Editorial: Atmospheric Aerosol and Pollution: Characterization Techniques and Source Identification

Mounia TAHRI ^* Abdelfettah Benchrif

• National Centre for Nuclear Energy, Science and Technology (Morocco), Rabat, Morocco

The complex behavior of atmospheric aerosols and air pollutants is an issue of great interest I the quest for an integrative understanding of environmental health and climate change. Due to the worldwide trend of urbanization and fast industrialization, the need for intensive scientific research on atmospheric aerosols has become an urgent necessity. In this context, we present this special volume titled "Atmospheric Aerosol and Pollution Characterization Techniques and Source Identification", that seeks to provide an overview of the recent progress and methods in this area.Atmospheric aerosols are a mixture of solid and liquid particles suspended in the air, of high ecological and societal importance, as they are related to the global Earth's climate and human health. Their complex relationships with radiation, could formation, and precipitation can have far-reaching implications. Furthermore, aerosols have the potential to carry toxic agents and pathogens and cause considerable health and ecosystem consequences. Therefore, information about their origin, their function, and their mechanism of action if very relevant. This volume summarizes a multidisciplinary perspective on aerosol characterization, bringing together contributions from scientists all over the world, who are focused on the challenging issues of atmospheric science. Every paper gives useful information on the characterization techniques, including advanced spectrometric analysis, satellite remote sensing, and groundbased observational strategies, which help to promote more efficient observation of the aerosol composition, characterization and identification of pollution sources, analysis of the effectiveness of mitigation strategies on air quality. The special emphasis coming out of our discussion is on source identification methods, which are the core issues for designing practical pollution control measures. Using chemical fingerprints, trajectory modeling and statistical analysis, this volume highlight how scientists identify sources of pollution (e.g., vehicle exhaust, industrial discharge, biomass burning). Interpreting these sources is of great importance not only for regulatory compliance, but also for effective development of useful interventions for both environmental and human health.Yan Zha et al. investigate the response of pak choi (Brassica pekinensis) to combined stress from acid rain (AR) stress plus cadmium-enriched atmospheric fine particulate matter (PM2.5-Cd). Based on integrated transcriptomic and metabolomic analyses, the authors found 735 differentially expressed genes (DEGs) and 451 differentially expressed metabolites (DEMs) as a response to stress. Major conclusions are the upregulation of genes in detoxification, antioxidant defense and metabolic pathways, including flavonoid and phenylpropanoid biosynthesis. The findings indicate that these pathways are critical in the plant's response to AR-Cd stress and suggest directions for understanding potential mechanisms by which the tolerance of leafy vegetables to environmental pollutants can be improved.Sanjit Gaikwad et al. examine the morphology and phase state of fine particulate matter (PM2.5) collected near urban (Seoul) and coastal-rural (Seosan) regions in South Korea in June 2021. Researchers reported by means of optical microscopy and the poke-and-flow method that PM2.5 showed varied phases-liquid, semisolid phase and (semi)solid phase-over a range of relative humidity (RH) and chemical composition. In Seoul, PM2.5 was mainly liquid contaminated days and semisolid noncontaminated days, whereas in Seosan it mostly remained as a liquid because of higher levels of ambient VHR (relative humidity). Results underscore the necessity to clarify the physical properties of PM2.5 in atmospheric chemistry and air pollution prediction.Xuwei Li et al. To understand the spatiotemporal variation of and sources of volatile organic compounds (VOCs) in a pesticide-polluted site in China from 2016 to 2021. This study presents a series of concentration-time curves of VOCs in four layers of the pollutant atmosphere (the urban level, the low-elevation hills, the middle-elevation hills, and the higher-elevation hills) and in the ground-level and near-soil levels under specific meteorological conditions. It characterizes BTEX (benzene, toluene, ethylbenzene, and xylenes) and alkanes as major contaminants with large time and space concentration fluctuations. The authors use statistical analysis, GIS spatial interpolation, and Positive Matrix Factorization (PMF), to study the VOC sources, and the contribution from site-specific emission, pharmaceutical production, and nearby petrochemical activities are found out. The results demonstrate the necessity of future monitoring and efficient pollution management programs for ATSs.Miftah Fekadu et al. detail the effects of different types of wood cookstoves on indoor and outdoor air pollution and deforestation in rural Ethiopia. It concludes that better cookstoves reduce considerably carbon monoxide and particulate matter emissions compared to simple three-stone stove, and CO exposure in some places is higher than WHO standards. Improved stoves' use has further contributed to decreasing deforestation rates. This study underscores the importance of improved cooker designs, effective ventilation, and improved understanding of health hazards of indoor air pollution along with stricter regulatory authorities to deal with those problems.Stefania Renna et al. review the major role of agricultural activities in PM10 pollution and its health consequences in Lombardy. The authors show that the ammonium salts represent over 30 of the PM10 daily burden, PM10 annual contribution is close to the limit set by the European Union. They reported that agricultural emissions, especially livestock emissions, cause around 589 death per year in the city of Milan, and this gives a loss of about 7000 years of life. The paper also stresses the need for practical action of integrated policies, aimed at emission from multiple sectors for truly effective reduction of air pollution and its impact upon human health. Barbara Harm-Altstädter et al. explore the vertical distribution of aerosol particles in the vicinity of Berlin Brandenburg Airport (BER) based on fixed-wing drone ALADINA. Carriedout between 11 and 19 October 2021, the study obtained 140 vertical profiles of aerosol concentrations and meteorological variables up to 750 m above ground level. The results show that aerosol concentrations tend to be highest close to the ground, driven by atmospheric boundary layer stability and by aircraft and roadside emissions generated at the airport and roadside sources, respectively. The research shows the crucial role of ultrafine particles (UFP) in ambient air quality and potential health effects of both, in particular the importance of a further investigation of airport pollution.In this special volume, the importance of international working together and data sharing to overcome these challenges is highlighted. Air pollution is all about borders and therefore effective strategies and policies need to be collaborative across countries, research institutions, and communities. We appeal to readers to envision the interdisciplinary character of aerosol science encompassing meteorology, environmental science, public health data science as a base for future research and policymaking.Finally, we express our deepest thanks to all the authors, the reviewers, and other contributors that have made this volume possible. Your dedication to advancing our understanding of atmospheric aerosols and pollution is commendable. We expect this compilation not only to be a reference tool for the current approaches and results but also to stimulate new investigations and creative approaches for addressing international air quality issues.