circular Economy, recycling, reuse, and recovery of materials are the most important components when it comes to solid waste management. Even though recyclable packaging materials such as plastic, paper, metal, and glass are traditionally used in the Food Industry as raw materials, recovered materials are also being incorporated in order to address the global waste problem. The challenge, however, is to strike a balance between sustainability and food safety. This study developed and compared two rapid and simple methods, Ultrasound-Assisted Extraction (UAE) and Head Space Solid-Phase Microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) analysis, to evaluate the concentrations of a mixture of nitrogen-containing compounds in commercially recycled cardboards. HS-SPME showed slightly better analytical performance than UAE. Considering that HS-SPME additionally constitutes a solvent free “green” method, the appliance of this method appears to be more environmentally friendly. Additionally, an approach to evaluate the possible migration from recycled cardboard samples was made to create a tool for assessing the use of these materials for safe food packaging. Trials simulated storage in room temperature for 6–12 months (“mild” conditions, 40 °C for 10 days) and the worst forcible conditions (“extreme” conditions, 70 °C for 6 h) using Tenax as a food simulant. The migration rates of the contaminants varied according to the nature of the substance, the grammage of the cardboard packaging, contact time, and temperature. Under both conditions studied, two of the substances migrated into Tenax, and their migration rates ranged from 15 to 90 %.

Study of two approaches for the process water management from hydrothermal carbonization of swine manure: Anaerobic treatment and nutrient recovery

Hydrothermal carbonization (HTC) is a promising alternative to transform biomass waste into a solid carbonaceous material (hydrochar) and a process water with potential for material and energy recovery. In this study, two alternatives for process water treatment by conventional and acid-assisted HTC of swine manure are discussed. Process water from conventional HTC at 180 °C showed high biodegradability (55% COD removal) and methane production (∼290 mL STP CH4 g−1 CODadded) and the treatment in an upflow anaerobic sludge blanket reactor allowed obtaining a high methane production yield (1.3 L CH4 L−1 d−1) and COD removal (∼70%). The analysis of the microbiota showed a high concentration of Synergistota and Firmicutes phyla, with high degradation of organic nitrogen-containing organic compounds. Acid-assisted HTC proved to be a viable option for nutrient recovery (migration of 83% of the P to the process water), which allowed obtaining a solid salt by chemical precipitation with Mg(OH)2 (NPK of 4/4/0.4) and MgCl2 (NPK 8/17/0.5), with a negligible content of heavy metals. The characteristics of the precipitated solid complied with the requirements of European Regulation (2019)/1009 for fertilizers and amendments in agricultural soils, being a suitable alternative for the recycling of nutrients from wastes.

Secondary Brown Carbon Formation From Photooxidation of Furans From Biomass Burning

AbstractFurans are a major class of volatile organic compounds emitted from biomass burning. Their high reactivity with atmospheric oxidants leads to the formation of secondary organic aerosol (SOA), including secondary brown carbon (BrC) that can affect global climate via interactions with solar radiation. Here, we investigate the optical properties and chemical composition of SOA generated via photooxidation of furfural, 2‐methylfuran, and 3‐methylfuran under dry (RH &lt; 5%) and humid (RH ∼ 50%) conditions in the presence of nitrogen oxides (NOx) and ammonium sulfate seed aerosol. Dry furfural oxidation has the greatest BrC formation, including reduced nitrogen‐containing organic compounds (NOCs) in SOA, which are dominated by amines and amides formed from reactions between carbonyls and ammonia/ammonium. Based on the products detected, we propose novel formation pathways of NOCs in furfural photooxidation, which can contribute to BrC via accretion reactions during the photochemical aging of biomass burning plumes.

Spectroscopic and imaging considerations of THz-TDS and ULF-Raman techniques towards practical security applications.

Nitrogen-containing high-energy organic compounds represent a class of materials with critical implications in various fields, including military, aerospace, and chemical industries. The precise characterization and analysis of these compounds are essential for both safety and performance considerations. Spectroscopic characterization in the far-infrared region has great potential for non-destructive investigation of high energetic and related compounds. This research article presents a comprehensive study of common organic energetic materials in the far-infrared region (5-200 cm-1), aiming to enhance security measures through the utilization of cutting-edge spectroscopic techniques. Broadband terahertz time-domain spectroscopy and ultra-low frequency Raman spectroscopy are employed as powerful tools to probe the vibrational and rotational modes of various explosive materials. One of the key objectives of this present work is unveiling the characteristic spectral features and optical parameters of five common nitrogen based high energy organic compounds towards rapid and accurate identification. Further, we have explored the potential of terahertz reflection imaging for non-contact through barrier sensing, a critical requirement in security applications. Based on the spectral features obtained from the spectroscopic studies and using advanced imaging algorithms we have been able to detect these compounds under various barriers including paper, cloth, backpack, etc. Subsequently, this study highlights the capabilities of the two techniques offering a pathway to enhance their utility over a wide range of practical security applications.

A Review of Electroactive Nanomaterials in the Detection of Nitrogen-Containing Organic Compounds and Future Applications.

