Wavelength-Resolved Photon Fluxes of Indoor Light Sources: Implications for HO_x Production

摘要

Photochemistry is a largely unconsidered potential source of reactive species such as hydroxyl and peroxy radicals (OH and HO_2, "HO_x") indoors. We present measured wavelength-resolved photon fluxes and distance dependences of indoor light sources including halogen, incandescent, and compact fluorescent lights (CFL) commonly used in residential buildings; fluorescent tubes common in industrial and commercial settings; and sunlight entering buildings through windows. We use these measurements to predict indoor HO_x production rates from the photolysis of nitrous acid (HONO), hydrogen peroxide (H_2O_2), ozone (O_3), formaldehyde (HCHO), and acetaldehyde (CH_3CHO). Our results suggest that while most lamps can photolyze these molecules, only sunlight and fluorescent tubes will be important to room-averaged indoor HO_x levels due to the strong distance dependence of the fluxes from compact bulbs. Under ambient conditions, we predict that sunlight and fluorescent lights will photolyze HONO to form OH at rates of 10~6-10~7 molecules cm~(-3) s~(-1), and that fluorescent lights will photolyze HCHO to form HO_2 at rates of ~10~6 molecules cm~(-3) s~(-1); rates could be 2 orders of magnitude higher under high precursor concentrations. Ozone and H_2O_2 will not be important photochemical OH sources under most conditions, and CH_3CHO will generally increase HO_2 production rates only slightly. We also calculated photolysis rate constants for nitrogen dioxide (NO_2) and nitrate radicals (NO_3) in the presence of the different light sources. Photolysis is not likely an important fete for NO_3 indoors, but NO_2 photolysis could be an important source of indoor O_3.