Search

In recent years, there has been a growing concern about air pollution and its impact on the air quality and human health, especially for fine particulate matter (PM 2.5 ) and its associated secondary aerosols in urban areas. This study conducted a year-long field campaign to collect PM 2.5 samples day and night in an urban area of central Taiwan. Higher PM 2.5 mass concentrations were observed in winter (27.7 ± 9.7 μg/m 3 ), followed by autumn (22.5 ± 8.3 μg/m 3 ), spring (19.2 ± 6.4 μg/m 3 ), and summer (11.0 ± 3.1 μg/m 3 ). The dominant formation mechanism of secondary inorganic aerosols was heterogeneous reactions of NO 3 - at night and homogeneous reactions of SO 4 2- during the day. Additionally, significant correlations were observed between aerosol liquid water content (ALWC) and NO 3 - during nighttime, indicating the importance of aqueous-phase NO 3 - formation. The role of aerosol acidity was explored and a unique alkaline condition was found in spring and summer, which showed lower PM 2.5 concentrations than the neutralized condition. Under the neutralized condition, higher PM 2.5 concentrations were commonly found when combining the ammonium-rich regime with molar ratios of [NO 3 - ]/[SO 4 2- ] exceeding 1.6, suggesting the importance of reducing both NH 3 and NO x . Furthermore, the results showed that reducing NH 3 should be prioritized under high temperature conditions, while reducing NO x became important under low temperature conditions. Clustering of backward trajectories showed that long-range transport could enhance the formation of secondary aerosols, but local emissions emerged as the main factor driving high PM 2.5 concentrations. This study provides insights for policymakers to improve air quality, suggesting that different mitigation strategies should be formulated based on meteorological variables and that using clean energy for vehicles and electricity generation is important to alleviate air pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Despite the well-established recognition of the health hazards posed by PM 2.5 -bound PAHs, a comprehensive understanding of their source-specific impact has been lacking. In this study, the health risks associated with PM 2.5 -bound polycyclic aromatic hydrocarbons (PAHs) and source-specific contributions were investigated in the urban region of Taipei during both cold and warm seasons. The levels of PM 2.5 -bound PAHs and their potential health risks across different age groups of humans were also characterized. Diagnostic ratios and positive matrix factorization analysis were utilized to identify the sources of PM 2.5 -bound PAHs. Moreover, potential source contribution function (PSCF), concentration-weighted trajectory (CWT) and source regional apportionment (SRA) analyses were employed to determine the potential source regions. Results showed that the total PAHs (TPAHs) concentrations ranged from 0.08 to 2.37 ng m -3 , with an average of 0.69 ± 0.53 ng m -3 . Vehicular emissions emerged as the primary contributor to PM 2.5 -bound PAHs, constituting 39.8 % of the TPAHs concentration, followed by industrial emissions (37.6 %), biomass burning (13.8 %), and petroleum/oil volatilization (8.8 %). PSCF and CWT analyses revealed that industrial activities and shipping processes in northeast China, South China Sea, Yellow Sea, and East China Sea, contributed to the occurrence of PM 2.5 -bound PAHs in Taipei. SRA identified central China as the primary regional contributor of ambient TPAHs in the cold season and Taiwan in the warm season, respectively. Evaluations of incremental lifetime cancer risk demonstrated the highest risk for adults, followed by children, seniors, and adolescents. The assessments of lifetime lung cancer risk showed that vehicular and industrial emissions were the main contributors to cancer risk induced by PM 2.5 -bound PAHs. This research emphasizes the essential role of precisely identifying the origins of PM 2.5 -bound PAHs to enhance our comprehension of the related human health hazards, thus providing valuable insights into the mitigation strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Over the past decades, the pollution of ozone (O 3 ) and secondary organic aerosols (SOA) in the atmosphere has become a major concern worldwide due to their adverse effects on human health, air quality and climate. Volatile organic compounds (VOCs) are crucial precursors of O 3 and SOA, but identifying the primary sources of VOCs that contribute to the formation of O 3 and SOA has been challenging due to the rapid consumption of VOCs by oxidants in the air. To address this issue, a study was conducted in a Taipei urban area in Taiwan, where the hourly data of 54 VOC species were collected from March 2020 to February 2021 detected by Photochemical Assessment Monitoring Stations (PAMS). The initial mixing ratios of VOCs (VOCs ini ) were determined by combining the observed VOCs (VOCs obs ) and the consumed VOCs resulting from photochemical reactions. Additionally, the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) were estimated based on VOCs ini . The OFP derived from VOCs ini (OFP ini ) was found to exhibit a strong correlation with O 3 mixing ratios (R 2  = 0.82), whereas the OFP obtained from VOCs obs did not show such a correlation. Isoprene, toluene and m,p-xylene were the top three species contributing to OFP ini , while toluene and m,p-xylene were the top two contributors to SOAFP ini . Positive matrix factorization analysis revealed that biogenic, consumer/household products, and industrial solvents were the major contributors to OFP ini in four seasons, and SOAFP ini mostly came from consumer/household products and industrial solvents. This study highlights the importance of considering photochemical loss caused by different VOCs reactivity in the atmosphere when evaluating OFP and SOAFP. Moreover, it emphasizes the need to prioritize controlling the sources emitting the dominant VOC precursors of O 3 and SOA to effectively alleviate the scenarios of elevated O 3 and particulate matter., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)