Bioaccumulation of potentially toxic elements within the soil-plant system in Central Balkan region: analysis of the forest ecosystem capacity to mediate toxic elements

The accumulation of potentially toxic elements (PTEs) in terrestrial ecosystems has become a global concern, as PTEs may exert a wide range of negative impacts on forest's ecological state due to local or transboundary pollution. Forest vegetation and soil display great potential as means of coping with the accumulation mechanisms, absorption and dissolving the pollutants. Therefore, it is crucial to study the transfer of PTEs across these basic components of the forest ecosystem. Investigation on the PTEs concentrations in the soil-plant system in relatively non-polluted environment of Central Balkan National Park (Sredna Stara Planina Mountain) provides more information about the role of the forest patterns and soil properties for the bioaccumulation processes in the context of ecosystem services concept. In this paper, the transfer of PTEs in soil-plant system in relatively clean environment is studied in order to assess and map the ecosystem capacity of different types of forest ecosystems to mediate toxic elements. Based on in situ observations and sampling, the PTEs concentrations in soil and aboveground vegetation were analyzed. The potential of each forest type to reduce the impact of PTEs and bioaccumulation as an indicator of ecosystem service is also discussed. The GIS analysis supports the study by creating a common database and setting the basis for ecosystem services assessment. The generated maps represent areas where the forest ecosystems have the greatest capacity to provide related ecosystem service and mediate toxic elements. The bioaccumulation of PTEs in forest territories results in medium to low rates and higher supply capacity is not present at any spatial unit as the accumulation process is focused in the soil. The obtained results highlight the ecological importance of soil in terms of acting as a buffer against pollution, especially in areas with intensive road traffic.