Dinitrogen Pentoxide Research Articles

Modeling Analysis of Nocturnal Nitrate Formation Pathways during Co-Occurrence of Ozone and PM2.5 Pollution in North China Plain

The rapid formation of secondary nitrate (NO3−) contributes significantly to the nocturnal increase of PM2.5 and has been shown to be a critical factor for aerosol pollution in the North China Plain (NCP) region in summer. To explore the nocturnal NO3− formation pathways and the influence of ozone (O3) on NO3− production, the WRF-CMAQ model was utilized to simulate O3 and PM2.5 co-pollution events in the NCP region. The simulation results demonstrated that heterogeneous hydrolysis of dinitrogen pentoxide (N2O5) accounts for 60% to 67% of NO3− production at night (22:00 to 05:00) and is the main source of nocturnal NO3−. O3 enhances the formation of NO3 radicals, thereby further promoting nocturnal N2O5 production. In the evening (20:00 to 21:00), O3 sustains the formation of hydroxyl (OH) radicals, resulting in the reaction between OH radicals and nitrogen dioxide (NO2), which accounts for 48% to 64% of NO3− formation. Our results suggest that effective control of O3 pollution in NCP can also reduce NO3− formation at night.

Advancing DBD Plasma Chemistry: Insights into Reactive Nitrogen Species such as NO2, N2O5, and N2O Optimization and Species Reactivity through Experiments and MD Simulations.

This study aims to fine-tune the plasma composition with a particular emphasis on reactive nitrogen species (RNS) including nitrogen dioxide (NO2), dinitrogen pentoxide (N2O5), and nitrous oxide (N2O), produced by a self-constructed cylindrical dielectric barrier discharge (CDBD). We demonstrated the effective manipulation of the plasma chemical profile by optimizing electrical properties, including the applied voltage and frequency, and by adjusting the nitrogen and oxygen ratios in the gas mixture. Additionally, quantification of these active species was achieved using Fourier transform infrared spectroscopy. The study further extends to exploring the aerosol polymerization of acrylamide (AM) into polyacrylamide (PAM), serving as a model reaction to evaluate the reactivity of different plasma-generated species, highlighting the significant role of NO2 in achieving high polymerization yields. Complementing our experimental data, molecular dynamics (MD) simulations, based on the ReaxFF reactive force field potential, explored the interactions between reactive oxygen species, specifically hydroxyl radicals (OH) and hydrogen peroxide (H2O2), with water molecules. Understanding these interactions, combined with the optimization of plasma chemistry, is crucial for enhancing the effectiveness of DBD plasma in environmental applications like air purification and water treatment.

Plasma nitrogen fixation for plant cultivation with air‐derived dinitrogen pentoxide

Plasma nitrogen fixation for plant cultivation with air‐derived dinitrogen pentoxide

Identifying Driving Factors of Atmospheric N2O5 with Machine Learning.

Dinitrogen pentoxide (N2O5) plays an essential role in tropospheric chemistry, serving as a nocturnal reservoir of reactive nitrogen and significantly promoting nitrate formations. However, identifying key environmental drivers of N2O5 formation remains challenging using traditional statistical methods, impeding effective emission control measures to mitigate NOx-induced air pollution. Here, we adopted machine learning assisted by steady-state analysis to elucidate the driving factors of N2O5 before and during the 2022 Winter Olympics (WO) in Beijing. Higher N2O5 concentrations were observed during the WO period compared to the Pre-Winter-Olympics (Pre-WO) period. The machine learning model accurately reproduced ambient N2O5 concentrations and showed that ozone (O3), nitrogen dioxide (NO2), and relative humidity (RH) were the most important driving factors of N2O5. Compared to the Pre-WO period, the variation in trace gases (i.e., NO2 and O3) along with the reduced N2O5 uptake coefficient was the main reason for higher N2O5 levels during the WO period. By predicting N2O5 under various control scenarios of NOx and calculating the nitrate formation potential from N2O5 uptake, we found that the progressive reduction of nitrogen oxides initially increases the nitrate formation potential before further decreasing it. The threshold of NOx was approximately 13 ppbv, below which NOx reduction effectively reduced the level of night-time nitrate formations. These results demonstrate the capacity of machine learning to provide insights into understanding atmospheric nitrogen chemistry and highlight the necessity of more stringent emission control of NOx to mitigate haze pollution.

