Nitrogen Oxide Radicals Research Articles

Interpreting Geostationary Environment Monitoring Spectrometer (GEMS) geostationary satellite observations of the diurnal variation in nitrogen dioxide (NO2) over East Asia

Abstract. Nitrogen oxide radicals (NOx≡NO+NO2) emitted by fuel combustion are important precursors of ozone and particulate matter pollution, and NO2 itself is harmful to public health. The Geostationary Environment Monitoring Spectrometer (GEMS), launched in space in 2020, now provides hourly daytime observations of NO2 columns over East Asia. This diurnal variation offers unique information on the emission and chemistry of NOx, but it needs to be carefully interpreted. Here we investigate the drivers of the diurnal variation in NO2 observed by GEMS during winter and summer over Beijing and Seoul. We place the GEMS observations in the context of ground-based column observations (Pandora instruments) and GEOS-Chem chemical transport model simulations. We find good agreement between the diurnal variations in NO2 columns in GEMS, Pandora, and GEOS-Chem, and we use GEOS-Chem to interpret these variations. NOx emissions are 4 times higher in the daytime than at night, driving an accumulation of NO2 over the course of the day, offset by losses from chemistry and transport (horizontal flux divergence). For the urban core, where the Pandora instruments are located, we find that NO2 in winter increases throughout the day due to high daytime emissions and increasing NO2/NOx ratio from entrainment of ozone, partly balanced by loss from transport and with a negligible role of chemistry. In summer, by contrast, chemical loss combined with transport drives a minimum in the NO2 column at 13:00–14:00 local time (LT). Segregation of the GEMS data by wind speed further demonstrates the effect of transport, with NO2 in winter accumulating throughout the day at low winds but flat at high winds. The effect of transport can be minimized in summer by spatially averaging observations over the broader metropolitan scale, under which conditions the diurnal variation in NO2 reflects a dynamic balance between emission and chemical loss.

Changes to Peroxyacyl Nitrates (PANs) Over Megacities in Response to COVID‐19 Tropospheric NO2 Reductions Observed by the Cross‐Track Infrared Sounder (CrIS)

AbstractThe COVID‐19 pandemic perturbed air pollutant emissions as cities shut down worldwide. Peroxyacyl nitrates (PANs) are important tracers of photochemistry that are formed through the oxidation of non‐methane volatile organic compounds in the presence of nitrogen oxide radicals (NOx = NO + NO2). We use satellite measurements of free tropospheric PANs from the Suomi‐National Polar‐orbiting Partnership Cross‐track Infrared Sounder (CrIS) over eight of the world's megacities. We quantify the seasonal cycle of PANs over these megacities and find seasonal maxima in PANs correspond to seasonal peaks in local photochemistry. CrIS is used to explore changes in PANs in response to the COVID‐19 lockdowns. Statistically significant changes to PANs occurred over four megacities: with decreases over Los Angeles and Delhi, and increases over Mexico City and Beijing in the winter. Our analysis suggests that large perturbations in NOx may not result in significant declines in NOx export potential of megacities.

Gamma Radiolysis of Phenyl-Substituted TODGAs: Part II

ABSTRACT The radiolytic degradation chemistry of three phenylated analogs of N,N,N’,N’-tetraoctyl diglycolamide (TODGA) was investigated: 2-(2-(di-n-octylamino)-2-oxoethoxy)-N,N-di-n-octyl-2-phenylacetamide (PhTODGA), which has a phenyl substituent bound to a central methylene, 2-(2-(di-n-octylamino)-2-oxo-1-phenylethoxy)-N,N-di-n-octylpropanamide (PhMeTODGA), which also contains a methyl substituent bound to the methylene on the other side of the ether moiety, and, 2-(2-N-n-hexyl-N-phenylamino)-2-oxoethoxy)-N-n-hexyl-N-phenylacetamide (DHDPDGA), which has phenyl substituents located on the amide groups instead of the central methylenes. In Part II of this series of papers radiolytic degradation products were identified after separation with liquid chromatography by High Resolution, Accurate-Mass mass spectrometry and collision-induced dissociation. At least twenty-two radiolytic degradation products were identified for PhTODGA, twenty-nine for PhMeTODGA, and over three dozen for DHDPDGA. The suite of radiolytic degradation products of these three investigated ligands was significantly larger than has been reported for previously studied diglycolamides, owing to their asymmetric nature, and to the identification of several new degradation mechanisms, including addition of methyl, hydroxyl, and nitrogen oxide radicals, that have not been previously reported for diglycolamides. Degradation products that contained addition of a NO2 or NO3 group were particularly prevalent for DHDPDGA, likely due to the phenyl side-groups. Several of these newly observed mechanisms do not appear to depend on the presence of the phenyl groups, suggesting these novel mechanisms may apply to other diglycolamides

