Enhanced photochemical conversion of NO2 to HONO on humic acids in the presence of benzophenone

Han, Chong; Yang, Wenjun; Yang, He; Xue, Xiangxin

doi:10.1016/j.envpol.2017.08.107

Cited by 27 publications

(26 citation statements)

References 66 publications

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“…OH initiates daytime photochemistry and promotes the formation of secondary products (including ozone, O 3 , and peroxyacetyl nitrate, PAN) and secondary aerosols (Alicke et al, 2002;Tang et al, 2015;Kleffmann, 2007;An et al, 2012). In addition, HONO as a nitrosating agent forms carcinogenic nitrosamines (Hanst et al, 1977;Pitts et al, 1978), and its health effects have attracted increasing amounts of concern (Sleiman et al, 2010;Bartolomei et al, 2015;Gómez Alvarez et al, 2014).…”

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confidence: 99%

High-resolution vertical distribution and sources of HONO and NO2 in the nocturnal boundary layer in urban Beijing, China

et al. 2020

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Abstract. Nitrous acid (HONO), an important precursor of the hydroxyl radical (OH), plays a key role in atmospheric chemistry, but its sources are still debated. The production of HONO on aerosol surfaces or on ground surfaces in nocturnal atmospheres remains controversial. The vertical profile provides vertical information on HONO and NO2 to understand the nocturnal HONO production and loss. In this study, we report the first high-resolution (<2.5 m) nocturnal vertical profiles of HONO and NO2 measured from in situ instruments on a movable container that was lifted on the side wiring of a 325 m meteorological tower in Beijing, China. High-resolution vertical profiles revealed the negative gradients of HONO and NO2 in nocturnal boundary layers, and a shallow inversion layer affected the vertical distribution of HONO. The vertical distribution of HONO was consistent with stratification and layering in the nocturnal urban atmosphere below 250 m. The increase in the HONO ∕ NO2 ratio was observed throughout the column from the clean episode to the haze episode, and relatively constant HONO∕NO2 ratios in the residual layer were observed during the haze episode. Direct HONO emissions from traffic contributed 29.3 % ± 12.4 % to the ambient HONO concentrations at night. The ground surface dominates HONO production by heterogeneous uptake of NO2 during clean episodes. In contrast, the HONO production on aerosol surfaces (30–300 ppt) explained the observed HONO increases (15–368 ppt) in the residual layer, suggesting that the aerosol surface dominates HONO production aloft during haze episodes, while the surface production of HONO and direct emissions into the overlying air are minor contributors. Average dry deposition rates of 0.74±0.31 and 1.55±0.32 ppb h−1 were estimated during the clean and haze episodes, respectively, implying that significant quantities of HONO could be deposited to the ground surface at night. Our results highlight the ever-changing contributions of aerosol and ground surfaces in nocturnal HONO production at different pollution levels and encourage more vertical gradient observations to evaluate the contributions from varied HONO sources.

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confidence: 99%

High-resolution vertical distribution and sources of HONO and NO2 in the nocturnal boundary layer in urban Beijing, China

et al. 2020

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“…It appeared that the unknown HONO sources cannot be well explained by the heterogeneous reactions on wet surfaces alone. Previous studies have suggested that light intensity could be an important parameter influencing the heterogeneous conversion of NO 2 to HONO (Han et al, 2017b;Lee et al, 2016). The photo-enhanced HONO source during the daytime has also been identified in different environments ranging from remote (Villena et al, 2011;Zhou et al, 2002) to urban conditions (Lee et al, 2016).…”

Section: Photo-enhanced Conversion Of Nomentioning

confidence: 98%

“…(3) photosensitized reaction of NO 2 on surfaces of mineral dust (Ndour et al, 2008), humic acid (Han et al, 2017b;Wall and Harris, 2016), and ground surface (i.e., certain reactions such as NO 2 + humic acids on ground surfaces) (Wong et al, 2012), which has been considered as an important daytime HONO source (Lee et al, 2016); 4photolysis of adsorbed nitric acid (HNO 3 ) and nitrate (NO 3 -) (Ye et al, 2016;Ye et al, 2017;Zhou et al, 2002;Zhou et al, 2003;Zhou et al, 2011;Ziemba et al, 2010); (5) VOC-mediated conversion of HNO 3 into HONO https://doi.org/10.5194/acp-2019-944 Preprint. Discussion started: 9 December 2019 c Author(s) 2019.…”

