Modelling multiphase chemistry in deliquescent aerosols and clouds using CAPRAM3.0i

Modelling studies were performed with the multiphase mechanism RACM- MIM2ext/CAPRAM 3.0i to investigate the tropospheric multiphase chemistry in deli- quesced particles and non-precipitating clouds using the SPACCIM model framework. Simulations using a non-permanent cloud scenario were carried out for two different environmental conditions focusing on the multiphase chemistry of oxidants and other linked chemical subsystems. Model results were analysed by time-resolved reaction flux analyses allowing advanced interpretations. The model shows significant effects of multiphase chemical interactions on the tropospheric budget of gas-phase oxidants and organic com- pounds. In-cloud gas-phase OH radical concentration reductions of about 90 % and 75 % were modelled for urban and remote conditions, respectively. The reduced in-cloud gas- phase oxidation budget increases the tropospheric residence time of organic trace gases by up to about 30 %. Aqueous-phase oxidations of methylglyoxal and 1,4-butenedial were identified as important OH radical sinks under polluted conditions. The model revealed that the organic C3 and C4 chemistry contributes with about 38 %/48 % and 8 %/9 % consid- erably to the urban and remote cloud / aqueous particle OH sinks. Furthermore, the simulations clearly implicate the potential role of deliquescent particles to operate as a reactive chemical medium due to an efficient TMI/HOx,y chemical processing including e.g. an effective in-situ formation of OH radicals. Considerable chemical differences be- tween deliquescent particles and cloud droplets, e.g. a circa 2 times more efficient daytime iron processing in the urban deliquescent particles, were identified. The in-cloud oxidation of methylglyoxal and its oxidation products is identified as efficient sink for NO3 radicals in the aqueous phase

Process for the modification of polymers, in particular polymer nanoparticles

The present invention relates to a highly efficient and ultra fast process for the photo-initiated preparation of polymers by polymerization using photoinitiators comprising a phosphorous oxide or -sulfide group and modification of said polymers. In particular the invention relates to an ultra fast process for the photo-initiated preparation of latices comprising polymer nanoparticles by heterophase polymerization using photoinitiators comprising a phosphorous oxide or -sulfide group and their modification. In another aspect, the invention relates to polymers and polymer nanoparticles obtainable by said process

Molecular traffic control in single-file networks with fast catalysts

As a model for molecular traffic control (MTC) we investigate the diffusion of hard core particles in crossed single-file systems. We consider a square lattice of single-files being connected to external reservoirs. The (vertical) alpha-channels, carrying only A-particles, are connected to reservoirs with constant density ra. B-particles move along the (horizontal) beta-channels, which are connected to reservoirs of density rB. We allow the irreversible transition A to B at intersections. We are interested in the stationary density profile in the alpha- and beta- channels, which is the distribution of the occupation probabilities over the lattice. We calculate the stationary currents of the system and show that for sufficiently long channels the currents (as a function of the reservoir densities) show in the limit of large transition rates non analytic behavior. The results obtained by direct solution of the master equation are verified by kinetic Monte Carlo simulations.Comment: 11 page

Effects of surface modifications on molecular diffusion in mesoporous catalytic materials

In this work, we use pulsed-field gradient (PFG) NMR to probe molecular diffusion of liquids inside mesoporous structures and assess the influence of surface modifications, namely, deposition of palladium (Pd) nanoparticles over alumina (Al2O3) surfaces and passivation of titania (TiO2) surfaces with alkyl chains, on the diffusion pattern

Auswirkungen von Bewirtschaftungsmaßnahmen auf die Treibhausgasemissionen eines kleiüberdeckten Niedermoores

