Chelate facilitated phytoextraction of Pb, Cd, and Zn from a lead-zinc mine contaminated soil by three accumulator plants.

This study aims to evaluate the enhancement of phytoextraction of heavy metals (Pb, Cd, and Zn) by species Marrubium cuneatum, Stipa arabica, and Verbascum speciosum, through EDTA amendment. Assisted phytoextraction pot experiments were performed at different EDTA dosages (0, 1, 3, and 5 mmol kg-1 soil). The DTPA-extractable metal content increased in the presence of EDTA, followed by their contents in the tissues of all three studied species. Resulting from oxidative stress, the activity of antioxidant enzymes such as glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT) increased when the chelating agent was added. EDTA in higher doses partially decreased chlorophyll concentration, and 5 mmol kg-1 of that reduced the biomass of the studied species. The bioconcentration factor (BCF) for Cd was notably high in all studied plants and considerably elevated for Zn and Pb with the addition of EDTA in M. cuneatum and S. arabica (BCF > 1), whilst an accumulation factor greater than one (AF > 1) was found for Cd in all species and for Pb in the case of S. arabica. In general, the results demonstrated that EDTA can be an effective amendment for phytoextraction of Cd, Zn, and Pb by M. cuneatum, V. speciosum and S. arabica in contaminated soils.

Investigating metal pollution in the food chain surrounding a lead-zinc mine (Northwestern Iran); an evaluation of health risks to humans and animals.

The current study aims to evaluate the health risk of heavy metals for humans and animals in the Angouran mining complex (northwest of Iran). Twenty-five plant species and their corresponding soils (natural soils) were collected along with mine tailings samples. The carcinogenic and non-carcinogenic risks of heavy metals (Zn, Pb, Cd, Cr, and Co) for humans using the hazard quotient (HQ) and hazard index (HI) were evaluated. Moreover, the health risk caused by forage feeding to grazing ruminants (cow and sheep) and the risk associated with animal products consumption by humans in the soil-plant-animal transfer system were assessed. The value of HI in natural soils (rangeland use) was less than one (HI < 1), while regarding tailings, the HQ via oral ingestion and the HI were greater than one (HI & HQ > 1). The range of total carcinogenesis risk in natural soils exceeded the target risk (Risk < 10-6) and for tailings, it showed the probability of cancer risk, 1 person per 3636 populations, which is much higher than the acceptable or tolerable range (10-4 < Risk < 10-6). Regarding the animal health risk, the content of Pb and Cd in most of the animal organs was higher than the control values. In turn, dietary exposure to Pb and Cd is worrying for residents due to exceeding the provisional tolerable weekly intake (PTWI). This comprehensive study suggests the necessity of risk assessment of mining sites in Iran and immediate control measures to diminish pollutants.

Perspectives for phytoremediation capability of native plants growing on Angouran Pb-Zn mining complex in northwest of Iran.

Phytoremediation is a cost-effective, environmentally-friendly and emerging remediation technology that treats polluted areas using plants, having the potential to restore ecosystems and make compromised areas useable again, therefore returning a resource to community use. In the present work a study was conducted on the contamination of soil by heavy metals (Zn, Pb, Cr, Cd, and Co) in the mining area of Angouran (northwestern Iran) and on their uptake by 25 native species present in the mining district, in order to evaluate their potential use in phytoremediation interventions. Plant and soils from three sites around the mine were sampled and characterized, and metals accumulation and translocation were evaluated. Principal Component Analysis (PCA) and Cluster Analysis (CA) were applied to study the behavior of species in the accumulation and translocation of the elements in their tissues. The contents of Zn, Pb, Cr, Cd, and Co in the studied plants were, respectively, 31.77-723.05, 7.78-233.25, 1.77-21.57, 0.04-7.92, and 0.15-9.97 mg/kg. Among the 25 species, 13 plants showed translocation factor greater than one (TF > 1) for Zn, 14 for Pb, 3 for Cr, 10 for Co, and 6 for Cd. Marrubium cuneatum having an accumulation factor greater than one (AF > 1) for Zn and bioconcentration factor greater than one (BCF >1) for Cd can be considered as an accumulator and stabilizer for Zn and Cd, respectively. Also, the highest value of Pb (233.25 mg/kg) and Cr (21.57 mg/kg) were found in the shoot of this plant. Psathyrostachys fragilis with BCF >1 for Co and maximum Pb accumulation in the root can be used as a stabilizer plant for Pb and Co-contaminated soils. Besides, Stipa arabica and Verbascum speciosum, with TF > 1 and rather high AF, could be considered suitable species for removing Zn and Pb through phytoextraction. This research showed that some native species in the study area have considerable potential for developing phytoremediation strategies.