Unsaturated organic compounds are emitted in large quantities from natural and human-influenced sources. Atmospheric removal occurs significantly by reaction with ozone, initiating reaction sequences forming free radicals and organic pollutants in the gaseous and particulate phases. Due to their very large number, it is impossible to study the reaction rate for every compound, and most have to be estimated. Updated and extended estimation methods are reported for use in atmospheric models.

We showed that Icelandic dust has a fundamentally different chemical and mineralogical composition from low-latitude dust. In particular, magnetite is as high as 1 %–2 % of the total dust mass. Our results suggest that Icelandic dust may have an important impact on the radiation balance in the subpolar and polar regions.

We present direct measurements of NO₃ reactivity resulting from the oxidation of isoprene by NO₃ during an intensive simulation chamber study. Measurements were in excellent agreement with values calculated from measured isoprene amounts and the rate coefficient for the reaction of NO₃ with isoprene. Comparison of the measurement with NO₃ reactivities from non-steady-state and model calculations suggests that isoprene-derived RO₂ and HO₂ radicals account to ~ 50 % of overall NO₃ losses.

An incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) technique has been developed for the in situ monitoring of NO₃ radicals in the CSA simulation chamber at LISA. The optical cavity allows a high sensitivity for NO₃ detection up to 6 ppt for an integration time of 10 s. The technique is now fully operational and can be used to determine rate constants for fast reactions involving complex volatile organic compounds (with rate constants up to 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹).

The photooxidation of pinonaldehyde is investigated in a chamber study under natural sunlight and low NO conditions with and without an added hydroxyl radical (OH) scavenger. The experimentally determined pinonaldehyde photolysis frequency is faster by a factor of 3.5 than currently used parameterizations in atmospheric models. Yields of degradation products are measured in the presence and absence of OH. Measurements are compared to current atmospheric models and a theory-based mechanism.

When exposed to glyoxal in chamber experiments, dry ammonium or methylammonium sulfate particles turn brown immediately and reversibly without increasing in size. Much less browning was observed on wet aerosol particles, and no browning was observed with sodium sulfate aerosol. While estimated dry aerosol light absorption caused by background glyoxal (70 ppt) is insignificant compared to that of secondary brown carbon overall, in polluted regions this process could be a source of brown carbon.

A condensed multiphase halogen and DMS chemistry mechanism for application in chemical transport models has been developed and applied by 2D simulations to explore multiphase marine chemistry above the pristine open ocean. The model simulations have demonstrated the ability of the mechanism in studying aerosol cloud processing effects in the marine atmosphere. First 2D simulations have shown significant differences in the DMS processing under convective and stratiform cloud conditions.

In the present study, simulations with the SPACCIM-SpactMod multiphase chemistry model are performed. The investigations aim at assessing the impact of a detailed treatment of non-ideality in multiphase models dealing with aqueous aerosol chemistry. The model studies demonstrate that the inclusion of non-ideality considerably affects the multiphase chemical processing of transition metal ions, oxidants, and related chemical subsystems such as organic chemistry in aqueous aerosols.

In this paper, we present the new moist-air wind tunnel LACIS-T (Turbulent Leipzig Aerosol Cloud Interaction Simulator). It is used to study cloud physical processes in general and interactions between turbulence and cloud microphysical processes in particular. The operating principle of LACIS-T is explained, and the first results are depicted from deliquescence and droplet formation experiments observing clear indications on the effect of turbulence on these microphysical processes.

Experimental evidence from a simulation chamber study shows that the regeneration efficiency of the hydroxyl radical is maintained globally at values higher than 0.5 for a wide range of nitrogen oxide concentrations as a result of isomerizations of peroxy radicals originating from the OH oxidation of isoprene. The available models were tested, and suggestions on how to improve their ability to reproduce the measured radical and oxygenated volatile organic compound concentrations are provided.

Multifunctional organic nitrates are important atmospheric species that are known to play a key role in the transport of reactive nitrogen and in aerosol composition. However, very little is known about their atmospheric reactivity. Here we provide an experimental study on the photolysis and reaction of two carbonyl nitrates with OH radicals. Atmospheric implications and the influence of the chemical structure on the reactivity are discussed.

This paper presents the AtChem software, which can be used to build box models for atmospheric chemistry studies. The software is designed to facilitate the use of one of the most important chemical mechanisms used by atmospheric scientists, the Master Chemical Mechanism. AtChem exists in two versions: an on-line application for laboratory studies and educational or outreach activities and an offline version for more complex models and batch simulations. AtChem is open source under MIT License.

Here we present a study of the photooxidation of alpha-pinene, the most abundant monoterpene, by hydroxyl radicals (OH) conducted in the simulation chamber SAPHIR under low NO_x and atmospheric alpha-pinene concentrations. Yields of the main degradation products acetone, formaldehyde, and pinonaldehyde were determined and the HO_x (OH + HO₂) radical budget was investigated. Measurements were used to test current atmospheric models and a theory-based mechanism.