Measurement report: Spatiotemporal variability of peroxy acyl nitrates (PANs) over Mexico City from TES and CrIS satellite measurements

Abstract. Peroxy acyl nitrates (PANs) are photochemical pollutants with implications for health and atmospheric oxidation capacity. PANs are formed via the oxidation of non-methane volatile organic compounds (NMVOCs) in the presence of nitrogen oxide radicals (NOx = NO + NO2). While urban environments are large sources of PANs, in situ observations in urban areas are limited. Here we use satellite measurements of PANs from the Tropospheric Emission Spectrometer (TES) and the Suomi National Polar-orbiting Partnership (S-NPP) Cross-track Infrared Sounder (CrIS) to evaluate the spatiotemporal variability of PANs over and around Mexico City. Monthly mean maxima in PANs over the Mexico City Metropolitan Area (MCMA) occur during spring months (March–May). This time of year coincides with a peak in local photochemistry and more frequent air stagnation. Local fire activity also typically peaks between February and May, which leads to strong interannual variability of PANs over the MCMA. We use S-NPP CrIS data to probe the spatial outflow pattern of PANs produced within urban Mexico City during the month with the largest mixing ratios of PANs (April). Peak outflow in April occurs to the northeast of the city and over the mountains south of the city. Outflow to the northwest appears infrequently. Using observations during 2018 versus 2019, we also show that PANs were not significantly reduced during a year, with a significant decrease in NOx over Mexico City. Our analysis demonstrates that the space-based observations provided by CrIS and TES can increase understanding of the spatiotemporal variability of PANs over and surrounding Mexico City.

Novel Alcohol-Soluble Nitroxide Radical Conjugated Polymer for Cathode Modifier of Efficient Organic Solar Cells with Enhanced Stability.

Alcohol-soluble conjugated polymers with polar side-chain components have been regarded as one of the most promising cathode interfacial modifers (CIMs) to achieve high-performance organic solar cells (OSCs). Herein, a novel alcohol-soluble nitrogen oxide radical conjugated polymer (PBN-NO) containing dimethylamine groups for regulating metal work function and the dangling of 2,2,6, 6-tetramethylpiperidine 1-oxy (TEMPO) radical side-chain groups for theoretically improving the conductivity, was prepared and characterized. As compared to the OSCs from PM6:Y6 blends with the most common CIMs of PFN, PDINO, and PDINN, the OSCs with PBN-NO as CIMs provide better or comparable power conversion efficiencies (PCEs) (16.19% vs 13.10%, 15.60%, and 16.15%), enhanced photostability, and thermal stability. Besides that, the reasons for the improving PCEs of the OSCs with PBN-NO modifier are systematically investigated and supported by a set of comparative experiments such as exciton dissociation, charge recombination, capacitance-voltage (C-V), etc. To the best of our knowledge, this is the first report of an alcohol-soluble nitroxide radical conjugated polymer that successfully integrates the interfacial modification of polar groups and improves conductivity by dangling radicals, therefore contributing to efficient OSCs with enhanced stability.

