U. Pöschl

Max Planck Institute for Biogeochemistry Jena, Jena, Thuringia, Germany

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Publications (279)1047.03 Total impact

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    ABSTRACT: The Amazon Basin plays key roles in the carbon and water cycles, climate change, atmospheric chemistry, and biodiversity. It already has been changed significantly by human activities, and more pervasive change is expected to occur in the next decades. It is therefore essential to establish long-term measurement sites that provide a baseline record of present-day climatic, biogeochemical, and atmospheric conditions and that will be operated over coming decades to monitor change in the Amazon region as human perturbations increase in the future. The Amazon Tall Tower Observatory (ATTO) has been set up in a pristine rain forest region in the central Amazon Basin, about 150 km northeast of the city of Manaus. An ecological survey including a biodiversity assessment has been conducted in the forest region surrounding the site. Two 80 m towers have been operated at the site since 2012, and a 325 m tower is nearing completion in mid-2015. Measurements of micrometeorological and atmospheric chemical variables were initiated in 2012, and their range has continued to broaden over the last few years. The meteorological and micrometeorological measurements include temperature and wind profiles, precipitation, water and energy fluxes, turbulence components, soil temperature profiles and soil heat fluxes, radiation fluxes, and visibility. A tree has been instrumented to measure stem profiles of temperature, light intensity, and water content in cryptogamic covers. The trace gas measurements comprise continuous monitoring of carbon dioxide, carbon monoxide, methane, and ozone at 5 to 8 different heights, complemented by a variety of additional species measured during intensive campaigns (e.g., VOC, NO, NO2, and OH reactivity). Aerosol optical, microphysical, and chemical measurements are made above the canopy as well as in the canopy space. They include light scattering and absorption, aerosol fluorescence, number and volume size distributions, chemical composition, cloud condensation nuclei (CCN) concentrations, and hygroscopicity. Initial results from ecological, meteorological, and chemical studies at the ATTO site are presented in this paper.
    Atmospheric Chemistry and Physics 04/2015; 15(8):11599-11726. DOI:10.5194/acpd-15-11599-2015 · 4.88 Impact Factor
  • Ulrich Pöschl, Manabu Shiraiwa
    Chemical Reviews 04/2015; DOI:10.1021/cr500487s · 45.66 Impact Factor
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    ABSTRACT: Flow reactors, denuders, and sampling tubes are essential tools for many applications in analytical and physical chemistry and engineering. We derive a new method for determining radial diffusion effects and the penetration or transmission of gas molecules and aerosol particles through cylindrical tubes under laminar flow conditions using explicit analytical equations. In contrast to traditional methods based on Brown (1978) and Cooney, Kim and Davis (1974, CKD), the new approximation developed in this study (KPS) does not require interpolation or numerical techniques. The KPS method agrees well with the CKD method under all experimental conditions and also with the Brown method at low Sherwood numbers. At high Sherwood numbers corresponding to high uptake on the wall, flow entry effects become relevant and are considered in the KPS and CKD methods, but not in the Brown method. The practical applicability of the KPS method is demonstrated by the analysis of measurement data from experimental studies of rapid OH, intermediate NO3, and slow O3 uptake on various organic substrates. The KPS method also allows determining the penetration of aerosol particles through a tube, using a single equation to cover both the limiting cases of high and low deposition described by Gormley and Kennedy (1949). We demonstrate that the treatment of gas and particle diffusion converges in the KPS method thus facilitating the prediction of diffusional loss and penetration of gases and particles, the analysis of chemical kinetics data, and the design of fluid reactors, denuders, and sampling lines.
