Compositional features of Pb in agricultural soils and geochemical associations conditioning Pb contents in plants.

Soil geochemical data is compositional. Hence the studies targeting the potential of accumulation of toxic elements (TE) in plants have to consider the compositional nature of soil chemical environment. In this study, the combined application of compositional data analysis and geospatial mapping was used to investigate Pb geochemical associations in agricultural soils, revealing the link between these associations and Pb contents in plants, as well as identifying source-specific transfer of Pb from soil to plants. The obtained results showed that soil chemical composition was conditioned by the geological peculiarities of the study area and the potential sources of chemical elements' release. Particularly, k-means clustering and CoDa-biplot allows to identify three distinct subsamples and the application of HCA showed that both Pb soil and plants contents were in the same cluster in all subsamples. However, the geochemical association of elements in subsamples I and III suggested that Pb contents in plants were conditioned by the geochemical behaviors of carbonates whereas in subsample II Pb plant contents were presented in a geochemical association (K, Rb, Pb, and Zn) typical for both fertilizers and the potassium feldspar. The transfer factor (TF) for the comparatively higher values is observed for the subsample linked to K, Rb, Pb, and Zn geochemical association. At the same time, the negative influence of carbonates on the Pb availability in the plants was evidenced. The results of this study can serve as a good example for other investigations targeting the role of soil chemical elements compositional features in elements transfer to plant.