Low Concentrations Of NO Research Articles

Determining behavioural-based risk to SLODs of urban public open spaces: Key performance indicators definition and application on established built environment typological scenarios

A behavioural-based approach can be used to assess how users’ reactions to surrounding environmental conditions can alter the urban Built Environment (BE) risk to Slow Onset Disasters (SLODs). Public Open Spaces (POSs) in the BE are relevant scenarios, due to micro-climate-related stress, users’ vulnerabilities (e.g., age, health frailty) and exposure time. Simulation methods can support behavioural-based risk-assessment, but results are generally site-specific. Performing analysis on BE Typologies (BETs) can improve robustness, since BETs represent archetypes from real-world scenarios. This work adopts a behavioural-based approach to evaluate time-dependant users’ risks of POSs in different BETs due to SLODs-related stress (i.e., heat, air pollution). UTCI and AQI values are mapped within each BET. Users’ distributions are then calculated depending on thermal acceptability correlations. Key Performance Indicators are developed associating users’ distribution to SLODs effects on health (i.e., sweat rate, water loss; health affection rate probability). The approach is applied to Italian BETs, under one relevant climate, rating their heat and air pollution risks. Results suggest critical conditions for toddlers. In detail, about 2-hour high heat exposure could result in dehydration, while 1-hour exposure to low NO2 concentration could result in +1% mortality probability. This approach could potentially support decision-makers on BE risk-assessment.

Cobalt and Iron Phthalocyanine Derivatives: Effect of Substituents on the Structure of Thin Films and Their Sensor Response to Nitric Oxide.

In this work, we study the effect of substituents in cobalt(II) and iron(II) phthalocyanines (CoPcR4 and FePcR4 with R = H, F, Cl, tBu) on the structural features of their films, and their chemi-resistive sensor response to a low concentration of nitric oxide. For the correct interpretation of diffractograms of phthalocyanine films, structures of CoPcCl4 and FePcCl4 single crystals were determined for the first time. Films were tested as active layers for the determination of low concentrations of NO (10-1000 ppb). It was found that the best sensor response to NO was observed for the films of chlorinated derivatives MPcCl4 (M = Co, Fe), while the lowest response was in the case of MPc(tBu)4 films. FePcCl4 films exhibited the maximal response to NO, with a calculated limit of detection (LOD) of 3 ppb; the response and recovery times determined at 30 ppb of NO were 30 s and 80 s, respectively. The LOD of a CoPcCl4 film was 7 ppb. However, iron phthalocyanine films had low stability and their sensitivity to NO decreased rapidly over time, while the response of cobalt phthalocyanine films remained stable for at least several months. In order to explain the obtained regularities, quantum chemical calculations of the binding parameters between NO and phthalocyanine molecules were carried out. It was shown that the binding of NO to the side atoms of phthalocyanines occurred through van der Waals forces, and the values of the binding energies were in direct correlation with the values of the sensor response to NO.

NO2 Gas Sensor Based on Pristine Black Silicon Formed by Reactive Ion Etching

Nitrogen dioxide (NO2) is a serious environmental pollutant and can cause negative consequences on both human health and vegetation growth. Herein, the possibility and promise of using a resistive sensor based on pristine black silicon (BSi) to detect NO2 at room temperature are investigated. BSi is prepared using plasma‐based reactive ion etching. Scanning electron microscope (SEM) studies show that BSi consists of vertically standing nanoneedles and has a large surface area, which facilitates gas adsorption. The gas‐sensing properties of the BSi‐based sensor are tested for low NO2 concentrations (1–5 ppm). It is found that the prepared sensor samples without posttreatments of BSi exhibit high sensitivity, fast transient response, and good repeatability. In particular, the response and recovery time of the sensor are ≈35 and ≈25 s for 4 ppm NO2 gas exposure, respectively. Besides, the results indicate that the BSi‐based sensor has excellent selectivity. Finally, the sensing mechanism is discussed, the dominating factors of which are the large active sensing area and the vertical arrangement of the BSi nanoneedles. It is believed that with further optimization, BSi has good potential as a functional material for gas sensors.

