Assessing indoor gas phase oxidation capacity through real-time measurements of HONO and NO_xin Guangzhou, China

Abstract

The photolysis of nitrous acid (HONO) is the main initiation source of hydroxyl radical (OH) which in turn is the main oxidant controlling the oxidation capacity of the indoor atmosphere.

The atmospheric chemistry of indoor environments

“…215 Although likely proceeding for relatively high NO 2 mixing ratio conditions via the N 2 O 4 intermediate, 214 there is evidence that NO 2 uptake can also proceed via other mechanisms, including either the abstraction of weakly bound H-atoms or electron transfer to form nitrite on electron-rich soot and aromatic surfaces. 216,217 Although HONO is present at high mixing ratios indoors, frequently in the 5 to 10 ppb level or even higher when cooking is occurring, 21,59,218 its heterogeneous reactivity with organic molecules is not well known. For example, one important fate pathway is to react with third-hand smoke constituents, such as nicotine, leading to the formation of carcinogenic condensed-phase nitrosamines.…”

Factors affecting wavelength‐resolved ultraviolet irradiance indoors and their impacts on indoor photochemistry

“…(1) In this study, we used a HONO mixing ratio of 5 ppbv, as frequently observed in multiple indoor environments, 6,12,32,33 NO and NO 2 levels of 17 ppbv and 4 ppbv, respectively, as observed in a residence in Syracuse, NY, over the course of two months (September -November 2018), 6 and an HCHO mixing ratio of 10 ppbv, as observed in the same Syracuse residence in Spring 2018 (Text S2). Note that these are average mixing ratios observed over a period of time; much higher levels of all three nitrogen species were observed during cooking events, 6,27 which could result in higher or lower predicted OH ss concentrations, depending on the relative concentrations of OH sources and sinks.…”

“…Sunlight entering windows has been observed indoors at wavelengths shorter than ~400 nm where HONO photolysis can occur, resulting in OH levels indoors comparable to common outdoor levels. [6][7][8][9][10][11][12][13] Indoor sunlight has also been demonstrated to initiate photolysis of HOCl and Cl 2 , which are released when cleaning with bleach solution. 14,15 Artificial lights including fluorescent, incandescent, and halogen lamps are additional light sources in indoor environments that emit wavelengths short enough to induce photolysis of several chemicals.…”

Development of a Laser-Photofragmentation Laser-Induced Fluorescence instrument for the detection of nitrous acid and hydroxyl radicals in the atmosphere

“…50 HONO is also an important pollutant within the indoor environment. While outdoor mixing ratios during the daytime are typically within the range of tens to hundreds of ppt (Huang et al, 2002;Oswald et al, 2015), and can range from hundreds of ppt up to several ppb at night or during morning rush hour in urban environments (Stutz et al, 2010;Young et al, 2012;Xu et al, 2015;Lee et al, 2016), indoor HONO measurements have shown background levels of several ppb, and elevated mixing ratios as high as 20-90 ppb during cooking or other combustion events (Brauer et al, 1990;Vecera and Dasgupta, 1994;Zhou et al, 2018;Liu et al, 2019;Wang 55 et al, 2020a). In two studies, average outdoor mixing ratios were 0.9 and 0.3 ppb compared to 4.6 and 4.0 ppb in nearby suburban homes (Leaderer et al, 1999;Lee et al, 2002).…”