Assessing the Ratios of Formaldehyde and Glyoxal to NO₂ as Indicators of O₃–NO_x–VOC Sensitivity

Abstract

Ozone (O3) pollution has a negative effect on the public health and crop yields. Accurate diagnosis of O3 production sensitivity and targeted reduction of O3 precursors [i.e., nitrogen oxides (NO x ) or volatile organic compounds (VOCs)] are effective for mitigating O3 pollution. This study assesses the indicative roles of the surface formaldehyde-to-NO2 ratio (FNR) and glyoxal-to-NO2 ratio (GNR) on surface O3–NO x –VOC sensitivity based on a meta-analysis consisting of multiple field observations and model simulations. Thresholds of the FNR and GNR are determined using the relationship between the relative change of the O3 production rate and the two indicators, which are 0.55 ± 0.16 and 1.0 ± 0.3 for the FNR and 0.009 ± 0.003 and 0.024 ± 0.007 for the GNR. The sensitivity analysis indicated that the surface FNR is likely to be affected by formaldehyde primary sources under certain conditions, whereas the GNR might not be. As glyoxal measurements are becoming increasingly available, using the FNR and GNR together as O3 sensitivity indicators has broad potential applications.

Diagnosis of Ozone Formation Sensitivities in Different Height Layers via MAX‐DOAS Observations in Guangzhou

“…HCHO in the urban atmosphere originates from both background, primary, and secondary sources, and their respective contributions can be separated via a multi‐linear regression model (Hong et al., 2018; Liu, Li, et al., 2021; Su et al., 2019; Sun et al., 2021). As shown in Figure 5a, the sourced apportioned HCHO time series could roughly capture the trends of the measured HCHO results, achieving a moderate Pearson correlation coefficient R of 0.64 (Figure S6 in Supporting Information ).…”

“…The above‐fitted parameters of the third Fourier series are listed in Table S1 in Supporting Information , and the derived Fourier series are presented in Figure S4 in Supporting Information . Compared to the fixed background value of 1 ppbv in previous studies (Hong et al., 2018; Liu, Li, et al., 2021; Su et al., 2019), this method considers the seasonal variation in background HCHO value and slightly improves the agreement between simulated HCHO and measured HCHO (Figure S5 and S6 in Supporting Information ).…”

“…However, mainly the secondary portion in ambient HCHO participates in photochemical reactions directly, which can indicate the VOC reactivity more accurately. The non‐negligible contributions of background and primary HCHO attribute errors to FNR total and reduce the accuracy in diagnosing ozone formation sensitivity (Liu, Li, et al., 2021). Hence, the ratio of secondary HCHO to NO 2 (FNR sec ) is more favorable for indicating ozone formation sensitivities (Su et al., 2019).…”

Influence of photochemical loss of volatile organic compounds on understanding ozone formation mechanism

“…Tropospheric O 3 is mainly produced from photochemical reactions between volatile organic compounds (VOCs) and nitrogen oxides (NO x : NO + NO 2 ) (Seinfeld and Pandis, 2016;Liu et al, 2021). O 3 is generated from a collision of O 2 and O(3 P ) that is produced from photolysis of NO 2 in the atmosphere.…”

Examining the implications of photochemical indicators for O3–NOx–VOC sensitivity and control strategies: a case study in the Yangtze River Delta (YRD), China

“…It was found that the primary emissions of HCHO increased the value of HCHO/NO 2 , and therefore the O 3 sensitivity determined by the ratio could have been biased with given thresholds. For example, some VOC-limited regimes are misclassified as transitional (Liu et al, 2021). Du et al (2022) compared the spatial distribution of O 3 sensitivity regimes diagnosed using different indicators and pointed out that P H 2 O 2 /P HNO 3 could be more affected by local emissions than HCHO/NO 2 .…”