Abstract 6363: Short-term exposure of cancer cells to ultra-high concentrations nitric oxide induces PDL-1 upregulation

Abstract Background: We have previously shown that treating mouse colon carcinoma (CT26) tumor-bearing mice with ultra-high concentrations of nitric oxide (UNO) upregulates innate and adaptive immune cells both locally and systemically. As immune-checkpoint molecules, such as the PD-L1 receptor PD-1, are expressed on immune cells, our group assessed the potential synergy of UNO and an anti-PD-1 antibody for treating tumors in vivo. Indeed, primary tumors regressed in 53% of the CT26 tumor-bearing mice treated with UNO and anti-PD-1. Moreover, these mice were primary and distant tumor-free and survived 100 days post-treatment. In the current study, we assessed PD-L1 expression levels on cancer cells in vitro following short-term exposure to UNO. Methods: CT26 cells were exposed to 25,000 - 100,000 ppm NO for 10 - 60 seconds. The percentage of PD-L1-expressing cells was assessed by flow cytometry analysis. Results: 1. Exposing CT26 cells to 100,000 ppm NO for 10 seconds upregulated PD-L1 expression. 85.1% of cells, which are still viable or at early apoptosis, expressed PD-L1 compared to 71% of untreated cells (p<0.0001). Exposure of CT26 cells to 25,000 ppm or 50,000 ppm NO for 10 seconds did not change the level of PD-L1 expression significantly. 2. Exposure to 100,000 ppm NO for 30 seconds further increased the percentage of cells expressing PD-L1 to 96.7% (p<0.0001 compared to untreated cells). For this duration, lower concentrations of NO also increased PD-L1-expression in viable early apoptotic CT26 cells to 82.8% - 92.3% when treated with 25,000 ppm or 50,000 ppm NO, respectively. 3. Finally, a 60 second exposure of CT26 cells to 25,000 ppm, 50,000 ppm, or 100,000 ppm NO resulted in the highest percentage of PD-L1 expressing cells. Approximately 95% of all viable or early apoptotic CT26 cells express PD-L1 under all NO conditions. This finding is significant compared to 71% of cells in the control arm that express PD-L1 (p<0.0001). Conclusion: Short-term exposure (10 - 60 seconds) to UNO upregulates PD-L1 expression on cancer cells in an NO concentration-dependent and exposure-dependent process. A 10-second exposure to 100,000 ppm NO is sufficient to significantly induce PDL-1 expression. Therefore, NO therapy can potentially be combined with anti-PD-L1 antibody treatment to improve therapeutic outcomes. Citation Format: Yana Epshtein, Matan Goldshtein, Selena Chaisson, Jedidiah Monson, Matt Johnson, Amir Avniel, Steve Lisi, Hila Confino. Short-term exposure of cancer cells to ultra-high concentrations nitric oxide induces PDL-1 upregulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6363.

Investigation of High-Sensitivity NO2 Gas Sensors with Ga2O3 Nanorod Sensing Membrane Grown by Hydrothermal Synthesis Method

In this work, Ga2O3 nanorods were converted from GaOOH nanorods grown using the hydrothermal synthesis method as the sensing membranes of NO2 gas sensors. Since a sensing membrane with a high surface-to-volume ratio is a very important issue for gas sensors, the thickness of the seed layer and the concentrations of the hydrothermal precursor gallium nitrate nonahydrate (Ga(NO3)3·9H2O) and hexamethylenetetramine (HMT) were optimized to achieve a high surface-to-volume ratio in the GaOOH nanorods. The results showed that the largest surface-to-volume ratio of the GaOOH nanorods could be obtained using the 50-nm-thick SnO2 seed layer and the Ga(NO3)3·9H2O/HMT concentration of 12 mM/10 mM. In addition, the GaOOH nanorods were converted to Ga2O3 nanorods by thermal annealing in a pure N2 ambient atmosphere for 2 h at various temperatures of 300 °C, 400 °C, and 500 °C, respectively. Compared with the Ga2O3 nanorod sensing membranes annealed at 300 °C and 500 °C, the NO2 gas sensors using the 400 °C-annealed Ga2O3 nanorod sensing membrane exhibited optimal responsivity of 1184.6%, a response time of 63.6 s, and a recovery time of 135.7 s at a NO2 concentration of 10 ppm. The low NO2 concentration of 100 ppb could be detected by the Ga2O3 nanorod-structured NO2 gas sensors and the achieved responsivity was 34.2%.

