Biogeochemical assessment of the impact of Zn mining activity in the area of the Jebal Trozza mine, Central Tunisia.

Soil pollution associated with potentially toxic elements (PTEs) from mining residues is a significant problem worldwide. The decommissioned Jebal Trozza mine, located in central Tunisia, may pose a serious problem because of the possible high concentrations of PTEs present in its wastes. This mine is a potential source of contamination for agriculture in this area due to both direct causes (pollution of agricultural soils) and indirect causes (pollution of sediments that accumulate in a dam used for irrigation). The aim of the study reported here was to assess the effects of local mining activity in two respects: (1) in terms of soil quality, as determined by soil edaphological parameters and PTEs contents in the mining wastes and local soils; and (2) in terms of biological quality, as evaluated by quantification of enzymatic activity as an indicator of bacterial activity in soils and wastes. The mine tailings contained high levels of Pb (1.83-5.95%), Zn (7.59-12.48%) and Cd (85.95-123.25 mg kg