Section: Introductionmentioning

confidence: 99%

Contribution of HONO to the atmospheric oxidation capacity in an industrial zone in the Yangtze River Delta region of China

Zheng¹,

Shi²,

Ma³

et al. 2019

Preprint

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Abstract. A suite of instruments were deployed to simultaneously measure nitrous acid (HONO), nitrogen oxides (NOx = NO + NO2), carbon monoxide (CO), ozone (O3), volatile organic compounds (VOCs, including formaldehyde (HCHO)) and meteorological parameters near a typical industrial zone in Nanjing of the Yangtze River Delta region, China. High levels of HONO were detected using a wet chemistry-based method. HONO ranged from 0.03&#8211;7.04&#8201;ppbv with an average of 1.32&#8201;&#177;&#8201;0.92&#8201;ppbv. Elevated daytime HONO was frequently observed with a minimum of several hundreds of pptv on average, which cannot be explained by the homogeneous OH + NO reaction (POH+NO) alone, especially during periods with high loadings of particulate matters (PM2.5). The HONO chemistry and its impact on atmospheric oxidation capacity in the study area were further investigated using a MCM-box model. The results show that the average hydroxyl radical (OH) production rate was dominated by the photolysis of HONO (7.13&#215;106&#8201;molecules&#8201;cm&#8722;3&#8201;s&#8722;1), followed by ozonolysis of alkenes (3.94&#215;106&#8201;molecules&#8201;cm&#8722;3&#8201;s&#8722;1), photolysis of O3 (2.46&#215;106&#8201;molecules&#8201;cm&#8722;3&#8201;s&#8722;1) and photolysis of HCHO (1.60&#215;106&#8201;molecules&#8201;cm&#8722;3&#8201;s&#8722;1), especially within the plumes originated from the industrial zone. The observed similarity between HONO/NO2 and HONO in diurnal profiles strongly suggests that HONO in the study area was likely originated from NO2 heterogeneous reactions. The average nighttime NO2 to HONO conversion rate was determined to be ~&#8201;0.9&#8201;% hr&#8722;1. Good correlation between nocturnal HONO/NO2 and the products of particle surface area density (S/V) and relative humidity (RH), S/V&#183;RH, supports the heterogeneous NO2/H2O reaction mechanism. The other HONO source, designated as Punknonwn, was about twice as much as POH+NO on average and displayed a diurnal profile with an evidently photo-enhanced feature, i.e., photosensitized reactions of NO2 may be an important daytime HONO source. Nevertheless, our results suggest that daytime HONO formation was mostly due to the light-induced conversion of NO2 on aerosol surfaces but heterogeneous NO2 reactions on ground surface dominated nocturnal HONO production. Concurred elevated HONO and PM2.5 levels strongly indicate that high HONO may increase the atmospheric oxidation capacity and further promote the formation of secondary aerosols, which may in turn synergistically boost NO2/HONO conversion by providing more heterogeneous reaction sites.

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“…As a result, several studies suggested the possibility of HONO being formed by heterogeneous reactions occurring on surfaces. Several laboratory and outdoor studies considered aqueous and dry surfaces as reaction catalysts (Bari et al, 2003;Finlayson-Pitts et al, 2003;Wang et al, 2017;Spataro et al, 2017), including aerosol (Hendrick et al, 2014;Tong et al, 2016;Bernard et al, 2016;Wang et al, 2016;Lu et al, 2018), black carbon (Liang et al, 2017), and humic acid (Han et al, 2017;Yang et al, 2018) (R6~R10). Moreover, the surface includes https://doi.org/10.5194/acp-2019-1012 Preprint.…”

Section: Introductionmentioning

confidence: 99%

“…For these reactions, the measurement of active surface area hinders the accurate estimation of HONO formation (Romer et al, 2016). Recently, the photochemical reaction involving a nitrate series (HNO3, NO3 -) was considered as a major daytime HONO source (Han et al, 2017;Li et al, 2018;Ye et al, 2017;Tsai et al, 2018;Cui et al, 2019). The HONO production reaction is still controversial due to a wide variety of environments involving NOx, RH, and surfaces and incomplete understanding of multi-phase reaction (Bao et al, 2018;Zhang et al, 2019c;Wen et al, 2019;Zhang et al, 2019b).…”

