Advances in Air Quality Research – Current and Emerging Challenges

Abstract

Abstract. This review provides a community’s perspective on air quality research focussing mainly on developments over the past decade. The article provides perspectives on current and future challenges as well as research needs for selected key topics. While this paper is not an exhaustive review of all research areas in the field of air quality, we have selected key topics that we feel are important from air quality research and policy perspectives. After providing a short historical overview, this review focuses on improvements in characterising sources and emissions of air pollution, new air quality observations and instrumentation, advances in air quality prediction and forecasting, understanding interactions of air quality with meteorology and climate, exposure and health assessment, and air quality management and policy. In conducting the review, specific objectives were (i) to address current developments that push the boundaries of air quality research forward, (ii) to highlight the emerging prominent gaps of knowledge in air quality research and (iii) and to make recommendations to guide the direction for future research within the wider community. This review also identifies areas of particular importance for air quality policy. The original concept of this review was borne at the International Conference on Air Quality 2020 (held online due to the COVID 19 restrictions during 18–26 May 2020), but the article incorporates a wider landscape of research literature within the field of air quality science. On air pollution emissions the review highlights, in particular, the need to reduce uncertainties in emissions from diffuse sources, particulate matter chemical components, shipping emissions and the importance of considering both indoor and outdoor sources. There is a growing need to have integrated air pollution and related observations from both ground based and remote sensing instruments, including especially those on satellites. The research should also capitalize on the growing area of lower cost sensors, while ensuring a quality of the measurements which are regulated by guidelines. Connecting various physical scales in air quality modelling is still a continual issue, with cities being affected by air pollution gradients at local scales and by long range transport. At the same time, one should allow for the impacts from climate change on a longer timescale. Earth system modelling offers considerable potential by providing a consistent framework for treating scales and processes, especially where there are significant feedbacks, such as those related to aerosols, chemistry and meteorology. Assessment of exposure to air pollution should consider both the impacts of indoor and outdoor emissions, as well as apply more sophisticated, dynamic modelling approaches. With particulate matter being one of the most important pollutants for health, research is indicating the urgent need to understand, in particular, the role of particle number and chemical components in terms of health impact, which in turn requires improved emission inventories and models for predicting high resolution distributions of these metrics over cities. The review also examines, how air pollution management needs to adapt to the above-mentioned new challenges and briefly considers the implications from the COVID-19 pandemic for air quality. Finally, we provide recommendations for air quality research and support for policy.

Impact of urbanization on gas-phase pollutant concentrations: a regional-scale, model-based analysis of the contributing factors

“…The choice of the cities used the same criteria as in Huszar et al (2021): the size of the city comparable to one 9 km × 9 km grid cell, sufficient distance between cities to eliminate intercity influences, minimal orographic variability to reduce orographic effects (Ganbat et al, 2015), and no coastal cities to eliminate the effect of asymmetric land use like the sea breeze effect (Ribeiro et al, 2018). Although strict emission control policies, these cities are still often burdened with high air pollution for pollutants as NO 2 and O 3 (EEA, 2019;Khomenko et al, 2021;Sokhi et al, 2022). a Information on whether urban land surface was considered.…”

“…Urbanization, however, influences the final air pollution in other ways too. One of the most studied aspects of RUT is the modulation of the pollutant concentration due to the meteorological forcing represented by the urban canopy, which includes effects like increased temperatures (urban heat island, UHI) (Oke, 1982;Oke et al, 2017;Karlický et al, 2018Karlický et al, , 2020Sokhi et al, 2022), lower wind speeds (Jacobson et al, 2015;Zha et al, 2019), or elevated boundary layer height along with enhanced vertical eddy diffusion (Ren et al, 2019;Huszar et al, 2020a;. Huszar et al (2020a) introduced the term urban canopy meteorological forcing (UCMF), which represents the forcing that the land surface modified by RUT represents for the physical state of the air above via perturbed exchange of momentum, heat, radiation, and moisture.…”

Impact of urbanization on gas-phase pollutant concentrations: a regional scale, model based analysis of the contributing factors

“…The choice of the cities used the same criteria as in Huszar et al (2021): the size of the city comparable to one 9 km × 9 km grid cell, sufficient distance between cities to eliminate intercity influences, minimal orographic variability to reduce orographic effects (Ganbat et al, 2015), and no coastal cities to eliminate the effect of asymmetric land use like the sea breeze effect (Ribeiro et al, 2018). Although strict emission control policies, these cities are still often burdened with high air pollution for pollutants as NO 2 and O 3 (EEA, 2019;Khomenko et al, 2021;Sokhi et al, 2022). a Information on whether urban land surface was considered.…”

“…Urbanization, however, influences the final air pollution in other ways too. One of the most studied aspects of RUT is the modulation of the pollutant concentration due to the meteorological forcing represented by the urban canopy, which includes effects like increased temperatures (urban heat island, UHI) (Oke, 1982;Oke et al, 2017;Karlický et al, 2018Karlický et al, , 2020Sokhi et al, 2022), lower wind speeds (Jacobson et al, 2015;Zha et al, 2019), or elevated boundary layer height along with enhanced vertical eddy diffusion (Ren et al, 2019;Huszar et al, 2020a;. Huszar et al (2020a) introduced the term urban canopy meteorological forcing (UCMF), which represents the forcing that the land surface modified by RUT represents for the physical state of the air above via perturbed exchange of momentum, heat, radiation, and moisture.…”