Urban soils are often contaminated by metals deriving from human activities. Urban polluted soils can affect human health through direct physical contact or through the food chain. The behaviour of metals is affected by chemical and physical soil properties. Heavy metal concentration was determined in some soils of three medium sized towns of coastal Tuscany, Central Italy. Soil samples were collected in roadsides, urban agricultural soils (allotments), playgrounds and public parks. The analysis included total metal content (Pb, Cu, Zn, Ni, Cd), and sequential extraction. Lead reached the highest levels in the soils and was higher near roads. In urban agricultural soils and in allotments Cu was present in noticeable quantities (300 mg kg(-1)). The presence of Cu in urban soils seems to be typical of soils used for a long period as agricultural land, especially vineyards in the area covered by this study. Sequential extraction was performed to evaluate the mobility of the metals and to better understand the impact of the anthropogenic activity on urban sites. In the present study principal components analysis (PCA) is employed to describe the characteristics of urban soils.
The effects of the chemical and physical factors associated with geothermal activity on plant community structure and composition were investigated in one of the largest geothermal fields of central Italy. The study site was located in the geothermal area of Sasso Pisano GÇô Monte Rotondo Marittimo, Southern Tuscany. The percentage cover of all vascular plant, bryophyte and lichen species was estimated within 119 circular plots of 0.25 m2. For each plot the soil pH, soil temperature, slope, aspect, incident radiation, soil nitrogen and carbon contents were also quantified. Two vascular plants, Calluna vulgaris and Agrostis castellana, were found to be the most widespread species tolerating the harshest conditions in terms of low soil pH and high soil temperature. The most widespread cryptogam species was Hypnum cupressiforme. Spatially autoregressive models showed that a proportion of about 41GÇô51% of the variance in species richness of one group of plants (vascular or cryptogamic plants) could be modelled by using three or four uncorrelated environmental factors respectively (soil temperature, soil nitrogen and soil C/N ratio and these three plus incident radiation). For the total number of species (vascular and cryptogamic plants), the variance explained by the same three uncorrelated variables was about 57%. This study evidenced a strong environmental control of community composition and species richness, in a site subjected to extreme soil values of soil pH and temperature. The dominance of vascular over cryptogamic vegetation in this geothermal site can be explained by the combined effects of geothermal stress (low soil pH and high soil temperature) with the summer drought typical of the Mediterranean climat
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