An improved and sensitive method for nitrotyrosine estimation by reverse phase-high performance liquid chromatography

Reactive nitrogen species such as peroxynitrite anion (ONOO-), nitrogen oxide radical (NO.) may lead to nitrotyrosine formation by oxidative nitration of tyrosine. Nitrotyrosine is considered as an important marker to estimate the severity of biological oxidative damage. Therefore, in the present study, we evaluated a reverse phase-high performance liquid chromatography (RP-HPLC) method to improve the sensitivity and specificity of the nitrotyrosine estimation. The mobile phase used in the present study was methanol (pH 4.7) and 0.1% phosphoric acid (60:40%). The standard serial dilutions were injected onto the HPLC column (C-18) at a flow rate of 1 ml/min mobile phase with a time window of 6 min. The results were monitored on the Diode Array detector at wavelength 210 nm. The evaluation and quantification of output signals were made on the Chromelion software version 6.80 which controls the whole liquid chromatography system. The same standard serial dilutions were monitored spectrophotometrically at 210nm. We found the standard curves were linear over the concentration range of 0.3 to 20 ng/ml for both RP-HPLC with UV detector (r2 = 0.997) and spectrophotometric (r2 = 0.999) methods. In spectrophotometric method, only four standard points were detected out of seven and represented on a straight line, this shows the spectrophotometric method was unable to measure less than 2.5 ng/ml concentration. On the other hand, in RP-HPLC method, all the seven standards were lying on a straight line and HPLC machine can detect up to 1ng/ml or 1pg/µl. The present study established the highly specific, sensitive, accurate and cost-effective RP-HPLC with UV detector method for nitrotyrosine estimation.

Ultraviolet Light-Driven gaining of hydroxyl and nitrogen oxide radicals in Plasma–Treated water

Here we numerically demonstrate that photolytic processes induced by external ultraviolet (UV) sources considerably affect the chemical properties of plasma–water systems. When describing the chemical transport between surface dielectric barrier discharge (SDBD) and deionized water, the plasma is simulated using a global model, while the gas (air) and liquid (water) regions are considered in a one-dimensional space. Our simulation involving exposure of plasma-treated water (PTW) to UV shows that long-lived species in PTW are readily photolyzed and form hydroxyl radical (OH) and nitric oxide (NO) over the entire liquid region. The total OH concentration was enhanced by 11.6 times at 100 s under exposure to a conventional UV lamp, while the total NO concentration was remarkably enhanced up to 45.8 times at 300 s. The time at which the OH concentration notably increases was advanced by more than 100 s by photolytic processes. The results directly reveal that the exposure of PTW to UV is an attractive approach to selectively releasing extra OH and NO, thereby increasing the PTW reactivity and applicability. Owing to their high reactivity and oxidizing power, the short lifetime of radicals including OH and NO in PTW, which is crucial in diverse applications, has been troublesome. In this regard, our findings will provide new guidance in utilizing PTW for various applications.

A facile approach of improving the inhibition of arylfulleropyrrolidine on the thermal decomposition of nitrocellulose by enhancing the thermal interaction

A series of aryl[70]fulleropyrrolidine (5a–5b’) were successfully designed and synthesized using Prato reaction. The results of non-isothermal thermal analysis showed that 5a–5b’ can increase the critical explosion temperature of nitrocellulose by 0.8–1.8 K. The results of isothermal experiments proved that 5a–5b’ can prolong the discoloration time of methyl violet test paper of nitrocellulose at 407.65 K and the safe storage life of nitrocellulose at 323.15 K by 87 min and 34.46 years, respectively. The adiabatic accelerated calorimetry analysis showed that 5a–5b’ can reduce the initial autocatalytic decomposition reaction of nitrocellulose. The thermal stability of 5a–5b’ to nitrocellulose was proved to mainly depends on the nitrogen oxide radical scavenging ability of fullerene. Obviously, a small amount of aryl[70]fulleropyrrolidine mixed with aryl[60]fulleropyrrolidine can significantly improve the inhibition of aryl[60]fulleropyrrolidine on the thermal decomposition of nitrocellulose. Subsequently, the feasibility of low-cost and large-scale preparation of arylfulleropyrrolidine stabilizer using fullerene soot as precursor was explored.

