Evidence of heterogeneous HONO formation from aerosols and the regional photochemical impact of this HONO source

Lu, Xingcheng; Wang, Yuhang; Li, Jianfeng; Shen, Lu; Fung, Jimmy Chi Hung

doi:10.1088/1748-9326/aae492

Cited by 36 publications

(40 citation statements)

References 58 publications

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“…The abundance of other gaseous acids and bases affected the efficiency of HONO collection by AIM due to the relationship between Henry's law constant and pH. This measurement method and its details have been successfully evaluated in many field studies (Markovic et al, 2012;Wang et al, 2019;Yang et al, 2020), as shown in the Supplement. In addition, a QXZ1.0 automatic weather station (Yigu Technologies, China) was used for the synchronous observation of meteorological parameters, including temperature (T ), RH, wind direction (WD), and wind speed (WS).…”

Section: Instrumentsmentioning

confidence: 99%

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Characteristics, sources, and reactions of nitrous acid during winter at an urban site in the Central Plains Economic Region in China

et al. 2020

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Abstract. Nitrous acid (HONO) in the core city of the Central Plains Economic Region in China was measured using an ambient ion monitor from 9 to 31 January 2019. Measurement time intervals were classified into the following periods in accordance with the daily mean values of PM2.5: clean days (CDs), polluted days (PDs), and severely polluted days (SPDs). The HONO concentrations during CD, PD, and SPD periods were 1.2, 2.3, and 3.7 ppbv, respectively. The contributions of the homogeneous reaction, heterogeneous conversion, and direct emissions to HONO sources varied under different pollution levels. The mean values of the net HONO production of the homogeneous reaction (POH+NOnet) in CD, PD, and SPD periods were 0.13, 0.26, and 0.56 ppbv h−1, respectively. The average conversions of NO2 (CHONO) in CD, PD, and SPD periods were 0.72×10-2, 0.64×10-2, and 1.54×10-2 h−1, respectively, indicating that the heterogeneous conversion of NO2 was less important than the homogeneous reaction. Furthermore, the net production of the homogeneous reaction may have been the main factor in the increase of HONO under high-NOx conditions (i.e., when the concentration of NO was higher than that of NO2) at nighttime. Daytime HONO budget analysis showed that the mean values of the unknown source (Punknown) during CD, PD, and SPD periods were 0.26, 0.40, and 1.83 ppbv h−1, respectively. The values of POH+NOnet, CHONO, and Punknown in the SPDs period were comparatively larger than those in other periods, indicating that HONO participated in many reactions. The proportions of nighttime HONO sources also changed during the entire sampling period. Direct emissions and a heterogeneous reaction controlled HONO production in the first half of the night and provided a contribution that is larger than that of the homogeneous reaction. The proportion of homogenization gradually increased in the second half of the night due to the steady increase in NO concentrations. The hourly level of HONO abatement pathways, except for OH + HONO, was at least 0.22 ppbv h−1 in the SPDs period. The cumulative frequency distribution of the HONOemission∕HONO ratio (less than 20 %) was approximately 77 %, which suggested that direct emission was not important. The heterogeneous HONO production increased when the relative humidity (RH) increased, but it decreased when RH increased further. The average HONO∕NOx ratio (4.9 %) was more than twice the assumed globally averaged value (2.0 %).

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Section: Instrumentsmentioning

confidence: 99%

“…The present analysis simplified this process by treating the ground and aerosol surfaces in the same way. The uptake co-efficient is mainly dependent on the surface characteristics, e.g., surface type and moisture (Lu et al, 2018).…”

Section: Heterogeneous Conversion Of No 2 To Honomentioning

confidence: 99%

Characteristics, sources, and reactions of nitrous acid during winter at an urban site in the Central Plains Economic Region in China

et al. 2020

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“…(1). However, the field observations in the last decade have indicated that the [HONO] PSS can only account for a small portion of the measured concentrations in a variety of environments (Kleffmann et al, 2005;Zhou et al, 2007;Michoud et al, 2014), suggesting the action of additional daytime HONO sources. To explain the observed HONO levels, some new formation mechanisms have been proposed and tested in the lab or through field studies (Bejan et al, 2006;Monge et al, 2010;Su et al, 2011;Li et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Sources of nitrous acid (HONO) in the upper boundary layer and lower free troposphere of the North China Plain: insights from the Mount Tai Observatory

Jiang

Xue

et al. 2020

Atmos. Chem. Phys.

