Model simulations of the changing distribution of Ozone and its radiative forcing of climate: past, present and future

A background tropospheric chemistry model that is coupled to the general circulation model ECHAM4 is used to calculate tropospheric ozone with preindustrial, present-day and future (IS92a) emission scenarios as boundary conditions. The model calculates separate contributions to tropospheric ozone levels from stratosphere-troposphere exchange (STE) and from photo- chemical production in the troposphere. In the preindustrial atmosphere, the simulated annual tropospheric ozone content is 190 Tg 03, of which about 110 Tg 03 originates from the strato- sphere. In the present-day simulation the ozone content is about 80 Tg 03 larger, mainly due to O3 precursor emissions from industrial processes in the NH and from biomass burning in trop- ical regions. In the next few decades, industrial growth is expected to occur mainly at NH (sub) tropical latitudes, leading to an additional increase of the tropospheric ozone budget by 60 Tg 03. We calculate a global and annual average radiative forcing by tropospheric ozone perturbations of 0.42 w m-2 creases in the next few decades of 0.31 W m-2 for the present-day simulation, and an additional forcing due to ozone in- The model results indicate that the amount of tropospheric ozone from stratospheric origin remains relatively unaffected by the changing pho- tochemistry

Aerosol activation and cloud processing in the global aerosol-climate model ECHAM5-HAM

A parameterization for cloud processing is presented that calculates activation of aerosol particles to cloud drops, cloud drop size, and pH-dependent aqueous phase sulfur chemistry. The parameterization is implemented in the global aerosol-climate model ECHAM5-HAM. The cloud processing parameterization uses updraft speed, temperature, and aerosol size and chemical parameters simulated by ECHAM5-HAM to estimate the maximum supersaturation at the cloud base, and subsequently the cloud drop number concentration (CDNC) due to activation. In-cloud sulfate production occurs through oxidation of dissolved SO2 by ozone and hydrogen peroxide. The model simulates realistic distributions for annually averaged CDNC although it is underestimated especially in remote marine regions. On average, CDNC is dominated by cloud droplets growing on particles from the accumulation mode, with smaller contributions from the Aitken and coarse modes. The simulations indicate that in-cloud sulfate production is a potentially important source of accumulation mode sized cloud condensation nuclei, due to chemical growth of activated Aitken particles and to enhanced coalescence of processed particles. The strength of this source depends on the distribution of produced sulfate over the activated modes. This distribution is affected by uncertainties in many parameters that play a direct role in particle activation, such as the updraft velocity, the aerosol chemical composition and the organic solubility, and the simulated CDNC is found to be relatively sensitive to these uncertainties

Long-range transport and multimedia partitioning of semivolatile organic compounds: A case study on two modern agrochemicals

The global environmental fate of two modern pesticides was studied using a multimedia model based on a three- dimensional atmosphere general circulation model. The emissions are predicted dynamically based on agricultural application inventories. The insecticide methyl parathion, when assuming properties at the high mobility end of the respective data uncertainties, was found to be distributed on continental and even global scales. This finding implies that based on present knowledge one cannot exclude that methyl parathion reaches regions as far from the sources as e.g. the Arctic. Two scenarios of the environmental cycling of the herbicide atrazine were studied which reflect a lower and an upper estimate of the substance’ mobility. Atrazine largely remains in the source (application) regions and the neighbouring seas. But also atrazine seems to have an albeit limited potential for long-range transport. The findings on substance mobilities are quantified by indicators which address spatial range in the zonal direction in individual media. The seasonal variability of the total environmental burden of both pesticides is governed by the degradation in soil and vegetation which together host 73 % of methyl parathion and 90-99 % of atrazine. Also, the cycling between compartments was studied. Methyl parathion undergoes more deposition and re-emission cycles than atrazine, a characteristics of the environmental fate of semivolatile substances. Persistence is addressed by determination of global total environmental decay times during periods without introduction of new substance into the environment. These are in the range 4-7 months. It is found that the seasonal variability of persistence is pronounced

