To better understand the pollution characteristics and formation mechanisms of atmospheric carbonyl compounds, continuous measurements of carbonyl compounds in Jinan were taken for one month at a sampling frequency of 2h. The sources, pollution characteristics, and concentration changes of carbonyl compounds during the summers of 2018 and 2020 were compared. The total concentrations of carbonyl compounds were 10.51±0.13ppbV and 6.30±1.08ppbV in 2018 and 2020, respectively. In both years, formaldehyde, acetone, and acetaldehyde were the major carbonyls. Diurnal variations and correlation analyses showed that exhaust emissions from motor vehicles during peak traffic periods significantly contributed to the concentrations of carbonyl compounds in Jinan, with formaldehyde exhibiting net production. The ratio of formaldehyde/acetaldehyde (C₁/C₂) was 2.64 in 2018 and 2.03 in 2020, indicating that carbonyl compounds are jointly affected by anthropogenic sources and photochemical reactions. Master Chemical Mechanism model analyses showed that the formation of formaldehyde in Jinan was controlled by RO+O₂ reactions, and formaldehyde was mainly consumed via photolysis and its reaction with the hydroxyl radical. In situ photochemistry can further promote formaldehyde production. The comparison of the reactivities of different carbonyl compounds revealed that formaldehyde, acetaldehyde, butyraldehyde, and propionaldehyde play an important role in hydroxyl radical reactions and ozone generation. Among all the measured carbonyl compounds, benzaldehyde contributed the most to secondary organic aerosols (SOAs). Overall, this study provides new insights into the formation mechanisms of carbonyl compounds as well as their pollution characteristics.

Enhanced ozone (O₃) pollution has emerged as a pressing environmental concern in China, particularly for densely populated megacities and major city clusters. However, volatile organic compounds (VOCs), the key precursors to O₃ formation, have not been routinely measured. In this study, we characterize the spatial and temporal patterns of VOCs and examine the role of VOCs in O₃ production in five cities (Dongying (DY), Rizhao (RZ), Yantai (YT), Weihai (WH), and Jinan (JN)) in the North China Plain (NCP) for two sampling periods (June and December) in 2021 through continuous field observations. Among various VOC categories, alkanes accounted for the largest proportion of VOCs in the cities. For VOCs, chemical reactivities, aromatic hydrocarbons, and alkenes were dominant contributors to O₃ formation potential (OFP). Unlike inland regions, the contribution to OFP from OVOCs increased greatly at high O₃ concentrations in coastal regions (especially YT). Model simulations during the O₃ episode show that the net O₃ production rates were 27.87, 10.24, and 10.37 ppbv/h in DY, RZ, and JN. The pathway of HO₂ + NO contributed the most to O₃ production in JN and RZ, while RO₂ + NO was the largest contributor to O₃ production in DY. The relative incremental reactivity (RIR) revealed that O₃ formation in DY was the transitional regime, while it was markedly the VOC-limited regime in JN and RZ. The O₃ production response is influenced by NOx concentration and has a clear daily variation pattern (the sensitivity is greater from 15:00 to 17:00). The most efficiencies in O₃ reduction could be achieved by reducing NOx when the NOx concentration is low (less than 20 ppbv in this study). This study reveals the importance of ambient VOCs in O₃ production over the NCP and demonstrates that a better grasp of VOC sources and profiles is critical for in-depth O₃ regulation in the NCP.

Urban ozone (O₃) pollution has become a prominent environmental threat to public health while the relationship between O₃ formation and driving factors remains elusive, particularly for megacities in the Shandong Peninsula of China. In this study, we use intensive ambient measurements of trace gases to comprehensively investigate the magnitude of O₃ pollution in Jinan city from 2013 to 2020. Further, emission inventory and OMI NO₂ columns are used for probing changes in precursor emissions. Ground-level measurements indicate degraded O₃ air quality afterward in 2015 and depict city-wide elevated O₃ levels (higher than 140 μg/m³ in the warm season). For precursor emissions, it is found that NO_x emissions have decreased more than 30% due to successful regulation efforts, which is in excellent agreement with NO₂ columns from OMI. The method of objective synoptic weather pattern classification [T-Mode principal component analysis (PCT)] is adopted to distinguish the associated meteorological parameters under various synoptic patterns which govern the variability in regional O₃ levels. Among identified synoptic patterns, Type 2 and Type 8 featured by low sea level pressure (SLP), high temperature, and strong ultraviolet radiation are the most prevalent synoptic patterns in spring and summer, respectively, which are prone to the occurrence of O₃ exceedances. This work provides a detailed view of long-term O₃ levels and the relationship between precursors and meteorological conditions in a typical densely populated city in northern China, showing implications for developing O₃ mitigation strategies.

