Description: Das Projekt "Heterogeneous Chemistry of Atmospheric Radicals Nitrate Radical and Sea Salts (HECAR)" wird vom Umweltbundesamt gefördert und von Universität-Gesamthochschule Essen, Fachbereich 8 Chemie, Institut für Physikalische und Theoretische Chemie durchgeführt. General Information: Nitrate radical plays a central role in chemistry of the troposphere. It is a major oxidant at night time. It increases night hydroxyl abundance by initiating hydrocarbon oxidation processes. NO3 is also an important species in initiating radical reactions in cloud droplets and aerosols. Quite recently it was obtained a series of evidences for the fact that the halogens Cl and Br could released from sea-salt aerosols NaCl, NaBr. Two possible sources of active halogen are now discussed in literature (N2O5 and NO3 reactions with sea-salts). In the night, marine boundary layer reactions: NO3 + NaX = NaNO3 + X (1a) NO3 + NaX = NaNO3 +1/2X2 (1b) X = Cl, Br could be even more effective than corresponding reactions with N2O5. In case if reactions (1a,1b) are intensive enough they could sufficiently increase the oxidation potential of the troposphere, since Cl has higher reactivity than NO3. 9The aim of this project is to understand the kinetic mechanism and to get numerical data on the parameters which determine the NO3-to-active-halogen transformation. Different aerosol strates (diluted salt solutions, dry and humidified solid salts of various kinds: powder, grain, single crystals and coherent films) will be studied in order to provide information for successive modelling of wide range of atmospheric situations and scenarios. For solutions the salt concentrations will vary from 0 to 1M. Uptake coefficients study will be accomplished by other studies of NO3 aqueous phase chemistry represented by Essen group. In frame of this project uptake coefficients and yield of X, X2 from aqueous phase in reactions (1a,1b) will be studied. For more deep understanding of the mechanism of NO3 interaction with solid salts FTI apparatus will be adjusted in Lille to follow the products formed on the surface in course of heterogeneous reactions. Other groups will study the detailed mechanism of reaction (1) for dry/humidified salts. Original methods and modern techniques will be used to follow NO3 consumption and gas products formation. Since the role of water vapor is expected to be significant, a series of experiments with additives of water vapor from 10 (-7) to 10 (-2)Torr. will be carried out. An important part of kinetic mechanism of NO3-X atoms heterogeneous transformation is supposed to be the secondary reactions of halogen atoms with surface. Special attention will be paid to investigating the influence of secondary processes on the primary atoms release. Above stated combination of experimental studies, no doubts, will provide a wide, motivated understanding of the possible role of reaction (1) in the troposphere. Prime Contractor: Universite des Sciences et Technologies de Lille, UFER de Chimie, Laboratoire de Cinetique et Chimie de la Combustion URA-CNRS 876; Villeneuve d'Ascq; France.
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Wolkenbildung ? Bewölkung ? Ufer ? Nitrat ? Brom ? Chlor ? Getreide ? Oxidationsmittel ? Frankreich ? Atmosphärisches Aerosol ? Halogen ? Kohlenwasserstoff ? Spurengas ? Wasserdampf ? Zusatzstoff ? Salz ? Halogenverbindung ? Kind ? Sekundärreaktion ? Stickstoffverbindung ? Szenario ? Aerosol ? Chemie ? Gasförmiger Stoff ? Meeresgewässer ? Daten ? Studie ? Konsum ? Troposphäre ? Oxidation ? Reaktionsmechanismus ? Redoxpotential ? Modellierung ? Chemische Reaktion ? Reaktionskinetik ? Atmosphärenchemie ? Physikalische Größe ? Grenzschicht ? Tageszeitabhängigkeit ? Hydroxylradikal ? Radikal [Chemie] ?
Region: Nordrhein-Westfalen
Bounding boxes: 6.76339° .. 6.76339° x 51.21895° .. 51.21895°
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 1997-09-01 - 1999-08-31
Accessed 1 times.