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

Abstract

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 oxidation capacity and O3 formation in the region. Oxygenated VOCs (OVOCs) played an essential role in the ROx primary 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.

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

“…Tai were substantially lower than those derived from most of the ground-level sites over China, such as Beijing (Liu et al, 2012;Yang et al, 2018), Wuhan (Lu et al, 2017), Chengdu (Tan et al, 2018), Hong Kong (Xue et al, 2016;Z. Li et al, 2018), and a rural site in the Yellow River Delta region (Chen et al, 2020). Note that most of these previous studies were based on modeling of the polluted photochemical episodes, but the modeled highest RO x production rates at Mt.…”

“…However, the contributions of the individual surface types to ambient HONO formation have not been figured out. Most previous studies have suggested the dominance of the ground surface in heterogeneous HONO formation at the ground level (Alicke et al, 2003;Elshorbany et al, 2009;Ziemba et al, 2010), while some studies have argued that aerosol surface may also play an important role (Colussi et al, 2013;Liu et al, 2014;Tong et al, 2016;Lu et al, 2018)…”

Source Apportionment of Regional Ozone Pollution Observed at Mount Tai, North China: Application of Lagrangian Photochemical Trajectory Model and Implications for Control Policy

“…The applied homogeneous chemical mechanism was the state-of-the-art MCM version 3.3.1 (MCMv3.3.1; http://mcm.leeds.ac.uk/MCM/; Jenkin et al, 2003;Saunders et al, 2003), which near-explicitly describes the reactions of 143 VOC species and has been widely used to reproduce the nonlinear chemistry between O 3 and its precursors in the atmosphere (Chen et al, 2020;Xue, Wang, Gao, et al, 2014). In addition to homogeneous chemistry, heterogeneous chemistry including N 2 O 5 hydrolysis, HO 2 loss on aerosols, and HONO formation from NO 2 surface reactions were also considered in this model (Xue et al, 2016;Xue, Wang, Gao, et al, 2014).…”

“…Several studies have examined O 3 pollution characteristics, formation regimes, and source apportionment (Wang, Xue, et al, 2017;and references therein). In summer, high O 3 episodes (defined in this study as a maximum daily 8-h average O 3 mixing ratio (MDA8 O 3 ) that exceeds 75 ppbv) have occurred frequently in various environments covering urban, suburban, rural, and mountainous sites (Chen et al, 2020;Lyu et al, 2019;Ma et al, 2019;Sun et al, 2016;Wei et al, 2015;Zong et al, 2018). The maximum hourly O 3 concentration at a rural site downwind of Beijing reached as high as 286 ppbv in June-July 2005 (Wang et al, 2006) and long-term trend analyses have confirmed the rapid increase of regional O 3 concentrations (Sun et al, 2016(Sun et al, , 2019Xu et al, 2020).…”

“…Specifically, 0-D models generally adopt detailed chemical mechanisms but only consider chemical processes, with little to no consideration of important physical processes, such as vertical and horizontal transport. As a result, 0-D models can reproduce the in situ chemistry of O 3 but their applications are largely limited by their small spatial representativeness (Chen et al, 2020;Ling et al, 2014;Lyu et al, 2016;Xue, Wang, Gao, et al, 2014). In comparison, 3-D models incorporate meteorological fields and can track O 3 sources at different spatial scales.…”