Associations between ambient air pollutants and childhood hand, foot, and mouth disease in Sichuan, China: a spatiotemporal study

Hand, foot, and mouth disease (HFMD) is a major public health concern in the Asia–Pacific region. Previous studies have implied that ambient air pollution may affect the incidence of HFMD, but the results among different regions are inconsistent. We aimed to deepen the understanding of the associations between air pollutants and HFMD by conducting a multicity study. Daily data on childhood HFMD counts and meteorological and ambient air pollution (PM2.5, PM10, NO2, CO, O3, and SO2) concentrations in 21 cities in Sichuan Province from 2015 to 2017 were collected. A spatiotemporal Bayesian hierarchical model framework was established, and then a distributed lag nonlinear models (DLNMs) was constructed to reveal exposure-lag-response relationships between air pollutants and HFMD while controlling for spatiotemporal effects. Furthermore, given the differences in the levels and seasonal trends of air pollutants between the basin region and plateau region, we explored whether these associations varied between different areas (basin and plateau). The associations between air pollutants and HFMD were nonlinear, with different lag responses. Low NO2 concentrations and both low and high PM2.5 and PM10 concentrations were associated with a decreased risk of HFMD. No significant associations between CO, O3, and SO2 and HFMD were found. The associations between air pollutant concentrations and HFMD were different between the basin and plateau regions. Our study revealed associations between PM2.5, PM10, and NO2 concentrations and HFMD, deepening the understanding of the relationships between air pollutants and HFMD. These findings provide evidence to support the formulation of relevant prevention measures and the establishment of an early warning system.

Blending Effects of Nitrogenous Bio-Fuel on Soot and NOx Formation during Gasoline Combustion

Bio-fuel plays an important role in addressing the issue of CO2 and pollutant emission during cocombustion with fossil fuels. In this work, the effects of nitrogenous bio-fuel on soot and NOx formation during gasoline combustion were numerically investigated. Three bio-fuels, modeled by mixtures of pyridine, ethyl acetate, and ethanol with different volume fractions of pyridine and named SIM1 (0%), SIM2 (0.5%), and SIM3 (1%), were adopted to investigate the formation of soot and NOx when coburning with gasoline. Two mechanisms, i.e., the Glarborg mechanism and the Okafor mechanism, were employed to study the difference in soot and NOx formation. Results showed that pyridine exhibited different effects on soot formation in different regions. Based on the Okafor mechanism, soot formation was suppressed at the height of z = 3–4 cm, while it was promoted at the height of z = 4.5–5.5 cm. However, a reverse trend was predicted by the Glarborg mechanism. Moreover, the peak soot volume fraction (SVF) calculated by the Okafor mechanism was obviously higher than that calculated by the Glarborg mechanism; the major reason for the inconsistency of SVF in the two mechanisms was that more C6H5CH3 reacted with OH radicals to form C6H5CH2 in the Glarborg mechanism, resulting in less C6H5CH3 forming benzene (A1). Along with the increase of the pyridine proportion in the bio-fuel, the concentrations of NO increased by 92.1 and 91.4% in both mechanisms, attributed to the pyrolysis of pyridine into HCN, which promoted the formation of NO precursors (N, NH, NCO, and HNO) and thus NO. The difference in NO formation between the two mechanisms was because the reaction rate of NO converted from NO precursors in the Glarborg mechanism was higher than that in the Okafor mechanism. The NO2 was converted from NO via the reaction of NO + HO2 = NO2 + OH, and it distributed in the region with a lower NO concentration.

Two-dimensional titanium nitride as a highly active electrocatalyst for ammonia production via NO electroreduction

Promising downhill and natural electrocatalysis characteristics for NO-reduction are obtained from the single-layer hexagonal TiN. Interestingly, the highest yield of NH3 by TiN electrocatalysis is shown to be at atmospheric pressure, indicating its feasibility for applications under ambient conditions. Two possible adsorption configurations for NOER, side-on and end-on are achieved. The NO side-on configuration binds more strongly to the TiN surface rather than the end-on. The mentioned NO-reduction leads to the formation of two byproducts (NH3 and N2H2) controlled by the coverage of NO molecules. The NH3 formation under low NO coverage has an overall downhill free-energy profile, indicating that the TiN structure is an excellent catalyst for NOER at the early stages of NO contamination. Favorably, low NO concentration leads to a higher yield of NH3 formation, which is also fascinating.

