Oxidation of urban aromatic atmospheric aerosol can produce cloud condensation nuclei capable of changing the reflectivity and lifetime of clouds. The oxidation of organic film on atmospheric aqueous particles may activate into cloud droplets. To assess the atmospheric importance the chemical lifetime of the organic material to a common atmospheric oxidant (OH radical) must be measured and compared to deposition lifetime of the aerosol (4-10 days). The chemical lifetime will be assessed by measuring the rate of oxidation of a monolayer sourced from photo-oxidation chamber experiments with deuterated toluene (a petrochemical atmospheric pollutant), using neutron reflection and first order kinetics. The generation of deuterated secondary organic aerosol matter in photochemical chamber is novel and comparable to other atmospheric chamber studies. Preliminary studies show great viability.