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Untangling the relationship between network complexity and ecological stability under climate change is an arduous challenge for theoretical and empirical ecology. Even more so, when considering extreme climatic events. Here, we studied the effects of extreme climatic events (heatwaves) on the complexity of realistic freshwater ecosystems using topological and quantitative trophic network metrics. Next, we linked changes in network complexity with the investigation of four stability components (temporal stability, resistance, resilience, and recovery) of community's functional, compositional, and energy flux stability. We found reduction in topological network complexity to be correlated with reduction of functional and compositional resistance. However, temperature-driven increase in link-weighted network complexity increased functional and energy flux recovery and resilience, but at the cost of increased compositional instability. Overall, we propose an overarching approach to elucidate the effects of climate change on multidimensional stability through the lens of network complexity, providing helpful insights for preserving ecosystems stability under climate change.

Due to the collision of the European and Adriatic plates, about 3 mm/yr of N-S convergence are accommodated in the Eastern and Southern Alps. This shortening is mainly taken up by c. E-W-trending reverse faults along the South Alpine Front and on NW-SE-trending dextral strike-slip faults in western Slovenia. Strong historical earthquakes and instrumental seismicity, however, show that some deformation also occurs in the interior of the Southern Alps. Little is known about which faults are active here. In this study we present results from a regional-scale remote sensing analysis focusing on the Bellunese and Friulian sectors of the Southern Alps in northeastern Italy. Our aim was to identify areas with relatively increased tectonic activity based on landscape features. We made use of high-resolution digital elevation models from aerial laser scanning campaigns. We downsampled the data to 5 m resolution and calculated the most widely used geomorphic indices that might indicate active tectonics: normalised steepness index, the Chi­ value, terrain ruggedness index, and stream knickpoints. The results were checked with geological data, mapped faults, and seismicity. We also conducted extensive field work to verify the results on the ground. Our results show that the application of large-scale tectonic geomorphology in this particular Alpine region is complicated by numerous factors. Small-scale variations in lithologies with variable erodibility strongly influence the analysis. The same holds true for variations in dip direction and dip angles of bedding planes; occasionally, vertical strata erroneously suggest linearly trending faults. In addition, we found that glacial features and alluvial deposits have locally overprinted the traces of known faults. Despite of these challenges, we found hints for active deformation in the landscape, in particular in the epicentral area of the 1976 Friuli earthquakes. We highlight potential pitfalls of the applied methods and discuss ways to overcome some of the problems we encountered.

Background: With the intention to quantify the importance of a medical journal, the Impact Factor (IF) was introduced. It has become a de facto fictive rating instrument of the importance of medical journals. Also, it is often used to assess the value of the individual publications within the specific journal. The aim of the present study was to analyze publication trends over 20 years in five high-ranked anesthesiology journals. Methods: The Medline (NCBI) database PubMed was used for analysis which was restricted to the following journals: 1. Anesthesiology; 2. British Journal of Anaesthesia; 3. Journal of Neurosurgical Anesthesiology; 4. Anesthesia & Analgesia; and 5. Anaesthesia. Specific publication parameters (IFs, number of pages and authors, etc.) were retrieved using the PubMed download function and imported into Microsoft Excel for further analysis. Results: The mean IF of the five journals analyzed increased significantly within the study period (1991 vs. 2010; +61.81%). However, the absolute number of case reports decreased significantly by 54.7% since 1991. The journals Br J Anaesth (12.2%), J Neurosurg Anesthesiol (51.9%), and Anesth Analg (57.2%) showed significant increases in the number of publications per year. The mean number of authors increased significantly in all the journals from 1991 to 2010 (3.0 vs. 4.3; +43.3%). Conclusions: The IF, as well as the number of articles per year and the number of authors per article, increased significantly. In contrast, the number of pages per article remained comparable during the period analyzed.

Small-angle X-ray scattering (SAXS) is a widely used experimental technique, providing structural and dynamic insight into soft-matter complexes and biomolecules under near-native conditions. However, interpreting the one-dimensional scattering profiles in terms of three-dimensional structures and ensembles remains challenging, partly because it is poorly understood how structural information is encoded along the measured scattering angle. We combined all-atom SAXS-restrained ensemble simulations, simplified continuum models, and SAXS experiments of a n-dodecyl-β-d-maltoside (DDM) micelle to decipher the effects of model asymmetry, shape fluctuations, atomic disorder, and atomic details on SAXS curves. Upon interpreting the small-angle regime, we find remarkable agreement between (i) a two-component triaxial ellipsoid model fitted against the data and (ii) a SAXS-refined all-atom ensemble. However, continuum models fail at wider angles, even if they account for shape fluctuations, disorder, and asymmetry of the micelle. We conclude that modeling atomic details is mandatory for explaining SAXS curves at wider angles.

