TY - JOUR
T1 - Ultrafine particles and PM 2.5 in the air of cities around the world
T2 - are they representative of each other?
AU - de Jesus, Alma Lorelei
AU - Rahman, Md Mahmudur
AU - Mazaheri, Mandana
AU - Thompson, Helen
AU - Knibbs, Luke D.
AU - Jeong, Cheol
AU - Evans, Greg
AU - Nei, Wei
AU - Ding, Aijun
AU - Qiao, Liping
AU - Li, Li
AU - Portin, Harri
AU - Niemi, Jarkko V.
AU - Timonen, Hilkka
AU - Luoma, Krista
AU - Petäjä, Tuukka
AU - Kulmala, Markku
AU - Kowalski, Michal
AU - Peters, Annette
AU - Cyrys, Josef
AU - Ferrero, Luca
AU - Manigrasso, Maurizio
AU - Avino, Pasquale
AU - Buonano, Giorgio
AU - Reche, Cristina
AU - Querol, Xavier
AU - Beddows, David
AU - Harrison, Roy M.
AU - Sowlat, Mohammad H.
AU - Sioutas, Constantinos
AU - Morawska, Lidia
PY - 2019/8/1
Y1 - 2019/8/1
N2 -
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 PM
2.5
(mass concentration of particles with aerodynamic diameter < 2.5 μm) and factors that influence their concentrations. Hourly average PNC and PM
2.5
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 × 10
3
to 19.5 × 10
3
particles·cm
−3
and from 7.0 to 65.8 μg·m
−3
for PNC and PM
2.5
, 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 PM
2.5
, attributed to the high contributions of UFP from vehicular emissions to PNC. The variation in both PNC and PM
2.5
due to seasonality is linked to the cities' geographical location and features. Clustering the cities based on annual median concentrations of both PNC and PM
2.5
demonstrated that a high PNC level does not lead to a high PM
2.5
, and vice versa. The particle number-to-mass ratio (in units of 10
9
particles·μg
−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 PM
2.5
. Therefore, PNC and PM
2.5
measurements are not representative of each other; and regulating PM
2.5
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.
AB -
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 PM
2.5
(mass concentration of particles with aerodynamic diameter < 2.5 μm) and factors that influence their concentrations. Hourly average PNC and PM
2.5
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 × 10
3
to 19.5 × 10
3
particles·cm
−3
and from 7.0 to 65.8 μg·m
−3
for PNC and PM
2.5
, 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 PM
2.5
, attributed to the high contributions of UFP from vehicular emissions to PNC. The variation in both PNC and PM
2.5
due to seasonality is linked to the cities' geographical location and features. Clustering the cities based on annual median concentrations of both PNC and PM
2.5
demonstrated that a high PNC level does not lead to a high PM
2.5
, and vice versa. The particle number-to-mass ratio (in units of 10
9
particles·μg
−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 PM
2.5
. Therefore, PNC and PM
2.5
measurements are not representative of each other; and regulating PM
2.5
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.
KW - Particle number concentration
KW - PM2.5
KW - Urban aerosol
UR - http://www.scopus.com/inward/record.url?scp=85065858791&partnerID=8YFLogxK
U2 - 10.1016/j.envint.2019.05.021
DO - 10.1016/j.envint.2019.05.021
M3 - Article
AN - SCOPUS:85065858791
SN - 0160-4120
VL - 129
SP - 118
EP - 135
JO - Environment International
JF - Environment International
ER -