Chemistry Contribution to Stratospheric Ozone Depletion After the Unprecedented Water‐Rich Hunga Tonga Eruption

AbstractFollowing the Hunga Tonga–Hunga Ha'apai (HTHH) eruption in January 2022, stratospheric ozone depletion was observed at Southern Hemisphere mid‐latitudes and over Antarctica during the 2022 austral wintertime and springtime, respectively. The eruption injected sulfur dioxide and unprecedented amounts of water vapor into the stratosphere. This work examines the chemistry contribution of the volcanic materials to ozone depletion using chemistry‐climate model simulations with nudged meteorology. Simulated 2022 ozone and nitrogen oxide (NOx = NO + NO2) anomalies show good agreement with satellite observations. We find that chemistry yields up to 4% ozone destruction at mid‐latitudes near ∼70 hPa in August and up to 20% ozone destruction over Antarctica near ∼80 hPa in October. Most of the ozone depletion is attributed to internal variability and dynamical changes forced by the eruption. Both the modeling and observations show a significant NOx reduction associated with the HTHH aerosol plume, indicating enhanced dinitrogen pentoxide hydrolysis on sulfate aerosol.

Utilizing plasma-generated N2O5 gas from atmospheric air as a novel gaseous nitrogen source for plants

Fixing atmospheric nitrogen for use as fertilizer is a crucial process in promoting plant growth and enhancing crop yields in agricultural production. Currently, the chemical production of nitrogen fertilizer from atmospheric N2 relies on the energy-intensive Haber–Bosch process. Therefore, developing a low-cost and easily applicable method for fixing nitrogen from the air would provide a beneficial alternative. In this study, we tested the utilization of dinitrogen pentoxide (N2O5) gas, generated from oxygen and nitrogen present in ambient air with the help of a portable plasma device, as a nitrogen source for the model plant Arabidopsis thaliana. Nitrogen-deficient plants supplied with medium treated with N2O5, were able to overcome nitrogen deficiency, similar to those provided with medium containing a conventional nitrogen source. However, prolonged direct exposure of plants to N2O5 gas adversely affected their growth. Short-time exposure of plants to N2O5 gas mitigated its toxicity and was able to support growth. Moreover, when the exposure of N2O5 and the contact with plants were physically separated, plants cultured under nitrogen deficiency were able to grow. This study shows that N2O5 gas generated from atmospheric nitrogen can be used as an effective nutrient for plants, indicating its potential to serve as an alternative nitrogen fertilization method for promoting plant growth.

Investigating the potential of carbon nitride as a new sensing material for NOx (N2O, N2O3, N2O4, and N2O5): a DFT study

Herein, DFT study was used to investigate the carbon nitride C6N8 as a potential detector of noxious gases, specifically nitrous oxide (N2O), dinitrogen tri-oxide (N2O3), dinitrogen tetra-oxide (N2O4), and dinitrogen penta-oxide. (N2O5). The Physiosorption process was notified after the adsorption of N2O (−12.6463 kJ mol–1), N2O3 (−40.1466 kJ mol–1), N2O4 (−23.8512 kJ mol–1), and N2O5 (−29.7947 kJ mol−1) on C6N8. The adsorption behavior shows weak interactions in the complexes which depicts the stability trend as N2O3@C6N8 > N2O5@C6N8 > N2O4@C6N8 > N2O@C6N8. Various analyses and techniques were employed to evaluate the sensing capability. Electronic parameters such as FMO, ELF, NBO, UV-visible spectrum, and DOS were performed to notify the detectable change in the sensing surface after the adsorption of the gases being studied. The existence of non-covalent interactions was confirmed by Symmetry Adopted Perturbation Theory (SAPT0), QTAIM, NCI, and IRI plots. Moreover, SAPT0 confirmed the greater contribution of Edispersion in N2O@C6N8. ESP (MEPs) visualization confirmed the interactions, as the nitrogen atoms of the surface are electron dense regions for the analytes to attack. Chemical stability and selectivity were evidenced by the stability parameters and the formation of new states in the DOS spectrum, respectively. Significant recovery time performance was observed after evaluating the recovery of analyte@C6N8 complexes at an appropriate temperature. These results suggest C6N8 theoretically as a potentially active sensing surface and it will enhance the interest of the experimental researchers in fabricating a sensing device using this material for the determination of even minute concentrations of the toxic gases.

