Advances in air quality research – current and emerging challenges

Abstract

Abstract. This review provides a community's perspective on air quality research focusing 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 characterizing 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) 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 in particular those on satellites. The research should also capitalize on the growing area of low-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 the impacts of both indoor and outdoor emissions, as well as application of more sophisticated, dynamic modelling approaches to predict concentrations of air pollutants in both environments. 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.

High-Resolution Urban Air Quality Mapping for Multiple Pollutants Based on Dense Monitoring Data and Machine Learning

“…Because of the severe urban air pollution, there is a growing demand for air quality monitoring services, which aim to understand the real-time air quality of any area in the city (e.g., street, community, school), as well as their spatial-temporal variations at a higher resolution [5]. Such information could greatly help public decision making (such as whether to take exercise outdoors) and urban fine-management and policy making (such as performing controls for the area that often produce severe air pollution) to reduce public health and capital loss.…”

“…Even in affluent regions, air quality monitors are also sparse (i.e., there are 18 continuous regulatory monitors in the New York metropolitan area [6] and 35 in Beijing, China [7]), which provide only limited coverage of air quality monitoring. Second, the air pollutants' distribution can vary greatly at both small spatial and temporal scales due to complex physical-chemical transformations and multiple emission sources, especially in populous urban areas [5,8]. Third, urban air pollution is a complex dynamic system, which not only has a strong spatial dependency with adjacent areas [9], but also can be affected by a variety of factors (e.g., meteorological, urban structures).…”

Simulating PM2.5 Concentrations during New Year in Cuenca, Ecuador: Effects of Advancing the Time of Burning Activities

“…Particulate matter (PM) concentrations in ambient air are the result of a complex two-way interaction between emissions and atmospheric physical–chemical processes [ 19 , 20 ]. The dynamic of the planetary boundary layer (PBL)—the turbulent bottom layer of the atmosphere, which experiences a daily cycle of depth, temperature, wind, and pollution variations—directly influences air pollutant concentrations.…”

“…Radiation, cloud cover, wind speed, and direction also influence the behavior of air quality [ 22 , 23 ]. Other processes, such as accumulation, condensation, fragmentation, and sedimentation, also influence PM concentrations [ 19 , 24 , 25 , 26 ].…”

Heterogeneity of On-Road Traffic Emissions in Norway: A Model for Transition

“…15,16]. There are, however, substantial benefits of having an integrated approach to tackle both climate change and air pollution, and in order to do this co-emitted emissions should be viewed holistically [17,18].…”