Impact of regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants - examples of DDT and g-HCH

A global multicompartment model which is based on a 3-D atmospheric general circulation model (ECHAM5) coupled to 2-D soil, vegetation and sea surface mixed layer reservoirs, is used to simulate the atmospheric transports and total environmental fate of dichlorodiphenyltrichloroethane (DDT) and γ-hexachlorocyclohexane (γ-HCH, lindane). Emissions into the model world reflect the substance's agricultural usage in 1980 and 1990 and same amounts in sequential years are applied. Four scenarios of DDT usage and atmospheric decay and one scenario of γ-HCH are studied over a decade. The global environment is predicted to be contaminated by the substances within ca. 2a (years). DDT reaches quasi-steady state within 3-4a in the atmosphere and vegetation compartments, ca. 6a in the sea surface mixed layer and near to or slightly more than 10a in soil. Lindane reaches quasi-steady state in the atmosphere and vegetation within 2a, in soils within 8 years and near to or slightly more than 10a and in the sea surface mixed layer. The substances' differences in environmental behaviour translate into differences in the compartmental distribution and total environmental residence time, τoverall. τoverall≈0.8a for γ-HCH's and ≈1.0-1.3 a for the various DDT scenarios. Both substances' distributions are predicted to migrate in northerly direction, 5-12° for DDT and 6.7° for lindane between the first and the tenth year in the environment. Cycling in various receptor regions is a complex superposition of influences of regional climate, advection, and the substance's physico-chemical properties. As a result of these processes the model simulations show that remote boreal regions are not necessarily less contaminated than tropical receptor regions. Although the atmosphere accounts for only 1% of the total contaminant burden, transport and transformation in the atmosphere is key for the distribution in other compartments. Hence, besides the physico-chemical properties of pollutants the location of application (entry) affects persistence and accumulation emphasizing the need for georeferenced exposure models

Diagnose und Graduierung zervikaler intraepithelialer Neoplasien

Zusammenfassung: Diagnose und Graduierung von zervikalen intraepithelialen Neoplasien (CIN) gehören zu den häufigen Fragestellungen in der histopathologischen Diagnostik. Trotzdem kann die Unterscheidung zwischen reaktiven Veränderungen und CIN1 bzw. die Graduierung einer CIN Schwierigkeiten bereiten. In dieser Studie wurde untersucht, ob die Bestimmung der Proliferationsmarker Ki-67 und Mcm2 sowie von p16 zur Beantwortung dieser Fragestellungen beitragen. Untersucht wurden die immunhistochemischen Expressionsprofile dieser Marker an 297Proben aus dysplasiefreiem Portioepithel, CIN1, CIN2 und CIN3 mittels Gewebemikroarrays. Die mittels Ki-67 bzw. Mcm2 ermittelte Proliferationsrate zeigte eine Zunahme von dysplasiefreiem Epithel über CIN1, CIN2 zu CIN3 (p<0.001 bei beiden Markern). Mittels Ki-67 ließ sich am besten zwischen dysplasiefreiem Epithel und CIN1 unterscheiden. Zur Abgrenzung von CIN1 zu CIN2 bot sich eine Kombination von Ki-67 und p16 an. Bei einer Ki-67-Expression von<25% handelte es sich um eine CIN1 mit einer Sensitivität von 91,7% und einer Spezifität von 54,3%. Die zusätzliche Untersuchung der Expression von p16 konnte einen weiteren Teil der Fälle mit einer Ki-67-Expression von<25% stratifizieren. Die Anzahl p16-positiver Fälle betrug bei normalen Epithelien 0%, bei CIN1 7%, bei CIN2 46% und bei CIN3 86%. Somit war mittels p16 eine Abgrenzung der CIN2 zur CIN3 nur zum Teil möglich. Die histopathologische Evaluation am HE-Schnitt bleibt Grundlage der Beurteilung von zervikalen intraepithelialen Neoplasien, jedoch kann die Analyse von Ki-67 und p16 zur Diagnose und Graduierung beitrage

