Urban conditions affect soil characteristics and physiological performance of three evergreen woody species

Physiological studies conducted mainly in metropolitan areas demonstrated that urban environments generate stressful conditions for plants. However, less attention has been paid to plant response to urban conditions in small cities. Here, we evaluated to what extent the health and physiological functions of some Mediterranean urban species [Quercus ilex L., Nerium oleander L. and Pittosporum tobira (Thunb.) W.T. Aiton] were impacted by urban and peri-urban conditions in Pisa (Italy), a small medieval city with narrow streets that impede efficient public transport causing oversized private transport. Experimental period spanned from late-summer to winter in concomitance with the sharp increase in air pollutants. Climate and air quality, soil physical and chemical properties, and plant physiological traits including leaf gas exchanges, chlorophyll fluorescence and leaf pigments were assessed. In soil, the organic carbon affected aggregates and water stability and the concentrations of some micro-elements decreased in winter. Air pollutants impaired leaf gas exchanges and photochemical processes at photosystem II, depending on species, season, and urban conditions. Shrubs were more susceptible than the tree species, highlighting that the latter adapted better to pollutants along an urban-peri-urban transect in Mediterranean environments. This study gives information on the physiological adaptability of some of the most frequent Mediterranean urban species to stressful conditions and demonstrated that, even in a small city, urban conditions influence the physiology and development of vegetation, affecting the plant health status and its ability to provide key ecosystem services.

Plant-microorganisms interaction promotes removal of air pollutants in Milan (Italy) urban area

Plants and phyllosphere microorganisms may effectively contribute to reducing air pollution in cities through the adsorption and biodegradation of pollutants onto leaves. In this work, during all seasons, we sampled atmospheric particulate matter (PM₁₀) and leaves of southern magnolia Magnolia grandiflora and deodar cedar Cedrus deodara, two evergreen plant species widespread in the urban area of Milan where the study was carried out. We then quantified Polycyclic Aromatic Hydrocarbons (PAHs) both in PM₁₀ and on leaves and used sequencing of 16S rRNA gene, shotgun metagenomics and qPCR analyses to investigate the microbial communities hosted by the sampled leaves. Taxonomic and functional profiles of epiphytic bacterial communities differed between host plant species and seasons and the microbial communities on leaves harboured genes involved in the degradation of hydrocarbons. Evidence collected in this work also suggested that the abundance of hydrocarbon-degrading microorganisms on evergreen leaves increased with the concentration of hydrocarbons when atmospheric pollutants were deposited at high concentration on leaves, and that the biodegradation on the phyllosphere can contribute to the removal of PAHs from the urban air.

210Po in popular medicinal herbs from Poland

Herbs are an important part of traditional medicine in Poland. Therefore, the aim of this study was the determination of polonium ²¹⁰Po in 48 selected medicinal herb samples from the Polish market. The activity concentrations of ²¹⁰Po were measured using alpha spectrometry. The activity concentration of ²¹⁰Po was in the range from 0.3 ± 0.1 to 28.2 ± 0.4 Bq kg^-1. The obtained results were compared with corresponding studies conducted worldwide. A higher ²¹⁰Po activity concentration was observed in the above-ground part of plants. The obtained results show that the highest ²¹⁰Po activity concentration was observed in evergreen plants and winter-hardy plants. Yet even infusions with 2 g of the most contaminated herbs examined were considered to be radiologically safe.

Accumulation of particulate matter and trace elements on vegetation as affected by pollution level, rainfall and the passage of time

Particulate matter is harmful to human health. To reduce its concentration in air, plants could be used as biological filters, accumulating particulate matter on their foliage. In a study carried out at three sites with differing pollution levels and exposure to precipitation, the capacity of evergreen species (Taxus baccata L., Hedera helix L. and Pinus sylvestris L.) to accumulate particulate matter and trace elements from ambient air in urban areas was investigated. The effects of rainfall and the passage of time on particulate matter deposition on foliage were also determined. The results showed that foliage accumulated an increasing quantity of particulate matter in successive months, but the actual amount of particulate matter and trace elements accumulated differed considerably between sites and plant species. The greatest accumulation of air pollutants occurred on the foliage of plants protected from the rain at a site exposed to traffic related pollution and the smallest accumulation at a rural site. Among the species analysed, the deposited mass of particulate matter and trace elements was the greatest on P. sylvestris. In all species, precipitation removed a considerable proportion of particles accumulated on foliage. Most of the removed particulate matter was large size fraction, but little belong to the smallest size fraction. These results showed that both, the dynamics of deposition and leaf washing by rain during the season need to be considered when evaluating the total effect of vegetation in pollutant remediation.