We report on the developments that enabled the field deployment of a fully-automated aerosol mass spectrometer, specially designed for high-altitude measurements on unpressurised aircraft. The merits of the two main categories of real-time aerosol mass spectrometry, i.e. (a) single particle laser desorption and ionization, and (b) continuous thermal desorption / electron impact ionization of aerosols, have been integrated into one compact apparatus with the aim to perform in-situ real-time analysis of aerosol chemical composition. The demonstrated instrument, named ERICA (European Research council Instrument for the Chemical composition of Aerosols), operated successfully aboard the high-altitude research aircraft M-55 Geophysica at altitudes up to 20 km, while being exposed to ambient conditions of very low atmospheric pressure and temperature. A primary goal of those field deployments was the in-situ study of the Asian Tropopause Aerosol Layer (ATAL). During 11 research flights, the instrument operated for more than 49 hours and collected chemical composition information of more than 150,000 single particles combined with quantitative chemical composition analysis of aerosol particle ensembles. This paper presents in detail the technical characteristics of the main constituent parts of the instrument, as well as the design considerations for its integration into the aircraft and its autonomous operation in the upper troposphere and lower stratosphere (UT/LS). Additionally, system performance data from the first field deployments of the instrument are presented and discussed, together with exemplary mass spectrometry data collected during those flights.

Freshwater ecosystems are strongly influenced by weather extremes such as heatwaves, which are predicted to increase in frequency and magnitude in the future. In addition to these climate extremes, the freshwater realm is impacted by the exposure to various classes of chemicals emitted by anthropogenic activities. Currently, there is limited knowledge on how the combined exposure to heatwaves and chemicals affects the structure and functioning of freshwater ecosystems. Here, we review the available literature describing the single and combined effects of heatwaves and chemicals on different levels of biological organization, to obtain a holistic view of their potential interactive effects. We only found a few studies (13 out of the 61 studies included in this review) that investigated the biological effects of heatwaves in combination with chemical pollution. The reported interactive effects of heatwaves and chemicals varied largely not only within the different trophic levels, but also depending on the studied endpoints for populations or individuals. Hence, owing also to the little number of studies available, no consistent interactive effects could be highlighted at any level of biological organization. Moreover, we found an imbalance towards single species and population experiments, with only 5 studies using a multitrophic approach. This results in a knowledge gap for relevant community and ecosystem level endpoints, which prevents the exploration of important indirect effects that can compromise food web stability. Moreover, this knowledge gap impairs the validity of chemical risk assessments and our ability to protect ecosystems. Finally, we highlight the urgency of integrating extreme events into multiple stressors studies and provide specific recommendations to guide further experimental research in this regard.

IAGOS (www.iagos.org) is a European Research Infrastructure using commercial aircraft (Airbus A340, A330, and soon A350) for automatic and routine measurements of atmospheric composition including reactive gases (ozone, carbon monoxide, nitrogen oxides, volatile organic compounds), greenhouse gases (water vapour, carbon dioxide, methane), aerosols and cloud particles along with essential thermodynamic parameters. The main objective of IAGOS is to provide the most complete set of high-quality essential climate variables (ECV) covering several decades for the long-term monitoring of climate and air quality. The observations are stored in the IAGOS data centre along with added-value products to facilitate the scientific interpretation of the data. IAGOS began as two European projects, MOZAIC and CARIBIC, in the early 1990s. These projects demonstrated that commercial aircraft are ideal platforms for routine atmospheric measurements. IAGOS then evolved as a European Research Infrastructure offering a mature and sustainable organization for the benefits of the scientific community and for the operational services in charge of air quality and climate change issues such as the Copernicus Atmosphere Monitoring Services (CAMS) and the Copernicus Climate Change Service (C3S). IAGOS is also a contributing network of the World Meteorological Organization (WMO). IAGOS provides measurements of numerous chemical compounds which are recorded simultaneously in the critical region of the upper troposphere – lower stratosphere (UTLS) and geographical regions such as Africa and the mid-Pacific which are poorly sampled by other means. The data are used by hundreds of groups worldwide performing data analysis for climatology and trend studies, model evaluation, satellite validation and the study of detailed chemical and physical processes around the tropopause. IAGOS data also play an important role in the re-assessment of the climate impact of aviation. Most important in the context of weather-related research, IAGOS and its predecessor programmes provide long-term observations of water vapour and relative humidity with respect to ice in the UTLS as well as throughout the tropospheric column during climb-out and descending phases around airports, now for more than 25 years. The high quality and very good resolution of IAGOS observations of relative humidity over ice are used to better understand the role of water vapour and of ice-supersaturated air masses in the tropopause region and to improve their representation in numerical weather and climate forecasting models. Furthermore, CAMS is using the water vapour vertical profiles in near real time for the continuous validation of the CAMS atmospheric models.

