Chemical Characterization of PM_(1-2.5) and its Associations with PM_1, PM_(2.5-10) and Meteorology in Urban and Suburban Environments

Jana Kozáková ； Cecilia Leoni ； Miroslav Klán ； Jan Hovorka ； Martin Racek ； Martin Kostejn ； Jakub Ondráček ； Pavel Moravec ； Jaroslav Schwarz

《Aerosol and Air Quality Research》 18卷7期 (2018/07) Pp. 1684-1697

https://doi.org/10.4209/aaqr.2017.10.0479

摘要

This study investigated the PM_(1-2.5) (the intermodal fraction of particulate matter) representing the transition area between the fine and coarse size ranges. Due to this characteristic, PM_(1-2.5) may contain particles from both modes. The aim of this work was to examine the associations between PM_(1-2.5) and the coarse (PM_(2.5-10))/fine (PM_1) fraction under different meteorological conditions at various sites in the Czech Republic during winter and summer. Size-resolved PM mass concentrations were determined and meteorological parameters recorded at an urban industrial and a suburban site in Ostrava during winter 2014 and at an urban traffic site and a suburban site in Prague during summer 2014 and winter 2015. The influence of sources producing the coarse/fine fraction on PM_(1-2.5) was investigated with an elemental composition analysis and an ion analysis (Ca^(2+)-representing PM_(2.5-10) and SO_4^(2-)-representing PM_1). During all campaigns, PM_(1-2.5) accounted for 1-26% of PM_(10). In winter, crustal elements (Si, Fe, and Ca) significantly influenced the coarse fraction and even PM_(1-2.5) at all sites, while sulfur was significant in PM_(1-2.5) and the fine fraction at suburban sites. The median SO_4^(2-) concentration was higher than the Ca^(2+) concentration in PM_(1-2.5) at all sites, except the industrial site, due to a specific source. The increased SO_4^(2-) amount in PM_(1-2.5) was also observed in summer during rainy days (Prague urban site). In summer, crustal elements were important in both PM_(1-2.5) and the coarse fraction, while S still dominated in PM_1. Median SO_4^(2-) concentrations in PM_(1-2.5) and the coarse fraction were significantly lower than in winter. The enrichment factors and wind speed-direction analysis helped to reveal potential air pollution sources. To conclude, according to the performed analyses, PM_(1-2.5) was influenced by the sources of the coarse fraction during all campaigns. The additional significant influence of sources producing the fine fraction was evident under increased relative humidity conditions.

關鍵字

Aerosol intermodal fraction ； Personal cascade impactor sampler ； Enrichment factor ； Elemental composition ； Scanning electron microscope ； Multisite measurement