Evaluation of the behavior and distribution of mercury and associated heavy metals in contaminated soils from an abandoned mercury complex in the Azzaba region (Northeast Algeria)

This research is about the mercury and toxic metals pollution caused by the mining processes of cinnabar deposits at Ismail abandoned mercury complex in Algeria. This complex has caused many health and environmental problems in Azzaba area. The effect has continued to date with the presence of toxic elements even after almost 20 years since the site closed. Planning for remediation was never considered. However, this study aims to characterize the soil, by mercury and associated metals concentrations and physicochemical parameters. Also, to evaluate the behavior and distribution of toxic elements in samples based on the physicochemical parameters of the environment. The results show that all samples have a high level of toxic metals (Hg, Zn, Pb, As, Cr, Cu, and Sb) with averages in ppm, respectively (1526, 8421, 4372, 238, 134, 389, 124), these concentrations exceed standards, which increase the environmental risks. The statistical results show a correlation between pH–(Zn, Pb, Cr), Ec–(Pb, Cr and Cu), CEC–(Zn, Cu and As), OM–Zn and CaCO3–(Zn, Pb, Cr, Cu and Sb) indicate that physicochemical parameters can affect the behavior and the mobility of metals. Except for Hg, which behaves in a particular way. In addition, according to ANOVA tests, Hg and As are evenly distributed throughout the study area. Unlike other metals, Pb, Cu and Sb to move to the surrounding soil or accumulate at a distance of 150 m while Zn and Cr accumulate in the upper part of the waste dump. This research investigates how toxic elements disperse or accumulate, make an assumption about their geochemical origin, and analyses their interactions with different soil characteristics. In addition, it contributes to the assessment of environmental risks and provides a relevant scientific support for planning appropriate decontamination and site restoration strategies.