Heterogeneous chemistry in the troposphere: Experimental approaches and applications to the chemistry of sea salt particles

Abstract

Halogen atoms, particularly chlorine atoms, are well known to be highly reactive and to play a central role in the chemistry of the upper atmosphere. A large potential source of these halogens in the lower atmosphere (troposphere) exists in the form of sea salt particles. A variety of laboratory, ® eld and modelling studies strongly suggests that there are heterogeneous reactions of sea salt particles which generate photochemically active halogen species such as Cl # in marine areas. In addition, there is increasing evidence for a contribution of bromine atoms to tropospheric chemistry in marine regions at high latitudes. We review here brie¯y the potential importance of such halogen reactions and evidence for their role in the chemistry of the troposphere. Studies carried out in this laboratory to elucidate, at a molecular level, the mechanisms of reaction of synthetic sea salt and its components with gases of tropospheric interest are reviewed. Initial results obtained using a new aerosol apparatus recently constructed in this laboratory to study the reactions of aerosol particles above and below the deliquescence point of the salts are also discussed.

Investigation of the formaldehyde differential absorption cross section at high and low spectral resolution in the simulation chamber SAPHIR

“…Multiple reflection cells, however, allow the setup of DOAS measurements with long light paths inside simulation chambers of different sizes (e.g. De Haan et al, 1999;Kleffmann et al, 2006;Schlosser et al, 2006;Bossmeyer, 2006).…”

Ice nucleation from aqueous NaCl droplets with and without marine diatoms

“…They are important for climate, principally due to their role in the atmosphere as a source for highly reactive halogen species in gas phase, liquid phase, and heterogeneous reactions (Vogt et al, 1996;De Haan et al, 1999;Finlayson-Pitts, 2003;Sander et al, 2003). Sea salt aerosol particles can also act as CCN at low supersaturations with respect to liquid water compared with sulfate particles according to Köhler theory and thus, compete for water vapour in warm clouds despite their relatively low particle concentrations in air (Ghan et al, 1998;O'Dowd et al, 1999;Twohy and Anderson, 2008).…”

Production of gas phase NO2 and halogens from the photolysis of thin water films containing nitrate, chloride and bromide ions at room temperature

“…[33][34][35][36][37] The OH radical formed from the O À reaction 58 with H 2 O oxidizes Br À and Cl À to form Br 2 , Cl 2 and BrCl. 30,[59][60][61][62][63][64][65][66][67][68][69][70][71] These reactive halogen gases play a significant role in the chemistry and composition of the marine boundary layer (MBL). 45,[72][73][74][75][76][77][78][79][80][81] In the coastal MBL, the photochemical cycling of chlorine enhances tropospheric ozone, whereas gaseous bromine species cause ozone destruction during polar sunrise in polar regions 75,76,[82][83][84][85] as well as in midlatitudes.…”