Content and cycling of main biogenic and toxic elements in fragmented ecosystems of the Sofia city, Bulgaria

Abstract

This article deals with the content and cycling of main biogenic and toxic elements within six fragmented ecosystems of the Sofia city. All of them are part of recreational areas and have been modified to varying degree by urbanization. Depending on the degree of profile sequence disorder, studied soils can be divided into four groups: 1. Buried soils; 2. New soils; 3. Soils with undisturbed profile and 4. Cultivated soils. Presented classification follows the principles of the Bulgarian and WBR classification schemes. The results indicate that urbanization activities do not lead to soil pollution with Cr, Zn, Pb, Cu, Ni, and Co, but significantly increase the spatial variability of Pb, Co and Mn content. Therefore, these elements could be considered as an indicator of geochemical remodelling of urban soils. All studied elements prevail in background total and bioavailable concentrations in soils except for available phosphorus which occurs in extremely low amount (< 7 g 100-1 g soil) independently on the degree of soils reformations, and Pb. occurs in toxic available concentrations in four soil types, but plant communities slightly accumulate it. No aberrant concentrations of trace elements were found in the aboveground biomass of vascular plants in studied urban habitats.

Keywords

• bioavailability
• ferromagnesian trace elements
• geochemistry
• lead toxicity
• urban soils