Heterojunction and exposed facet engineering of ZnO/ WO3 flower structure for fast and sensitive low-concentration NO2 sensing

A novel silybum flower-like ZnO/ hexagonal WO3 heterostructure is synthesized via hydrothermal method and applied in gas sensors for NO2 detection. The morphology, composition, and possible growth mechanism are systematically investigated by a series of characterizations. In comparison with the pure WO3 and other ZnO/WO3 samples, the silybum flower-like ZnO/ hexagonal WO3 sensor presents superior NO2 sensing performance at 190 °C, particularly at low concentrations, consisting of high response (5.9), quick response (7–12 s)/recovery time (9–13 s), strong selectivity and stability toward 100 ppb NO2. The excellent sensing characteristics are attributed to the synergy of heterojunction and exposed (001) facet with more oxygen vacancies. Furthermore, the well-defined open flower structure provides unique opportunities to form n-n heterostructures, inducing the adequate sensing reactions and ultrafast the response/recovery kinetics. The findings in this study open a new route for WO3-based hierarchical materials to detect NO2 efficiently and accurately.

Synergistic coupling of 0D–2D heterostructure from ZnO and Ti3C2Tx MXene-derived TiO2 for boosted NO2 detection at room temperature

2D MXenes are highly attractive for fabricating high-precision gas sensors operated at room temperature (RT) due to their high surface-to-volume ratio. However, the limited selectivity and low sensitivity are still long-standing challenges for their further applications. Herein, the self-assembly of 0D–2D heterostructure for highly sensitive NO2 detection was achieved by integrating ZnO nanoparticles on Ti3C2Tx MXene-derived TiO2 nanosheets (designated as ZnO@M−TiO2). ZnO nanoparticles can not only act as spacers to prevent the restacking of M−TiO2 nanosheets and ensure effective transfer for gas molecules, but also enhance the sensitivity of the sensor the through trapping effect on electrons. Meanwhile, M−TiO2 nanosheets facilitate gas diffusion for rapid sensor response. Benefiting from the synergistic effect of individual components, the ZnO@M−TiO2 0D–2D heterostructure-based sensors revealed remarkable sensitivity and excellent selectivity to low concentration NO2 at RT. This work may facilitate the sensing application of MXene derivative and provide a new avenue for the development of high-performance gas sensors in safety assurance and environmental monitoring.

Assessment of the NO2 Spatio-Temporal Variability over Thessaloniki, Greece, Using MAX-DOAS Measurements and Comparison with S5P/TROPOMI Observations

In this article, we investigate the spatio-temporal variability of tropospheric NO2 Vertical Column Densities (VCDs) and surface concentrations that were retrieved using Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements over Thessaloniki, Greece, for the period June 2020 to November 2022. The MAX-DOAS system captures the NO2 seasonal variability very well, reporting low concentrations during summer and higher concentrations in the winter, as well as the diurnal cycle with higher NO2 amounts in the morning followed by a reduction towards noon. The “weekend effect” is evident, with approximately 30% lower NO2 concentrations on the weekends compared to the working days. An excellent agreement is found with in situ data from a nearby air quality monitoring station with Pearson’s correlation coefficients ranging between R = 0.90 and R = 0.99. The spatial variability is assessed by comparing the NO2 concentrations at four azimuth viewing directions of the MAX-DOAS system. Despite the large variability due to short- and long-term temporal variations, higher NO2 concentrations of up to 25% (statistically significant at the 95% confidence level) are reported for the azimuth that crosses the entire city center and an urban area compared to those pointing towards the sea. The MAX-DOAS tropospheric NO2 columns are then compared to those measured by the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel-5P satellite. Despite the generally good correlation (R = 0.72 and R = 0.89 for the daily and monthly data, respectively), a clear underestimation of TROPOMI is found (approximately 55% in winter, 21% in spring and 40% during autumn and summer), mainly due to the much larger satellite footprint that provides a smoother perception of the NO2 concentration, while the MAX-DOAS measurements are more affected by local emissions.