    Analytical Chemistry 03/2015; DOI:10.1021/ac5042395 · 5.83 Impact Factor
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    ABSTRACT: Multiphase reactions of OH radicals are among the most important pathways of chemical aging of organic aerosols in the atmosphere. Reactive uptake of OH by organic compounds has been observed in a number of studies, but the kinetics of mass transport and chemical reaction are still not fully understood. Here we apply the kinetic multi-layer model of gas-particle interactions (KM-GAP) to experimental data from OH exposure studies of levoglucosan and abietic acid, which serve as surrogates and molecular markers of biomass burning aerosol (BBA). The model accounts for gas-phase diffusion within a cylindrical coated-wall flow tube, reversible adsorption of OH, surface-bulk exchange, bulk diffusion, and chemical reactions at the surface and in the bulk of the condensed phase. The non-linear dependence of OH uptake coefficients on reactant concentrations and time can be reproduced by KM-GAP. We find that the bulk diffusion coefficient of the organic molecules is approximately 10-16 cm2 s-1, reflecting an amorphous semi-solid state of the organic substrates. The OH uptake is governed by reaction at or near the surface and can be kinetically limited by surface-bulk exchange or bulk diffusion of the organic reactants. Estimates of the chemical half-life of levoglucosan in 200 nm particles in a biomass burning plume increase from one day at high relative humidity to one week under dry conditions. In BBA particles transported to the free troposphere, the chemical half-life of levoglucosan can exceed one month due to slow bulk diffusion in a glassy matrix at low temperature.
    The Journal of Physical Chemistry A 02/2015; DOI:10.1021/jp510489z · 2.78 Impact Factor
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    ABSTRACT: Phase transitions of nanoparticles are of fundamental importance in atmospheric sciences, but current understanding is insufficient to explain observations at the nano-scale. In particular, discrepancies exist between observations and model predictions of deliquescence and efflorescence transitions and the hygroscopic growth of salt nanoparticles. Here we show that these discrepancies can be resolved by consideration of particle size effects with consistent thermodynamic data. We present a new method for the determination of water and solute activities and interfacial energies in highly supersaturated aqueous solution droplets (Differential Köhler Analysis). Our analysis reveals that particle size can strongly alter the characteristic concentration of phase separation in mixed systems, resembling the influence of temperature. Owing to similar effects, atmospheric secondary organic aerosol particles at room temperature are expected to be always liquid at diameters below ~20 nm. We thus propose and demonstrate that particle size should be included as an additional dimension in the equilibrium phase diagram of aerosol nanoparticles.
    Nature Communications 01/2015; 6:5923. DOI:10.1038/ncomms6923 · 10.74 Impact Factor
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    ABSTRACT: Cloud glaciation is critically important for the global radiation budget (albedo) and for initiation of precipitation. But the freezing of pure water droplets requires cooling to temperatures as low as 235 K. Freezing at higher temperatures requires the presence of an ice nucleator, which serves as a template for arranging water molecules in an ice-like manner. It is often assumed that these ice nucle-ators have to be insoluble particles. We point out that also free macromolecules which are dissolved in water can efficiently induce ice nucleation: the size of such ice nucleating macromolecules (INMs) is in the range of nanometers, corresponding to the size of the critical ice embryo. As the latter is temperature-dependent, we see a correlation between the size of INMs and the ice nucleation temperature as predicted by classical nucleation theory. Different types of INMs have been found in a wide range of biological species and comprise a variety of chemical structures including proteins, sac-charides, and lipids. Our investigation of the fungal species Acremonium implicatum, Isaria farinosa, and Mortierella alpina shows that their ice nucleation activity is caused by proteinaceous water-soluble INMs. We combine these new results and literature data on INMs from fungi, bacteria, and pollen with theoretical calculations to develop a chemical interpretation of ice nucleation and water-soluble INMs. This has atmospheric implications since many of these INMs can be released by fragmentation of the carrier cell and subsequently may be distributed independently. Up to now, this process has not been accounted for in atmospheric models.
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    ABSTRACT: Biological residues in soil dust are a potentially strong source of atmospheric ice nuclei (IN). So far, however , the abundance, diversity, sources, seasonality, and role of biological – in particular, fungal – IN in soil dust have not been characterized. By analysis of the culturable fungi in topsoils, from a range of different land use and ecosystem types in southeast Wyoming, we found ice-nucleation-active (INA) fungi to be both widespread and abundant, particularly in soils with recent inputs of decomposable organic matter. Across all investigated soils, 8 % of fungal isolates were INA. All INA isolates initiated freezing at −5 to −6 • C, and belonged to a single zygomycotic species, Mortierella alpina (Mortierellales, Mortierellomycotina). To our knowledge this is the first report of ice nucleation activity in a zy-gomycotic fungi because the few known INA fungi all belong to the phyla Ascomycota and Basidiomycota. M. alpina is known to be saprobic and widespread in soil, and Mortierella spores are present in air and rain. Sequencing of the ITS region and the gene for γ-linolenic elongase revealed four distinct clades, affiliated to different soil types. The IN produced by M. alpina seem to be proteinaceous, < 300 kDa in size, and can be easily washed off the mycelium. Ice nucleat-ing fungal mycelium will ramify topsoils and probably also release cell-free IN into it. If these IN survive decomposition or are adsorbed onto mineral surfaces, their contribution might accumulate over time, perhaps to be transported with soil dust and influencing its ice nucleating properties.
