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Emerging research indicates that ground-level ozone (O3) has become a leading contributor to air quality concerns in many Chinese cities, with the Yangtze River Delta (YRD) region facing particular challenges. This study investigated the characterization of air pollutants in Wujiang, which is located within the YRD demonstration zone, during the warm season (April–September) of 2022. The contributions of emission and meteorology to O3 were identified, the O3-NOX-VOC sensitivities were discussed, and the VOC sources and their contributions to O3 formation were analyzed. A random forest model revealed that the high O3 concentration was mainly caused by a combination of increased emission intensity due to the resumption of work and production after the COVID-19 pandemic, along with adverse meteorological conditions. The results revealed more than 92% of the pollution days were related to O3 during the warm season, and the impact of O3 precursor emissions was slightly greater than that of the meteorological conditions. O3 formation was in the VOC-limited regime, and emission reduction strategies targeting VOCs, particularly aromatics such as toluene and xylene, have been identified as the most effective approach for mitigating O3 pollution. Changes in O3-NOX-VOC sensitivity were also observed from the VOC-limited regime to the transitional regime, which was primarily driven by variations in the NOX concentrations. The VOC source analysis results showed that the contributions of gasoline vehicle exhaust and diesel engine exhaust (mobile source emissions) were significantly greater than those of the other sources, accounting for 20.8% and 16.5% of the total VOC emissions, respectively. This study highlights the crucial role of mobile source emission control in mitigating O3 pollution. Furthermore, prioritizing the control of VOC emission sources with minimal NOX contributions is highly recommended within the VOC-limited regime. [ABSTRACT FROM AUTHOR]

Here we present seasonal chemical characteristics, formations, sources of PM 2.5 in the year 2020 in Suzhou, Yangtze River Delta, China. Expectedly, organic matter (OM) found to be the most dominant component of PM 2.5 , with a year-average value of 10.3 ± 5.5 μg m -3 , followed by NO 3 - (6.7 ± 6.5 μg m -3 ), SO 4 2- (3.3 ± 2.5 μg m -3 ), NH 4 + (3.2 ± 2.8 μg m -3 ), EC (1.1 ± 1.3 μg m -3 ), Cl - (0.57 ± 0.56 μg m -3 ), Ca 2+ (0.55 ± 0.91 μg m -3 ), K + (0.2 ± 1.0 μg m -3 ), Na + (0.18 ± 0.45 μg m -3 ), and Mg 2+ (0.09 ± 0.15 μg m -3 ). Seasonal variations of PM 2.5 showed the highest average value in spring, followed by winter, fall, and summer. Meanwhile, the formation mechanisms of the major PM 2.5 species (NO 3 - , SO 4 2- , and OM) varied in seasons. Interestingly, NO 2 may have the highest conversion rate to NO 3 - in spring, which might be linked with the nighttime chemistry due to the high relative humidity. Moreover, OM in summer was mainly produced by the daytime oxidation of volatile organic compounds, while local primary organic aerosols might play a significant role in other seasons. Source apportionment showed that the more-aged PM 2.5 contributed significantly to the PM 2.5 mass (42%), followed by the dust-related PM 2.5 (38%) and the less-aged PM 2.5 (21%). Potential contribution source function (PSCF) results indicated that aged PM 2.5 were less affected by transportation than dust-related PM 2.5 ., (Copyright © 2022 Elsevier Inc. All rights reserved.)