Advanced oxidation processes (AOPs) based wastewater treatment - unexpected nitration side reactions - a serious environmental issue: A review

• Unexpected nitration processes led to formation of several nitro-derivatives. • Nitrogen fixation importantly contributes to formation of reactive nitrogen species in sonolysis. • Denitration and renitration processes in persulfate based AOPs causes nitration of intermediates. • Post-treatment and nitro-derivatives monitoring are important in AOPs. • Risk of low water quality in case of unexpected nitration during treatment process. Chemical compounds containing nitro group (nitro-products) are a one of toxic by-products, that can be formed during wastewater treatment processes. In case of presence of nitrite or nitrate ions, the formation of nitro-products during advanced oxidation processes (AOPs) is very common. It is caused by the reactive nitrogen species (RNs) such as nitrate radical (NO 3 • ), nitrite radical (NO 2 • ), nitrogen oxide radical (NO • ) and peroxynirite (ONOO–). In fact, the oxidative degradation of N-containing pollutants releases nitrate, nitrite and ammonium ions. In some cases, secondary reactions of mineralised nitrogen species (nitrate and nitrite ions) with the parent or intermediate compound generate next several nitro-products. The nitro-products are more toxic comparing to the primary pollutants and act as the precursors of the nitrogenous disinfection by-products. Moreover, some studies reported unexpected nitro-products formation during the oxidative degradation. In case of such processes a special attention should be made to monitor and minimize these effects. De-nitration of the initial nitro-compounds induces the formation of various nitro-products in AOPs. It was observed for UV light driven, Fenton and persulfate based AOPs. The sonochemical nitrogen fixation is a key mechanism for the formation of nitro-compounds in ultrasounds based AOPs. Therefore, this paper is focused on comparison of various AOPs in terms of nitro-products formation mechanisms and the associated environmental issues.

ANTIOXIDANT AND ANTIRADICAL ACTIVITY IN VITRO OF EXTRACTS FROM THE LEAVES OF RUBUS CHAMAEMORUS L. (ROSACEAE)

Cloudberry (Rubus chamaemorus L.) is the leader among northern berries in the content of phenolic compounds, which can cause a wide range of biological activity. Currently, there is an increased interest in the study of the antioxidant activity of plant extracts in order to search for promising sources of raw materials for the pharmaceutical and food industries. The article presents the results of a comparative analysis of interpopulation and gender differences in antioxidant and antiradical activities in vitro of cloudberry leaf extracts growing on the territory of the Republic of Belarus. Classical spectrophotometric methods were used for determination: phosphomolibdenic method, Fe + 2-chelating activity, NO-inhibiting activity, inhibition of hydroxyl radicals (OH), method of superoxide radical inhibition in an alkaline solution of dimethylsulfoxide, DPPH, ABTS. Differences in the content of phenolic compounds and flavonoids in the alcoholic extracts of leaf blades of Rubus chamaemorus L. It was found that the population of the Bolshoi Mokh preserve possesses the highest inhibition rates of hydroxyl radicals and superoxide radicals. The maximum iron-chelating activity was exhibited by the extracts of the male plant of the Bolshoy Moh preserve. The least inhibitory activity of Rubus chamaemorus L. leaf extracts was shown to the nitrogen-oxide radical. The established values of antioxidant and antiradical activities, as well as the content of phenolic compounds and flavonoids of the leaf blades of Rubus chamaemorus L. may be important for the development of measures to preserve the species and specific populations on the southern border of the habitat.