    Biogeosciences 01/2015; 12:1057-1071. DOI:10.5194/bg-12-1057-2015 · 3.75 Impact Factor
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    ABSTRACT: Real-time mass spectra of the non-refractory species in submicron aerosol particles were recorded in a tropical rainforest in the central Amazon Basin during the wet season from February to March 2008, as a part of the Amazonian Aerosol Characterization Experiment (AMAZE-08). Organic material accounted on average for more than 80 % of the non-refractory submicron particle mass concentrations during the period of measurements. There was insufficient ammonium to neutralize sulfate. In this acidic, isoprene-rich, HO 2-dominant environment, positive-matrix factorization of the time series of particle mass spectra identified four statistical factors to account for the 99 % of the variance in the signal intensities of the organic constituents. The first factor was identified as associated with regional and local pollution and labeled " HOA " for its hydrocarbon-like characteristics. A second factor was associated with long-range transport and labeled " OOA-1 " for its oxygenated characteristics. A third factor, labeled " OOA-2, " was implicated as associated with the reactive uptake of isoprene oxidation products, especially of epoxydiols to acidic haze, fog, or cloud droplets. A fourth factor, labeled " OOA-3, " was consistent with an association with the fresh production of secondary organic material (SOM) by the mechanism of gas-phase oxidation of biogenic volatile organic precursors followed by gas-to-particle conversion of the oxidation products. The suffixes 1, 2, and 3 on the OOA labels signify ordinal ranking with respect to the extent of oxidation represented by the factor. The process of aqueous-phase oxidation of water-soluble products of gas-phase photochemistry might also have been associated to some extent with the OOA-2 factor. The campaign-average factor loadings had a ratio of 1.4 : 1 for OOA-2 : OOA-3, suggesting the comparable importance of particle-phase compared to gas-phase pathways for the production of SOM during the study period. Published by Copernicus Publications on behalf of the European Geosciences Union. 3688 Q. Chen et al.: Submicron particle mass concentrations and sources in AMAZE-08
    Atmospheric Chemistry and Physics 01/2015; 15:3687-3701. DOI:10.5194/acp-15-3687-2015 · 5.51 Impact Factor
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    ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2015; 15:2969-2983. DOI:10.5194/acp-15-2969-2015 · 5.30 Impact Factor
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    ABSTRACT: Archaea are widespread and abundant in many terrestrial and aquatic environments, and are thus outside extreme environments, accounting for up to ~10% of the prokaryotes. Compared to bacteria and other microorganisms, however, very little is known about the abundance, diversity, and dispersal of archaea in the atmosphere. By means of DNA analysis and Sanger sequencing targeting the 16S rRNA (435 sequences) and amoA genes in samples of air particulate matter collected over 1 year at a continental sampling site in Germany, we obtained first insights into the seasonal dynamics of airborne archaea. The detected archaea were identified as Thaumarchaeota or Euryarchaeota, with soil Thaumarchaeota (group I.1b) being present in all samples. The normalized species richness of Thaumarchaeota correlated positively with relative humidity and negatively with temperature. This together with an increase in bare agricultural soil surfaces may explain the diversity peaks observed in fall and winter. The detected Euryarchaeota were mainly predicted methanogens with a low relative frequency of occurrence. A slight increase in their frequency during spring may be linked to fertilization processes in the surrounding agricultural fields. Comparison with samples from the Cape Verde islands (72 sequences) and from other coastal and continental sites indicates that the proportions of Euryarchaeota are enhanced in coastal air, which is consistent with their suggested abundance in marine surface waters. We conclude that air transport may play an important role in the dispersal of archaea, including assumed ammonia-oxidizing Thaumarchaeota and methanogens.
