TY - JOUR
T1 - Long-term trends in PM2.5 mass and particle number concentrations in urban air
T2 - the impacts of mitigation measures and extreme events due to changing climates
AU - de Jesus, Alma Lorelei
AU - Thompson, Helen
AU - Knibbs, Luke D.
AU - Kowalski, Michal
AU - Cyrys, Josef
AU - Niemi, Jarkko V.
AU - Kousa, Anu
AU - Timonen, Hilkka
AU - Luoma, Krista
AU - Petaja, Tuukka
AU - Beddows, David
AU - Harrison, Roy
AU - Hopke, Philip K.
AU - Morawska, Lidia
PY - 2020/8
Y1 - 2020/8
N2 - Urbanisation and industrialisation led to the increase of ambient particulate matter (PM) concentration. While subsequent regulations may have resulted in the decrease of some PM matrices, the simultaneous changes in climate affecting local meteorological conditions could also have played a role. To gain an insight into this complex matter, this study investigated the long-term trends of two important matrices, the particle mass (PM
2.5) and particle number concentrations (PNC), and the factors that influenced the trends. Mann-Kendall test, Sen's slope estimator, the generalised additive model, seasonal decomposition of time series by LOESS (locally estimated scatterplot smoothing) and the Buishand range test were applied. Both PM
2.5 and PNC showed significant negative monotonic trends (0.03–0.6 μg m
−3. yr
−1 and 0.40–3.8 × 10
3 particles. cm
−3. yr
−1, respectively) except Brisbane (+0.1 μg m
−3. yr
−1 and +53 particles. cm
−3. yr
−1, respectively). For the period covered in this study, temperature increased (0.03–0.07 °C.yr
−1) in all cities except London; precipitation decreased (0.02–1.4 mm. yr
−1) except in Helsinki; and wind speed was reduced in Brisbane and Rochester but increased in Helsinki, London and Augsburg. At the change-points, temperature increase in cold cities influenced PNC while shifts in precipitation and wind speed affected PM
2.5. Based on the LOESS trend, extreme events such as dust storms and wildfires resulting from changing climates caused a positive step-change in concentrations, particularly for PM
2.5. In contrast, among the mitigation measures, controlling sulphur in fuels caused a negative step-change, especially for PNC. Policies regarding traffic and fleet management (e.g. low emission zones) that were implemented only in certain areas or in a progressive uptake (e.g. Euro emission standards), resulted to gradual reductions in concentrations. Therefore, as this study has clearly shown that PM
2.5 and PNC were influenced differently by the impacts of the changing climate and by the mitigation measures, both metrics must be considered in urban air quality management.
AB - Urbanisation and industrialisation led to the increase of ambient particulate matter (PM) concentration. While subsequent regulations may have resulted in the decrease of some PM matrices, the simultaneous changes in climate affecting local meteorological conditions could also have played a role. To gain an insight into this complex matter, this study investigated the long-term trends of two important matrices, the particle mass (PM
2.5) and particle number concentrations (PNC), and the factors that influenced the trends. Mann-Kendall test, Sen's slope estimator, the generalised additive model, seasonal decomposition of time series by LOESS (locally estimated scatterplot smoothing) and the Buishand range test were applied. Both PM
2.5 and PNC showed significant negative monotonic trends (0.03–0.6 μg m
−3. yr
−1 and 0.40–3.8 × 10
3 particles. cm
−3. yr
−1, respectively) except Brisbane (+0.1 μg m
−3. yr
−1 and +53 particles. cm
−3. yr
−1, respectively). For the period covered in this study, temperature increased (0.03–0.07 °C.yr
−1) in all cities except London; precipitation decreased (0.02–1.4 mm. yr
−1) except in Helsinki; and wind speed was reduced in Brisbane and Rochester but increased in Helsinki, London and Augsburg. At the change-points, temperature increase in cold cities influenced PNC while shifts in precipitation and wind speed affected PM
2.5. Based on the LOESS trend, extreme events such as dust storms and wildfires resulting from changing climates caused a positive step-change in concentrations, particularly for PM
2.5. In contrast, among the mitigation measures, controlling sulphur in fuels caused a negative step-change, especially for PNC. Policies regarding traffic and fleet management (e.g. low emission zones) that were implemented only in certain areas or in a progressive uptake (e.g. Euro emission standards), resulted to gradual reductions in concentrations. Therefore, as this study has clearly shown that PM
2.5 and PNC were influenced differently by the impacts of the changing climate and by the mitigation measures, both metrics must be considered in urban air quality management.
KW - PM2.5
KW - particle number concentration
KW - ultrafine particles
KW - mitigation
KW - climate variabilities
KW - Mitigation
KW - Particle number concentration
KW - Climate variabilities
KW - Ultrafine particles
KW - PM
UR - http://www.scopus.com/inward/record.url?scp=85082708504&partnerID=8YFLogxK
U2 - 10.1016/j.envpol.2020.114500
DO - 10.1016/j.envpol.2020.114500
M3 - Article
SN - 0269-7491
VL - 263
JO - Environmental Pollution
JF - Environmental Pollution
IS - Part A
M1 - 114500
ER -