Reaction Mechanisms Underlying Unfunctionalized Alkyl Nitrate Hydrolysis in Aqueous Aerosols

Alkyl nitrates (ANs) are both sinks and sources of nitrogen oxide radicals (NOx = NO + NO2) in the atmosphere. Their reactions affect both the nitrogen cycle and ozone formation and therefore air quality and climate. ANs can be emitted to the atmosphere or produced in the gas phase. In either case, they can partition into aqueous aerosols, where they might undergo hydrolysis, producing highly soluble nitrate products, and act as a permanent sink for NOx. The kinetics of AN hydrolysis partly determines the extent of AN contribution to the nitrogen cycle. However, kinetics of many ANs in various aerosols is unknown, and there are conflicting arguments about the effect of acidity and basicity on the hydrolysis process. Using computational methods, this study proposes a mechanism for the reactions of methyl, ethyl, propyl, and butyl nitrates with OH– (hydroxyl ion; basic hydrolysis), water (neutral hydrolysis), and H3O+ (hydronium ion; acidic hydrolysis). Using quantum chemical data and transition state theory, we follow the effect of pH on the contribution of the basic, neutral, and acidic hydrolysis channels, and the rate coefficients of AN hydrolysis over a wide range of pH. Our results show that basic hydrolysis (i.e., AN reaction with OH–) is the most kinetically and thermodynamically favorable reaction among our evaluated reaction schemes. Furthermore, comparison of our kinetics results with experimental data suggests that there is an as yet unknown acidic mechanism responsible for acidic catalysis of AN hydrolysis.

Transport and chemistry of isoprene and its oxidation products in deep convective clouds

Deep convective clouds can transport trace gases from the planetary boundary layer into the upper troposphere where subsequent chemistry may impact aerosol particle formation and growth. In this modelling study, we investigate processes that affect isoprene and its oxidation products injected into the upper troposphere by an isolated deep convective cloud in the Amazon. We run a photochemical box model with coupled cloud microphysics along hundreds of individual air parcel trajectories sampled from a cloud-resolving model simulation of a convective event. The box model simulates gas-phase chemical reactions, gas scavenging by liquid and ice hydrometeors, and turbulent dilution inside a deep convective cloud. The results illustrate the potential importance of gas uptake to anvil ice in regulating the intensity of the isoprene oxidation and associated low volatility organic vapour concentrations in the outflow. Isoprene transport and fate also depends on the abundance of lightning-generated nitrogen oxide radicals (NOx = NO + NO2). If gas uptake on ice is efficient and lightning activity is low, around 30% of the boundary layer isoprene will survive to the cloud outflow after approximately one hour of transport, while all the low volatile oxidation products will be scavenged by the cloud hydrometeors. If lightning NOx is abundant and gas uptake by ice is inefficient, then all isoprene will be oxidised during transport or in the immediate outflow region, while several low volatility isoprene oxidation products will have elevated concentrations in the cloud outflow. Reducing uncertainties associated with the uptake of vapours on ice hydrometeors, especially HO2 and oxygenated organics, is essential to improve predictions of isoprene and its oxidation products in deep convective outflows and their potential contribution to new particle formation and growth.

Interaction of nitrocellulose with pentaacyloxyphenyl fullerene derivatives: autocatalytic inhibition in thermal decomposition of nitrocellulose

The safe storage of nitrocellulose has become challenging due to their requirements of extreme storage environments, and existing stabilizers cannot fully meet the demand. Thus, developing new high-performance stabilizers to improve the stability of nitrocellulose is urgently needed. Considering the stabilizing mechanism of stabilizers and the excellent free radical scavenging ability of fullerenes, two novel fullerene-based stabilizers, pentaacyloxyphenyl fullerene derivatives (PAOP-C60), were designed and synthesized, and their structures were characterized by FTIR, UV–Vis and NMR. The thermal action of PAOP-C60 during thermal decomposition process of nitrocellulose was studied by thermal analysis, which indicating that the thermal stability of nitrocellulose was increased with addition of PAOP-C60 and the PAOP-C60 was found to exhibit superior thermal stability than traditional stabilizer. The results of electron spin resonance showed that fullerene-based stabilizers had a significant scavenging effect on nitrogen oxide radicals, and the IC50 of PAOP-C60 (0.674–0.818 g L−1) was smaller than that of diphenylamine (1.717 g L−1). Moreover, the intermediate product produced by PAOP-C60 and nitrocellulose action was extracted and characterized by FTIR. A possible stabilization mechanism of PAOP-C60, which was different from traditional stabilization mechanism, was proposed.

