Volatile organic compounds (VOCs) tend to be consumed by atmospheric oxidants, resulting in substantial photochemical loss during transport. An observation-based model was used to evaluate the influence of photochemical loss of VOCs on the sensitivity regime and mechanisms of ozone formation. Our results showed that a VOC-limited regime based on observed VOC concentrations shifted to a transition regime with a photochemical initial concentration of VOCs (PIC-VOCs) in the morning. The net ozone formation rate was underestimated by 3 ppb h⁻¹ (∼36 ppb d⁻¹) based on the measured VOCs when compared with the PIC-VOCs. The relative contribution of the RO₂ path to ozone production based on the PIC-VOCs accordingly increased by 13.4 %; in particular, the contribution of alkene-derived RO₂ increased by approximately 10.2 %. In addition, the OH–HO₂ radical cycle was obviously accelerated by highly reactive alkenes after accounting for photochemical loss of VOCs. The contribution of local photochemistry might be underestimated for both local and regional ozone pollution if consumed VOCs are not accounted for, and policymaking on ozone pollution prevention should focus on VOCs with a high reactivity.

Hydrogen peroxide (H₂O₂) acts as a terminal sink for atmospheric HO_x radicals (OH and HO₂), playing a key role in tropospheric O₃ formation. However, there are few field measurements of atmospheric H₂O₂ to assess its role in O₃ formation, especially for the seriously polluted region of the North China Plain. In this study, H₂O₂ concentrations were measured at the foot of Mt. Tai from May to July 2018 and the summit of Mt. Tai from May to June 2019, with average values of 0.93 ± 1.01 and 2.05 ± 1.20 ppb, respectively. H₂O₂ exhibited a pronounced diurnal variation with a noon‐peak at the foot of Mt. Tai, which could be well reproduced by a gas‐phase box model with H₂O₂ dry deposition velocity of 3 cm s⁻¹ included, indicating H₂O₂ was mainly photochemically produced. Modeling analysis showed H₂O₂ production at the foot was most sensitive to alkenes and aromatics, while the source and sink for H₂O₂ were dominated by HO₂ recombination and dry deposition, respectively. Compared with the summer‐measurement in 2007, the remarkable elevation of H₂O₂ at the summit might be ascribed to volatile organic compounds (VOCs) increase and SO₂ decline. Both H₂O₂‐O₃ correlation and H₂O₂/NO_z ratio suggested O₃ formation at the foot of Mt. Tai was mainly VOC‐sensitive in the early morning and shifted to NO_x‐sensitive thereafter. Therefore, reduction of VOCs emission especially for the reactive species of alkenes and aromatics in the morning as well as NO_x emission around noontime will be effective for mitigating the serious O₃ (as well as H₂O₂) pollution in Tai'an city.

The surface atmospheric O₃ concentration in Kunming shows a significant upward trend, with high values mainly occurring in March–May. Volatile organic compounds (VOCs) are one of the most important precursors of O₃. However, the sources of VOCs are complex and difficult to identify. In order to understand the pollution levels, the spatial distribution characteristics, and possible sources of VOCs, we conducted simultaneous offline sampling at representative sites in six different functional areas of Kunming using SUMMA canisters for one week. The VOC samples were analyzed via GC/MS. The VOC data were analyzed (using the feature ratio method, ozone formation potential (OFP), and Positive Matrix Factorization (PMF) model). Some important conclusions were drawn. Firstly, VOCs during the spring in Kunming were mainly derived from oxygenated VOCs, aromatic hydrocarbons, and halogenated hydrocarbons, with significant spatial differences. Secondly, we found that the potential for atmospheric ozone formation is higher in Kunming for aromatic hydrocarbons and oxygenated VOCs. Finally, the results of the Positive Matrix Factorization model (PMF) showed that Kunming’s ambient atmospheric VOCs mainly originate from anthropogenic source emissions. These conclusions can provide useful reference information for O₃ pollution control in Kunming.