Air pollution has become a major threat to human health in the last decades, with an increase of acute air pollution episodes in many cities worldwide. Source apportionment modelling provides valuable information on the contribution from different emission source sectors and source regions to distinct air pollutants concentrations. In this study, the CAMx model, with its PSAT tool, was applied to quantify the contribution of multiple source areas, categories and pollutant types to ambient air pollution, namely to PM and NO₂ concentrations, over six European urban areas: Bristol (United Kingdom), Amsterdam (The Netherlands), Ljubljana (Slovenia), Liguria Region (Italy), Sosnowiec (Poland) and Aveiro Region (Portugal). Results indicate overall higher annual NO₂ and PM concentrations located in the urban centres of the case studies. A comparison between the different areas showed that Liguria is the region with highest NO₂ annual mean concentrations, while Ljubljana, Liguria Region and Sosnowiec are the case studies with the highest PM annual mean concentrations. The annual average contributions denote a major influence from road transport to NO₂ concentrations, with up to 50%, except in Aveiro region, where road transport presents a lower contribution to NO₂ concentrations, and the greatest contributor is the industrial combustion and processes sector with 45%. These results indicate a negligible contribution of the transboundary transport to NO₂ concentrations, highlighting the relevance of local sources, while for PM concentrations the transboundary transport is the major contributor. The results highlight the relevance of long-range transport of PM across Europe. The transboundary transport reduces its importance during winter, when residential and commercial combustion increases its contribution. In the case of the Aveiro region, the industrial combustion and processes sector also plays an important contribution to PM concentrations.

Notwithstanding the improvements already achieved in recent decades through regional and urban scale actions implemented across Europe, air pollution is still a major environment and health concern for Europeans. The quantitative assessment of the different sources of air pollution in regional/urban areas is crucial to support the design of accurate air quality plans. Source apportionment techniques are capable to relate air pollutant concentrations to existing emission sources activities and regions. The selection of the appropriate source apportionment technique to apply to a given area should take into account the ultimate goal of the study. Despite the growing number of studies that include source apportionment techniques, there is still a lack of works that summarise information on this topic in a systematic way. In this work, a literature review of studies applying SA techniques, published between 2010 and 2021, was performed. Additionally, this review summarizes the differences among the different source apportionment techniques, with focus on source-oriented models, highlighting their purpose and their advantages and disadvantages. Results shows that the number of studies using source apportionment source-oriented models has been increasing across the years, with 59% using tagged species methods, 28% brute force methods, and 13% other methods. This source-oriented models have been mostly applied for PM2.5, to assess the causes of air pollution levels.

The World Health Organization estimates that every year air pollution kills seven million people worldwide. As it is expected that climate change will affect future air quality patterns, the full understanding of the links between air pollution and climate change, and how they affect human health, are challenges for future research. In this scope, a methodology to assess the air quality impacts on health was developed. The WRF-CAMx modelling framework was applied for the medium-term future climate (considering the SSP2-4.5 scenario) and for the recent past (considered as baseline). Following the WHO recommendations, mortality health indicators were used to estimate the health impacts of long-term exposures. For that, the Aveiro Region, in Portugal, was considered as a case study. Future climate results indicate the occurrence of higher temperatures, and lower total precipitation. Despite that, improvements in the main pollutants’ concentrations, and consequently in the reduction of the related premature deaths are foreseen, mainly due to the reduction of pollutants emissions imposed by the European legislation for the upcoming years. The applied approach constitutes an added value in this research field, being crucial to anticipate the effects of climate change on air quality and evaluate their impacts on human health.