Electrochemical and impedimetric detection of nitrogen-containing organic compounds (NOCs) in blood, urine, sweat, and saliva is widely used in clinical diagnosis. NOC detection is used to identify illnesses such as chronic kidney disease (CKD), end-stage renal disease (ESRD), cardiovascular complications, diabetes, cancer, and others. In recent years, nanomaterials have shown significant potential in the detection of NOCs using electrochemical and impedimetric sensors. This potential is due to the higher surface area, porous nature, and functional groups of nanomaterials, which can aid in improving the sensing performance with inexpensive, direct, and quick-time processing methods. In this review, we discuss nanomaterials, such as metal oxides, graphene nanostructures, and their nanocomposites, for the detection of NOCs. Notably, researchers have considered nanocomposite-based devices, such as a field effect transistor (FET) and printed electrodes, for the detection of NOCs. In this review, we emphasize the significant importance of electrochemical and impedimetric methods in the detection of NOCs, which typically show higher sensitivity and selectivity. So, these methods will open a new way to make embeddable electrodes for point-of-detection (POD) devices. These devices could be used in the next generation of non-invasive analysis for biomedical and clinical applications. This review also summarizes recent state-of-the-art technology for the development of sensors for on-site monitoring and disease diagnosis at an earlier stage.

Aqueous-Phase Reactions of Anthropogenic Emissions Lead to the High Chemodiversity of Atmospheric Nitrogen-Containing Compounds during the Haze Event.

Nitrogen-containing organic compounds (NOCs), a type of important reactive-nitrogen species, are abundant in organic aerosols in haze events observed in Northern China. However, due to the complex nature of NOCs, the sources, formation, and influencing factors are still ambiguous. Here, the molecular composition of organic matters (OMs) in hourly PM2.5 samples collected during a haze event in Northern China was characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We found that CHON compounds (formulas containing C, H, O, and N atoms) dominated the OM fractions during the haze and showed high chemodiversity and transformability. Relying on the newly developed revised-workflow and oxidation-hydrolyzation knowledge for CHON compounds, 64% of the major aromatic CHON compounds (>80%) could be derived from the oxidization or hydrolyzation processes. Results from FT-ICR MS data analysis further showed that the aerosol liquid water (ALW)-involved aqueous-phase reactions are important for the molecular distribution of aromatic-CHON compounds besides the coal combustion, and the ALW-involved aromatic-CHON compound formation during daytime and nighttime was different. Our results improve the understanding of molecular composition, sources, and potential formation of CHON compounds, which can help to advance the understanding for the formation, evolution, and control of haze.

Single-Photon Ionization Induced New Covalent Bond Formation in Acrylonitrile(AN)-Pyrrole(Py) Clusters.

The formation of nitrogen-containing organic compounds is crucial for understanding chemical evolution and the origin of life in the interstellar medium (ISM). In this study, we explore whether acrylonitrile (AN) and pyrrole (Py) can form new nitrogen-containing compounds after single-photon ionization in their gaseous clusters by vacuum ultraviolet (VUV)-infrared (IR) spectroscopy and theoretical calculations. The results show that a strong linear H-bond is formed in neutral AN-Py, while cyclic or bicyclic H-bonded networks are formed in the neutral AN-Py2 cluster. It is found that the structure containing a new C-C covalent bond between two moieties in (AN-Py)+ is formed besides the formation of H-bonded structures after AN-Py is ionized by VUV light. In (AN-Py2)+ cluster cations, new C-C or C-N covalent bonds tend to be formed between two Py, with (Py)2+ as the core in the cluster. The results reveal that new covalent bonds are more likely to be formed between two Py species when AN and Py are present in the cationic clusters. These results provide spectroscopic evidence of the formation of new nitrogen-containing organic compounds from AN and Py induced by VUV, which are helpful for our understanding of the formation of diverse prebiotic molecules in interstellar space.

Aging effects on residential biomass burning emissions under quasi-real atmospheric conditions

Emissions from biomass burning (BB) vastly contribute to the atmospheric trace gases and particles, which affect air quality and human health. After emission, the chemical evolution changes the mass and composition of organic aerosol (OA) in the diluted and aged plume. In this study, we used a quasi-real atmospheric smog chamber system to conduct aging experiments and investigated the multiphase oxidation of primary organic aerosol (POA) and the formation of secondary organic aerosols (SOA) in residential biomass burning plumes. We found that the emissions in the gas and particle phases were interlinked during the plume evolution. During photochemical aging, more oxidized OA was produced, and SOA formation increased by a factor of 2 due to functionalization reactions of gaseous precursors such as furans, phenols, and carbonyls. On the other hand, dark aging resulted in a lower OA mass enhancement by a factor of 1.2, with weaker oxidation from gaseous reactions. Dark aging experiments resulted in the generation of substantial quantities of nitrogen-containing organic compounds in both gas and particulate phases, while photochemical aging led to a notable increase in the concentration of gaseous carboxylic acids. Our observations show that the properties of SOA are influenced by exposure to sunlight radiation and oxidants such as OH or NO3 radicals. These results reflect the aging process of BB plumes in real-world atmospheric conditions and highlight the importance of considering various aging mechanisms.