MOCVD of Hierarchical C‐MoS2 Nanobranches for ppt‐Level NO2 Detection

In the past decades, toxic gas emissions have increased significantly owing to the rapid growth of industry and road transportation. Therefore, monitoring major pollutants, such as NO2, is crucial to protecting human health. The 2D materials that contain numerous adsorption sites and exhibit ultrahigh chemical reactivity can be used as sensor materials to detect these toxic gases. Herein, highly uniform, large‐area carbon‐incorporating hierarchical MoS2 nanobranches are synthesized by metal–organic chemical vapor deposition (MOCVD). An in situ carbon‐incorporation method that uses the carbon impurity present in the precursor as the seed during the MOCVD process is employed to form a hierarchical structure containing abundant adsorption sites. A gas sensor based on the resulting C‐MoS2 nanobranches contains many edge sites exhibits high adsorption energy, and consequently, has high NO2 gas sensitivity. Hence, this hierarchical C‐MoS2 gas sensor shows excellent sensing properties, exhibiting a device response of 1.67 at an extremely low NO2 concentration (≈5 ppb). The limit of detection of the gas sensor for NO2 is calculated to be low (≈1.58 ppt), further confirming its exceptional performance. Thus, the hierarchical C‐MoS2 nanobranches deposited herein provide novel insights regarding the properties of 2D materials and are highly suited for fabricating high‐performance NO2 sensors.

Solution-Processed Functionalized Graphene Film Prepared by Vacuum Filtration for Flexible NO2 Sensors.

Large-scale production of graphene nanosheets (GNSs) has led to the availability of solution-processable GNSs on the commercial scale. The controlled vacuum filtration method is a scalable process for the preparation of wafer-scale films of GNSs, which can be used for gas sensing applications. Here, we demonstrate the use of this deposition method to produce functional gas sensors, using a chemiresistor structure from GNS solution-based techniques. The GNS suspension was prepared by liquid-phase exfoliation (LPE) and transferred to a polyvinylidene fluoride (PVDF) membrane. The effect of non-covalent functionalization with Co-porphyrin and Fe-phthalocyanines on the sensor properties was studied. The pristine and functionalized GNS films were characterized using different techniques such as Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and electrical characterizations. The morphological and spectroscopic analyses both confirm that the molecules (Co-porphyrin and Fe-phthalocyanine) were successfully adsorbed onto the GNSs surface through π-π interactions. The chemiresistive sensor response of functionalized GNSs toward the low concentrations of nitrogen dioxide (NO2) (0.5-2 ppm) was studied and compared with those of the film of pristine GNSs. The tests on the sensing performance clearly showed sensitivity to a low concentration of NO2 (5 ppm). Furthermore, the chemical modification of GNSs significantly improves NO2 sensing performance compared to the pristine GNSs. The sensor response can be modulated by the type of adsorbed molecules. Indeed, Co-Por exhibited negative responsiveness (the response of Co-Por-GNS sensors and pristine GNS devices was 13.1% and 15.6%, respectively, after exposure to 0.5 ppm of NO2). Meanwhile, Fe-Phc-GNSs induced the opposite behavior resulting in an increase in the sensor response (the sensitivity was 8.3% and 7.8% of Fe-Phc-GNSs and pristine GNSs, respectively, at 0.5 ppm NO2 gas).

UV Irradiation of Au-Modified SnO2 Nanorods Enabling the Rapid Detection of Low-Concentration NO2 at Room Temperature

The development of simple and low-cost materials and methods that are suitable for use in sensors with excellent NO2-sensing properties is of great importance to the commercialization of NO2 sensors. Here, Au-modified SnO2 nanorods (Au/SnO2 nanorods) were synthesized via a hydrothermal method combined with photodeposition. The UV light-activated sensor fabricated from Au/SnO2 nanorods was found to exhibit excellent sensing properties for NO2 at room temperature, including a high response of 10 (at a concentration of 1 ppm), a theoretical detection limit of 21 ppt, and a fast response/recovery time of 1/5 s ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}_{{60}}$ </tex-math></inline-formula> ) and 22/38 s ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}_{{90}}$ </tex-math></inline-formula> ). In addition, the sensor exhibited good selectivity, repeatability, and long-term stability. The sensor was found to have a good response to NO2 in a high-humidity environment. The excellent sensing properties of Au/SnO2 nanorods for NO2 can be attributed to the charge transfer between Au and SnO2, and the catalytic sensitization of noble metals. The presence of water molecules in the high-humidity environment was found to enhance the NO2-sensing performance of the developed material.

Facile fabrication of nanoflower-like WO3/WS2 heterojunction for highly sensitive NO2 detection at room temperature.