    Biogeosciences 11/2014; 11:6067-6079. DOI:10.5194/bg-11-6067-2014 · 3.75 Impact Factor
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    ABSTRACT: We report first measurements of ultrafine particles from a semi-rural location, Gadanki, from tropical Southern India. Measurements of particle number size distributions in the diameter range of 5 nm–32 μm were performed during 2 May–31 July 2012. The mean number concentrations of nucleation (NNUC), Aitken (NAIT), accumulation (NACCU), and total particles (NTOT) at this site were (1.1 ± 0.9) × 103 cm−3, (2.2 ± 1.3) × 103 cm−3, (1.5 ± 1.2) × 103 cm−3 and (4.8 ± 2.4) × 103 cm−3, respectively, comparable to other rural to semi-rural locations globally and declined as the season progressed, perhaps due to wet removal of aerosols with onset of monsoon in early June. Particle bursts in the nucleation mode size range (5–25 nm), followed by a sustained growth in size were observed very rarely (only 5 out of 79 observation days) at this site, less frequently than at most other locations around the world during May–July. Most factors affecting new particle formation (NPF) were similar on NPF and nonNPF event days, such as condensation sink, relative humidity, temperature, wind speed and direction, and mixing layer height. Thus, the infrequent occurrence of NPF at our site appeared to be linked to lower precursor gas concentrations and weak gas-phase oxidation chemistry due to diminished solar radiation on persistently cloudy days with the onset of the monsoon in early June over this region. The derived particle growth rates (GR > 5 nm) and formation rates of 5 nm particles (J5) ranged from 2.2 to 4.7 nm h−1 and 0.4–2.4 cm−3 s−1, with a mean and standard deviation of 3.4 ± 0.9 nm h−1 and 1.2 ± 2.3 cm−3 s−1, respectively, comparable to previous investigations at rural to semi-rural locations. The observed behavior in aerosol and meteorological parameters on NPF and nonNPF event days appeared to be distinctive compared to other rural to urban locations across the globe. However, this distinct behavior is limited and restricted to this site and season of the year, and should therefore not be generalized over a larger spatio-temporal scale. This emphasizes the need for long-term aerosol and precursor measurements over this and other regions of India.
    Atmospheric Environment 09/2014; 94:264–273. DOI:10.1016/j.atmosenv.2014.05.046 · 3.06 Impact Factor
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    ABSTRACT: Dynamical and microphysical processes in pyro-convective clouds in mid-latitude conditions are investigated using idealized three-dimensional simulations with the Ac-tive Tracer High resolution Atmospheric Model (ATHAM). A state-of-the-art two-moment microphysical scheme build-ing upon a realistic parameterization of cloud condensation nuclei (CCN) activation has been implemented in order to study the influence of aerosol concentration on cloud devel-opment. The results show that aerosol concentration influ-ences the formation of precipitation. For low aerosol concen-trations (N CN = 200 cm −3), rain droplets are rapidly formed by autoconversion of cloud droplets. This also triggers the formation of large graupel and hail particles, resulting in an early onset of precipitation. With increasing aerosol concen-tration (N CN = 1000 cm −3 and N CN = 20 000 cm −3) the for-mation of rain droplets is delayed due to more but smaller cloud droplets. Therefore, the formation of ice crystals and snowflakes becomes more important for the eventual forma-tion of graupel and hail, which is delayed at higher aerosol concentrations. This results in a delay of the onset of precipi-tation and a reduction of its intensity with increasing aerosol concentration. This study is the first detailed investigation of the interaction between cloud microphysics and the dy-namics of a pyroconvective cloud using the combination of a high-resolution atmospheric model and a detailed micro-physical scheme.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 07/2014; 14(7):7573-7583. DOI:10.5194/acp-14-7573-2014 · 5.30 Impact Factor
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    ABSTRACT: Gaseous nitrous acid (HONO), the protonated form of nitrite, contributes up to ~ 60% to the primary formation of hydroxyl radical (OH), which is a key oxidant in the degradation of most air pollutants. Field measurements and modeling studies indicate a large unknown source of HONO during daytime. Here, we developed a new tracer method based on gas-phase stripping-derivatization coupled to liquid chromatography-mass spectrometry (LC-MS) to measure the 15N relative exceedance, ψ(15N), of HONO in the gas-phase. Gaseous HONO is quantitatively collected and transferred to an azo dye, purified by solid phase extraction (SPE) and analyzed using high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). In the optimal working range of ψ(15N) = 0.2 - 0.5, the relative standard deviation of ψ(15N) is < 4%. The optimum pH and solvents for extraction by SPE and potential interferences are discussed. The method was applied to measure HO15NO emissions from soil in a dynamic chamber with and without spiking 15N labeled urea. The identification of HO15NO from soil with 15N urea addition confirmed biogenic emissions of HONO from soil. The method enables a new approach of studying the formation pathways of HONO and its role for atmospheric chemistry (e.g. ozone formation), and environmental tracer studies on the formation and conversion of gaseous HONO or aqueous NO2- as part of the biogeochemical nitrogen cycle, e.g., in the investigation of fertilization effects on soil HONO emissions and microbiological conversion of NO2- in the hydrosphere.
