Work

Effect of dispersion normalisation on long-term source apportionment and trends of ultrafine particles in Barcelona (NE Spain)

Year: 2025

Type: article

Abstract: Ultrafine particles (UFPs, ≤ 100 nm) are a major component of urban air pollution, influenced by source emission rates (of UFPs and precursors) and meteorological conditions, both of which vary over time. This study evaluates the effect of dispersion normalisation on UFP source apportionment and long-term trends in the urban background of Barcelona (NE Spain) over a 12-year period (2013-2024). Hourly particle number size distributions (PNSD) were normalised using the ventilation coefficient (VC), derived from boundary layer height and wind speed, and analysed with positive matrix factorisation (PMF) for cold (October-March) and warm (April-September) seasons. Seven factors were identified, with road traffic as the dominant contributor. Dispersion corrected (DC) traffic contributions averaged 57% of particle number concentrations (PNCs), compared with 64% in the uncorrected (UC) analysis, indicating overestimation of local sources when dispersion is not considered. Photonucleation and Nucleation growth showed higher DC contributions (37% compared with 31% for UC), consistent with midday occurrence under favourable mixing conditions. Trend analysis revealed significant decreases in PNCs (-4.4 % yr -1 ), strongest in the Aitken mode, likely linked to reduced traffic emissions following EURO 5/6 regulations, the introduction of diesel particulate filters (DPFs), and the implementation of Barcelona’s low emission zone (LEZ). Traffic-related factors declined by -4.6 % yr -1 , with the largest decrease in the diesel-related source. Nucleation growth and Regional-1 also declined, while Photonucleation and Regional-2 showed no clear trend. These findings highlight the value of dispersion normalisation in source apportionment and provide strong evidence of the effectiveness of emission control-policies in reducing traffic-related UFPs.

Source: Atmospheric Environment

DOI: 10.1016/j.atmosenv.2025.121752

Authors: Meritxell Garcia-Marlès, Cristina Reche, Noemí Pérez, Andrés Alastuey, Xavier Querol

Institutions: Institute of Environmental Assessment and Water Research, Universitat de Barcelona

Language: English

Topic: Atmospheric chemistry and aerosols

Subfield: Atmospheric Science

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDGs: Climate action, Sustainable cities and communities, Good health and well-being

Open Access status: hybrid

Estimated APC paid: $2,910