Stratospheric aerosol has long been seen as a pure mixture of sulfuric acid and water. Recent measurements, however, found a considerable carbonaceous fraction extending at least 8 km into the stratosphere. This fraction affects the aerosol optical depth (AOD) and the radiative properties, and hence the radiative forcing and climate impact of the stratospheric aerosol. Here we present an investigation based on a decade (2005–2014) of airborne aerosol sampling at 9–12 km altitude in the tropics and the northern hemisphere (NH) aboard the IAGOS-CARIBIC passenger aircraft. We find that the chemical composition of tropospheric aerosol in the tropics differs markedly from that at NH midlatitudes, and, that the carbonaceous stratospheric aerosol is oxygen-poor compared to the tropospheric aerosol. Furthermore, the carbonaceous and sulfurous components of the aerosol in the lowermost stratosphere (LMS) show strong increases in concentration connected with springtime subsidence from overlying stratospheric layers. The LMS concentrations significantly exceed those in the troposphere, thus clearly indicating a stratospheric production of not only the well-established sulfurous aerosol, but also a considerable but less understood carbonaceous component.

Breaking down the calculated interaction energy between two or more fragments into well-defined terms enables a physically meaningful understanding of chemical bonding. Energy decomposition analysis (EDA) is a powerful method that connects the results of accurate quantum chemical calculations with the Lewis electron-pair bonding model. The combination of EDA with natural orbitals for chemical valence (NOCV) links the heuristic Lewis picture with quantitative molecular orbital theory complemented by Pauli repulsion and Coulombic interactions. The EDA-NOCV method affords results that provide a physically sound picture of chemical bonding between any atoms. We present and discuss results for the prototypical main-group diatomics H2, N2, CO and BF, before comparing bonding in N2 and C2H2 with that in heavier homologues. The discussion on multiply bonded species is continued with a description of B2 and its N-heterocyclic carbene adducts. This Perspective introduces energy decomposition analysis as a means of providing a quantum chemically derived bonding model that we can use to rationalize molecular geometries and bonding. The model serves as a bridge between the simple Lewis electron-pair bond and the complicated quantum theoretical nature of the chemical bond.

Background The implementation of emission mitigation policies in Europe over the last two decades has generally improved the air quality, which resulted in lower aerosol particle mass, particle number, and black carbon mass concentration. However, little is known whether the decreasing particle concentrations at a lower-altitude level can be observed in the free troposphere (FT), an important layer of the atmosphere, where aerosol particles have a longer lifetime and may affect climate dynamics. In this study, we used data from two high-Alpine observatories, Zugspitze-Schneefernerhaus (ZSF) and Jungfraujoch (JFJ), to assess the long-term trends on size-resolved particle number concentrations (PNCs) and equivalent black carbon (eBC) mass concentration separated for undisturbed lower FT conditions and under the influence of air from the planetary boundary layer (PBL) from 2009 to 2018. Results The FT and PBL-influenced conditions were segregated for both sites. We found that the FT conditions in cold months were more prevalent than in warm months, while the measured aerosol parameters showed different seasonal patterns for the FT and PBL-influenced conditions. The pollutants in the PBL-influenced condition have a higher chance to be transported to high-altitudes due to the mountainous topography, leading to a higher concentration and more distinct seasonal variation, and vice versa. The long-term trends of the measured aerosol parameters were evaluated and the decreased aerosol concentrations were observed for both FT and PBL-influenced conditions. The observed decreasing trends in eBC concentration in the PBL-influenced condition are well consistent with the reported trends in total BC emission in Germany and Switzerland. The decreased concentrations in the FT condition suggest that the background aerosol concentration in the lower FT over Central Europe has correspondingly decreased. The change of back trajectories in the FT condition at ZSF and JFJ was further evaluated to investigate the other possible drivers for the decreasing trends. Conclusions The background aerosol concentration in the lower FT over Central Europe has significantly decreased during 2009–2018. The implementation of emission mitigation policies is the most decisive factor and the decrease of the regional airmass occurrence over Central Europe also has contributed to the decreasing trends.

