Unexpectedly High Indoor HONO Concentrations Associated with Photochemical NO₂ Transformation on Glass Windows

Abstract

Nitrous acid (HONO) is an important gaseous pollutant contributing to indoor air pollution because it causes adverse health effects and is the main source of hydroxyl radicals (OH). Here, we present direct measurements of HONO produced through light-induced heterogeneous reactions of NO2 with grime adsorbed on glass window. The uptake coefficients of NO2 [γ­(NO2)] on the glass plates from the kitchen increased markedly from (2.3 ± 0.1) × 10–6 at 0% RH to (4.1 ± 0.5) × 10–6 at 90% RH. We report a significant quantity of daytime HONO produced in the kitchen, compared to the living room and bedroom. Kinetic modeling suggests that phase state and bulk diffusivity play important roles in the NO2 uptake; the best fit to the measured uptake coefficients is obtained with fixed diffusion coefficients. Photon scattering may be occurring at the surface of the films, leading to enhanced photon-excitation rates of polycyclic aromatic hydrocarbons. By taking these effects into account, the results from this study indicate that the HONO yields obtained in this study can explain the missing HONO in the photochemical models describing the indoor air chemistry.

Impacts of Chinese spring festival on household PM 2.5 pollution and blood pressure of rural residents

“…14,15 Apart from only focusing on the concentrations of HAP, "Home-Chem" is becoming an issue in recent studies. 16,17 In indoor, chemical and physical transformations of air pollutants could occur under certain conditions. For example, a latest study found light-induced heterogeneous reactions of NO 2 with grime on glass window could produce HONO.…”

“…While for rural areas which are far from industry sources and have limited motor vehicles, indoor solid fuel burning and/or smoking contributed most to HAP 14,15 . Apart from only focusing on the concentrations of HAP, “Home‐Chem” is becoming an issue in recent studies 16,17 . In indoor, chemical and physical transformations of air pollutants could occur under certain conditions.…”

“…In indoor, chemical and physical transformations of air pollutants could occur under certain conditions. For example, a latest study found light‐induced heterogeneous reactions of NO 2 with grime on glass window could produce HONO 16 . In addition, air pollutants might be more toxic after chemical transformations.…”

Emerging investigator series: chemical and physical properties of organic mixtures on indoor surfaces during HOMEChem

“…This is consistent with a recent study which indicated that organic lm materials collected in a kitchen are highly viscous. 64 The higher viscosity of the intact lm may slow heterogeneous chemistry such as ozone reactions with C]C bonds and heterogeneous NO 2 conversion to HONO. The concentration of ozone in the house was, on average, fairly low: $8 AE 18 ppb.…”

Real‐time molecular characterization of air pollutants in a Hong Kong residence: Implication of indoor source emissions and heterogeneous chemistry

“…However, recent studies discovered the higher‐than‐expected concentrations of hydroxyl radical (OH) in special indoor settings, due primarily to the photolysis of combustion‐related nitrous acid (HONO) 20 and/or terpene‐ozone reactions during cleaning 21 . Besides, the high surface‐to‐volume ratios indoors enhance the possibility and significance of surface reactions, 22,23 accelerating heterogeneous formation of HONO for example 24,25 . Recently, by applying novel tools for studying atmospheric chemistry to indoor chemistry, researchers have made compelling breakthroughs in revealing indoor dynamic source emissions and ozone chemistry 26‐28 .…”