Comment on “Transport of substantial stratospheric ozone to the surface by a dying typhoon and shallow convection” by Chen et al. (2022)

Abstract. Chen et al. (2022) analyzed the event of rapid nocturnal O3 enhancement (NOE) observed on 31 July 2021 at the surface level in the North China Plain and proposed transport of substantial stratosphere ozone to the surface by Typhoon In-fa followed by downdraft of shallow convection as the mechanism of the NOE event. The analysis seems to be valid from the viewpoint of atmospheric physics. This comment revisits the NOE phenomenon on the basis of the China National Environmental Monitoring Center (CNEMC) network data used in Chen et al. (2022), together with the CNEMC data from Zibo (ZB) and O3, NOx, PAN (peroxyacetic nitric anhydride), and VOC (volatile organic compound) data from the Zibo supersite operated by the China Research Academy of Environmental Sciences (CRAES). We found (a) Ox (O3 + NO2) levels during the NOE period approaching those of O3 during 14:00–17:00 LT, (b) levels of PAN and the relationship between O3 and PAN consistent with dominance of chemical and physical processes within the boundary layer, and (c) estimated photochemical ages of air mass shorter than 1 d and showing no drastic increases during the NOE. We argue that the NOE was not caused by typhoon-induced stratospheric intrusion but originated from fresh photochemical production in the lower troposphere. Our argument is well supported by the analysis of atmospheric transport as well as ground-based remote sensing data.

Reconciling Modeled and Observed Δ17O(NO3−) in Beijing Winter Haze With Heterogeneous Chlorine Chemistry

AbstractThe fine particulate matter (PM2.5) in Chinese megacities has declined significantly after the implementation of strict mitigation strategies since 2013. However, the concentration of wintertime nitrate in PM2.5 (p‐NO3‐) has only changed slightly and became the dominant inorganic component despite considerable precursor emission reductions. Discerning chemical mechanisms leading to nitrate growth during haze events is critical to implementing effective pollution mitigation policies. The oxygen isotope anomaly of nitrate (Δ17O(NO3−)) is a powerful means to distinguish nitrate formation mechanisms. Nevertheless, the observed high Δ17O(NO3−) values were significantly underestimated by chemical transport models during extreme haze events (PM2.5 > 225 μg m−3) in Beijing, indicating an incomplete understanding of nitrate chemistry. To reconcile this model‐observation discrepancy, we compiled reported Δ17O(NO3−) data in Beijing haze along with relevant observational parameters (e.g., hydroxyl (OH) reactivity, peroxyl radical concentrations), then tested assumptions on Δ17O of key precursors (e.g., OH and nitrogen dioxide (NO2)), recalculated Δ17O(NO3−) and compared them with observations. Our results indicate that considering heterogeneous dinitrogen pentoxide reactions on chlorine‐containing aerosols (N2O5 + Cl− chemistry) with a nitryl chloride (ClNO2) yield of ∼0.75 can explain the observed high Δ17O(NO3−) during extreme haze events. According to the Δ17O(NO3−) data, on average this heterogeneous N2O5 + Cl− chemistry can explain ∼60% of nighttime nitrate production and make daytime and nocturnal pathways equally important in winter Beijing haze (PM2.5 > 75 μg m−3). Our results highlight the critical role of reactive chlorine chemistry in air pollution/chemistry in inland cities.

