Observational evidence reveals the significance of nocturnal chemistry in seasonal secondary organic aerosol formation.

Oxidized Organic Aerosol (OOA), a major component of fine atmospheric particles, impacts climate and human health. Previous experiments and atmospheric models emphasize the importance of nocturnal OOA formation from NO· oxidation of biogenic VOCs. This seasonal study extends the understanding by showing that nocturnal oxidation of biomass-burning emissions can account for up to half of total OOA production in fall and winter.

Hypnosis support in anaesthesia is rarely used in German anaesthesia departments - a nationwide survey among leading physicians of anaesthesia departments.

Background: The aim of this study was to investigate whether and to what extent perioperative hypnosis and relaxation techniques are used in German anaesthesia departments, what they are, where any difficulties in their application lie and how great the interest in this type of therapy is. Another research question was to find out whether there are specialist areas in which these methods are used more frequently than in other specialist areas.

Methods: A descriptive survey was conducted by means of a questionnaire in all hospitals with anaesthesia departments in Germany.

Properties and Processing of Aviation Exhaust Aerosol at Cruise Altitude Observed from the IAGOS-CARIBIC Flying Laboratory.

The characteristics of aviation-induced aerosol, its processing, and effects on cirrus clouds and climate are still associated with large uncertainties. Properties of aviation-induced aerosol, however, are crucially needed for the assessment of aviation's climate impacts today and in the future. We identified more than 1100 aircraft plume encounters during passenger aircraft flights of the IAGOS-CARIBIC Flying Laboratory from July 2018 to March 2020.

Correction: Impact of temperature-dependent non-PAN peroxynitrate formation, RONO, on nighttime atmospheric chemistry.

Correction for 'Impact of temperature-dependent non-PAN peroxynitrate formation, RONO, on nighttime atmospheric chemistry' by Michelle Färber , , 2024, https://doi.org/10.1039/d3cp04163h.

Impact of temperature-dependent non-PAN peroxynitrate formation, RONO, on nighttime atmospheric chemistry.

The formation of peroxynitrates (RONO) from the reaction of peroxy radicals (RO) and nitrogen dioxide (NO) and their subsequent redissociation are typically not included in chemical mechanisms. This is often done to save computational time as the assumption is that the equilibrium is strongly towards the RO + NO reaction for most conditions. Exceptions are the reactions of the methyl peroxy radical due to its abundance in the atmosphere and of acyl-RO radicals due to the long lifetime of peroxyacyl nitrates RONO (PANs).

Unimolecular and water reactions of oxygenated and unsaturated Criegee intermediates under atmospheric conditions.

Ozonolysis of unsaturated hydrocarbons (VOCs) is one of the main oxidation processes in the atmosphere. The stabilized Criegee intermediates (SCI) formed are highly reactive oxygenated species that potentially influence the HOx, NOx and SOx cycles, and affect aerosol formation by yielding low-volatility oxygenated compounds. The current knowledge spans mostly SCI formed from primary emitted VOCs, but little is known about the reactivity of oxygenated SCI.

Highly Oxygenated Organic Nitrates Formed from NO Radical-Initiated Oxidation of β-Pinene.

The reactions of biogenic volatile organic compounds (BVOC) with the nitrate radicals (NO) are major night-time sources of organic nitrates and secondary organic aerosols (SOA) in regions influenced by BVOC and anthropogenic emissions. In this study, the formation of gas-phase highly oxygenated organic molecules-organic nitrates (HOM-ON) from NO-initiated oxidation of a representative monoterpene, β-pinene, was investigated in the SAPHIR chamber (Simulation of Atmosphere PHotochemistry In a large Reaction chamber). Six monomer (C = 7-10, N = 1-2, O = 6-16) and five accretion product (C = 17-20, N = 2-4, O = 9-22) families were identified and further classified into first- or second-generation products based on their temporal behavior.

Chemical Production of Oxygenated Volatile Organic Compounds Strongly Enhances Boundary-Layer Oxidation Chemistry and Ozone Production.

Photolysis of oxygenated volatile organic compounds (OVOCs) produces a primary source of free radicals, including OH and inorganic and organic peroxy radicals (HO and RO), consequently increasing photochemical ozone production. The amplification of radical cycling through OVOC photolysis provides an important positive feedback mechanism to accelerate ozone production. The large production of OVOCs near the surface helps promote photochemistry in the whole boundary layer.

A structure activity relationship for ring closure reactions in unsaturated alkylperoxy radicals.

Terpenoids are an important class of multi-unsaturated volatile organic compounds emitted to the atmosphere. During their oxidation in the troposphere, unsaturated peroxy radicals are formed, which may undergo ring closure reactions by an addition of the radical oxygen atom on either of the carbons in the C[double bond, length as m-dash]C double bond. This study describes a quantum chemical and theoretical kinetic study of the rate of ring closure, finding that the reactions are comparatively fast with rates often exceeding 1 s-1 at room temperature, making these reactions competitive in low-NOx environments and allowing for continued autoxidation by ring closure.

Ubiquitous atmospheric production of organic acids mediated by cloud droplets.

Atmospheric acidity is increasingly determined by carbon dioxide and organic acids. Among the latter, formic acid facilitates the nucleation of cloud droplets and contributes to the acidity of clouds and rainwater. At present, chemistry-climate models greatly underestimate the atmospheric burden of formic acid, because key processes related to its sources and sinks remain poorly understood.

Experimental and theoretical study on the impact of a nitrate group on the chemistry of alkoxy radicals.