IAGOS (In-Service Aircraft for a Global Observing System; www.iagos.org) is a European Research Infrastructure which uses passenger aircraft equipped with autonomous instrumentation for the continuous and global-scale observation of atmospheric composition in the upper troposphere and lowermost stratosphere (UT/LS; see Petzold et al., 2015). Among others, IAGOS provides today detailed information on atmospheric trace species by the flying laboratory in IAGOS-CARIBIC. Since July 2018, number concentration and fraction of non-volatile particles for dp > 15 nm as well as size distributions for dp > 250 nm are measured (Bundke et al., 2015). Since lately, aerosol chemical composition is provided as well (Schulz et al., 2020). IAGOS-CARIBIC flight routes covered during the period from July 2018 to March 2020 include regular flights from Munich, Germany, to North America, East Asia and South Africa.On 22 June 2019, the Raikoke Volcano on the Kuril Islands erupted and transported vast amounts of gaseous and particulate matter into the UT/LS. Two months after the eruption CALIPSO observed enhanced aerosol optical depth and aerosol scattering across the entire lower stratosphere. IAGOS-CARIBIC conducted several flight series in the Northern Hemisphere before and after the eruption phase such that the pre- and post-eruption data provide profound information on the impact of the Raikoke eruption on the Northern Hemisphere UT/LS aerosol and the evolution of the plume during 9 months of regular observation.Data indicate an increase in the number concentration of particles with dp > 250 nm by a factor of 10 across the entire sampled altitude range, while the increase of the total aerosol number concentration (dp > 15 nm) is less pronounced but also significant. We present a detailed analysis of the changes in UT/LS aerosol load and properties caused by the Raikoke eruption, including the temporal evolution of the aerosol plume during 9 months past the eruption. In-situ observations are backed-up by CALIPSO products and results from associated volcanic plume modelling studies deploying the UK Earth System Model UKESM1.The authors gratefully acknowledge the continuous support of IAGOS by Deutsche Lufthansa. Without their commitment these observations would not have been possible. Parts of this study were funded by the German Ministry for Education and Research (BMBF) under Grant No. 01LK1301A as part of the joint research programme IAGOS Germany.Bundke, U., et al. (2015) Tellus B 67, 28339 https://doi.org/10.3402/tellusb.v67.28339.Petzold, A., et al. (2015) Tellus B 67, 28452 https://doi.org/10.3402/tellusb.v67.28452.Schulz, C., et al. (2020) EAC 2020 Abstract ID 1258

Environmental sequence data of microbial communities now makes up the majority of public genomic information. The assignment of a function to sequences from these metagenomic sources is challenging because organisms associated with the data are often uncharacterized and not cultivable. To overcome these challenges, we created a rationally designed expression library of metagenomic proteins covering the sequence space of the thioredoxin superfamily. This library of 100 individual proteins represents more than 22,000 thioredoxins found in the Global Ocean Sampling data set. We screened this library for the functional rescue of Escherichia coli mutants lacking the thioredoxin-type reductase (ΔtrxA), isomerase (ΔdsbC), or oxidase (ΔdsbA). We were able to assign functions to more than a quarter of our representative proteins. The in vivo function of a given representative could not be predicted by phylogenetic relation but did correlate with the predicted isoelectric surface potential of the protein. Selected proteins were then purified, and we determined their activity using a standard insulin reduction assay and measured their redox potential. An unexpected gel shift of protein E5 during the redox potential determination revealed a redox cycle distinct from that of typical thioredoxin-superfamily oxidoreductases. Instead of the intramolecular disulfide bond formation typical for thioredoxins, this protein forms an intermolecular disulfide between the attacking cysteines of two separate subunits during its catalytic cycle. Our functional metagenomic approach proved not only useful to assign in vivo functions to representatives of thousands of proteins but also uncovered a novel reaction mechanism in a seemingly well-known protein superfamily.

Highlights • Holocene cold-water coral mound formation started non-synchronous in Belgica province. • Coral mounds and slope sediments record changes in intermediate water mass dynamics. • Increased turbulent bottom currents steered slope erosion and mound formation. • Internal waves at the ENAW-MOW boundary enhance energy supply and particle flux. • Transition zone between the ENAW-MOW shifted 250 m upslope during the last deglacial. Abstract Turbulent bottom currents significantly influence the formation of cold-water coral mounds and sedimentation processes on continental slopes. Combining records from coral mounds and adjacent slope sediments therefore provide an unprecedented palaeo-archive to understand past variations of intermediate water-mass dynamics. Here, we present coral ages from coral mounds of the Belgica province (Porcupine Seabight, NE Atlantic), which indicate a non-synchronous Holocene re-activation in mound formation suggested by a temporal offset of ∼2.7 kyr between the deep (start: ∼11.3 ka BP at 950 m depth) and shallow (start: ∼8.6 ka BP at 700 m depth) mounds. A similar depth-dependent pattern is revealed in the slope sediments close to these mounds that become progressively younger from 22.1 ka BP at 990 m to 12.2 ka BP at 740 m depth (based on core-top ages). We suggest that the observed changes are the consequence of enhanced bottom-water hydrodynamics, caused by internal waves associated to the re-invigoration of the Mediterranean Outflow Water (MOW) and the development of a transition zone (TZ) between the MOW and the overlying Eastern North Atlantic Water (ENAW), which established during the last deglacial. These highly energetic conditions induced erosion adjacent to the Belgica mounds and supported the re-initiation of mound formation by increasing food and sediment fluxes. The striking depth-dependent patterns are likely linked to a shift of the ENAW-MOW-TZ, moving the level of maximum energy ∼250 m upslope since the onset of the last deglaciation.

