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Nanocluster aerosols (NCA, particles <3 nm) are associated with climate feedbacks and potentially with human health. Recent studies have revealed the formation of NCA through ozone reaction with human surfaces, primarily skin lipids, in indoor environments. However, the formation of NCA via ozone chemistry on worn clothing, acting as a reservoir for human skin lipids, remains unexplored, along with the influence of various environmental factors that may play a role in NCA formation and subsequent growth. To bridge this knowledge gap, our study experimentally investigated NCA generation from ozone-worn clothing chemistry in a climate-controlled chamber. We examined the dependence on ozone levels (30 vs. 80 ppb), ammonia (NH 3 , 300 vs. <150 ppb), relative humidity (RH, 40 vs. 65%), and background air condition (filtered vs. unfiltered air). We found that the ozonolysis of worn clothing contributes to NCA formation at a rate ranging from 1010 to 1011 NCA per hour. Elevated ozone levels caused a threefold increase in NCA generation, whereas reduced NH 3 levels were associated with a small decrease in larger-sized NCA formation. Elevated RH caused a decrease in total NCA, especially for 1.27–1.55 nm. The influence of background air condition was inconsistent, probably owing to dynamic NCA behavior influenced by two opposing forces: enhanced generation by synergic reactions of ozone, background chemicals, and the worn clothing, and increased loss by coagulation and condensation. This study highlights the nuanced factors driving NCA generation from ozone-clothing chemistry. • Ozone reaction with worn clothing generates nanocluster aerosols (NCA). • The higher the ozone levels, the stronger the NCA formation. • The effect of NH 3 level was marginal, yet remains to be further explored. • Elevated humidity decreased NCA formation. • The influence of background air cleanliness on NCA formation showed inconsistency. [ABSTRACT FROM AUTHOR]

This work computationally studies homogeneous and inhomogeneous ozone addition in hydrogen-oxygen ignition and transition to detonation, with emphasis on the ozone-induced two-stage behaviors in the chemical kinetics and wave dynamics. In 0D homogenous ignitions, ozone addition induces an additional first-stage reaction and substantially reduces the ignition delay time (IDT). At intermediate initial temperatures, e.g. T 0 = 600 K, a critical value, α cr , is identified to delineate different regimes for ozone fraction in the total oxidizer, α. Specifically, the first-stage ignition occurs several orders earlier than IDT for α < α cr , while the IDTs for two stages are comparable for α > α cr. Mechanistically, low-to-intermediate temperature HO 2 chemistry introduces a quasi-steady intermediate state in the former regime, whereas ozone reactions directly accelerate high-temperature H 2 O 2 reactions in the latter one. Furthermore, according to the Zel'dovich mechanism, ozone concentration non-uniformity can establish reactivity gradient and hence further initiate double spontaneous waves with multiple dynamics. Coherent coupling between the second-stage heat release and pressure (shock) wave can further evolve into detonation, whereas such synchronized enhancement is not observed in the first-stage ignition due to its large excitation time. Corresponding to the multi-timescales in 0D ignition, when the initial α interval are respectively below, across and above α cr , the low- and high- temperature reaction fronts always separate, first separate then merge, and always merge, respectively. It is also noted that at higher initial temperatures α cr decreases, and that the first-stage reaction becomes less concentrated. Consequently, detonation can be initiated with smaller amounts of ozone and is minimally influenced by the first-stage reaction. [ABSTRACT FROM AUTHOR]

Abstract: Emissions of nitrogen oxides (NOx) lead to formation of ozone, which is an important greenhouse gas. Despite its relevance, little emphasis was previously given on verifying approaches to calculate contributions of individual emissions to ozone and hence to climate change. Basically two methods (perturbation method and tagging method) were used in the past. We demonstrate that both methods are valid and have their area of application, but only tagging calculates contributions of emissions to concentrations, whereas the perturbation method identifies changes in the ozone concentrations due to emission changes. Our results show that the contribution of road traffic emissions to climate change is underestimated by a factor of 5 in the perturbation method. This is caused by non-linear compensating effects from other emission sectors, which are concealed in the perturbation method but disclosed with tagging. Consequently, the effectiveness of mitigation measures for individual sectors (i.e. concentrating on road traffic induced ozone) is only correctly expressed by the tagging method. The perturbation method provides accurately the total impact (i.e. total ozone) of a mitigation measure. However, current approaches, which evaluate the effectiveness of a mitigation measure based on the perturbation approach, do not reflect changes in the chemical state of the atmosphere (i.e. ozone production rates). These largely affect the effectiveness of subsequent measures and hence make the evaluation of the effectiveness of two measures dependent on their chronology of application. We show that also in this regard, the tagging method is better suited to evaluate the effectiveness of a mitigation measure than the perturbation method. [Copyright &y& Elsevier]