Mechanistic insight into the competition between interfacial and bulk reactions in microdroplets through N2O5 ammonolysis and hydrolysis

Reactive uptake of dinitrogen pentaoxide (N2O5) into aqueous aerosols is a major loss channel for NOx in the troposphere; however, a quantitative understanding of the uptake mechanism is lacking. Herein, a computational chemistry strategy is developed employing high-level quantum chemical methods; the method offers detailed molecular insight into the hydrolysis and ammonolysis mechanisms of N2O5 in microdroplets. Specifically, our calculations estimate the bulk and interfacial hydrolysis rates to be (2.3 ± 1.6) × 10−3 and (6.3 ± 4.2) × 10−7 ns−1, respectively, and ammonolysis competes with hydrolysis at NH3 concentrations above 1.9 × 10−4 mol L−1. The slow interfacial hydrolysis rate suggests that interfacial processes have negligible effect on the hydrolysis of N2O5 in liquid water. In contrast, N2O5 ammonolysis in liquid water is dominated by interfacial processes due to the high interfacial ammonolysis rate. Our findings and strategy are applicable to high-chemical complexity microdroplets.

Measurement report: Atmospheric nitrate radical chemistry in the South China Sea influenced by the urban outflow of the Pearl River Delta

Abstract. The nitrate radical (NO3) is a critical nocturnal atmospheric oxidant in the troposphere, which widely affects the fate of air pollutants and regulates air quality. Many previous works have reported the chemistry of NO3 in inland regions of China, while fewer studies target marine regions. Here, we present a field measurement of the NO3 reservoir, dinitrogen pentoxide (N2O5), and related species at a typical marine site (Da Wan Shan Island) located in the South China Sea in the winter of 2021. Two patterns of air masses were captured during the campaign, including the dominant airmass from inland China (IAM) with a percentage of ∼ 84 %, and the airmass from eastern coastal areas (CAM) with ∼ 16 %. During the IAM period, the NO3 production rate reached 1.6 ± 0.9 ppbv h−1 due to the transportation of the polluted urban plume with high NOx and O3. The average nocturnal N2O5 and the calculated NO3 mixing ratios were 119.5 ± 128.6 and 9.9 ± 12.5 pptv, respectively, and the steady-state lifetime of NO3 was 0.5 ± 0.7 min on average, indicating intensive nighttime chemistry and rapid NO3 loss at this site. By examining the reaction of NO3 with volatile organic compounds (VOCs) and N2O5 heterogeneous hydrolysis, we revealed that these two reaction pathways were not responsible for the NO3 loss (< 20 %) since the NO3 reactivity (k(NO3)) towards VOCs was small (5.2×10-3 s−1) and the aerosol loading was low. Instead, NO was proposed to significantly contribute to nocturnal NO3 loss at this site, despite the nocturnal NO concentration always below the parts per billion by volume level and near the instrument detection limit. This might be from the local soil emission or something else. We infer that the nocturnal chemical NO3 reactions would be largely enhanced once without NO emission in the open ocean after the air mass passes through this site, thus highlighting the strong influences of the urban outflow to the downwind marine areas in terms of nighttime chemistry. During the CAM period, nocturnal ozone was higher, while NOx was much lower. The NO3 production was still very fast, with a rate of 1.2 ppbv h−1. With the absence of N2O5 measurement in this period, the NO3 reactivity towards VOCs and N2O5 uptake were calculated to assess NO3 loss processes. We showed that the average k(NO3) from VOCs (56.5 %, 2.6 ± 0.9 × 10−3 s−1) was higher than that from N2O5 uptake (43.5 %, 2.0 ± 1.5 × 10−3 s−1) during the CAM period, indicating a longer NO3 / N2O5 lifetime than that during IAM period. This study improves the understanding of the nocturnal NO3 budget and environmental impacts with the interaction of anthropogenic and natural activities in marine regions.

Deville rebooted - practical N2O5 synthesis.