Impact of the regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants - examples of DDT and &gamma;-HCH

A global multicompartment model which is based on a 3-D atmospheric general circulation model (ECHAM5) coupled to 2-D soil, vegetation and sea surface mixed layer reservoirs, is used to simulate the atmospheric transports and total environmental fate of dichlorodiphenyltrichloroethane (DDT) and &gamma;-hexachlorocyclohexane (&gamma;-HCH, lindane). Emissions into the model world reflect the substance's agricultural usage in 1980 and 1990 and same amounts in sequential years are applied. Four scenarios of DDT usage and atmospheric decay and one scenario of &gamma;-HCH are studied over a decade. <P style='line-height: 20px;'> The global environment is predicted to be contaminated by the substances within ca.&nbsp;2a (years). DDT reaches quasi-steady state within 3-4a in the atmosphere and vegetation compartments, ca.&nbsp;6a in the sea surface mixed layer and near to or slightly more than 10a in soil. Lindane reaches quasi-steady state in the atmosphere and vegetation within 2a, in soils within 8&nbsp;years and near to or slightly more than 10a and in the sea surface mixed layer. The substances' differences in environmental behaviour translate into differences in the compartmental distribution and total environmental residence time, &tau;_overall. &tau;_overall&asymp;0.8a for &gamma;-HCH's and &asymp;1.0-1.3 a for the various DDT scenarios. Both substances' distributions are predicted to migrate in northerly direction, 5-12&deg; for DDT and 6.7&deg; for lindane between the first and the tenth year in the environment. Cycling in various receptor regions is a complex superposition of influences of regional climate, advection, and the substance's physico-chemical properties. As a result of these processes the model simulations show that remote boreal regions are not necessarily less contaminated than tropical receptor regions. Although the atmosphere accounts for only 1% of the total contaminant burden, transport and transformation in the atmosphere is key for the distribution in other compartments. Hence, besides the physico-chemical properties of pollutants the location of application (entry) affects persistence and accumulation emphasizing the need for georeferenced exposure models

Gas/particle partitioning and global distribution of polycyclic aromatic hydrocarbons – A modelling approach

The global atmospheric distribution and long-range transport (LRT) potential of three polycyclic aromatic hydrocarbons (PAH) - anthracene, fluoranthene and benzo[a]pyrene - are studied. The model used is a global aerosol-chemistry-transport-model, which is based on an atmospheric general circulation model. The model includes an in-built dynamic aerosol model coupled to two-dimensional surface compartments. Several parameterisations of gas/particle partitioning and different assumptions of degradation in the aerosol particulate phase were tested. PAHs are mostly distributed in the source regions but reach the Arctic and the Antarctic. The Canadian Arctic is predicted to be significantly less affected by mid-latitude PAH emissions than the European Arctic. Re-volatilisation is significant for semivolatile PAHs. Accumulation of semivolatile PAHs in polar regions, however, is not indicated. The model study suggests that gas/particle partitioning in air drastically influences the atmospheric cycling, the total environmental fate (e.g. compartmental distributions) and the LRT potential of the substances studied. A parameterisation which calculates the gas/particle partitioning assuming absorption into organic matter and adsorption to black carbon (soot) agrees best with the observations at remote sites. The study provides evidence that the degradation in the particulate phase must be slower than that in the gas-phase. The predicted concentrations of the semivolatile PAHs anthracene and fluoranthene in near-ground air at remote sites in mid and high northern latitudes are in line with measured concentrations, if adsorption of the substances to soot combined with absorption in particulate organic matter is assumed to determine gas/particle partitioning, but cannot be explained by adsorption alone (Junge-Pankow parameterisation of gas/particle partitioning). The results suggest that PAHs absorbed in the organic matrix of particulate matter is shielded from the gas-phase. (C) 2009 Elsevier Ltd. All rights reserved. [References: 42

