## 5 Conclusions  
The present study outlined the advantages of biomonitoring for the pollution risk assessment of an abandoned mine region including different soil types. The obtained element TFs and AFs confirm that only soil element concentrations are insufficient for reliable risk assessment. In the present study, the Cu soil concentrations exceeded 2 to 16 times the maximum permissible values, but Cu had no significant TF and AF values. The combination of TFs and AFs provides a reliable assessment for elemental uptake and could reveal some differences in the behavior of PTEs. The obtained results for PTEs show significant TFs for Cd and Sn, while the AFs outlined a significant accumulation of Cd and Sb. The correlation analysis of TFs and AFs pointed out that soil-to-plant transfer is mainly related to the CEC of the soil samples, while for the accumulation of elements in plants, the pH and CEC of the soil samples are equally important. These findings outline the necessity of using both factors in biomonitoring studies. The PCA analysis of the transfer and accumulate factor datasets revealed the relationships between the obtained coefficients and CEC. The proposed assessment approach including traditional soil analysis, the use of a well-investigated biomonitor for the respective region (_Tanxacum officinal_ in this study), and multivariate statistical analysis could not only be successfully applied for the pollution risk assessment of PTEs in abandoned mining regions, but also in the other anthropogenically influenced areas including different types of soils. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app132111860/s1](https://www.mdpi.com/article/10.3390/app132111860/s1)]([https://www.mdpi.com/article/10.3390/app132111860/s1](https://www.mdpi.com/article/10.3390/app132111860/s1)), Table S1: Comparison of the ICP-MS results obtained from the plant, soil, and sediment reference materials with certified/literature values and experimentally determined detection limits, Figure S1: Correlation map of the TF, pH (H\({}_{2}\)O), pH (KCI), and CEC (variables are reordered by absolute value of correlation coefficients), Figure S2: Correlation map of AF, pH (H\({}_{2}\)O), pH (KCI), and CEC (variables are reordered by absolute value of correlation coefficients). Conceptualization, V.M. and S.T. ; Methodology, V.M. and S.T. ; Software, S.T. ; Validation, V.M., K.M., A.B. and V.L. ; Formal analysis, V.M., K.M., A.B. and V.L. ; Investigation, V.M., G.Y., K.M., A.B., V.L. and S.T. ; Resources, V.M., G.Y., K.M., A.B., V.L. and S.T. ; Data curation, V.M., G.Y., K.M., A.B., V.L. and S.T. ; Writing-original draft preparation, V.M., G.Y., K.M., A.B., V.L. and S.T. ; Writing-review and editing, V.M., G.Y. and S.T. ; Visualization, V.M., G.Y. and S.T. ; Supervision, A.B., V.L. and S.T. ; Project administration, A.B. and S.T. ; Funding acquisition, A.B. and S.T. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Science Program \"Environmental Protection and Reduction of Risks of Adverse Events and Natural Disasters\", approved by the Resolution of the Council of Ministers, No. 577/17 August 2018, and supported by the Ministry of Education and Science (MES) of Bulgaria (agreement no. _J_I01-271/9 December 2022). Not applicable. The data presented in this study are available on request from the authors. This work was carried out within the framework of the National Science Program \"Environmental Protection and Reduction of Risks of Adverse Events and Natural Disasters\", approved by the Resolution of the Council of Ministers, No. 577/17 August 2018, and supported by the Ministry of Education and Science (MES) of Bulgaria (agreement no. _J_I01-271/9 December 2022). Research equipment from Distributed Research Infrastructure INFRAMAT, part of the Bulgarian National Roadmap for Research Infrastructures, supported by the Bulgarian Ministry of Education and Science, was used in this investigation.