Uptake of Cl and Br by organic surfaces—A perspective on organic aerosols processing by tropospheric oxidants

Abstract

The reactive uptake of Cl and Br atoms by closely packed organic thin films was studied in a flow reactor. For Cl, the reactive uptake coefficient, γ, was near collision rate for alkane and alkene surfaces. For Br, γ =(3±1)×10 −2 for alkane and γ=(5±2)×10 −2 for alkene surfaces. The processing of the surface was monitored using FTIR, XPS and contact angle measurements. Oxidized surface‐bound products and a concurrent increase in hydrophilicity were observed. The probability of a reactive collision between Br, Cl, O(³P), O 3 and NO 3 and surface‐bound organics is compared with that of comparable gas‐phase reactions, showing that reactions with a high activation energy in the gas‐phase have an enhanced surface reaction probability. The uptake coefficients for these tropospheric oxidants are used to estimate the processing time for an organic coated aerosol.