Reactive Nitrogen Species Are Also Involved in the Transformation of Micropollutants by the UV/Monochloramine Process.

The UV/monochloramine (NH2Cl) process is an emerging advanced oxidation process (AOP) in water treatment via radicals produced from the UV photolysis of NH2Cl. This study investigated the degradation of micropollutants by the UV/NH2Cl AOP, with ibuprofen (IBP) and naproxen (NPX) selected as representative micropollutants. Hydroxyl radical (HO•) and chlorine atom (Cl•) were identified in the process, and unexpectedly, we found that reactive nitrogen species (RNS) also played important roles in the transformation of micropollutants. The electron paramagnetic resonance (EPR) analysis proved the production of •NO as well as HO•. The concentrations of HO•, Cl•, and •NO in UV/NH2Cl remained constant at pH 6.0-8.6, resulting in the slightly changed UV fluence-based pseudo-first-order rate constants (k') of IBP and NPX, which were about 1.65 × 10-3 and 2.54 × 10-3 cm2/mJ, respectively. For IBP, the relative contribution of RNS to k' was 27.8% at pH 7 and 50 μM NH2Cl, which was higher than that of Cl• (6.5%) but lower than that of HO• (58.7%). For NPX, the relative contribution of RNS to k' was 13.6%, which was lower than both Cl• (23.2%) and HO• (46.9%). The concentrations of HO•, Cl•, and •NO increased with the increasing NH2Cl dosage. Water matrix components of natural organic matter (NOM) and bicarbonate can scavenge HO•, Cl•, and RNS. The presence of 5 mg/L NOM decreased the k' of IBP and NPX by 66.9 and 57.6%, respectively, while 2 mM bicarbonate decreased the k' of IBP by 57.4% but increased the k' of NPX by 10.5% due to the contribution of CO3•- to NPX degradation. Products containing nitroso-, hydroxyl-, and chlorine-groups were detected during the degradation of IBP and NPX by UV/NH2Cl, indicating the role of nitrogen oxide radical (•NO) as well as HO• and Cl•. Trichloronitromethane formation was strongly enhanced in the UV/NH2Cl-treated samples, further indicating the important roles of RNS in this process. This study first demonstrates the involvement of RNS in the transformation of micropollutants in UV/NH2Cl.

A new model mechanism for atmospheric oxidation of isoprene: global effects on oxidants, nitrogen oxides, organic products, and secondary organic aerosol

Abstract. Atmospheric oxidation of isoprene, the most abundantly emitted non-methane hydrocarbon, affects the abundances of ozone (O3), the hydroxyl radical (OH), nitrogen oxide radicals (NOx), carbon monoxide (CO), oxygenated and nitrated organic compounds, and secondary organic aerosol (SOA). We analyze these effects in box models and in the global GEOS-Chem chemical transport model using the new reduced Caltech isoprene mechanism (RCIM) condensed from a recently developed explicit isoprene oxidation mechanism. We find many similarities with previous global models of isoprene chemistry along with a number of important differences. Proper accounting of the isomer distribution of peroxy radicals following the addition of OH and O2 to isoprene influences the subsequent distribution of products, decreasing in particular the yield of methacrolein and increasing the capacity of intramolecular hydrogen shifts to promptly regenerate OH. Hydrogen shift reactions throughout the mechanism lead to increased OH recycling, resulting in less depletion of OH under low-NO conditions than in previous mechanisms. Higher organonitrate yields and faster tertiary nitrate hydrolysis lead to more efficient NOx removal by isoprene and conversion to inorganic nitrate. Only 20 % of isoprene-derived organonitrates (excluding peroxyacyl nitrates) are chemically recycled to NOx. The global yield of formaldehyde from isoprene is 22 % per carbon and less sensitive to NO than in previous mechanisms. The global molar yield of glyoxal is 2 %, much lower than in previous mechanisms because of deposition and aerosol uptake of glyoxal precursors. Global production of isoprene SOA is about one-third from each of the following: isoprene epoxydiols (IEPOX), organonitrates, and tetrafunctional compounds. We find a SOA yield from isoprene of 13 % per carbon, much higher than commonly assumed in models and likely offset by SOA chemical loss. We use the results of our simulations to further condense RCIM into a mini Caltech isoprene mechanism (Mini-CIM) for less expensive implementation in atmospheric models, with a total size (108 species, 345 reactions) comparable to currently used mechanisms.

