**4. Conclusions**

The combination of soil microanalyses and earthworm bioavailability testing proposed in this study allowed us to comprehensively assess Pb occurrence and distribution in the investigated shooting range soil, suggesting a rather limited mobility and bioaccessibility of Pb. In these soils, Pb occurred as metallic slivers, which over time underwent weathering processes resulting in the formation of a phosphate superficial crust, in some cases encap-

sulating other soil materials within, such as small silicate minerals. The coexistence of Pb and Ca, combined with different ratios to P, suggested Pb2+ to Ca2+ exchange mechanisms, hence the stabilization of Pb into Pb orthophosphates. These latter were attributed to insoluble Cl pyromorphite formation due to the presence of Cl in the weathered regions of the particles. The occurrence of these processes is likely to strongly reduce Pb mobility and leachability in the studied soil. Earthworm bioassays confirmed this prevision, since exposure to the contaminated soil did not show acute toxicity effects (although not in the aims of the present study, these toxicity results can be extended to the other PTEs found in the investigated soils, i.e., Cd and Sb) nor high levels of Pb bioconcentration. Additional tests would be required to investigate chronic exposure effects and/or plant availability. Based on the overall results of this study, we believe that the approach pursued in this work could be successfully used for other polluted soils.

**Author Contributions:** Conceptualization, C.P., R.T. and M.S.; methodology, C.P. and I.A.; software, C.P. and I.A.; investigation, C.P., I.A., C.E.G. and N.F.; data curation, C.P.; writing—original draft preparation, C.P.; writing—review and editing, C.E.G., I.A., R.T., N.F., M.F. and M.S.; visualization, C.P.; supervision, M.S.; project administration, M.S.; funding acquisition, M.S., M.F. and R.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by PRIN 2017 (Progetti di Ricerca di Rilevante Interesse Nazionale)—2017BHH84R—"Role of Soil-Plant-Microbial Interactions at Rhizosphere Level on the Biogeochemical Cycle and Fate of Contaminants in Agricultural Soils Under Phytoremediation with Biomass Crops (RIZOBIOREM)." Ignazio Allegretta was supported by a research gran<sup>t</sup> for the project PON R&I "Studio del sistema suolo-pianta mediante tecniche analitiche innovative che impiegano raggi X"—Progetto AIM1809249—attività 1, linea 1.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data are available upon request by contacting Dr. Carlo Porfido (e-mail: carlo.porfido@uniba.it).

**Acknowledgments:** Micro-XRF and TXRF analyses were performed at the Micro-X-ray Lab of the University of Bari Aldo Moro (Italy).

**Conflicts of Interest:** The authors declare no conflict of interest.