Abstract: A new model of the mesosphere is introduced which incorporates the effects of polar mesospheric clouds in an interactive fashion. The model predicts ice layers and perturbed water vapor layers in good agreement with observations and previous calculations. In addition, the model predicts changes in ozone which anticorrelate with the perturbed H2O changes. Above the cloud layer (850–90 km), ozone can increase by as much as 30–40% and this leads to a 1–3 K temperature increase. [Copyright &y& Elsevier]

Abstract: The oxywater cation H2OO+ was generated in the gas phase by ionization of mixtures containing O3, O2 and H2O. Different ionic mixtures, rich in either the H2OO+ or the HOOH+ isomer, were obtained by O3/O2/H2O–O2/H2O CI, and by CH3OH/O2–CH2O/O2 CI, respectively. The H2O2 + ions were characterized by high-resolution CAD mass spectrometry, and structural and energetic effects were examined. [Copyright &y& Elsevier]

The gaseous protonated ozone has been experimentally observed in FT-ICR conditions to react with carbon monoxide promoting its oxidation to protonated carbon dioxide according to the reaction HO3++CO=O2+HCO2+. This process, which in the past has been postulated to potentially represent a source of atmospheric ozone depletion, has been computationally addressed in this work. The singlet potential energy surface has been exhaustively investigated at the density functional theory and coupled cluster levels. The picture emerged from the quantum-chemical investigation describes such oxidation process as occurring essentially through a two-step mechanism in which the oxygen and hydrogen atoms are sequentially transferred from protonated ozone to carbon monoxide. By the use of standard statistical kinetics theories, the overall rate constants of the process has been also calculated in a temperature range between 50 and 500 K. Our computational work succeeds in reproducing both the 300 K overall rate constant and the nature of the products. [Copyright &y& Elsevier]

Energetic particle precipitation is one of the main processes by which the sun influences atmospheric composition and structure. The polar middle atmosphere is chemically disturbed by the precipitation-induced production of nitric oxides (NO x) and hydrogen oxides (HO x) and the associated ozone (O 3) loss, but the importance for the dynamics is still debated. The role of precipitating medium energy electrons (MEEs), which are able to penetrate into the mesosphere, has received increased attention, but has only recently begun to be incorporated in chemistry-climate models. We use the NCAR Whole Atmosphere Community Climate Model (WACCM) to study the climate impact from MEE precipitation by performing two idealized ensemble experiments under pre-industrial conditions, with and without the MEE forcing, over the period of the solar cycle 23 (only full calendar years, 1997–2007). Each experiment includes 20 11-year ensemble members, total 220 years. Our results indicate a strong month-to-month variability in the dynamical response to MEE throughout the winter period. We find a strengthening of the polar vortex in the northern hemisphere during December, but the signal decays rapidly in the following months. The polar vortex strengthening is likely attributable to planetary wave reduction due to increased zonal symmetries in upper stratospheric ozone heating, initially triggered by MEE-induced NO x advected into the sunlit regions. We also find a similar early winter polar vortex strengthening in the southern hemisphere during June. Changes in mean meridional circulation accompany these anomalous wave forcings, leading to dynamically-induced vertical temperature dipoles at high latitudes. The associated weakening of the stratospheric mean meridional circulation results in an upper stratospheric polar ozone deficit in early winter. This polar cap ozone deficit is strongest in the southern hemisphere and contributes to a polar vortex weakening in late winter, in concert with increased planetary wave forcing. In both hemispheres, the stratospheric polar vortex signal seems to migrate downwards into the troposphere and to the surface. • Sub-polar O 3 depletion by NO x perturb zonally asymmetric O 3 and short wave heating and thereby planetary wave (PW) driving. • The reduced PW forcing strengthens the polar vortices in early winter, while the SH polar vortex is weakened in late winter. • Vertical dipoles in temperatures are induced at high latitudes by dynamically induced anomalous mean meridional circulations. • The early (late) winter dynamical changes migrate downward into the troposphere in NH (SH). [ABSTRACT FROM AUTHOR]