Dinitrogen pentoxide (N2O5), the anhydride of nitric acid, was synthesised by Henri Étienne Sainte-Claire Deville in Paris in 1849 using silver nitrate and chlorine gas. Herein, we revisit, optimise, and modify Deville's method using photocatalysis to enable a safe, clean, practical, and reproducible alternative for N2O5 synthesis in quantitative yields. Moreover, it is predicted that the modifications can accommodate an industrial scale-up, but the silver chloride generated must be recycled.

The chemical assessment of surfaces and air (CASA) study: using chemical and physical perturbations in a test house to investigate indoor processes.

The Chemical Assessment of Surfaces and Air (CASA) study aimed to understand how chemicals transform in the indoor environment using perturbations (e.g., cooking, cleaning) or additions of indoor and outdoor pollutants in a well-controlled test house. Chemical additions ranged from individual compounds (e.g., gaseous ammonia or ozone) to more complex mixtures (e.g., a wildfire smoke proxy and a commercial pesticide). Physical perturbations included varying temperature, ventilation rates, and relative humidity. The objectives for CASA included understanding (i) how outdoor air pollution impacts indoor air chemistry, (ii) how wildfire smoke transports and transforms indoors, (iii) how gases and particles interact with building surfaces, and (iv) how indoor environmental conditions impact indoor chemistry. Further, the combined measurements under unperturbed and experimental conditions enable investigation of mitigation strategies following outdoor and indoor air pollution events. A comprehensive suite of instruments measured different chemical components in the gas, particle, and surface phases throughout the study. We provide an overview of the test house, instrumentation, experimental design, and initial observations - including the role of humidity in controlling the air concentrations of many semi-volatile organic compounds, the potential for ozone to generate indoor nitrogen pentoxide (N2O5), the differences in microbial composition between the test house and other occupied buildings, and the complexity of deposited particles and gases on different indoor surfaces.

Regime‐Dependence of Nocturnal Nitrate Formation via N2O5 Hydrolysis and Its Implication for Mitigating Nitrate Pollution

AbstractThe heterogeneous hydrolysis of dinitrogen pentoxide (N2O5) is an important pathway in nitrate formation; however, its formation rate and relative contribution to total particulate nitrate () are highly variable. Here we report that nocturnal formation via N2O5 hydrolysis is dependent on the regime defined by the ratio of NO2 to O3. Nocturnal formation via N2O5 hydrolysis is suppressed in an O3‐limited regime but enhanced in a NO2‐limited regime. The results have crucial implications for effective control of nitrate pollution in the future. An exclusive decrease in NO2 will decrease nocturnal formation in a NO2‐limited regime but may be less effective or even increase nocturnal formation in an O3‐limited regime.

Dominant physical and chemical processes impacting nitrate in Shandong of the North China Plain during winter haze events

Nitrate has been a dominant component of PM2.5 since the stringent emission control measures implemented in China in 2013. Clarifying key physical and chemical processes influencing nitrate concentrations is crucial for eradicating heavy air pollution in China. In this study, we explored dominant processes impacting nitrate concentrations in Shandong of the North China Plain during three haze events from 9 to 25 December 2021, named cases P1 (94.46 (30.85) μg m−3 for PM2.5 (nitrate)), P2 (148.95 (50.12) μg m−3) and P3 (88.03 (29.21) μg m−3), by using the Weather Research and Forecasting/Chemistry model with an integrated process rate analysis scheme and updated heterogeneous hydrolysis of dinitrogen pentoxide on the wet aerosol surface (HET−N2O5) and additional nitrous acid (HONO) sources (AS−HONO). The results showed that nitrate increases in the three cases were attributed to aerosol chemistry, whereas nitrate decreases were due mainly to the vertical mixing process in cases P1 and P2 and to the advection process in case P3. HET−N2O5 (the reaction of OH + NO2) contributed 45 % (51 %) of the HNO3 production rate during the study period. AS−HONO produced a nitrate enhancement of 24 % in case P1, 12 % in case P2 and 19 % in case P3, and a HNO3 production rate enhancement of 0.79– 0.97 (0.18– 0.60) μg m−3 h−1 through the reaction of OH + NO2 (HET−N2O5) in the three cases. This study implies that using suitable parameterization schemes for heterogeneous reactions on aerosol and ground surfaces and nitrate photolysis is vital in simulations of HONO and nitrate, and the MOSAIC module for aerosol water simulations needs to be improved.

