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• ALWC contributed 66.68% to PM 2.5 , with higher mass – based growth factor appearing when RH > 85%. • NO 3 – tended to form under higher ALWC conditions (RH > 80%), while SOC was favorable under lower ALWC levels. • ALWC was more sensitive to NO 3 – (R = 0.94) than SO 4 2– (R = 0.90) under heavy pollution. • SOC had a good correlation with ALWC (daytime: R = 0.84; nighttime: R = 0.54) with high atmospheric oxidation capacity (daytime: O X = 130 – 140 µg/m3; nighttime: O X = 100 – 140 µg/m3) in winter. Aerosol liquid water content (ALWC) plays an important role in secondary aerosol formation. In this study, a whole year field campaign was conducted at Shanxi in north Zhejiang Province during 2021. ALWC estimated by ISORROPIA-II was then investigated to explore its characteristics and relationship with secondary aerosols. ALWC exhibited a highest value in spring (66.38 µg/m3), followed by winter (45.08 µg/m3), summer (41.64 µg/m3), and autumn (35.01 µg/m3), respectively. It was supposed that the secondary inorganic aerosols (SIA) were facilitated under higher ALWC conditions (RH > 80%), while the secondary organic species tended to form under lower ALWC levels. Higher RH (> 80%) promoted the NO 3 – formation via gas-particle partitioning, while SO 4 2– was generated at a relative lower RH (> 50%). The ALWC was more sensitive to NO 3 – (R = 0.94) than SO 4 2– (R = 0.90). Thus, the self-amplifying processes between the ALWC and SIA enhanced the particle mass growth. The sensitivity of ALWC and O X (NO 2 + O 3) to secondary organic carbon (SOC) varied in different seasons at Shanxi, more sensitive to aqueous-phase reactions (daytime R = 0.84; nighttime R = 0.54) than photochemical oxidation (daytime R = 0.23; nighttime R = 0.41) in wintertime with a high level of O X (daytime: 130–140 µg/m3; nighttime: 100–140 µg/m3). The self-amplifying process of ALWC and SIA and the aqueous-phase formation of SOC will enhance aerosol formation, contributing to air pollution and reduction of visibility. [Display omitted] [ABSTRACT FROM AUTHOR]

As "fuel" for atmospheric photochemical reactions, volatile organic compounds (VOCs) play a key role in the secondary generation of ozone (O3) and fine particulate matter (PM2.5, an aerodynamic diameter ≤ 2.5 μm). To determine the characteristics of VOCs in a high-level ozone period, comprehensive monitoring of O3 and its precursors (VOCs and NOx) was continuously conducted in an industrial area in Shanghai from 18 August to 30 September 2021. During the observation period, the average concentration of VOCs was 47.33 ppb, and alkanes (19.64 ppb) accounted for the highest proportion of TVOCs, followed by oxygenated volatile organic compounds (OVOCs) (13.61 ppb), alkenes (6.92 ppb), aromatics (4.65 ppb), halogenated hydrocarbons (1.60 ppb), and alkynes (0.91 ppb). Alkenes were the predominant components that contributed to the ozone formation potential (OFP), while aromatics such as xylene, toluene, and ethylbenzene contributed the most to the secondary organic aerosol production potential (SOAFP). During the study period, O3, NOx, and VOCs showed significant diurnal variations. Industrial processes were the main source of VOCs, and the second largest source of VOCs was vehicle exhaust. While the largest contribution to OFP was from vehicle exhaust, the second largest contribution was from liquid petroleum gas (LPG). High potential source contribution function (PSCF) values were observed in western and southeastern areas near the sampling sites. The results of a health risk evaluation showed that the Hazard Index was less than 1 and there was no non-carcinogenic risk, but 1,3-butadiene, benzene, chloroform, 1,2-dibromoethane, and carbon tetrachloride pose a potential carcinogenic risk to the population. [ABSTRACT FROM AUTHOR]

Atmospheric metals have recently attracted the attention of governments recently due to their significant health risks. In retrospect, a five-year (2017–2021) continuous measurement of airborne metals (13 elements) was conducted in northern Zhejiang Province. A declining trend of total metals (22%) was found from 2017 to 2021, with K, Fe, Zn, Ca, and Mn being its predominant compositions (95.3%). The Random Forest model simulation demonstrated the important roles of meteorological conditions in the trace metal reduction, such as Ca, As, K, Cr, and Zn. In addition, the emission controls contributed more than 50% to most of the remaining metals, especially for Cu (92.6%) and V (85.9%), which demonstrated the effectiveness of the government policies. The relative humidity, wind speed and wind direction were found to be the most important variables affecting the ambient concentration of trace metals. Meteorology was demonstrated to be the worst for trace metal diffusion in 2018. The primary noncarcinogenic metal was Mn (85.9%), while the major carcinogenic metal was Cd (63.4%). Six sources were resolved by positive matrix factorization (PMF). Anthropogenic source emission was largest in winter, followed by spring, summer, and autumn. The reduction of ferrous metal smelting and coal combustion emissions might be the major goal for reducing the public health risk of trace metals in the future. [Display omitted] • A declining trend by 22% of total trace metals was observed from 2017 to 2021. • Random forest model was applied to study meteorological effect on the reduction of metals. • Emission control strategies more than 50% to source concentration reduction since 2020. • Mn and Cd predominated the noncarcinogenic (85.9%) and carcinogenic (63.4%) risks. • Ferrous metal smelting and coal combustion contributed largely to health risk. [ABSTRACT FROM AUTHOR]