Audio vs. Video: Does Viewing Support Learning? A Comparision of an Audio-Visual with an Auditory Virtual Lecture

Häufig wird behauptet, dass audiovisuelle Informationen gegenüber auditiven lernwirksamer sind. Dies wird meist mit der kognitiv-anregenden Funktion begründet, die der audiovisuellen Darstellung zugeschrieben wird. Bisherige empirische Arbeiten konnten das auch tendenziell bestätigen; allerdings beziehen sich diese Befunde überwiegend auf das video- oder fernsehgestützte Lernen, bei dem den Lernenden keine zusätzlichen textbasierten Informationen zur Verfügung stehen. Für den Bereich der virtuellen Vorlesung wurde noch nicht untersucht, ob sich eine audiovisuelle Präsentation des Vortragenden gegenüber einer rein auditiven Präsentation positiv auf den Lernerfolg auswirkt. In einer empirischen Studie mit 61 Versuchspersonen wurde daher Lernenden ein Ausschnitt aus einer Online-Vorlesung in zwei Variationen präsentiert. Während die eine Gruppe eine Lerneinheit bearbeitete, in der sie neben textbasierten Informationen eine Videosequenz (Aufnahme des Dozenten) präsentiert bekam, bearbeitete die zweite Gruppe die gleiche Lerneinheit; hier war jedoch nur die Stimme des Dozenten hörbar. In einem direkt anschließenden Wissens- und späteren Behaltenstest zeigten sich keine signifikanten Leistungsunterschiede zwischen den beiden Gruppen. Jedoch berichtete die Mehrheit der Versuchspersonen, dass sie die Videovariante für affektiv-unterstützender hält als die Tonvariante. (ZPID

Ferntransport von persistenten Chemikalien und Verteilung über verschiedene Umweltmedien - Modelluntersuchungen

Viele Schadstoffe zeichnen sich durch eine Kombination aus schwerer Abbaubarkeit (Persistenz) und hoher Mobilität aus. Sie sind mittelflüchtig, d. h. sie verteilen sich über die Umweltmedien Boden, Wasser, Luft und werden über weite Strecken transportiert. Klima und Stoffeigenschaften wirken in komplexer Weise zusammen und bestimmen globale Transportwege und Verteilung dieser Stoffe, zu denen die so genannten persistenten organischen Schadstoffe (persistent organic pollutants, POPs) und weitere Pestizide und Industriechemikalien zählen. Um Informationen über ihr Umweltverhalten, d. h. Transporte und Umwandlungen, zu gewinnen, muss man Böden, Vegetation, Luft, Ozeane und Eis mit in die Untersuchungen einbeziehen. Von der Gruppe Aerosolchemie des Max-Planck-Instituts für Meteorologie wurde Verteilung, Persistenz und Ferntransport-Potenzial (Reichweite) von einigen POPs mithilfe eines globalen Multikompartiment-Modells, das auf einem allgemeinen Zirkulationsmodell der Atmosphäre aufbaut, studiert

Urban eddy covariance measurements reveal significant missing NOx emissions in Central Europe

Nitrogen oxide (NOx) pollution is emerging as a primary environmental concern across Europe. While some large European metropolitan areas are already in breach of EU safety limits for NO2, this phenomenon does not seem to be only restricted to large industrialized areas anymore. Many smaller scale populated agglomerations including their surrounding rural areas are seeing frequent NO2 concentration violations. The question of a quantitative understanding of different NOx emission sources is therefore of immanent relevance for climate and air chemistry models as well as air pollution management and health. Here we report simultaneous eddy covariance flux measurements of NOx, CO2, CO and non methane volatile organic compound tracers in a city that might be considered representative for Central Europe and the greater Alpine region. Our data show that NOx fluxes are largely at variance with modelled emission projections, suggesting an appreciable underestimation of the traffic related atmospheric NOx input in Europe, comparable to the weekend-weekday effect, which locally changes ozone production rates by 40%