We present, for the first time, the dual effect of GDI-vehicle exhaust on α-pinene SOA mass yield suppression. The first effect is a well-known NOx effect, but the second effect is more complex. Our results imply that this second effect is related to change of reaction pathways of α-pinene in the presence of GDI exhaust. The presence of vehicle exhaust caused more than 50 % suppression in α-pinene SOA mass yield compared to the α-pinene SOA mass yield measured in the absence of GDI emissions.

Reactive oxygen species (ROS) are believed to contribute to the adverse health effects of aerosols. We measured particle-bound ROS (PB-ROS) with an online instrument in two distinct environments, i.e., Beijing (China) and Bern (Switzerland). In both cities these exogenic ROS are predominantly related to secondary organic aerosol (SOA). PB-ROS content in SOA from various anthropogenic emission sources tested in the laboratory was comparable to that in the ambient measurements.

Atmospheric furan is a primary and secondary pollutant in the atmosphere, and its emission contributes to the formation of ultrafine particles and ground-level ozone. The present study demonstrates the effect of NO_x and humidity on secondary organic aerosol (SOA) formation during the furan–NO_x–NaCl photooxidation. Furthermore, the results illustrate the importance of studying SOA formation over a comprehensive range of environmental conditions.

This paper presents a new dataset of laboratory measurements of the shortwave (SW) spectral complex refractive index and single-scattering albedo (SSA) for global mineral dust aerosols of varying origin and composition. Our results show that the dust refractive index and SSA vary strongly from source to source, mostly due to particle iron content changes. We recommend that source-dependent values of the SW spectral refractive index and SSA be used in models and remote sensing applications.

The article presents a new protocol for computer-assisted automated aqueous-phase chemistry mechanism generation, which has been validated against chamber experiments. Together with a large kinetics database and improved prediction methods for kinetic data, the novel protocol provides an unmatched tool for detailed studies of tropospheric aqueous-phase chemistry in complex model studies and for the design and analysis of chamber experiments.

Box model simulations, based on the volatility basis set approach, of smog chamber wood combustion experiments conducted at different temperatures (−10 °C, 2 °C, 15 °C), emission loads, combustion conditions (flaming and smoldering) and residential stoves fabricated in the last 2 decades. Novel parameterization methods based on a genetic algorithm approach allowed estimation of precursor class contributions to SOA and evaluation of the effect of emission variability on SOA yield predictions.

A portable dual-smog-chamber system was developed using two identical pillow-shaped smog chambers surrounded by UV lamps. The system has been designed to use ambient air as the starting point of the experiments. It can be easily disassembled and transported, enabling the study of various atmospheric environments and it can be used with natural sunlight. The results of test experiments using ambient air are discussed as examples of applications of this system.

The chemical transport model PMCAMx was extended to investigate the effects of partitioning and photochemical aging of biomass burning emissions on organic aerosol (OA) concentrations and was applied in Europe. During the summer, the contribution of biomass burning to total OA levels over continental Europe was 16 % and during winter 47 %. Intermediate volatility organic compounds are predicted to be important precursors of secondary OA from biomass burning.

We explore the morphologies of multicomponent nanoparticles through atomistic molecular dynamics simulations under atmospherically relevant conditions. Phase separation is predicted for almost all simulated nanoparticles either between organics and inorganics or between hydrophobic and hydrophilic constituents. Three main particle types were identified: organic islands at the surface, inorganic core-organic shell morphologies and complex structures with hydrophobic and hydrophilic domains.

Within this study we demonstrate reliable measurement of hydroperoxy (HO₂) radicals via chemical ionisation mass spectrometry. HO₂ is detected as an ion cluster with bromide ions, which allows a selective detection. This direct and sensitive measurement provides reliable data of HO₂ radical concentrations in the atmosphere as demonstrated in the first application in simulation chamber experiments.

The photooxidation of methyl vinyl ketone MVK, one of the most important products of isoprene that is emitted by plants, was investigated in the atmospheric simulation chamber SAPHIR for conditions found in forested areas. The comparison of measured trace gas time series with model calculations shows a gap in the understanding of radical chemistry in the MVK oxidation scheme. The possibility of unimolecular isomerization reactions were investigated by means of quantum-chemical calculations.

The impact of photooxidation of 2-methyl-3-butene-2-ol (MBO) on the concentration of radical species was studied in the atmospheric simulation chamber SAPHIR. MBO is a volatile organic compound mainly emitted by ponderosa and lodgepole pines which are very abundant in forests in the central-west USA. A very good agreement between measured and modelled radical concentrations and products from the oxidation of MBO was observed in an environment with NO of ~ 200 pptv.