Small- and wide-angle X-ray scattering (SAXS/WAXS/SWAXS) have evolved to be accurate tools used to gain structural information of biomolecules in solution. However, the interpretation of SWAXS data remains challenging owing to the low information content of the data and scattering contributions from the solvent. In recent years, methods for the interpretation of SWAXS data based on explicit-solvent molecular dynamics (MD) simulations have become increasingly popular. The physicochemical information in the MD force fields complements the low-information SWAXS data, thereby greatly reducing the risk of overfitting, and the explicit-solvent models may accurately account for scattering contributions from the solvent. In this chapter, we provide a practical introduction to MD-based methods for the interpretation of SWAXS data. First, we present the back-calculation of a SWAXS curve from an MD trajectory as required to validate an MD simulation against experimental SWAXS data. Second, we present the structure refinement of an atomic model against SWAXS data using SAXS-driven MD simulations. Common technical problems together with appropriate solutions are discussed.

Resolving the structural dynamics of the initial steps of chemical reactions is challenging. We report the femtosecond time-resolved wide-angle x-ray scattering of the photodissociation of diiodomethane in cyclohexane. The data reveal with structural detail how the molecule dissociates into radicals, how the radicals collide with the solvent, and how they form the photoisomer. We extract how translational and rotational kinetic energy is dispersed into the solvent. We also find that 85% of the primary radical pairs are confined to their original solvent cage and discuss how this influences the downstream recombination reactions.

The formation and X-ray structure analysis of the PtIV complex [(CH2C{PPh2C6H4}2)PtI2] is reported. The molecule possesses the orthometalated ligand (PPh3)2C→CH2, which serves via its C2 fragment as an unprecedented four-electron σ donor.

The progress in experimental and theoretical research in the area of main group compounds that possess dative bonds, which was made in the last decade, is summarized. The focus lies on the information about the bonding situation that is available from the analysis of the electronic structure using modern methods of quantum chemistry and the implication on experimental work. The account describes complexes EL2 and E2L2 of group 13–15 atoms E where a single- or diatomic centre is stabilized by donor ligands L. The work is complemented by didactical excursions which demonstrate the strength of the dichotomous interpretation of chemical bonding in terms of dative or electron-sharing interactions. It is important to distinguish between the description of a bonding situation and the explanation of the molecular electronic structure, which provides the fundament for the pictorial representation of the bonds.

Quantum chemical calculations of the main-group compounds E[C(NHCMe )2 ]2 (E=Be, B+ , C2+ , N3+ , Mg, Al+ , Si2+ , P3+ ) have been carried out using density functional theory at the BP86/def2-TZVPP and BP86-D3(BJ)/def2-TZVPP levels of theory. The geometry optimization at BP86/def2-TZVPP gives equilibrium structures with two-coordinated species E and bending angles C-E-C between 152.5° (E=Be) and 110.5° (E=Al). Inclusion of dispersion forces at BP86-D3(BJ)/def2-TZVPP yields a three-coordinated beryllium compound Be[C(NHCMe )2 ]2 as the only energy minimum form. Three-coordinated isomers are found besides the two-coordinated energy minima for the boron and carbon cations B[C(NHCMe )2 ]2+ and C[C(NHCMe )2 ]22+ . The three-coordinated form of the boron compound is energetically lower lying than the two-coordinated form, while the opposite trend is calculated for the carbon species. The theoretically predicted bond dissociation energies suggest that all compounds are viable species for experimental studies. The X-ray structure of the benzoannelated homologue of P[C(NHCMe )2 ]23+ that was recently reported by Dordevic et al. agrees quite well with the calculated geometry of the molecule. A detailed bonding analysis using charge and energy decomposition methods shows that the two-coordinated neutral compounds Be[C(NHCMe )2 ]2 and Mg[C(NHCMe )2 ]2 possess strongly positively charged atoms Be and Mg. The carbodicarbene groups C(NHCMe )2 serve as acceptor ligands in the compounds and may be sketched with dative bonds (NHCMe )2 C←E→C(NHCMe )2 (E=Be, Mg). Dative bonds in which the carbones C(NHCMe )2 are donor ligands are suggested for the cations (NHCMe )2 C→E←C(NHCMe )2 (E=B+ , Al+ ). The dications and trications possess electron-sharing bonds in which the bonding situation is best described with the formula [(NHCMe )2 C]+ -E-[C(NHCMe )2 ]+ (E=C, Si, N+ , P+ ).

