Alramzi Yousef, Aghaei Yashar, Badami Mohammad Mahdi, Aldekheel Mohammad, Tohidi Ramin, Sioutas Constantinos
University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
Kuwait University, Department of Civil Engineering, P.O Box 5969, Safat, 13060, Kuwait.
Environ Pollut. 2025 Feb 15;367:125651. doi: 10.1016/j.envpol.2025.125651. Epub 2025 Jan 7.
Airborne particulate matter (PM) in urban environments poses significant health risks by penetrating the respiratory system, with concern over lung-deposited surface area (LDSA) as an indicator of particle exposure. This study aimed to investigate the diurnal trends and sources of LDSA, particle number concentration (PNC), elemental carbon (EC), and organic carbon (OC) concentrations in Los Angeles across different seasons to provide a comprehensive understanding of the contributions from primary and secondary sources of ultrafine particles (UFPs). Hourly measurements of PNC and LDSA were conducted using the DiSCmini and Scanning Mobility Particle Sizer (SMPS), while OC and EC concentrations were measured using the Sunset Lab EC/OC Monitor. The results showed distinct diurnal trends in PNC and EC, with peaks occurring in the early morning and evening, which were consistent with periods of increased traffic volume. During warmer periods, a midday increase in PNC was observed, attributed to photochemical reactions. In contrast, a nighttime peak during colder months suggested the formation of secondary aerosols through aqueous-phase chemistry. Additionally, the DiSCmini consistently reported higher LDSA values than SMPS, indicating the presence of irregularly shaped UFPs, particularly during periods of heavy traffic flow. Positive Matrix Factorization (PMF) analysis identified three primary sources. Factor 1 (photochemically influenced processes), driven by secondary organic aerosol formation during warmer periods, contributed to 19% of LDSA. Factor 2, in which primarily traffic influenced emissions were the dominant contributor, accounting for 70% of LDSA and associated with high loadings of OC (61%), EC (78%), and NO (94%). Factor 3 (aqueous phase secondary process influenced emissions) during colder months, accounted for 11% of LDSA. Both Factor 1 and 3 sources exhibited comparable contributions of OC (52% and 48%, respectively), underscoring their roles in secondary aerosol formation. These findings emphasize the need to address both primary and secondary emissions to mitigate health risks associated with UFP exposure.
城市环境中的空气颗粒物（PM）通过穿透呼吸系统对健康构成重大风险，人们关注肺沉积表面积（LDSA）作为颗粒物暴露的指标。本研究旨在调查洛杉矶不同季节LDSA、颗粒物数量浓度（PNC）、元素碳（EC）和有机碳（OC）浓度的日变化趋势和来源，以全面了解超细颗粒物（UFP）一次和二次来源的贡献。使用DiSCmini和扫描迁移率颗粒物粒径谱仪（SMPS）对PNC和LDSA进行每小时测量，同时使用日落实验室EC/OC监测仪测量OC和EC浓度。结果显示PNC和EC有明显的日变化趋势，峰值出现在清晨和傍晚，这与交通流量增加的时段一致。在较温暖时期，观察到PNC在中午增加，这归因于光化学反应。相比之下，较冷月份夜间出现峰值表明通过水相化学形成了二次气溶胶。此外，DiSCmini报告的LDSA值始终高于SMPS，表明存在形状不规则的UFP，特别是在交通流量大的时期。正定矩阵因子分解（PMF）分析确定了三个主要来源。因子1（受光化学影响的过程）在较温暖时期由二次有机气溶胶形成驱动，对LDSA的贡献为19%。因子2中，主要受交通影响的排放是主要贡献者，占LDSA的70%，并与高含量的OC（61%）、EC（78%）和NO（94%）相关。较冷月份的因子3（受水相二次过程影响的排放）占LDSA的11%。因子1和3来源的OC贡献相当（分别为52%和48%），突出了它们在二次气溶胶形成中的作用。这些发现强调需要同时解决一次和二次排放问题，以减轻与UFP暴露相关的健康风险。