Realizing efficient detection of ultra-low concentrations of hazardous gases contributes to air pollution monitoring, ecosystem and human health protection. Herein, we firstly fabricated the nanoflower-like WO3/WS2 composites by a facile process to highly sensitively detect NO2 at room temperature. The WO3 content in the WO3/WS2 composites can be adjusted by altering the calcination temperature, and the WO3 nanoparticles disperse uniformly on the WS2 surface, forming the WO3/WS2 heterojunction. The room-temperature responses of WO3/WS2 composites gradually climb with the NO2 concentration increasing from 0.005 to 5ppm, and the WW-280 and WW-300 composites possess the optimal gas sensitivity when the NO2 concentrations are lower and higher than 100 ppb, respectively. In particular, the two WO3/WS2 composites present the limitation of detection (LOD) of ≤5 ppb, and they exhibit the excellent selectivity, good reproducibility and long-term stability towards NO2. A possible gas sensing mechanism was also proposed from the point of views of gas adsorption, redox reactions and electron transfer. The appropriate WO3 content and molar ratio of hexagonal to monoclinic WO3, and the formation of WO3/WS2 p-n heterojunction can contribute to the high sensitivity of WO3/WS2 composite to various concentrations of NO2. This work offers a promising gas sensing material for room-temperature detection to low concentrations of NO2.

Tunable and optimal interlayer spacing of 2D VS2 with high response and fast recovery for NO2 detection

Due to the restricted interlayer spacing, the large active regions between the interlayers of most two-dimensional (2D) materials are difficult to be utilized efficiently, which greatly limits their performance for gas sensing. Herein, a novel NO2 sensor based on expanded VS2 (abbreviated as VS2-E) is reported by regulating the interlayer spacing to 11.6 Å (VS2-E3). Compared with VS2-N (natural interlayer spacing of 5.8 Å), VS2-E1 (10.0 Å) and VS2-E2 (10.2 Å), the increased interlayer spacing of the VS2-E3 significantly improved its NO2 sensing performance. With a high response (∼2.77–10 ppm NO2), rapid response/recovery speed (∼10/10 s), low detection limits (distinct response to 200 ppb NO2), and good stability at 100 °C, the sensor based on VS2-E3 demonstrates excellent NO2 sensing qualities. In addition, the interlayer sensing mechanism is explained by simulating the diffusion movement of NO2 between different spacing VS2 interlayers. Enlarging the interlayer space boosts the interaction of VS2 and NO2, increases the diffusion coefficient of NO2 and accelerates their desorption between interlayers, thereby evidently enhancing the response intensity and the recovery speed. These results suggest that VS2-E3 has promising prospect in the realm of low-concentration and rapid NO2 detection.

A Comparative Study of Air Pollutant Concentrations before the COVID-19 Pandemic and in the New Normal in the Región de Murcia (Spain)

The management of the COVID-19 pandemic, which required global lockdowns and mobility restrictions, positively impacted air quality (especially the concentrations of primary pollutants). With the progressive return to normal activity during the last few months of 2020 and 2021, air pollutant concentrations were expected to rise again. In this work, together with meteorological conditions and traffic intensity, the concentrations of NO, NO2, O3, PM10, and SO2 measured at three different locations (urban, industrial, and rural) in southeast Spain, from January 2016 to December 2021, were analyzed. For the three locations, PM10 concentrations did not change significantly in 2020 or 2021. SO2 concentrations did not experience changes at the industrial site in 2020 or 2021, but SO2 concentrations did slightly increase in five months of 2021 in the urban location (with a maximum monthly average concentration of 11 μg·m−3). In 2020, NO and NO2 concentrations were, in general, lower than those measured in previous years (2016–2019). Interestingly, at the urban site (San Basilio), the levels of NO and NO2 were significantly lower in 2021 than in 2020 despite the higher traffic intensity in 2021. While the concentrations of NO and NO2 decreased, in VOC-limited areas, O3 concentrations increased. This was clearly observed at the industrial and the urban sites. Despite the increase, O3 concentrations were still below the European O3 target value for the protection of human health. An analysis of new registrations of EVs and HEVs in the latter years and their impact on the vehicle fleet of Murcia and, subsequently, on road emissions was carried out. Regardless of the steep increase in environmentally friendly vehicles in 2021, their share of the vehicle fleet is still negligible; thus, the lower concentrations of NO and NO2 are likely due to more favorable weather conditions in 2021 than in 2020.