Small-angle X-ray scattering (SAXS) is a widely used experimental technique, providing structural and dynamic insight into soft-matter complexes and biomolecules under near-native conditions. However, interpreting the one-dimensional scattering profiles in terms of three-dimensional structures and ensembles remains challenging, partly because it is poorly understood how structural information is encoded along the measured scattering angle. We combined all-atom SAXS-restrained ensemble simulations, simplified continuum models, and SAXS experiments of a n-dodecyl-β-D-maltoside (DDM) micelle to decipher the effects of model asymmetry, shape fluctuations, atomic disorder, and atomic details on SAXS curves. Upon interpreting the small-angle regime, we find remarkable agreement between (i) a two-component tri-axial ellipsoid model fitted against the data with (ii) a SAXS-refined all-atom ensemble. However, continuum models fail at wider angles, even if they account for shape fluctuations, disorder, and asymmetry of the micelle. We conclude that modelling atomic details is mandatory for explaining the entire SAXS curve, and that SAXS-restrained ensemble simulations are a useful tool for interpreting SAXS data of soft-matter complexes in terms of both average structures and conformational heterogeneity.

Intrinsically disordered proteins (IDPs) play key roles in biology and disease, rationalizing the wide interest in deriving accurate solution ensembles of IDPs. Molecular dynamics (MD) simulations of IDPs often suffer from force-field inaccuracies, suggesting that simulations must be complemented by experimental data to obtain physically correct ensembles. We present a method for integrating small-angle X-ray scattering (SAXS) data on-the-fly into MD simulations of disordered systems, with the aim to bias the conformational sampling toward agreement with ensemble-averaged SAXS data. By coupling a set of parallel replicas to the data and following the principle of maximum entropy, this method applies only a minimal bias. Using the RS peptide as a test case, we analyze the influence of (i) the number of parallel replicas, (ii) the scaling of the force constant for the SAXS-derived biasing energy with the number of parallel replicas, and (iii) the force field. The refined ensembles are cross-validated against experimental

Aerosol composition and optical scattering from particles in the lowermost stratosphere (LMS) have been studied by comparing in-situ aerosol samples from the IAGOS-CARIBIC passenger aircraft with vertical profiles of aerosol backscattering obtained from the CALIOP lidar aboard the CALIPSO satellite. Concentrations of the dominating fractions of the stratospheric aerosol, being sulphur and carbon, have been obtained from post-flight analysis of IAGOS-CARIBIC aerosol samples. This information together with literature data on black carbon concentrations were used to calculate the aerosol backscattering which subsequently is compared with measurements by CALIOP. Vertical optical profiles were taken in an altitude range of several kilometres from and above the northern hemispheric extratropical tropopause for the years 2006-2014. We find that the two vastly different measurement platforms yield different aerosol backscattering, especially close to the tropopause where the influence from tropospheric aerosol is strong. The best agreement is found when the LMS is affected by volcanism, i.e., at elevated aerosol loadings. At background conditions, best agreement is obtained some distance (>2 km) above the tropopause in winter and spring, i.e., at likewise elevated aerosol loadings from subsiding aerosol-rich stratospheric air. This is to our knowledge the first time the CALIPSO lidar measurements have been compared to in-situ long-term aerosol measurements.

Condensation reaction of asymmetric triamine (spermidine) with guanidine hydrochloride provides a phantom structure with selective formation of rings in the repeat unit. The intermolecular condensation between amine and guanidine hydrochloride can provide either a linear structure or six- or seven-membered rings in the repeat unit by elimination of one or three molecules of ammonia, respectively, per repeat unit. The preference of formation of rings and mechanistic aspects are studied by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, 1D, 2D NMR, and quantum chemical calculations.

The particle number size distribution is an important parameter to characterize the atmospheric aerosol and its influence on the Earth's climate. Here we describe a new Optical Particle Size Spectrometer (OPSS) for measurements of the accumulation mode particle number size distribution in the tropopause region onboard a passenger aircraft (IAGOS-CARIBIC observatory (In-service Aircraft for a Global Observing System – Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container)). A modified "KS93 particle sensor" from RION Co., Ltd. together with a new airflow system and a dedicated data acquisition system are the key components of the CARIBIC OPSS. The instrument records individual particle pulses in the particle size range 130–1110 nm diameter (for a particle refractive index of 1.47-i0.006 for an upper tropospheric (UT) aerosol particle) and thus allows the post-flight choice of the time resolution and the size distribution bin width. The CARIBIC OPSS has a 50 % particle detection diameter of 152 nm and a maximum asymptotic counting efficiency of 98 %. The instruments measurement performance shows no pressure dependency and no coincidence for free tropospheric conditions. The size response function of the CARIBIC OPSS was obtained by a polystyrene latex calibration in combination with model calculations. Particle number size distributions measured with the new OPSS in the lowermost stratosphere agreed within a factor of two in concentration with balloon-borne measurements over western North America. Since June 2010 the CARIBIC OPSS is deployed once per month in the IAGOS-CARIBIC observatory.

Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes.

Die vorgestellte Arbeit ist Teil des BMBF-Verbundprojekts „SchussenAktivplus“, das an den Bodenseezuflüssen Schussen und Argen durchgeführt wird. Die Kläranlage (KA) Langwiese bei Ravensburg, welche in die Schussen einleitet, wurde im Winter 2013 mit einer Pulveraktivkohlestufe aufgerüstet. Im hier vorgestellten Teil des Projektes wurde der Gesundheitszustand von Flohkrebsen (Gammarus spec.) und die Integrität der Makrozoobenthosgemeinschaft an Probestellen ober- und unterhalb der KA sowie vor und nach Ausbau der KA untersucht. Die Ergebnisse zeigen, dass sich der Ausbau der KA mit einer Pulveraktivkohlestufe bereits 15 Monate nach Einbau positiv auf den Gesundheitszustand von Flohkrebsen und die Artengemeinschaft des Makrozoobenthos auswirkt.

Quantum chemical calculations using the complete active space of the valence orbitals have been carried out for Hn CCHn (n=0-3) and N2. The quadratic force constants and the stretching potentials of Hn CCHn have been calculated at the CASSCF/cc-pVTZ level. The bond dissociation energies of the C-C bonds of C2 and HC≡CH were computed using explicitly correlated CASPT2-F12/cc-pVTZ-F12 wave functions. The bond dissociation energies and the force constants suggest that C2 has a weaker C-C bond than acetylene. The analysis of the CASSCF wavefunctions in conjunction with the effective bond orders of the multiple bonds shows that there are four bonding components in C2, while there are only three in acetylene and in N2. The bonding components in C2 consist of two weakly bonding σ bonds and two electron-sharing π bonds. The bonding situation in C2 can be described with the σ bonds in Be2 that are enforced by two π bonds. There is no single Lewis structure that adequately depicts the bonding situation in C2. The assignment of quadruple bonding in C2 is misleading, because the bond is weaker than the triple bond in HC≡CH.

Significance Unique information about the abundance and evolution of wildfire-emitted black carbon (BC) in the lowermost part of the stratosphere (LMS) was obtained from long-term airborne measurements made in cooperation with Lufthansa through the Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) project, part of the In-service Aircraft for a Global Observing System (IAGOS) framework. Our results demonstrate that wildfires can dramatically increase BC mass concentration in the LMS, substantially enhance regional climate forcing, and are a challenge for model simulations. Climate change is expected to increase the frequency and spread of wildfires. Thus, recording a present-day baseline with extensive and long-term measurements should help to constrain model estimations of the climate impact of BC and foster our fundamental understanding of future climate change., Wildfires inject large amounts of black carbon (BC) particles into the atmosphere, which can reach the lowermost stratosphere (LMS) and cause strong radiative forcing. During a 14-month period of observations on board a passenger aircraft flying between Europe and North America, we found frequent and widespread biomass burning (BB) plumes, influencing 16 of 160 flight hours in the LMS. The average BC mass concentrations in these plumes (∼140 ng·m−3, standard temperature and pressure) were over 20 times higher than the background concentration (∼6 ng·m−3) with more than 100-fold enhanced peak values (up to ∼720 ng·m−3). In the LMS, nearly all BC particles were covered with a thick coating. The average mass equivalent diameter of the BC particle cores was ∼120 nm with a mean coating thickness of ∼150 nm in the BB plume and ∼90 nm with a coating of ∼125 nm in the background. In a BB plume that was encountered twice, we also found a high diameter growth rate of ∼1 nm·h−1 due to the BC particle coatings. The observed high concentrations and thick coatings of BC particles demonstrate that wildfires can induce strong local heating in the LMS and may have a significant influence on the regional radiative forcing of climate.