Section: Introductionmentioning

confidence: 99%

The role of HONO in O3 formation and insight into its formation mechanism during the KORUS-AQ Campaign

Gil

Kim

Lee

et al. 2019

Preprint

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Abstract. Photolysis of nitrous acid (HONO) has long been recognized as an early morning source of OH radicals in urban air, but the detailed mechanism of its formation is still unclear. During the Korea-US Air Quality (KORUS-AQ) campaign, HONO was measured using Quantum Cascade Tunable Diode Laser Absorption Spectroscopy (QC-TDLAS) at Olympic Park in Seoul from 17 May to 10 June, 2016. HONO concentrations ranged from 0.07 ppbv to 3.46 ppbv with an average of 0.93 ppbv. HONO remained high at night from 1 am to 5 am, during which the mean concentration was higher in high-O3 episodes (1.82 ppbv) than non-episode (1.20 ppbv). In the morning, OH budget due to HONO photolysis were higher by 50 % (0.95 pptv) during high-O3 episodes compared to non-episode. Diurnal variations of HOx and O3 simulated by the F0AM model demonstrated a difference of ~ 20 ppbv in daily maximum O3 between the two periods. The HONO concentration increased with relative humidity (RH) until 80 %, of which the highest HONO was associated with the top 10 % NOx, confirming that NOx is a crucial precursor of HONO and its formation is facilitated by humidity. The conversion ratio of NOx to HONO was estimated to be 0.86 × 10−2 h−1 at night and also increased with RH. As surrogate for the catalyst surface, the mass concentrations of black carbon (eBC) and the surface areas of particles smaller than 120 nm showed a tendency for RH similar to conversion ratio. Using an Artificial Neuron Network (ANN) model, HONO concentrations were successfully simulated with measured variables (r = 0.8 for the best suite), among which NOx, surface area, and RH were found to be main factors affecting ambient HONO concentrations with weigh values of 26.2 %, 11.9 %, and 10.6 %, respectively. This study demonstrates the coupling of HONO with HOx-VOCs-O3 cycle in Seoul Metropolitan Areas (SMA) and provides practical evidence for heterogeneous formation of HONO by employing the ANN model to atmospheric chemistry.

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Enhanced photochemical conversion of NO2 to HONO on humic acids in the presence of benzophenone

Cited by 27 publications

References 66 publications

High-resolution vertical distribution and sources of HONO and NO<sub>2</sub> in the nocturnal boundary layer in urban Beijing, China

High-resolution vertical distribution and sources of HONO and NO<sub>2</sub> in the nocturnal boundary layer in urban Beijing, China

Contribution of HONO to the atmospheric oxidation capacity in an industrial zone in the Yangtze River Delta region of China

The role of HONO in O<sub>3</sub> formation and insight into its formation mechanism during the KORUS-AQ Campaign

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Enhanced photochemical conversion of NO2 to HONO on humic acids in the presence of benzophenone

Cited by 27 publications

References 66 publications

High-resolution vertical distribution and sources of HONO and NO&lt;sub&gt;2&lt;/sub&gt; in the nocturnal boundary layer in urban Beijing, China

High-resolution vertical distribution and sources of HONO and NO&lt;sub&gt;2&lt;/sub&gt; in the nocturnal boundary layer in urban Beijing, China

Contribution of HONO to the atmospheric oxidation capacity in an industrial zone in the Yangtze River Delta region of China

The role of HONO in O&lt;sub&gt;3&lt;/sub&gt; formation and insight into its formation mechanism during the KORUS-AQ Campaign

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High-resolution vertical distribution and sources of HONO and NO<sub>2</sub> in the nocturnal boundary layer in urban Beijing, China

High-resolution vertical distribution and sources of HONO and NO<sub>2</sub> in the nocturnal boundary layer in urban Beijing, China

The role of HONO in O<sub>3</sub> formation and insight into its formation mechanism during the KORUS-AQ Campaign