Oxidizing capacity of the rural atmosphere in Hong Kong, Southern China

Li, Zeyuan; Xue, Likun; Yang, Xue; Zha, Qiaozhi; Tham, Yee Jun; Yan, Chao; Louie, Peter K.K.; Luk, Connie W.Y.; Wang, Tao; Wang, Wenxing

doi:10.1016/j.scitotenv.2017.08.310

Cited by 82 publications

(78 citation statements)

References 44 publications

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“…The average values in the three cases were 11.65 ± 2.91 s -1 , 13.70 ± 4.60 s -1 and 7.27 ± 1.80 s -1 , 250 respectively. The OH reactivity of Case 3 in the clean environment was significantly lower than that of Case 2 and Case 3, which is consistent with previous studies (Mao et al, 2010;Li et al, 2018). In general, the OH reactivity assessed in Shanghai was in the range of 4.6-28.0 s -1 under different air quality conditions, which was at a relatively low level compared to that calculated for other big cities in China such as Guangzhou (20-30 s -1 ), Chongqing (15-25 s -1 ) and Beijing (15-25 s -1 ) (Tan et al, 2019), reflecting that the abundance of pollutants in Shanghai is relatively lower compared to other metropolitan areas in Total OH reactivity has been measured in many urban areas over the past two decades.…”

Section: Shanghai During (A) Case 1 (B) Case 2 and (C) Casesupporting

confidence: 92%

Observationally constrained modelling of atmospheric oxidation capacity and photochemical reactivity in Shanghai, China

Zhu¹,

Wang²,

Wang³

et al. 2019

Preprint

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An observation-based model coupled to the Master Chemical Mechanism (V3.3.1) and constrained by a full suite of observations was developed to study atmospheric oxidation capacity (AOC), OH reactivity, OH chain length, and HOx (= OH + HO2) budget for three different ozone (O3) concentration levels in Shanghai, China. Five months of observation from 1 May to 30 September 2018 showed that 10 days with ozone as the primary pollutant occurred and the days with good air quality 20 (AQI < 100) accounted for 92.2% during this spring-summer time. The levels of ozone and its precursors, as well as meteorological parameters revealed the significant differences among different ozone levels, indicating that the high level of precursors is the premise of ozone pollution, and strong radiation is an essential driving force. By increasing the input JNO 2 value by 40%, the simulated O3 level increased by 30-40% correspondingly under the same level of precursors. The simulation results show that AOC, dominated by reactions involving OH radical during the daytime, has a positive correlation with ozone 25 levels. The reactions with non-methane volatile organic compounds (NMVOCs) (30%-36%), carbon monoxide (CO) (26%-31%), and nitrogen dioxide (NO2) (21%-29%) dominated the OH reactivity under different ozone levels in Shanghai. Among the NMVOCs, alkenes and oxygenated VOCs (OVOCs) played a key role in OH reactivity defined as the inverse of OH lifetime. A longer OH chain length was found in clean condition primarily due to low NO2 in the atmosphere. The high level of radical precursors (e.g., O3, HONO, and OVOCs) promotes the production and cycling of HOx, and the daytime HOx primary 30 source shifted from the HONO photolysis in the morning to the O3 photolysis in the afternoon. For the sinks of radicals, the reaction with NO2 completely dominated radicals termination during the morning rush hour, while the reactions of radicalradical also contributed to the sinks of HOx in the afternoon. Furthermore, the top four species contributing to ozone formation potential (OFP) were HCHO, toluene, ethylene, and m/p-xylene. The concentration ratio (~23%) of these four species is not proportional to their contribution (~55%) to OFP, implying that controlling key VOC species emission is more effective than 35 https://doi.

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Section: Shanghai During (A) Case 1 (B) Case 2 and (C) Casesupporting

confidence: 92%

Observationally constrained modelling of atmospheric oxidation capacity and photochemical reactivity in Shanghai, China

Zhu¹,

Wang²,

Wang³

et al. 2019

Preprint

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“…The daily maxima and daily mean values of AOC during the selected episodes were in the range of 0.7-1.8×10 8 and 2.6-4.8×10 7 molecules cm -3 s -1 , respectively. AOC levels in the YelRD region are comparable to those obtained in some urban areas (Elshorbany et al, 2009;Xue et al, 2016), but are higher than those derived from rural areas (Geyer et al, 2001;Li et al, 2018). As expected, OH is the predominant oxidant during the daytime, accounting for 85.3±16.4% of AOC.…”

Section: Atmospheric Oxidative Capacity and Radical Chemistrysupporting

confidence: 76%

“…The Observation-Based Model for investigating the Atmospheric Oxidative Capacity and Photochemistry (OBM-AOCP) was used to simulate the in-situ atmospheric photochemical processes and to quantify the O3 production rate, OH reactivity and radical budgets (ROx: OH, HO2 and RO2). This model has been successfully adopted in many previous studies (e.g., Xue et al, 2014a;Xue et al, 2016;Yang et al, 2018;Li et al, 2018;Sun et al, 2018). In short, it is based on the latest version of the Master Chemical Mechanism (MCM v3.3.1), a nearly explicit mechanism describing the gas phase chemical reactions that involve 143 primary VOC species (Saunders et al, 2003).…”

Section: Observation-based Chemical Box Modelmentioning

confidence: 99%

Volatile organic compounds and ozone air pollution in an oil production region in northern China