Microplastics inhibit biofloc formation and alter microbial community composition and nitrogen transformation function in aquaculture

Biofloc technology, extensively used in intensive aquaculture systems, can prompt the formation of microbial aggregates. Microplastics (MPs) are detected abundantly in aquaculture waters. This study explored the effects of MPs on biofloc formation, microbial community composition and nitrogen transformation function in simulated biofloc aquaculture production systems. The formation process and settling performance of bioflocs were examined. High-throughput sequencing of 16S and 18S rRNA genes was used to investigate the microbial community compositions of bioflocs. Nitrogen dynamics were monitored and further explained from functional genes and microorganisms related to nitrogen transformation by metagenome sequencing. We found that the aggregates consisting of bioflocs and MPs were formed and the systems with MPs had relatively weak settling performance. No significant differences in bacterial diversity (p > 0.05) but significant differences in eukaryotic diversity (p < 0.05) were found between systems without and with MPs. Significant separations in the microbial communities of prokaryotes (p = 0.01) and eukaryotes (p = 0.01) between systems without and with MPs were observed. The peak concentration of nitrite nitrogen (NO2−-N) in systems with MPs was lower than that in systems without MPs (pControl/MPs Low = 0.02 and pControl/MPs High = 0.03), probably due to the low abundance of hao and affiliated Alphaproteobacteria_bacterium_HGW-Alphaproteobacteria-1 and Alphaproteobacteria_bacterium, but the high abundance of nxrA and affiliated Alphaproteobacteria_bacterium_SYSU_XM001 and Hydrogenophaga_pseudoflava that related to nitrification. The low concentration of NO2−-N in systems with MPs suggested that the presence of MPs might inhibit ammonia oxidation but promote nitrite oxidation by altering the microbial community structure and function. These results indicated that aggregates consisting of bioflocs and MPs could be formed in aquaculture water, and thus, inhibiting their settlement and altering nitrogen transformation function by affecting the microbial community composition.

Redox mediators promote electrochemical oxidation of nitric oxide toward ambient nitrate synthesis

Under ambient conditions, using low concentration NO (1%), ultrahigh nitrate formation rates in a two-electrode system can be achievedviathe eCOR-NOOR. The structure changes of electrode materials under real reaction conditions are revealed.

Efficient adsorption removal of NO2 by covalent triazine frameworks with fine-tuned binding sites

One promising method for mitigating low-temperature and low-concentration NO 2 pollution is selective adsorption using porous solid materials. However, the corrosive nature of NO 2 renders the development of an adsorbent with high and cyclable NO 2 uptake a formidable challenge. Herein, we attempted to address this challenge by developing a microporous covalent triazine framework (CTF) as effective adsorbents for NO 2 capture, achieving unprecedented high cyclable capacity enabled by simultaneous high adsorbent stability and moderate adsorption affinity via tuning specific binding sites. Using dynamic column breakthrough experiments, we demonstrated that the pristine CTF exhibited a high NO 2 adsorption capacity (dry: 3.83 mmol/g; wet: 5.26 mmol/g) overtaking most reported solid adsorbents, thanks to abundant active sites (e.g., nitrogen/carbon/triazine rings). Post-synthesis converted the surface nitrogen to protonated nitrogen site and further to transition metal site affording more effective binding sites that allows for moderately strong adsorption, resulting in elevated NO 2 adsorption capacity (dry: 6.11 mmol/g; wet: 8.97 mmol/g) and a highest reversible NO 2 adsorption (retaining 91% and 64% at dry and wet conditions after five cycles, respectively), as illustrated by our mechanistic study using in-situ DRIFTS and DFT calculations. This work affords not only promising adsorbents for real-world applications in mitigating NO 2 pollution, but also a strategy of developing robust adsorbents with desired affinity generally applicable to adsorptive capture of corrosive and toxic gases. • Covalent triazine frameworks (CTFs) were firstly demonstrated as effective NO 2 adsorbents with highly reversible capacity. • Various active bindings sites were rationally introduced to CTFs via postsynthesis. • The functionalized CTFs exhibited the highest cyclable NO 2 capacity (5.74 mmol/g after 5 th cycle) to date. • Combined in situ DRIFTS and DFT calculations revealed the NO 2 adsorption mechanism.