    Environmental Science and Technology 06/2014; 48(14). DOI:10.1021/es501353x · 5.48 Impact Factor
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    ABSTRACT: Inhalation of nitrogen and reactive oxygen species (ROS) is known to induce lung inflammation, which is prevented by enzymatic and nonenzymatic antioxidant systems. These agents form nitrated allergens that were shown to enhance allergenicity. The aim of this study was to examine the influence of nitrated proteins on inflammation and antioxidant status of the lung. Ovalbumin (OVA) in nitrated form (nOVA) was intraperitoneally (ip) injected in mice for sensitization and in nitrated or unmodified form for challenge to induce allergic bronchial inflammation. To study the allergen potential of unrelated protein and verify cross-reactivity, nitrated and unmodified keyhole limpet hemocyanin (nKLH, KLH) was used for challenge. Challenge with OVA or nOVA reduced lung function and increased eosinophilia and protein content in bronchoalveolar lavage fluid (BALF). Challenge with nitrated or native OVA or KLH elevated glutathione (GSH) ratio in type II pneumocytes. Reduced mRNA expression of glutathione peroxidase (GPX) 3, glutathione reductase (GR), superoxide dismutase (SOD) 2, and catalase (CAT) was most prominent after challenge with nitrated OVA and nitrated KLH, respectively. Challenge with nOVA enhanced SOD1 mRNA reduction. Immunostaining of GPX 3 and SOD2 increased after challenge with OVA or nOVA, while reactivity of GR and reactivity of SOD2 were reduced after challenge with KLH or nKLH. SOD1 immunostaining was diminished after challenge with nonnitrated OVA or KLH. CAT immunoreaction was similar in all groups. Nitrated proteins without allergenic potential triggered mRNA reduction of antioxidants in type II cells after sensitization with a nitrated allergen but did not induce bronchial inflammation.
    Journal of Toxicology and Environmental Health Part A 05/2014; 77(12):679-695. DOI:10.1080/15287394.2014.888023 · 1.83 Impact Factor

Publication Stats

7k Citations
1,047.03 Total Impact Points

Institutions

  • 2007–2014
    • Max Planck Institute for Biogeochemistry Jena
      Jena, Thuringia, Germany
  • 1999–2014
    • Max Planck Institute for Chemistry
      • Department of Atmospheric Chemistry
      Mayence, Rheinland-Pfalz, Germany
  • 2013
    • Johannes Gutenberg-Universität Mainz
      Mayence, Rheinland-Pfalz, Germany
  • 2010
    • Paul Scherrer Institut
      • Laboratory of Radiochemistry and Environmental Chemistry
      Aargau, Switzerland
  • 2000–2010
    • University of Technology Munich
      • Chair of Analytical Chemistry
      München, Bavaria, Germany
  • 2006
    • Ludwig-Maximilians-University of Munich
      München, Bavaria, Germany
  • 1998
    • Massachusetts Institute of Technology
      • Department of Earth Atmospheric and Planetary Sciences
      Cambridge, Massachusetts, United States