Für die klassische landwirtschaftliche Nutzung von Moorflächen ist die Entwässerung unerlässlich, verursacht aber Emissionen der Treibhausgase (THG) Kohlendioxid (CO2) und Lachgas (N2O). THG-Emissionen aus "echten" Torfböden sind hinsichtlich der Auswirkungen von Hydrologie und Bewirtschaftung gut untersucht, aber es gibt wenig Daten zu THG-Emissionen von überdeckten organischen Böden. Die Mineralbodenhorizonte können entweder anthropogen Ursprungs sein oder sind, z.B. durch die Ablagerung von fluviatilen oder marinen Sedimenten natürlich entstanden. Überdeckte Moorstandorte sind in Nordwestdeutschland und anderen Regionen mit intensiv genutzten Torfgebieten oder (ehemaliger) Überflutungsdynamik weit verbreitet. Hier wollen wir die Auswirkungen der Bewirtschaftung, des Wasserstandes und der Eigenschaften der Kleiauflage auf die Emissionen von CO2, N2O und Methan (CH4) quantifizieren. Das Untersuchungsgebiet wird als Intensivgrünland genutzt (4 bis 5 Schnitte pro Jahr, N-Düngung von 112 bis 157 kg/ha a) und künstlich entwässert. Der Niedermoortorf mit einer Mächtigkeit von 0,6 bis 1,50 m ist mit Klei überdeckt. Es wurden sechs Messstandorte ausgewählt, welche für das Gebiet typische Bedingungen repräsentieren. Die Standorte unterscheiden sich im Gehalt des organischen Bodenkohlenstoffes (SOC) der Kleiauflage (4 – 1 % SOC), im Auftreten eines Pflughorizontes sowie der Entwässerung und der Bewirtschaftung. Wir verwenden manuelle Hauben zur Messung von CO2-, CH4- und N2O-Flüssen. Ganztägige CO2-Messkampagnen mit transparenten und nicht-transparenten Hauben finden je nach Jahreszeit jede dritte oder vierte Woche statt. Gasproben für die Messung der CH4 und N2O-Flüsse werden alle zwei Wochen und zusätzlich am ersten, dritten und siebten Tag nach Düngeranwendung genommen und gaschromatographisch analysiert. Erste Ergebnisse zeigen aufgrund des niedrigen Grundwasserspiegels sehr geringe CH4-Flüsse. Kumulierte N2O-Emissionen spiegeln vor allem die unterschiedlichen Düngergaben wieder, obwohl es im bisherigen Messzeitraum selten N2O-Peaks direkt nach der Düngerapplikation gab. Dies ist wahrscheinlich durch die geringe Bodenfeuchte zu erklären. Hochgerechnet von den Daten der ersten sechs Monaten zeigte sich, dass die N2O-Emissionen des kleiüberdeckten Niedermoores gleiche Größenordnungen wie die Emissionen von „echten“ Torfböden mit vergleichbarer N-Düngung erreichen. Die Ergebnisse der CO2-Messungen des ersten Jahres werden ebenfalls präsentiert werden

Explicit modeling of volatile organic compounds partitioning in the atmospheric aqueous phase

The gas phase oxidation of organic species is a multigenerational process involving a large number of secondary compounds. Most secondary organic species are water-soluble multifunctional oxygenated molecules. The fully explicit chemical mechanism GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere) is used to describe the oxidation of organics in the gas phase and their mass transfer to the aqueous phase. The oxidation of three hydrocarbons of atmospheric interest (isoprene, octane and α-pinene) is investigated for various NOx conditions. The simulated oxidative trajectories are examined in a new two dimensional space defined by the mean oxidation state and the solubility. The amount of dissolved organic matter was found to be very low (yield less than 2% on carbon atom basis) under a water content typical of deliquescent aerosols. For cloud water content, 50% (isoprene oxidation) to 70% (octane oxidation) of the carbon atoms are found in the aqueous phase after the removal of the parent hydrocarbons for low NOx conditions. For high NOx conditions, this ratio is only 5% in the isoprene oxidation case, but remains large for α-pinene and octane oxidation cases (40% and 60%, respectively). Although the model does not yet include chemical reactions in the aqueous phase, much of this dissolved organic matter should be processed in cloud drops and modify both oxidation rates and the speciation of organic species

Explicit modeling of volatile organic compounds partitioning in the atmospheric aqueous phase

The gas phase oxidation of organic species is a multigenerational process involving a large number of secondary compounds. Most secondary organic species are water-soluble multifunctional oxygenated molecules. The fully explicit chemical mechanism GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere) is used to describe the oxidation of organics in the gas phase and their mass transfer to the aqueous phase. The oxidation of three hydrocarbons of atmospheric interest (isoprene, octane and α-pinene) is investigated for various NOx conditions. The simulated oxidative trajectories are examined in a new two dimensional space defined by the mean oxidation state and the solubility. The amount of dissolved organic matter was found to be very low (yield less than 2% on carbon atom basis) under a water content typical of deliquescent aerosols. For cloud water content, 50% (isoprene oxidation) to 70% (octane oxidation) of the carbon atoms are found in the aqueous phase after the removal of the parent hydrocarbons for low NOx conditions. For high NOx conditions, this ratio is only 5% in the isoprene oxidation case, but remains large for α-pinene and octane oxidation cases (40% and 60%, respectively). Although the model does not yet include chemical reactions in the aqueous phase, much of this dissolved organic matter should be processed in cloud drops and modify both oxidation rates and the speciation of organic species