Historical assessment approach of the evolution of the toxic trace element contents, transformation, distribution and redistributions, environmental risk levels and stability of Jbel Ressas tailings and agricultural soil (N-E Tunisia), to predict their management plan

Abstract

The jbel Ressas Pb-Zn mining wastes that had more than 600,000 m3 and their surrounding agricultural soil, that are in Northeastern Tunisia had ecological a high hazards. To suggest the wastes protection and soil remediation plan the evaluation of the historical evolution of their total and labile TTE contents, stability and distributions since their abundance (1952) and until today, which is not often possible, was a crucial step. The of Pb, Zn and Cd quantities in the initial wastes were 46640 t, 134780 t and 1150 t. the released Pb, Zn and Cd quantities in 2009 was 50% and in 2021 was 22.6%. The remained quantities are 15.6 t of Pb, 64.2 t de Zn and 0.4 t de Cd that presented a worrying environmental hazard. The pollutants speed migration was accelerated, particularly during the last 10 years. Thus, the risk of these pollutant sources is still high. Of the TTE that migrated from the tailings, only 6.1, 4.8, and 4.1% of Pb, Zn, and Cd, respectively were retained in soil. However, the soil potential ecological risk (Eri.) was high. From 1952 and until 2009 around 60% of the TTE tailings have been mobilized and from 2009 to 2021 around 6%. The estimation of the future evolution of redistributions and transformations of current TTE showed that the risk of Jbel Ressas residues is worrying. The whole-soil removal (Uts) and relative binding intensity index (IR) of the TEE in initial tailings sediments and soil ≈ 1 meaning that had any environemental risk. The Uts and IR evolution from 1952 and until today showed that the TTE stability and risk level increased with exposition time. Therefore, the overall historical assessment is of great interest in order to suggest solutions for polluted areas.