Плазмохимический синтез нитропроизводных аценафтена в поле токов высокой частоты при пониженном давлении

Plasma-chemical processing devices are widely used in practice and are an integral part in microelectronics, medicine, light industry and nanotechnology. In addition, they are used as methods for modifying the modern materials surfaces and in liquids processing. The paper considers preparation of the aromatic compound nitro derivatives under the action of capacitive high-frequency electrodeless discharge at the gas--liquid interface with the reduced pressure. During the plasma-chemical treatment of the reaction mixture containing the 1,2-dihydroacenaphthylene (acenaphthene), its complete conversion was observed, which was confirmed by detection of the acenaphthene mono- and dinitro-derivatives, as well as of the side chain oxidation products, in the reaction products. The proposed method of implementing nitration reaction of the aromatic substances, which belongs to the new instrumental methods of organic synthesis along with photochemistry and electrochemical synthesis, allows direct binding of the molecular nitrogen and oxygen into the valuable nitrogen-containing organic compounds. Study results demonstrate effective introduction of the plasma chemistry methods in chemical technology not only for the purposes of oxidative destruction of the organic substances, but also as the physicochemical tools for the fine organic synthesis allowing selective functionalization of the polynuclear aromatic compounds

Efficient selective combustion of n-butylamine on hierarchical Cu-Mn/SAPO-34 catalysts: The effect of mesoporosity and acidity

The efficient catalytic oxidation of nitrogen-containing volatile organic compounds remains a big challenge due to unmanaged production of harmful byproducts. Herein, a series of Cu-Mn modified hierarchical SAPO-34 zeolite catalysts with different pore structures were synthesized for n-butylamine oxidation. The physicochemical properties and catalytic performance of catalysts were investigated and analyzed in detail. Among them, CuMn/S-1 shows the highest activity (T90 = 279 °C, GHSV = 12,000 h−1), which is attributed to its higher porosity, higher surface acidity and superior reducibility. Meanwhile, it is found that the hierarchical structure and mesopore play an important role in improvement of N2 selectivity. Meanwhile, CuMn/S-1 also exhibits high stability and water resistance. The catalytic mechanism of n-butylamine on CuMn/SAPO-34 was investigated by in situ DRIFTS, showing that propanol, methanol and acetate are the main intermediates.

Evolution of dissolved organic nitrogen (DON) during sludge reject water treatment revealed by FTICR-MS

This study evaluated the ability to remove dissolved organic matter (DOM), particularly dissolved organic nitrogen (DON), at a molecular level using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) in a full-scale reject water treatment project comprising three steps of short-cut nitrification and denitrification, two-stage AO, and ultrafiltration membrane system. The results indicated that short-cut nitrification and denitrification were effective in reducing the DON concentration from an average of about 180 mg/L to 43 mg/L. The average molecular weight of DOM showed a decreasing trend from 238 Da to 160 Da. The percentage of nitrogen-containing organic compounds (CHON-DOM), which is the primary component of reject water DOM, increased from 65.79 % to 72.35 %, while the percentage of CHO-DOM decreased from 20.67 % to 15.24 %. The percentage of CHOS-DOM remained stable at 12.21 %–13.54 %. The percentage of protein-DOM decreased from 50.32 % to 18.40 %, while lignin-DOM increased from 36.16 % to 55.88 % and carbohydrate-DOM increased from 2.68 % to 9.74 %. The short-cut nitrification and denitrification and ultrafiltration membrane system both generated more unsaturated, highly aromatic DOM. This study provides insights into the effects of different wastewater treatment processes on the evolution of DOM/DON, which can be useful for effective DON control.

Secondary aerosol formation in incense burning particles by O3 and OH oxidation via single particle mixing state analysis

Incense burning is a common religious activity that emits abundant gaseous and particulate pollutants into the atmosphere. During their atmospheric lifetime, these gases and particles are subjected to oxidation, leading to the formation of secondary pollutants. We examined the oxidation of incense burning plumes under O3 exposure and dark condition using an oxidation flow reactor connected to a single particle aerosol mass spectrometer (SPAMS). Nitrate formation was observed in incense burning particles, mainly attributable to the ozonolysis of nitrogen-containing organic compounds. With UV on, nitrate formation was significantly enhanced, likely due to HNO3/HNO2/NOx uptake triggered by OH chemistry, which is more effective than ozone oxidation. The extent of nitrate formation is insensitive to O3 and OH exposure, possibly due to the diffusion limitation on interfacial uptake. The O3-UV-aged particles are more oxygenated and functionalized than O3-Dark-aged particles. Oxalate and malonate, two typical secondary organic aerosol (SOA) components, were found in O3-UV-aged particles. Our work reveals that nitrate, accompanied by SOA, can rapidly form in incense-burning particles upon photochemical oxidation in the atmosphere, which could deepen our understanding of air pollution caused by religious activities.