ECOLOGICAL RISK ASSESSMENT OF HEAVY METALS ACCUMULATION IN SOIL AND ZYGOPHYLLUM ALBUM ALBUM: A CASE STUDY OF INDUSTRIAL PHOSPHATE VICINITY, TUNISIA

Abstract

Contents and spatial distribution of heavy metals (Zn, Cu, Cd, Ni, As, Pb, Al and Ba) in the fine fraction of surface sediments and in Zygophyllum album shrub of zones influenced by phosphate industry in the region of Gabès, as well as in a control site (Sidi Ejjehmi) were determined. For the assessment of the level of sediment pollution, several parameters were calculated, including enrichment factor (EF), contamination factor (CF), Pollutant Load Index (PLI), Risk factor (Er), potential ecological Risk Index (Ri), Geoaccumulation Index (Igeo), Electrical Conductivity (Ec), Organic Matter (OM) and pH.Whereas, Bio-Concentration Factors (BCF) and Translocation Factors (TF) are calculated for the evaluation of pollution degree in Zygophyllum album. The soils of Gabès are characterized by a high average relative concentration of As, Ba, Cd, Cu, Ni, Pb, Al and Zn in all the study sites, indicating contributions from anthropogenic sources. The Igeo and the PLI of heavy metals show that all study sites are heavily polluted. All the EF values of all trace metals from Gabes sites (above 10), indicate a very significant enrichment in soils. The PCA, AC and correlation matrix suggest that soils are mainly polluted by As, Ba, Cd, Cu, Ni, Pb, Al and Zn. For all studied metals, the values of TF in Z. album from Gabes sites are greater than 1 except for Al at S2. All metals studied, except Cd, are more accumulated in shoots than in roots. Values of BAF are greater than 1, as well as TF values are greater than 1, so Z. album of Gabes can be considered as phytoremediator in the case of those studied metals. For Cd, TF is greater than 1 and BCF is less than 1, Z. album can be considered as a phytostabiliser for this metal.