A systematic investigation was conducted on 56 persistent organic pollutants (POPs) in the atmosphere at seven functional regions of Jinan, China. The POPs included 16 polycyclic aromatic hydrocarbons (PAHs), 6 phthalic acid esters (PAEs), 17 polychlorinated biphenyls (PCBs), and 17 organochlorine pesticides (OCPs). The concentrations in gas-phase and particle-phase were monitored and analyzed to assess the contamination status and to identify the pollution sources according to the mass ratios between POP congeners and the distribution among the sampling regions and periods. The results show that the pollution level at a recreational area was lower than that in other regions of the city and it was higher in winter than in summer for all the 7 sampling sites. Sixteen polycyclic aromatic hydrocarbons (PAHs) were evenly distributed between gas-phase and particle-phase. The total concentration of phthalic acid esters (∑PAEs) in particle-phase was 96.4% larger than that in gas-phase, which was possibly derived from artificial plastics. PCB-126 was one of the major pollutants of the 17 polychlorinated biphenyls (PCBs) in the atmosphere. High-Cl PCBs favored adhering to airborne particles, while low-Cl PCBs tended to stay in gas-phase. The total concentration of 17 organochlorine pesticides (∑OCPs) in gas-phase accounted for 68.0%, while methoxychlor, dieldrin, and endrin aldehyde preferred to particle-phase. Additionally, the preliminary investigation suggests that local pollution sources contributed to most PAHs in urban sites, while the sources could be complex for the suburban area and adjacent towns in winter. Residues of some OCPs could also come from long-distance transportation.

Source inversion optimization using sensor observations is a key method for rapidly and accurately identifying unknown source parameters (source strength and location) in abrupt hazardous gas leaks. Sensor number and location distribution both play important roles in source inversion; however, their combined impacts on source inversion optimization remain poorly understood. In our study, the optimization inversion method is established based on the Gaussian plume model and the generation algorithm. A research strategy combining random sampling and coefficient of variation methods was proposed to simultaneously quantify their combined impacts in the case of a single emission source. The sensor layout impact difference was analyzed under varying atmospheric conditions (unstable, neutral, and stable) and source location information (known or unknown) using the Prairie Grass experiments. The results indicated that adding sensors improved the source strength estimation accuracy more when the source location was known than when it was unknown. The impacts of sensor location distribution were strongly negatively correlated (r ≤ −0.985) with the number of sensors across scenarios. For source strength estimation, the impacts of the sensor location distribution difference decreased non-linearly with more sensors for known locations but linearly for unknown ones. The impacts of sensor number and location distribution on source strength estimation were amplified under stable atmospheric conditions compared to unstable and neutral conditions. The minimum number of randomly scattered sensors required for stable source strength inversion accuracy was 11, 12, and 17 for known locations under unstable, neutral, and stable atmospheric conditions, respectively, and 24, 9, and 21 for unknown locations. The multi-layer arc distribution outperformed rectangular, single-layer arc, and downwind-axis distributions in source strength estimation. This study enhances the understanding of factors influencing source inversion optimization and provides valuable insights for optimizing sensor layouts.

Per- and polyfluoroalkyl substances (PFASs) are a global concern because of their toxicity and persistence, yet seasonal dynamics, pollution-level dependencies, and inhalation risks of PM_2.5-bound PFASs in haze-prone industrial cities remain underexplored. This study investigated 163 PM_2.5 samples collected from December 2023 to November 2024 in Jinan—a typical industrial city—and quantified 17 PFASs via LC-MS/MS. The results showed that total concentrations (∑PFASs) rank winter (133.8) > autumn (123.6) ≈ summer (123.5) > spring (97.1 pg·m⁻³). In summer and autumn, PFAS concentrations were numerically higher on clean days than on slightly polluted days. This may suggest that good air quality does not necessarily guarantee low PFAS levels. Spearman correlation analysis showed no significant monotonic relationships between ΣPFASs and individual meteorological variables. However, compound-specific responses to temperature, humidity, and wind speed exhibited chain-length dependence. Inhalation-risk evaluation of the 15 assessable PFASs showed that PFOA and short-chain PFCAs co-dominated estimated daily intake (73.1%), whereas PFOA dominated estimated risk (95.6%). Several compounds (e.g., PFHxA, PFOS) showed numerically higher risk values on clean or slightly polluted days than on polluted days. This suggests the need for species-specific evaluation. This study provides critical evidence of PFASs’ atmospheric behavior in haze-affected industrial settings and provides a scientific basis for prioritizing control species.