ROx Budgets and O3 Formation during Summertime at Xianghe Suburban Site in the North China Plain

Abstract

Photochemical smog characterized by high concentrations of ozone (O 3 ) is a serious air pollution issue in the North China Plain (NCP) region, especially in summer and autumn. For this study, measurements of O 3 , nitrogen oxides (NO x ), volatile organic compounds (VOCs), carbon monoxide (CO), nitrous acid (HONO), and a number of key physical parameters were taken at a suburban site, Xianghe, in the NCP region during the summer of 2018 in order to better understand the photochemical processes leading to O 3 formation and find an optimal way to control O 3 pollution. Here, the radical chemistry and O 3 photochemical budget based on measurement data from 1−23 July using a chemical box model is investigated. The daytime (0600−1800 LST) average production rate of the primary radicals referred to as RO x (OH + HO 2 + RO 2 ) is 3.9 ppbv h −1 . HONO photolysis is the largest primary RO x source (41%). Reaction of NO 2 + OH is the largest contributor to radical termination (41%), followed by reactions of RO 2 + NO 2 (26%). The average diurnal maximum O 3 production and loss rates are 32.9 ppbv h −1 and 4.3 ppbv h −1 , respectively. Sensitivity tests without the HONO constraint lead to decreases in daytime average primary RO x production by 55% and O 3 photochemical production by 42%, highlighting the importance of accurate HONO measurements when quantifying the RO x budget and O 3 photochemical production. Considering heterogeneous reactions of trace gases and radicals on aerosols, aerosol uptake of HO 2 contributes 11% to RO x sink, and the daytime average O 3 photochemical production decreases by 14%. The O 3 -NO x -VOCs sensitivity shows that the O 3 production at Xianghe during the investigation period is mainly controlled by VOCs.

Probing Into Ozone Production Through Photochemistry of Organic Peroxyl Radicals: Implications for Source Control

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O3-precursor relationship over multiple patterns of time scale: A case study in Zibo, Shandong Province, China

“…Nevertheless, due to the measurement limitation in our field campaign, we are unable to measure some important atmospheric species (i.e., HONO and oxygenated VOC (OVOC)), and these may arise uncertainty in box model simulation. For instance, Xue et al, (2021) performed a sensitivity test for HONO constraint in their box model simulation, and they showed that without HONO constraint would lead to O3 photochemical production rate decreasing by 42%. More recently, Wang et al, (2022) obtained a comprehensive VOC dataset at Guangzhou, and their results showed that box model simulation without OVOCs constraints would underestimate the productions of ROx and O3.…”

A Machine-Learning-Based Classification Method for Meteorological Conditions of Ozone Pollution

“…Due to accelerated urbanization and industrialization, as well as the rapid increase in the volume of traffic, surface ozone pollution has occurred frequently in China in recent years, especially during warm seasons. O3 has gradually become a primary pollutant in the atmosphere (Wang et al, 2019a;Shu et al, 2019;Xu et al, 2021;Li et al, 2021). As one of the most important detection method to provide both surface ozone and vertical ozone structure, ozonesonde has been successfully developed by Chinese scholars and used to conduct long-term observation at local site (Zhang et al, 2014(Zhang et al, , 2021.…”