Technical note: Gas-phase nitrate radical generation via irradiation of aerated ceric ammonium nitrate mixtures

Abstract. We present a novel photolytic source of gas-phase NO3 suitable for use in atmospheric chemistry studies that has several advantages over traditional sources that utilize NO2 + O3 reactions and/or thermal dissociation of dinitrogen pentoxide (N2O5). The method generates NO3 via irradiation of aerated aqueous solutions of ceric ammonium nitrate (CAN, (NH4)2Ce(NO3)6) and nitric acid (HNO3) or sodium nitrate (NaNO3). We present experimental and model characterization of the NO3 formation potential of irradiated CAN / HNO3 and CAN / NaNO3 mixtures containing [CAN] = 10−3 to 1.0 M, [HNO3] = 1.0 to 6.0 M, [NaNO3] = 1.0 to 4.8 M, photon fluxes (I) ranging from 6.9 × 1014 to 1.0 × 1016 photons cm−2 s−1, and irradiation wavelengths ranging from 254 to 421 nm. NO3 mixing ratios ranging from parts per billion to parts per million by volume were achieved using this method. At the CAN solubility limit, maximum [NO3] was achieved using [HNO3] ≈ 3.0 to 6.0 M and UVA radiation (λmax⁡ = 369 nm) in CAN / HNO3 mixtures or [NaNO3] ≥ 1.0 M and UVC radiation (λmax⁡ = 254 nm) in CAN / NaNO3 mixtures. Other reactive nitrogen (NO2, N2O4, N2O5, N2O6, HNO2, HNO3, HNO4) and reactive oxygen (HO2, H2O2) species obtained from the irradiation of ceric nitrate mixtures were measured using a NOx analyzer and an iodide-adduct high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS). To assess the applicability of the method for studies of NO3-initiated oxidative aging processes, we generated and measured the chemical composition of oxygenated volatile organic compounds (OVOCs) and secondary organic aerosol (SOA) from the β-pinene + NO3 reaction using a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to the HR-ToF-CIMS.

Multi-hollow Surface Dielectric Barrier Discharge: Production of Gaseous Species Under Various Air Flow Rates and Relative Humidities

An evaluation of the gaseous species production by the discharge, i.e., discharge chemical activity, is very important for determining its potential for practical applications. In this work, production of gaseous species by the multi-hollow surface dielectric barrier discharge generated in a perforated ceramic substrate with the air-exposed electrode is investigated under conditions of various discharge powers (1–5 W), air flow rates (0.25–2.4 L/min) and air relative humidities (0–80%). Production of ozone O3, nitrous oxide N2O, nitric oxide NO, nitrogen dioxide NO2, dinitrogen pentoxide N2O5 and nitric acid HNO3 is evaluated in terms of concentration (ppm), production yield (g/kWh) and production rate (mg/h). The work demonstrates a critical impact of both air flow rate and relative humidity on prevailing discharge mode (“O3 mode” vs. “NOx mode”) and, thus, on overall composition and concentration of produced gaseous species. For low discharge power, the discharge operates in the “O3 mode”, when O3, N2O, N2O5 and HNO3 are dominant gaseous products. With the increasing power, the discharge transfers into the “NOx mode”, when N2O and HNO3 along with NO and NO2 are mostly produced. In dry air, transition from “O3 mode” to “NOx mode” is found for the specific input energy of 1000–1100 J/L. With an increase of air relative humidity from 20 to 80%, the transition gradually decreases from approximately 600 to 450 J/L, respectively.

