Zn, Pb and Hg contents of Pistacia lentiscus L. grown on heavy metal-rich soils: implications for phytostabilization

In this study, we determined the metal (Zn, Pb and Hg) contents in epigean and hypogean organs of Pistacia lentiscus L., a Mediterranean native plant grown on heavy metal-rich soils of Iglesiente (southwestern Sardinia, Italy), in view of its perspective use for revegetation and phytostabilization of mine waste piles. Plant samples were collected from four different areas in the district. Metal contents in the different plant tissues are roughly dependent on their total and mobile (diethylene triamine penta acetic acid (DTPA)-extractable) contents in soil and are shown in the following ranges: 48–628 mg kg−1 (Zn), 2–354 mg kg−1 (Pb) and 13–530 μg kg−1 (Hg) and usually decrease in the following order: roots>stems>leaves; the apparent exception for Hg, with an order of leaves>stems, is ascribed to foliar absorption of this element. The biological concentration factors are consistently low (≤0.05) for all metals and support the concept that the strategy of metal tolerance of P. lentiscus is based on exclusion. These results are consistent with most previous literature data, confirming that P. lentiscus is well suited for revegetation actions and could decrease metal mobility through the soil stabilization strategy

Phytoremediation potentiality of Cistus Ssp. and Inula Viscosa in heavy metal contaminated soils

Aim of the study is the evaluation of native Mediterranean plants, e.g. Cistus ssp and Inula viscosa, to be used for the phytoremediation of dismissed mining areas on Elba Island. The study was focused on the area named Puppaio in the Mining Park near Rio Marina. Different parameters were considered: a) heavy metal composition of the soil; b) collection and sampling of Inula viscosa (L.) Aiton, C. monspeliensis L.and C. salvifolius L. growing on contaminated soil; c) chemical analysis of different plant organs (roots, stems, leaves) in order to evaluate metal uptake and translocation; d) activity of the main antioxidant enzymes and presence of secondary metabolites linked to oxidative stress; e) in vitro cultures of the selected species, grown on specific media mimicking some of the original conditions (presence of heavy metals, extremely acidic pH), in order to obtain a population of plantlets able to be possibly reintroduced in the considered polluted areas. Preliminary results showed: a) the ability of collected plants to take up and translocate metals to the aerial parts, b) an enhanced ability of the native plants to grow in media at low pH and high metal concentration

Comparative Evaluation of Technologies at a Heavy Metal Contaminated Site: The Role of Feasibility Studies

Many agricultural areas are contaminated by heavy metals to such a level that the growth of plants is drastically reduced. Based on the site’s specific characteristics, feasibility studies were carried out to choose the most effective technologies. Feasibility tests showed that soil washing and phytoremediation technologies could be used at the agricultural site under study. The efficiency of the technologies is highly dependent on soil characteristics, which determine the chemical form of the metals. The results indicate that water-based soil washing can be successfully used with the possibility of reaching the remediation objectives quickly. However, the technology in the first step essentially breaks down the soil. Moreover, phytoremediation cannot be used directly to overcome the toxicity derived from the very high bioavailability of the heavy metals. Still, there is the need to use “assisted” phytoremediation by adding compost that reduces metal bioavailability, allowing phytoextraction. In this case, a longer time is needed to reach the remediation target. The results provide a preliminary scenario for decision-makers and stakeholders to assess possible technologies applicable and a possible scheme to be applied in similar cases of polluted agricultural areas