Nitrous acid formation on Zea mays leaves by heterogeneous reaction of nitrogen dioxide in the laboratory

Abstract

Nitrous acid (HONO) is of considerable interest because it is an important precursor of hydroxyl radicals (OH), a key species in atmospheric chemistry. HONO sources are still not well understood, and air quality models fail to predict OH as well as HONO mixing ratios. As there is little knowledge about the potential contribution of plant surfaces to HONO emission, this laboratory work investigated HONO formation by heterogeneous reaction of NO2 on Zea mays. Experiments were carried out in a flow tube reactor; HONO, NO2 and NO were measured online with a Long Path Absorption Photometer (LOPAP) and a NOx analyzer. Tests were performed on leaves under different conditions of relative humidity (5 to 58 %), NO2 mixing ratio representing suburban to urban areas (10 to 80 ppbv), spectral irradiance (0 to 20 W m-2) and temperature (288 to 313 K). Additional tests on plant wax extracts from Zea mays leaves showed that this component can contribute to the observed HONO formation. Temperature and NO2 mixing ratios were the two environmental parameters that showed substantially increased HONO emissions from Zea mays leaves. The highest HONO emission rates on Zea mays leaves were observed at 313 K for 40 ppbv of NO2 and 40% RH and reached values of (5.6 ± 0.8) × 10 9 molecules cm-2 s-1. Assuming a mixing layer of 300 m, the HONO flux from Zea mays leaves was estimated to be 171 ± 23 pptv h-1 during summertime, which is comparable to what has been reported for soil surfaces.

Atmospheric Measurements at the Foot and the Summit of Mt. Tai – Part I: HONO Formation and Its Role in the Oxidizing Capacity of the Upper Boundary Layer

“…The impact could be achieved through: 1) the air mass ascending by valley breeze upslope wind (daytime) and by the north wind (daytime and night-time, Section 3.2.2.3), and 2) HONO formation during the air mass ascending process, i.e., HONO formation through the NO2 heterogeneous uptake on the mountain slope surfaces (George et al, 2005;Marion et al, 2021;Stemmler et al, 2006). The HONO production from the above processes was defined as P(HONO)transport and will be discussed in Section 3.6.…”

“…In the past two decades, atmospheric nitrous acid (HONO) has attracted numerous laboratory experiments and field campaigns because of its significant contribution to the atmospheric concentration of hydroxyl radicals (OH) and the incomplete understanding of its sources (Kleffmann, 2007). Besides the homogeneous reaction of NO with OH, various HONO formation pathways were proposed, including: a) emission from combustion processes, e.g., vehicle exhaust, domestic conbustion and biomass burning (Klosterköther et al, 2021;Kramer et al, 2020;Kurtenbach et al, 2001;Liu et al, 2017;Peng et al, 2020;Theys et al, 2020); b) heterogeneous dark and photosensitized reactions of NO2 on surfaces such as soot (Ammann et al, 1998;Monge et al, 2010), organic compounds (George et al, 2005;Han et al, 2017;Stemmler et al, 2006Stemmler et al, , 2007, acids (Kleffmann et al, 1998), urban grime (Liu et al, 2019a), MgO (Ma et al, 2017), mineral dust (Ndour et al, 2008), vegetation leaves (Marion et al, 2021), etc. ; c) photolytic reactions of total nitrate (particulate nitrate and adsorbed nitric acid) (Bao et al, 2018;Laufs and Kleffmann, 2016;Ye et al, 2016;Zhou et al, 2003Zhou et al, , 2011 and ortho-nitrophenols (Bejan et al, 2006); d) emissions https://doi.org/10.5194/acp-2021-529 Preprint.…”

Atmospheric measurements at Mt. Tai – Part I: HONO formation and its role in the oxidizing capacity of the upper boundary layer

“…In the past 2 decades, atmospheric nitrous acid (HONO) has attracted numerous laboratory experiments and field campaigns because of its significant contribution to the production of hydroxyl radicals (OH) and the incomplete understanding of its sources (Kleffmann, 2007). Besides the homogeneous reaction of NO with OH, various HONO formation pathways were proposed, including (a) emissions from combustion processes, e.g., vehicle exhaust, domestic combustion and biomass burning (Klosterköther et al, 2021;Kramer et al, 2020;Kurtenbach et al, 2001;Liu et al, 2017;Peng et al, 2020;Theys et al, 2020); (b) dark and photosensitized heterogeneous reactions of NO 2 on surfaces, such as soot (Ammann et al, 1998;Monge et al, 2010), organic compounds (George et al, 2005;Han et al, 2017;Stemmler et al, 2006Stemmler et al, , 2007, acids (Kleffmann et al, 1998), urban grime (J. , MgO (Ma et al, 2017), mineral dust (Ndour et al, 2008), and vegetation leaves (Marion et al, 2021); (c) photolytic reactions of total nitrate (particulate nitrate and adsorbed nitric acid) (Bao et al, 2018;Laufs and Kleffmann, 2016;Ye et al, 2016;Zhou et al, 2003Zhou et al, , 2011 and ortho-nitrophenols (Bejan et al, 2006); and (d) emissions from soil (Donaldson et al, 2014;Oswald et al, 2013;Su et al, 2011;Xue et al, 2019a). Though many potential HONO sources have been identified in the past, there is still a significant gap between model results and observations (Fu et al, 2019;Liu et al, 2017;Xue et al, 2020;Zhang et al, 2019a, b).…”

Amplified role of potential HONO sources in O<sub>3</sub> formation in North China Plain during autumn haze aggravating processes

“…The reaction of nitric oxide (NO) with OH (Pagsberg et al, 1997;Stuhl and Niki, 1972) is usually thought to be the dominant homogeneous reaction and is significant during daytime, but may be neglected at night due to low OH concentrations, other minor homogeneous HONO sources including nucleation of NO 2 , H 2 O, and NH 3 (Zhang and Tao, 2010), via the photolysis of orthonitrophenols (Bejan et al, 2006;Chen et al, 2021;Lee et al, 2016), via the electronically excited NO 2 and H 2 O (Crowley and Carl, 1997;Dillon and Crowley, 2018;Li et al, 2008) and via HO 2 q H 2 O + NO 2 reaction (Li et al, 2015(Li et al, , 2014Ye et al, 2015). The heterogeneous reactions mainly include nitrogen dioxide (NO 2 ) hydrolysis and reduction reactions on various humid surfaces (Finlayson-Pitts et al, 2003;Ge et al, 2019;Gómez Alvarez et al, 2014;Ma et al, 2013;Marion et al, 2021;Sakamaki et al, 1983;Tang et al, 2017; and nitrate photolysis (Phot nitrate ) (Romer et al, 2018;Ye et al, 2016a, b;Zhou et al, 2003), and are usually considered the main contributors to HONO concentrations in the atmosphere. Among these potential HONO sources, the photolysis of nitrate to produce HONO in the atmosphere has received extensive attention over the past few years, and the Phot nitrate frequency (J nitrate ) is still debated (Gen et al., 2022).…”