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Abstract. Nitrous acid (HONO) is a significant precursor of atmospheric “detergent” OH radicals and plays a vital role in tropospheric chemistry. The current knowledge about daytime HONO sources is incomplete, and its impact on the tropospheric radical chemistry has not been fully quantified. Existing observational studies of HONO were mostly conducted at the surface, with few efforts focusing on the high-elevation atmosphere. In order to better understand the characteristics and sources of HONO in the upper boundary layer and lower free troposphere, two intensive field observations were carried out at the summit of Mt. Tai (1534 m a.s.l.), the peak of the North China Plain (NCP), in winter 2017 and spring 2018. HONO showed moderate concentration levels (average ± standard deviation: 0.15±0.15 and 0.13±0.15 ppbv), with maximum values of 1.14 and 3.23 ppbv in winter and spring, respectively. Diurnal variation patterns with broad noontime maxima and lower nighttime concentrations were observed during both campaigns, which is distinct from most of the previous studies at the ground level. The Lagrangian particle dispersion model (LPDM, WRF-FLEXPART v3.3) simulations indicated the combined effects of the planetary boundary layer evolution and valley breeze on the daytime HONO peak. A photostationary state (PSS) analysis suggested a strong unknown daytime HONO source with production rates of 0.45±0.25 ppb h−1 in winter and 0.64±0.49 ppb h−1 in spring. Correlation analysis supported the important role of photo-enhanced heterogeneous conversion of NO2 to HONO on the aerosol surface at this high-elevation site. HONO photolysis is the predominant primary source of OH radical and plays a major role in the radical chemistry at Mt. Tai. The model only considering a homogenous HONO source predicted much lower levels of the HOx radicals and atmospheric oxidation capacity than the model constrained with measured HONO data. This study sheds light on the characteristics, sources, chemistry, and impacts of HONO in the upper boundary layer and lower free troposphere in the NCP region.

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“…HONO in both clean and haze periods shows a distinct diel pattern, with a large decrease in the morning from loss through photolysis and a minimum in the afternoon; a large increase in HONO concentration overnight probably originates from heterogeneous sources (i.e. NO2 converting to 305 HONO on humid surfaces) (Finlayson-Pitts et al, 2003;Lee et al, 2015;Li et al, 2012;Lu et al, 2018;Zhang et al, 2016b;Zhou et al, 2003). The HONO concentration was a factor of 3 higher on average during haze periods at midday than during the clearer periods.…”

Section: Chemical and Meteorological Conditionsmentioning

confidence: 97%

Elevated levels of OH observed in haze events during wintertime in central Beijing

Slater¹,

Whalley²,

Woodward-Massey³

et al. 2020

Preprint

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Abstract. Wintertime in situ measurements of OH, HO2 and RO2 radicals and OH reactivity were made in central Beijing during November and December 2016. Exceptionally elevated NO was observed on occasions, up to ~ 250 ppbv, believed to be the highest mole fraction for which there have then co-located radical observations. The daily maximum mixing ratios for radical species varied significantly day-to-day over the range 1–8 × 106 cm−3 (OH), 0.2–1.5 × 108 cm−3 (HO2) and 0.3–2.5 × 108 cm−3 (RO2). Averaged over the full observation period, the mean daytime peak in radicals was 2.7 × 106 cm−3, 0.39 × 108 cm−3 and 0.88 × 108 cm−3 for OH, HO2 and total RO2, respectively. The main daytime source of new radicals via initiation processes (primary production) was the photolysis of HONO (~ 83 %), and the dominant termination pathways were the reactions of OH with NO and NO2, particularly under polluted, haze conditions. The Master Chemical Mechanism (MCM) v3.3.1 operating within a box model was used to simulate the concentrations of OH, HO2 and RO2. The model underpredicted OH, HO2 and RO2, especially when NO mixing ratios were high (above 6 ppbv). The observation-to-model ratio of OH, HO2 and RO2 increased from ~ 1 (for all radicals) at 3 ppbv of NO to a factor of ~ 3, ~ 20 and ~ 91 for OH, HO2 and RO2, respectively, at ~ 200 ppbv of NO. The significant underprediction of radical concentrations by the MCM suggests a deficiency in the representation of gas-phase chemistry at high NOx. The OH concentrations were surprisingly similar (within 20 % during the day) inside and outside of haze events, despite j(O1D) decreasing by 50 % during haze periods. These observations provide strong evidence that gas-phase oxidation by OH can continue to generate secondary pollutants even under high pollution episodes, despite the reduction in photolysis rates within haze.

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Evidence of heterogeneous HONO formation from aerosols and the regional photochemical impact of this HONO source

Cited by 36 publications

References 58 publications

Characteristics, sources, and reactions of nitrous acid during winter at an urban site in the Central Plains Economic Region in China

Characteristics, sources, and reactions of nitrous acid during winter at an urban site in the Central Plains Economic Region in China

Sources of nitrous acid (HONO) in the upper boundary layer and lower free troposphere of the North China Plain: insights from the Mount Tai Observatory

Elevated levels of OH observed in haze events during wintertime in central Beijing

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