Dear Colleagues,

The use of cosmopolite organisms to assess pollution has developed notably over the last few decades. Bioindicators include biological processes, species, or communities and are used to assess the quality of the environment and how it changes over time. Changes in the environment are often attributed to anthropogenic disturbances (e.g., pollution and land-use changes) and natural stressors, although anthropogenic stressors form the primary focus of bioindicator research. Such organisms consume environmental contaminants and may be used as indicators of the bioavailability of a given contaminant over time, allowing, in certain cases, comparisons to be made between contamination levels in different areas. The advantage of this method is that it’s simple and low cost, which would be impossible with conventional analyses using automatic measuring devices. Plants are particularly useful as biological indicators to evaluate air pollution because of their wide distribution and low sampling cost. Mosses and lichens have also been recognized as the most appropriate biomonitors of atmospheric heavy metals. Additionally, trees are very efficient at trapping atmospheric particles, mostly on their foliage. The concentrations of metal and metalloids in plants depend on root uptake and dry and wet depositions on outer plant organs such as foliage or bark. Therefore, the elemental analysis of plant samples has, for many years, been an alternative, easy, and effective way of conducting ecological investigations in urban areas. The method of assessing air pollution by using bioindicators is not only in constant and widespread use, but it is also continuously being developed.

This Special Issue of the journal "Atmosphere" focuses on the current state of knowledge of air pollution in anthropized and natural areas, to determine the concentrations of the main pollutants, model their spatial distributions and identify their sources, measuring their concentrations through the use of bioindicators.

New research papers, reviews, case report, and conference papers are welcome to this Special Issue.

Dr. Maria Grazia Alaimo
Dr. Daniela Varrica
Guest Editors

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• bioindicators
• biological monitoring
• air pollution
• environmental impact assessment
• air quality
• biomonitoring

Varrica Daniela and Alaimo Maria Grazia. Influence of Saharan dust on the composition of urban aerosols.

The Mediterranean Basin is exposed to continuous incoming air masses loaded with dust from North Africa. The Sicily region is geographically close to North Africa, hence, the occurrence of Saharan dust events (SDE) in this region is quite common. Saharan dust has been associated with increased mortality and respiratory symptoms.  Palermo is a large coastal city, and in addition to the impact of desert dust particles, it has a mixture of anthropogenic sources of pollutants. In this study, we collected Saharan dust samples during May and July 2023, following a high-intensity Saharan dust event, and XRF measured concentrations of 27 major and trace elements and inductively coupled plasma (ICP-MS). The mineralogical characterization of the dry deposition dust revealed calcite, dolomite, quartz, and clay minerals. The presence of palygorskite is indicative of the Saharan events. Seven elements (Ca, Mg, Al, Ti, Fe, K, Na) account for 98% of the total analyzed inorganic burden. Elemental ratios are valuable tools in atmospheric sciences for estimating sources of air masses.  The results highlight that the city of Palermo is mainly affected by dust coming from the north-western Sahara.