Mechanism of ozone loss under enhanced water vapour conditions in the mid-latitude lower stratosphere in summer

Abstract. Water vapour convectively injected into the mid-latitude lowermost stratosphere could affect stratospheric ozone. The associated potential ozone loss process requires low temperatures together with elevated water vapour mixing ratios. Since this ozone loss is initiated by heterogeneous chlorine activation on liquid aerosols, an increase in sulfate aerosol surface area due to a volcanic eruption or geoengineering could increase the likelihood of its occurrence. However, the chemical mechanism of this ozone loss process has not yet been analysed in sufficient detail and its sensitivity to various conditions is not yet clear. Under conditions of climate change associated with an increase in greenhouse gases, both a stratospheric cooling and an increase in water vapour convectively injected into the stratosphere are expected. Understanding the influence of low temperatures, elevated water vapour and enhanced sulfate particles on this ozone loss mechanism is a key step in estimating the impact of climate change and potential sulfate geoengineering on mid-latitude ozone. Here, we analyse the ozone loss mechanism and its sensitivity to various stratospheric conditions in detail. By conducting a box-model study with the Chemical Lagrangian Model of the Stratosphere (CLaMS), chemistry was simulated along a 7 d backward trajectory. This trajectory was calculated neglecting mixing of neighbouring air masses. Chemical simulations were initialized using measurements taken during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) aircraft campaign (2013, Texas), which encountered an elevated water vapour mixing ratio of 10.6 ppmv at a pressure level around 100 hPa. We present a detailed analysis of the ozone loss mechanism, including the chlorine activation, chlorine-catalysed ozone loss cycles, maintenance of activated chlorine and the role of active nitrogen oxide radicals (NOx). Focussing on a realistic trajectory in a temperature range from 197 to 202 K, a threshold in water vapour of 10.6 ppmv has to be exceeded and maintained for stratospheric ozone loss to occur. We investigated the sensitivity of the water vapour threshold to temperature, sulfate content, inorganic chlorine (Cly), inorganic nitrogen (NOy) and inorganic bromine (Bry). The water vapour threshold is mainly determined by the temperature and sulfate content. However, the amount of ozone loss depends on Cly, Bry and the duration of the time period over which chlorine activation can be maintained. NOy affects both the potential of ozone formation and the balance between reactions yielding chlorine activation and deactivation, which determines the water vapour threshold. Our results show that in order to deplete ozone, a chlorine activation time of 24 to 36 h for conditions of the water vapour threshold with low temperatures must be maintained. A maximum ozone loss of 9 % was found for a 20 ppmv water vapour mixing ratio using North American Monsoon (NAM) tropopause standard conditions with a chemical box-model simulation along a realistic trajectory. For the same trajectory, using observed conditions (of 10.6 ppmv H2O), the occurrence of simulated ozone loss was dependent on the sulfate amount assumed. Detailed analysis of current and future possibilities is needed to assess whether enhanced water vapour conditions in the summertime mid-latitude lower stratosphere lead to significant ozone loss.

Polynitroxide-grafted-graphene: a superior cathode for lithium ion batteries with enhanced charge hopping transportation

The emergence of organic nitrogen-oxide (NO) radical polymers has brought hope in the pursuit of high performance lithium-ion batteries (LIBs).