This study describes the formation of freshly formed boundary layer aerosol particles under classical called non favourable conditions by the existence of low-level strato cumulus clouds. Airborne measurements for vertical profiling atmospheric boundary layer properties and aerosol particles in the diameter range between 5 nm and 10 μm were repeatedly performed with the unmanned aerial system ALADINA (Application of Light-weight Aircraft for Detecting IN-situ Aerosol) at the research site of TROPOS (Leibniz Institute for Tropospheric Research) in Melpitz during three seasons between October 2013 and July 2015. More than 100 measurement flights were performed during this period on 23 different days with a total flight duration of 53 h. On 26 % of the measurement days, new particle formation was measured close to the inversion layer and was observed to be transported downwards during short time intervals of cloud gaps. However, the typical banana shape of new particle formation and growth was not seen at ground, only sporadic events appeared with low particle growth rate and thus might not have been classified as NPF by pure surface studies. This presentation focuses on two cases influenced by the passage of a low pressure system and minimal concentrations of SO2 as indicator for precursor gases at ground; I) on April 4, 2014 by east wind and II) on June 21, 2015 under south-west wind. For a closure, an LES-model output was used for the second study in order to derive a full analysis of atmospheric boundary layer growth over the measurement site at small-scale with high spatial resolution. Pronounced turbulent fluxes of sensible and latent heat in the vertical distribution initiated fast mixing processes of freshly formed boundary layer aerosol. Furthermore, CO2 and particle fluxes indicated downward transport and high deposition during sporadic nucleation events, so that NPF occurrence above with subsequent downward transport was clearly identified.

In dieser Arbeit wurde erfolgreich ein Beschleuniger-Massenspektrometer für mittelschwere Radionuklide am Kölner FN-Tandembeschleuniger berechnet, aufgebaut und getestet. Mit diesem AMS-System konnten (53Mn/55Mn)-Isotopenverhältnisse im Bereich von 1e-9 bis 1e-10 mit einem Detektionslimit von 7,2e-13 erstmalig an einem 10MV Tandembeschleuniger gemessen werden. Das aufgebaute AMS-System ist dediziert für den Nachweis von mittelschweren Radionukliden. Es verfügt über einen achromatischen Injektor mit Fast-Injection-System sowie ein Hochenergie-Massenspektrometer mit einem 90°-Analysiermagneten (rho=1,1 m), hinter dem die Ionenströme der stabilen Nuklide in Offset-Farady-Cups gemessen werden. Die Isobarenunterdrückung kann über eine mehrstufige isotopenspezifische Energieverlust-Messung mit Kombinationen aus Siliziumnitrid-Folien, einem 30° elektrostatischen Analysierer (rho=3,5 m), einem 4 m Time-of-Flight-System sowie einem Gasionisationsdetektor erfolgen. Zusätzlich wurde das AMS-System für die Erhöhung der Transmission bei Radionuklidmessungen wie 60Fe um einen 135°-Magneten (rho=0,9 m) für den gasgefüllten Modus erweitert. Entscheidend sind bei allen AMS-Messungen die erreichbare Sensitivität und das Detektionslimit. Die hier gegebene Definition der fehlernormalisierten Sensitivität ermöglicht den Vergleich der Ergebnisse der (53Mn/55Mn)-Isotopenverhältnismessungen mit den Werten etablierter Labore. Das erreichte Detektionslimit ist trotz der niedrigen Ionenenergien mit anderen Forschungseinrichtungen vergleichbar, die über Tandembeschleuniger mit höherer Terminalspannung verfügen. Das gesamte AMS-System wurde mit Messungen von stabilen Isotopen und Isotopenverhältnissen überprüft. Bei den Testmessungen zu (41Ca/40Ca)-Isotopenverhältnissen wurde ohne passive Absorber ein Detektionslimit von

We analyze the influence of atmospheric boundary-layer development on new particle formation (NPF) during the morning transition. Continuous in-situ measurements of vertical profiles of temperature, humidity and aerosol number concentrations were quasi-continously measured near Melpitz, Germany, by unmanned aerial systems to investigate the potential connection between NPF and boundary-layer dynamics in the context of turbulence, temperature and humidity fluctuations. On 3 April 2014 high number concentrations of nucleation mode particles up to $$6.0 \times 10^4~\text {cm}^{-3}$$ were observed in an inversion layer located about 450 m above ground level. The inversion layer exhibited a spatial temperature structure parameter $$C_T^2$$ 15 times higher and a spatial humidity structure parameter $$C_q^2$$ 5 times higher than in the remaining part of the vertical profile. The study provides hints that the inversion layer is responsible for creating favorable thermodynamic conditions for a NPF event. In addition, this layer showed a strong anti-correlation of humidity and temperature fluctuations. Using estimates of the turbulent mixing and dissipation rates, it is concluded that the downward transport of particles by convective mixing was also the reason of the sudden increase of nucleation mode particles measured on ground. This work supports the hypothesis that many of the NPF events that are frequently observed near the ground may, in fact, originate at elevated altitude, with newly formed particles subsequently being mixed down to the ground.