Chen¹,

Xue²,

Zheng³

et al. 2019

Preprint

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Abstract. Oil and natural gas (O&NG) exploration presents a significant source of atmospheric volatile organic compounds (VOCs), which are central players of tropospheric chemistry and contribute to formations of ozone (O3) and secondary organic aerosols. The impacts of O&NG extraction on regional air quality have been investigated in recent years in North America, but have long been overlooked in China. To assess the impacts of O&NG exploration on tropospheric O3 and regional air quality in China, intensive field observations were conducted during February–March and June–July 2017 in the Yellow River Delta, an oil extraction region in northern China. Very high concentrations of ambient VOCs were observed at a rural site, with the highest alkane mixing ratios reaching 2498 ppbv. High O3 episodes were not encountered during wintertime but were frequently observed in summer. The emission profiles of VOCs from the oil fields were directly measured for the first time in China. The chemical budgets of ROx radicals and O3 were dissected with a detailed chemical box model constrained by in-situ observations. The highly abundant VOCs facilitated strong atmospheric oxidizing capacity and O3 formation in the region. Oxygenated VOCs (OVOCs) played an essential role in the ROx production, OH loss, and radical recycling. Photolysis of OVOCs, O3 and HONO, as well as ozonolysis reactions of unsaturated VOCs were major primary sources of ROx. NOx was the limiting factor of radical recycling and O3 formation. This study underlines the important impacts of O&NG extraction on atmospheric chemistry and regional air quality in China.

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“…As such, the total number of CO and VOC molecules depleted during daytime and nighttime were 2.4×10 12 and 6.1×10 10 , respectively, per cm −3 of air. Such AOC levels were lower than those determined at the Tung Chung air quality monitoring station (Xue et al, 2016) and from a polluted area in Santiago, Chile (Elshorbany et al, 2009), but comparable to that determined at the Hong Kong Polytechnic University's air monitoring station at Hok Tsui (Li et al, 2018).…”

Section: Overall Characteristics Of Aocsupporting

confidence: 48%

Parameterized reactivity of hydroxy radical, ozone, nitrate radical and atmospheric oxidation capacity during summer at a suburban site between Beijing and Tianjin

Yang

Wang

Yao

et al. 2019

Preprint

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Abstract. Hydroxyl (OH) radicals, nitrate (NO3) radicals, and ozone (O3) play central roles in the troposphere because they control the lifetimes of many trace gases that resulted from anthropogenic and biogenic origins. To estimate the self-cleaning capacity of the atmosphere, the reactivities of OH, NO3 and O3 was comprehensively analyzed for the first time based on a parameterization method at a suburban site in Xianghe in the North China Plain from 6 July 2018 to 6 August 2018. The total OH reactivity, ROHtotal, NO3 reactivity, RNO3total, and O3 reactivity, RO3total, at the site varied from 8.5 s−1 to 68.1 s−1, 0.7 s−1 to 27.5 s−1, and 3.3 × 10−4 s−1 to 1.8 × 10−2 s−1 with campaign-averaged values of 25.6 ± 9.7 s−1, 2.2 ± 2.6 s−1 and 1.2 ± 1.7 × 10-3 s−1 (± standard deviation), respectively. NOx (NO + NO2) were by far the main contributors to the ROHtotal, RNO3total and RO3total, with average values of 47, 99 and 99 %, respectively. Isoprene dominated the OH and NO3 reactivity towards TVOCs (ROHTVOCs and RNO3TVOCs), accounting for 40 % and 77 %, respectively. However, alkenes dominated the O3 reactivity towards TVOCs (RO3TVOCs), representing 66 % of RO3total. ROHtotal, RNO3total and RO3total displayed a similar diurnal variation with the lowest during the afternoon and the highest during rush hours, and the diurnal profile of NOx appears to be the major driver for the diurnal profiles of ROHtotal, RNO3total and RO3total. The calculated atmospheric oxidative capacity (AOC) was up to 4.4 × 108 molecules cm−3 s−1 with campaign-averaged values of 3.1 × 107 molecules cm−3 s−1 dominated by OH radicals (2.9 × 107 molecule cm−3 s−1, 95 %), O3 (1.2 × 106 molecule cm−3 s−1, 4 %) and NO3 radicals (1.7 × 105 molecule cm−3 s−1, 1 %). The reaction with OH radicals was the dominant volatile organic compounds (VOCs) loss except for trans-2-butene, cis-2-butene, trans-2-pentene, propylene, 1-butene, 1-pentene, 1-hexene, acetone and styrene, where the reaction with O3 was more important for their loss rates. Compared with anthropogenic hydrocarbons, the oxidation by the NO3 radical was more important for the nighttime integral of isoprene loss rates. Overall, the present study may provide some useful suggestions for VOC pollution control in the Xianghe and North China Plain. To better understanding the trace gas reactivity and AOC, further studies, especially direct observations of the OH and NO3 radical concentrations and their reactivities, are required.

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Oxidizing capacity of the rural atmosphere in Hong Kong, Southern China

Cited by 82 publications

References 44 publications

Observationally constrained modelling of atmospheric oxidation capacity and photochemical reactivity in Shanghai, China

Observationally constrained modelling of atmospheric oxidation capacity and photochemical reactivity in Shanghai, China

Volatile organic compounds and ozone air pollution in an oil production region in northern China

Parameterized reactivity of hydroxy radical, ozone, nitrate radical and atmospheric oxidation capacity during summer at a suburban site between Beijing and Tianjin

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