Ultrafine particles and PM2.5 in the air of cities around the world : Are they representative of each other?

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de Jesus , A L , Rahman , M M , Mazaheri , M , Thompson , H , Knibbs , L D , Jeong , C , Evans , G , Nei , W , Ding , A , Qiao , L , Li , L , Portin , H , Niemi , J V , Timonen , H , Luoma , K , Petäjä , T , Kulmala , M , Kowalski , M , Peters , A , Cyrys , J , Ferrero , L , Manigrasso , M , Avino , P , Buonano , G , Reche , C , Querol , X , Beddows , D , Harrison , R M , Sowlat , M H , Sioutas , C & Morawska , L 2019 , ' Ultrafine particles and PM2.5 in the air of cities around the world : Are they representative of each other? ' , Environment International , vol. 129 , pp. 118-135 . https://doi.org/10.1016/j.envint.2019.05.021

Title: Ultrafine particles and PM2.5 in the air of cities around the world : Are they representative of each other?
Author: de Jesus, Alma Lorelei; Rahman, Md Mahmudur; Mazaheri, Mandana; Thompson, Helen; Knibbs, Luke D.; Jeong, Cheol; Evans, Greg; Nei, Wei; Ding, Aijun; Qiao, Liping; Li, Li; Portin, Harri; Niemi, Jarkko V.; Timonen, Hilkka; Luoma, Krista; Petäjä, Tuukka; Kulmala, Markku; Kowalski, Michal; Peters, Annette; Cyrys, Josef; Ferrero, Luca; Manigrasso, Maurizio; Avino, Pasquale; Buonano, Giorgio; Reche, Cristina; Querol, Xavier; Beddows, David; Harrison, Roy M.; Sowlat, Mohammad H.; Sioutas, Constantinos; Morawska, Lidia
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2019-08
Language: eng
Number of pages: 18
Belongs to series: Environment International
ISSN: 0160-4120
URI: http://hdl.handle.net/10138/303445
Abstract: Can mitigating only particle mass, as the existing air quality measures do, ultimately lead to reduction in ultrafine particles (UFP)? The aim of this study was to provide a broader urban perspective on the relationship between UFP, measured in terms of particle number concentration (PNC) and PM2.5 (mass concentration of particles with aerodynamic diameter <2.5 mu m) and factors that influence their concentrations. Hourly average PNC and PM2.5 were acquired from 10 cities located in North America, Europe, Asia, and Australia over a 12-month period. A pairwise comparison of the mean difference and the Kolmogorov-Smirnov test with the application of bootstrapping were performed for each city. Diurnal and seasonal trends were obtained using a generalized additive model (GAM). The particle number to mass concentration ratios and the Pearson's correlation coefficient were calculated to elucidate the nature of the relationship between these two metrics. Results show that the annual mean concentrations ranged from 8.0 x 10 3 to 19.5 x 10(3) particles.cm(-3) and from 7.0 to 65.8 mu g.m(-3) for PNC and PM2.5, respectively, with the data distributions generally skewed to the right, and with a wider spread for PNC. PNC showed a more distinct diurnal trend compared with PM2.5, attributed to the high contributions of UFP from vehicular emissions to PNC. The variation in both PNC and PM2.5 due to seasonality is linked to the cities' geographical location and features. Clustering the cities based on annual median concentrations of both PNC and PM2.5 demonstrated that a high PNC level does not lead to a high PM2.5, and vice versa. The particle number-to-mass ratio (in units of 10(9) particles.mu g(-1)) ranged from 0.14 to 2.2, > 1 for roadside sites and <1 for urban background sites with lower values for more polluted cities. The Pearson's r ranged from 0.09 to 0.64 for the log-transformed data, indicating generally poor linear correlation between PNC and PM2.5. Therefore, PNC and PM2.5 measurements are not representative of each other; and regulating PM2.5 does little to reduce PNC. This highlights the need to establish regulatory approaches and control measures to address the impacts of elevated UFP concentrations, especially in urban areas, considering their potential health risks.
Subject: Urban aerosol
Particle number concentration
PM2.5
FINE PARTICULATE MATTER
AEROSOL-SIZE DISTRIBUTIONS
NUMBER CONCENTRATIONS
SOURCE APPORTIONMENT
TEMPORAL VARIATIONS
CHEMICAL-COMPOSITION
SPATIAL VARIATION
LOS-ANGELES
MASS CONCENTRATIONS
SEASONAL-VARIATION
114 Physical sciences
116 Chemical sciences
1172 Environmental sciences
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