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photocatalytic properties. Other commercial paints are marketed as having such properties. The white paint used in this study is reported
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Heterogeneous surface reactions play a key role in the chemistry of the indoor environment because of the large indoor surface to volume ratio. The presence of photocatalytic material in indoor paints may allow photochemical reactions to occur at wavelengths of light that are present indoors. One such potential reaction is the heterogeneous photoox...
Citations
... Although there was some discussion of the production of VOCs from the binder used in PA paint, reaction products arising from the removal of NO 2 were not discussed. Here we investigate the role of PA paint in renoxification indoors by conducting the same experiments as previously performed with NPA paint 31,32 i.e. illumination of PA paint with nitrate ions deposited on the surface and illumination of PA paint in the presence of NO to allow a direct comparison of the renoxification potential between different paints. As our point is to compare properties of representative commercial indoor paints, no analysis was done of the chemical components in either paint. ...
... The experimental methods have been described fully in our earlier publications 31,32 . Briefly, painted sample substrates (glass slides) were placed into in a ~ 250 mL stainless steel chamber and illuminated from above through a quartz window by a light source of interest. ...
... These were used here as well: a 150 W Xe arc lamp, which simulates solar illumination, and commercially-obtained indoor fluorescent and incandescent bulbs. Their emission spectra are shown in both earlier works 31 www.nature.com/scientificreports/ As the substrate, we used a commercially available paint, Fresh Air from Climasan StoColor (Produktblatt StoColor Climasan Master (sto-sea.com)/last ...
Surface chemistry plays an important role in the indoor environment owing to the large indoor surface to volume ratio. This study explores the photoreactivity of surfaces painted with a photoactive paint in the presence of NOx. Two types of experiments are performed; illumination of painted surfaces with a nitrate deposit and illumination of painted surfaces in the presence of gaseous NO. For both types of experiments, illumination with a fluorescent bulb causes the greatest change in measured gaseous NOx concentrations. Results show that relative humidity and paint composition play an important role in the photoreactivity of indoor painted surfaces. Painted surfaces could contribute to gas-phase oxidant concentrations indoors.
Road dust constitutes a prominent source of anthropogenic particulate matter, making its heterogeneous interactions with common atmospheric gas-phase compounds important. Here, we show that three distinct samples of urban road dust-including dust samples collected from city streets in summer and winter, and an urban park in summer-react with NO2 in the dark, forming NO and surface nitrite. The loss of NO2 ranged from ∼2 to 13% of its gas-phase concentration and scaled with its concentration as well as with the mass of the road dust sample. The uptake of NO2 by the winter dust was ∼4 times greater than that seen from summer street dust, which was in turn greater than that by the park dust. The conversion ratio of NO2 → NO ranged from 0.06 to 0.8 NO produced per NO2 lost and was greatest for the summer park dust. Exposure of the summer road dust to NO2 roughly doubles the concentration of inorganic nitrite anion in the dust but does not produce nitrate. The formation of NO and photolabile nitrite products means that heterogeneous NO x reactions occurring on the surface of road dust in the dark could have wide implications for the oxidative potential of urban areas.
We made intensive measurements of wavelength-resolved spectral irradiance in a test house during the HOMEChem campaign and report diurnal profiles and two-dimensional spatial distribution of photolysis rate constants (J) of several important indoor photolabile gases. Results show that sunlight entering through windows, which was the dominant source of ultraviolet (UV) light in this house, led to clear diurnal cycles, and large time- and location-dependent variations in local gas-phase photochemical activity. Local J values of several key indoor gases under direct solar illumination were 1.8–7.4 times larger—and more strongly dependent on time, solar zenith angle, and incident angle of sunlight relative to the window—than under diffuse sunlight. Photolysis rate constants were highly spatially heterogeneous and fast photochemical reactions in the gas phase were generally confined to within tens of cm of the region that were directly sunlit. Opening windows increased UV photon fluxes by 3 times and increased predicted local hydroxyl radical (OH) concentrations in the sunlit region by 4.5 times to 3.2 × 10⁷ molec cm⁻³ due to higher J values and increased contribution from O3 photolysis. These results can be used to improve the treatment of photochemistry in indoor chemistry models and are a valuable resource for future studies that use the publicly available HOMEChem measurements.