Cysteine‐metal Porous Frameworks as Biosensing Elements for the Adsorption of Reactive Oxygen Species

AbstractThe involvements of in vivo reactive oxygen species, such as superoxide radical (O2.−), peroxynitrite (ONOO−), hydrogen peroxide (H2O2), hydroxyl radical (.OH), peroxyl radical (.OOH), nitrogen oxide radical (NO.), etc in cancer and other diseases are well documented. However, the availability of biosensing elements to detect the presence of reactive oxygen species inside living cells is rare. Herein, B3LYP−D3 dispersion‐corrected density functional theory has been used to design different porous frameworks by coordinating several divalent transition metals, such as Mn+2, Fe+2, Co+2, Cu+2, and Zn+2 with cysteine (Cys) that can detect the presence of various reactive oxygen species. It is found that among all the metals, Cu+2 has the strongest interaction with Cys, thereby producing several stable porous frameworks. Among these frameworks, [Cys‐Cu+2]3(8‐1) is found to possess the largest pore and can adsorb both the anionic (O2.−, ONOO.−) and neutral reactive oxygen species (.OH, .OOH, and NO.) in the aqueous environment. It is thus proposed that the elongation of [Cys‐Cu+2]3(8‐1) framework can generate a novel biosensing element, which can be used for the sensing of various reactive oxygen species. However, experimental verification of the proposed material is required to confirm its applicability.

Ab Initio Study of Decay Dynamics of 1-Nitronaphthalene Initiated from the S2(ππ* + nNOπ*) State

Irradiation of nitro-PAHs in solution at ambient conditions leads to formation of its lowest excited triplet, dissociation intermediates nitrogen oxide (NO•) and aryloxy radical (Ar-O•). Experimental and theoretical studies demonstrated that Franck-Condon excited singlet state SFC(ππ*) to a receiver, higher-energy triplet state Tn(nπ*) controlled the ultrafast population of the triplet state and, hence, the slight fluorescence yield of nitronaphthalenes. However, the detailed information about the curve-crossings of potential energy surfaces and the major channels for forming T1 species and Ar-O• radical were unclear. Here, by using the CASSCF//CASPT2 method, an efficient decay channel is revealed: S2-FC-1NN → S2-MIN-1NN or S2T3-MIN-1NN → T3-MIN-1NN or T3T2-MIN-1NN→ T2-MIN-1NN or T2T1-MIN-1NN → T1-MIN-1NN. This explains the high yield of T1-1NN species and minor yield of Ar-O• and NO• radicals. The calculation results suggest the bifurcation processes take place predominantly after the internal conversion to the T1-1NN state via T2T1-MIN-1NN, one leads to T1-MIN-1NN, while the other to T1-MIN-ISO to produce Ar-O• and NO• radicals.

PAN in the eastern Pacific free troposphere: A satellite view of the sources, seasonality, interannual variability, and timeline for trend detection

AbstractPeroxyacetyl nitrate (PAN) is an important trace gas that serves to transport nitrogen oxide radicals throughout the troposphere. We present an analysis of satellite observations of PAN from the Tropospheric Emission Spectrometer (TES) over the eastern Pacific Ocean for April and July 2006–2010 and the spring‐to‐summer seasonal transition for 2006. TES can provide quantitative estimates of free tropospheric PAN in clear‐sky or thin cloud conditions where elevated PAN (>0.2 ppbv) is present. The percentage of successful PAN detections increases from April to July and then decreases in August and September. However, there are no significant differences in the tropospheric average PAN either interannually or between these months. Plumes containing elevated PAN are present almost every day in July. Elevated PAN observed in July has multiple sources, including fires in Siberia, anthropogenic sources in eastern China, and recirculated pollution from the continental U.S. We combined the observed variability in the TES PAN retrievals over the eastern Pacific Ocean with a range of possible trends in PAN to determine the observational requirements to detect such trends. Based on the variability observed in the PAN retrievals over this region, we predict that it would be faster to detect a trend of a given magnitude in PAN using satellite observations over the eastern Pacific Ocean region rather than in situ surface observations and that a trend of a given magnitude would be more quickly detected in summer than spring.