The chemistry of nitrated alkoxy radicals, and its impact on RO2 measurements using the laser induced fluorescence (LIF) technique, is examined by a combined theoretical and experimental study. Quantum chemical and theoretical kinetic calculations show that the decomposition of β-nitrate-alkoxy radicals is much slower than β-OH-substituted alkoxy radicals, and that the spontaneous fragmentation of the α-nitrate-alkyl radical product to a carbonyl product + NO2 prevents other β-substituents from efficiently reducing the energy barrier. The systematic series of calculations is summarized as an update to the structure-activity relationship (SAR) by Vereecken and Peeters (2009), and shows increasing decomposition rates with higher degrees of substitution, as in the series ethene to 2,3-dimethyl-butene, and dominant H-migration for sufficiently large alkoxy radicals such as those formed from 1-pentene or longer alkenes.

Theoretical and experimental study of peroxy and alkoxy radicals in the NO-initiated oxidation of isoprene.

The initial stages of the nitrate radical (NO3) initiated oxidation of isoprene, in particular the fate of the peroxy (RO2) and alkoxy (RO) radicals, are examined by an extensive set of quantum chemical and theoretical kinetic calculations. It is shown that the oxidation mechanism is highly complex, and bears similarities to its OH-initiated oxidation mechanism as studied intensively over the last decade. The nascent nitrated RO2 radicals can interconvert by successive O2 addition/elimination reactions, and potentially have access to a wide range of unimolecular reactions with rate coefficients as high as 35 s-1; the contribution of this chemistry could not be ascertained experimentally.

Wintertime NO uptake coefficients over the North China Plain.

The heterogeneous hydrolysis of dinitrogen pentoxide (NO) plays an important role in regulating NO. The NO uptake coefficient, γ(NO), was determined using an iterative box model that was constrained to observational data obtained in suburban Beijing from February to March 2016. The box model determined 2289 individual γ(NO) values that varied from <0.

No Evidence for a Significant Impact of Heterogeneous Chemistry on Radical Concentrations in the North China Plain in Summer 2014.

The oxidation of nitric oxide to nitrogen dioxide by hydroperoxy (HO) and organic peroxy radicals (RO) is responsible for the chemical net ozone production in the troposphere and for the regeneration of hydroxyl radicals, the most important oxidant in the atmosphere. In Summer 2014, a field campaign was conducted in the North China Plain, where increasingly severe ozone pollution has been experienced in the last years. Chemical conditions in the campaign were representative for this area.

Fast Photochemistry in Wintertime Haze: Consequences for Pollution Mitigation Strategies.

In contrast to summer smog, the contribution of photochemistry to the formation of winter haze in northern mid-to-high latitude is generally assumed to be minor due to reduced solar UV and water vapor concentrations. Our comprehensive observations of atmospheric radicals and relevant parameters during several haze events in winter 2016 Beijing, however, reveal surprisingly high hydroxyl radical oxidation rates up to 15 ppbv/h, which is comparable to the high values reported in summer photochemical smog and is two to three times larger than those determined in previous observations during winter in Birmingham (Heard et al. 2004, 31, (18)), Tokyo (Kanaya et al.

Winter photochemistry in Beijing: Observation and model simulation of OH and HO radicals at an urban site.

A field campaign was conducted from November to December 2017 at the campus of Peking University (PKU) to investigate the formation mechanism of the winter air pollution in Beijing with the measurement of hydroxyl and hydroperoxyl radical (OH and HO) with the support from comprehensive observation of trace gases compounds. The extent of air pollution depends on meteorological conditions. The daily maximum OH radical concentrations are on average 2.

Explicit diagnosis of the local ozone production rate and the ozone-NO-VOC sensitivities.

In the troposphere, ozone is a harmful gas compound to both human health and vegetation. Ozone is produced from the reaction of NO (NO + NO) and VOCs (volatile organic compounds) with light. Due to the highly nonlinear relationships between ozone and its precursors, proper ozone mitigation relies on the knowledge of chemical mechanisms.

Functional characterization of the mouse Serpina1 paralog DOM-7.

The generation of authentic mouse-models for human α1-antitrypsin (A1AT)-deficiency is difficult due to the high complexity of the mouse Serpina1 gene locus. Depending on the exact mouse strain, three to five paralogs are expressed, with different proteinase inhibitory properties. Nowadays with CRISPR-technology, genome editing of complex genomic loci is feasible and could be employed for the generation of A1AT-deficiency mouse models.

Upper tropospheric water vapour and its interaction with cirrus clouds as seen from IAGOS long-term routine in situ observations.

IAGOS (In-service Aircraft for a Global Observing System) performs long-term routine in situ observations of atmospheric chemical composition (O, CO, NO, NO, CO, CH), water vapour, aerosols, clouds, and temperature on a global scale by operating compact instruments on board of passenger aircraft. The unique characteristics of the IAGOS data set originate from the global scale sampling on air traffic routes with similar instrumentation such that the observations are truly comparable and well suited for atmospheric research on a statistical basis. Here, we present the analysis of 15 months of simultaneous observations of relative humidity with respect to ice (RH) and ice crystal number concentration in cirrus (N) from July 2014 to October 2015.

The Essential Role for Laboratory Studies in Atmospheric Chemistry.

Laboratory studies of atmospheric chemistry characterize the nature of atmospherically relevant processes down to the molecular level, providing fundamental information used to assess how human activities drive environmental phenomena such as climate change, urban air pollution, ecosystem health, indoor air quality, and stratospheric ozone depletion. Laboratory studies have a central role in addressing the incomplete fundamental knowledge of atmospheric chemistry. This article highlights the evolving science needs for this community and emphasizes how our knowledge is far from complete, hindering our ability to predict the future state of our atmosphere and to respond to emerging global environmental change issues.