Photodissociation of particulate nitrate as a source of daytime tropospheric Cl2

Peng, Xiang; Wang, Tao; Wang, Weihao; Ravishankara, A. R.; George, Christian; Xia, Men; Cai, Min; Li, Qinyi; Salvador, Christian Mark; Lau, C. Y. M.; Lyu, Xiaopu; Poon, C. N.; Mellouki, Abdelwahid; Mu, Yujing; Hallquist, Mattias; Saiz‐Lopez, Alfonso; Guo, Hai; Herrmann, Hartmut; Yu, Chuan; Dai, Jianing; Wang, Yanan; Wang, Xinke; Yu, Alfred L.C.; Leung, Kenneth K. M.; Lee, Shuncheng; Chen, Jianmin

doi:10.1038/s41467-022-28383-9

Cited by 44 publications

(93 citation statements)

References 61 publications

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“…Figure 4 shows the time series of observed OH concentrations, along with the concentrations of other trace gases and the meteorological parameters, during the campaign. The weather conditions during the study featured relatively high temperatures, high relative humidity (RH), and strong solar radiation, consistent with previously reported autumn observations at the same site (Li et al, 2018;Peng et al, 2022). The air temperature ranged from 20°C to 30°C and RH ranged from 40% to 96%.…”

Section: Overview Of Observationssupporting

confidence: 84%

“…The site is surrounded by ocean, vegetation, and scattered country roads (Figure 2) and is around 15 km away from the nearest urban centre. There is no strong anthropogenic emission source in the surrounding area apart from the ocean-going vessels travelling in nearby waters (Peng et al, 2022). Nonetheless, the site does occasionally receive polluted air masses from mainland China, including masses from the highly urbanised PRD region (Li et al, 2018;Peng et al, 2022).…”

Section: The Hok Tsui Supersitementioning

confidence: 99%

“…In this study, the first-order physical loss process, with a 24-hour lifetime for all species, was included in the model to represent physical processes such as advection, deposition, and dilution (Wolfe et al, 2016;(Chen et al, 2022)). The physical loss process has a negligible influence on OH simulation because the OH concentrations are controlled by fast in situ chemistry.…”

Section: Box Modellingmentioning

confidence: 99%

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OH measurements in the coastal atmosphere of South China: missing OH sinks in aged air masses

Zou

Chen²,

Xia³

et al. 2022

Preprint

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Abstract. The hydroxyl radical (OH) is the main oxidant responsible for the removal of many reduced trace gases and the formation of secondary air pollutants. However, due to technical difficulties in measuring OH, the existing measurements of atmospheric OH concentrations are limited, and its sources and sinks are not well understood under low NOx conditions. In this study, we observed the OH concentrations using chemical ionization mass spectrometry at a coastal site in Hong Kong from October to November 2020. The average noontime OH concentration over the study period was measured at 4.9 ± 2.1 × 106 cm-3. We found that a box model with comprehensive observational constraints reproduced the observed daytime OH concentrations when air parcels originated from the continental regions. However, this model overpredicted the observed daytime OH concentrations for coastal air parcels by 73 % on average. Missing OH reactivity is proposed to be the cause of this overprediction. High missing OH reactivity was found in the case of low concentrations of nitrogen oxides (NOx) and volatile organic compounds, as well as in aged air, suggesting that there could be unmeasured chemical species that cause the model to overestimate OH in aged coastal air parcels. Further studies are needed to identify these unmeasured chemical species and their contributions to the OH budget, in order to better quantify the formation of secondary air pollutants.

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Section: Overview Of Observationssupporting

confidence: 84%

Section: The Hok Tsui Supersitementioning

confidence: 99%

Section: Box Modellingmentioning

confidence: 99%

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OH measurements in the coastal atmosphere of South China: missing OH sinks in aged air masses

Zou

Chen²,

Xia³

et al. 2022

Preprint

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“…A recent study during the coal-burning period of winter documented surprisingly high concentrations of bromine chloride (BrCl) and Cl 2 at a site in Wangdu, and calculations from an observation-constrained model indicated that Cl and Br atoms collectively increased the total O x (O 3 + NO 2 ) mixing ratios at this site by 50% [104]. Another very recent study reported unprecedented levels of Cl 2 (up to 1 ppb) at a polluted coastal site of Hong Kong, and such high concentrations of Cl 2 increased O x daytime production by 16% [105]. However, existing CTMs cannot account for observed daytime Cl 2 or BrCl concentrations because they lack appropriate mechanistic and kinetic information.…”

Section: Hono and Photolabile Halogensmentioning

confidence: 97%

Ground-level ozone pollution in China: a synthesis of recent findings on influencing factors and impacts

Wang

Xue

Zhu

et al. 2022

Environ. Res. Lett.

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110

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Ozone (O3) in the troposphere is an air pollutant and a greenhouse gas. In mainland China, after the Air Pollution Prevention and Action Plan was implemented in 2013 – and despite substantial decreases in the concentrations of other air pollutants – ambient O3 concentrations paradoxically increased in many urban areas. The worsening urban O3 pollution has fuelled numerous studies in recent years, which have enriched knowledge about O3-related processes and their impacts. In this article, we synthesise the key findings of over 500 articles on O3 over mainland China that were published in the past six years in English-language journals. We focus on recent changes in O3 concentrations, their meteorological and chemical drivers, complex O3 responses to the drastic decrease in human activities during coronavirus disease 2019 lockdowns, several emerging chemical processes, impacts on crops and trees, and the latest government interventions.

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“…In Hong Kong – an isoprene‐rich area with influence from anthropogenic emissions (Peng et al., 2022 ) – there were two peaks, one during daytime and one during nighttime. The nighttime peak becomes more prevalent if the period with high ONs formation is selected (between 14–25 November, Figure S5 in Supporting Information S1 ).…”

Section: Resultsmentioning

confidence: 99%

A Four Carbon Organonitrate as a Significant Product of Secondary Isoprene Chemistry

Tsiligiannis

Lee

et al. 2022

Geophysical Research Letters

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Oxidation of isoprene by nitrate radicals (NO3) or by hydroxyl radicals (OH) under high NOx conditions forms a substantial amount of organonitrates (ONs). ONs impact NOx concentrations and consequently ozone formation while also contributing to secondary organic aerosol. Here we show that the ONs with the chemical formula C4H7NO5 are a significant fraction of isoprene‐derived ONs, based on chamber experiments and ambient measurements from different sites around the globe. From chamber experiments we found that C4H7NO5 isomers contribute 5%–17% of all measured ONs formed during nighttime and constitute more than 40% of the measured ONs after further daytime oxidation. In ambient measurements C4H7NO5 isomers usually dominate both nighttime and daytime, implying a long residence time compared to C5 ONs which are removed more rapidly. We propose potential nighttime sources and secondary formation pathways, and test them using a box model with an updated isoprene oxidation scheme.

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Photodissociation of particulate nitrate as a source of daytime tropospheric Cl2

Cited by 44 publications

References 61 publications

OH measurements in the coastal atmosphere of South China: missing OH sinks in aged air masses

OH measurements in the coastal atmosphere of South China: missing OH sinks in aged air masses

Ground-level ozone pollution in China: a synthesis of recent findings on influencing factors and impacts

A Four Carbon Organonitrate as a Significant Product of Secondary Isoprene Chemistry

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