Nighttime NO emissions strongly suppress chlorine and nitrate radical formation during the winter in Delhi

Abstract. Atmospheric pollution in urban regions is highly influenced by oxidants due to their important role in the formation of secondary organic aerosol (SOA) and smog. These include the nitrate radical (NO3), which is typically considered a nighttime oxidant, and the chlorine radical (Cl), an extremely potent oxidant that can be released in the morning in chloride-rich environments as a result of nocturnal build-up of nitryl chloride (ClNO2). Chloride makes up a higher percentage of particulate matter in Delhi than has been observed anywhere else in the world, which results in Cl having an unusually strong influence in this city. Here, we present observations and model results revealing that atmospheric chemistry in Delhi exhibits an unusual diel cycle that is controlled by high concentrations of NO during the night. As a result of this, the formation of both NO3 and dinitrogen pentoxide (N2O5), a precursor of ClNO2 and thus Cl, are suppressed at night and increase to unusually high levels during the day. Our results indicate that a substantial reduction in nighttime NO has the potential to increase both nocturnal oxidation via NO3 and the production of Cl during the day.

Cover Feature: Effects of Microhydration on the Mechanisms of Hydrolysis and Cl− Substitution in Reactions of N2O5 and Seawater (ChemPhysChem 5/2023)

The Cover Feature shows the nighttime reactions of dinitrogen pentoxide (N2O5) with chloride (Cl−) and water at the surface of sea spray aerosols. In this work we identify 3 reaction mechanisms in the competition between Cl− substitution and hydrolysis of N2O5 via quantum chemical and dynamics studies of model clusters. The competition of these reactions at aerosol interfaces significantly affects atmospheric levels of O3, NOx, and OH. Cover design by Jami Butler. More information can be found in the Research Article by Laura M. McCaslin, Benny Gerber and co-workers.

Measurement of Henry's law and liquid-phase loss rate constants of peroxypropionic nitric anhydride (PPN) in deionized water and in n-octanol

Abstract. The Henry's law solubility (HS) and liquid-phase loss rate constants (kl) of the tropospheric trace gas constituents peroxyacetic nitric anhydride (PAN; CH3C(O)O2NO2, commonly known as peroxyacetyl nitrate) and peroxypropionic nitric anhydride (PPN; C2H5C(O)O2NO2, also known as peroxypropionyl nitrate) in deionized (DI) water and of PPN in n-octanol were measured using a flow bubble apparatus at temperatures between 5.0 and 25.0 ∘C. For PAN in DI water, the observed values for HS,aq are consistent with the literature, whereas the solubility of PPN in DI water is slightly lower than literature values, ranging from HScp(PPN)aq = (1.49 ± 0.05) M atm−1 at 25.0 ∘C to HScp(PPN)aq = (7.01 ± 0.25) M atm−1 at 5.0 ∘C (stated uncertainties are at the 1σ level). The data are best described by ln⁡(HScp(PAN)aq/[Matm-1]) = -(17.8±0.3) + (5620±85)/T and ln⁡(HScp(PPN)aq/[Matm-1]) = -(19.5±1.7) + (5955±480)/T, where T is in kelvin. For n-octanol, the PPN solubility ranges from HScp(PPN)oct = (88±5)Matm-1 at 25.0 ∘C to HScpoct = (204±16)Matm-1 at 5.0 ∘C and is best described by ln⁡(HScp(PPN)oct/[Matm-1]) = -(6.92±0.75) + (3390±320)/T. n-Octanol–water partition coefficients (KOW) for PPN were determined for the first time, ranging from 59 ± 4 at 25.0 ∘C to 29 ± 3 at 5.0 ∘C. Observed loss rate constants in DI water are consistent with recent literature and larger than the thermal dissociation rates for both PAN and PPN, consistent with a hydrolysis mechanism, whereas kl values in n-octanol are significantly smaller than gas-phase dissociation rate constants, likely owing to a “cage effect” in the organic liquid. The results imply that uptake of either PAN or PPN on cloud water and organic aerosol is negligible but that uptake of PPN may constitute an overlooked source of peroxy radicals in organic aerosol.