Greenhouse investigation on the phytoremediation potential of pioneer tree Pinus halepensis Mill. in abandoned mine site.

Tailings and mine dumps are often pollutant sources that pose serious environmental threats to surrounding areas. The use of pioneer vascular plants to extract or stabilize metals is considered among the more effective mine tailing reclamation techniques. The study aimed at evaluating the phytoremediation potential of Pinus halepensis in abandoned mine-tailing (SW-Sardinia, Italy). Plant ability to tolerate high Zn, Pb, and Cd concentration and their accumulation in roots and aerial parts were assessed at greenhouse conditions. Experiments were performed on 45 seedlings planted in different substrates (mine-tailings, mine-tailings compost-amended, and reference) and on 15 seedlings grown spontaneously in the contaminated mine site investigated with their own substrates. The phytostabilization potential of plant was evaluated through biological accumulation and translocation indexes together with plant survival and biometric parameters. The outcomes showed the adaptability of P. halepensis to grow and survive in contaminated substrates. Compost addition did not improve plant survival and growth, however, it enhanced total carbon and nitrogen contents of soil, restricted metal bioavailability, and accumulation in plant aerial parts. These findings highlight that P. halepensis may be considered for phytostabilization given the great potential to limit Zn, Pb, and Cd toxicity in plant tissues by applying compost amendment in metal contaminated mine sites.

The novelty of this study is the selection of Pinus halepensis Mill. as a proper tree species for long-term phytoremediation of multi-heavy metal mine tailing sites. This plant species not only had adaptation to the Mediterranean climate and could tolerate high temperatures and high metal concentrations, but also showed high survival and growth percentage of its roots and epigean organs in highly contaminated mine tailing. Pinus halepensis could limit metal accumulation and toxicity in the aerial part of the plant with the addition of compost amendment. This study demonstrates that compost can enhance soil properties and modify metal bioavailability. The outcomes can be beneficial for the phytostabilization project and restoration of similar Mediterranean mine sites.

Using Mediterranean Native Plants for the Phytoremediation of Mining Sites: An Overview of the Past and Present, and Perspectives for the Future.

Mining exploitation in the Mediterranean Basin has left evident scars on the environment, and poses serious risks for human health and biodiversity, especially when mine wastes are left abandoned. This review analysed the main issues of metal(loid)s pollution related to mine exploitation in the Mediterranean Basin. Here, a list of Mediterranean native plant species studied for phytoremediation is given and, considering their biological forms, vegetational types, and ecology, we categorised them into halotolerant and hydro/hygrophilous vegetation, annual and perennial meadows, garrigues and maquis, and high maquis and woods. The main conclusions of the review are as follows: (1) plant communities established on mine environments are often rich in endemic taxa which ensure a high biodiversity and landscape value, and can help in the psychophysical health of local inhabitants; (2) political and land management should take greater account of the use of native plants for the remediation of contaminated soils; (3) a multidisciplinary approach that includes, among others, studies on biochemical response to metal(loid)s as well as the application of innovative soil amendments gives better results; (4) phytoextraction applications require a detailed recovery plan that takes into consideration several issues, including the negative influence on biodiversity due to extensive use of monotypic plantations, disposal of harvested hazardous plants, and the risk of phytoextracts entering the food chain; and (5) more studies are necessary to increase knowledge and to detect suitable species-especially halophytic ones-for phytoremediation purposes.

Germination and early seedling development of Helichrysum microphyllum Cambess. subsp. tyrrhenicum Bacch., Brullo & Giusso in the presence of arsenates and arsenites.

Arsenate, As(V), and arsenite, As(III), are the most available arsenicals present in the soil solutions, in particular in mine polluted substrates, and cause several symptoms of toxicity in plants (like inhibition of seed germination and reduction of seedling development). For these reasons, seeds germination studies are essential for the design of phytoremediation activities of mine sites. Seed germination and seedling development of Helichrysum microphyllum subsp. tyrrhenicum, were evaluated at 15 °C using various concentrations of As(V) and As(III) (0-500 mg/L and 0-200 mg/L, respectively). Seeds were harvested (I) into a mine dump contaminated in As, (II) nearby this site, and (III) faraway the As contaminated area and without mine activities. Seed germination, cotyledons emergence, and seedling mortality were evaluated for 90 days. As(V) and As(III) acted differently, showing a much higher toxicity when arsenite was added than arsenate. The taxon was able to germinate, develop cotyledons, and survive under all arsenate concentrations, whereas arsenite acted on these steps already at 2.5 mg/L. Moreover, a linear decrease in cotyledons emergence was assessed with the increase of both arsenicals' concentrations, as well as a linear decrease of seedling survival under arsenite. The taxon showed great adaptability to As pollution, giving an important contribution in phytoremediation of mining sites.

Ex situ phytoremediation trial of Sardinian mine waste using a pioneer plant species.

The mitigation of metals contamination is currently a crucial issue for the reclamation of mine sites. Indeed, mine wastes are often disposed in open dumps and consequently pollutants are subjected to dispersion in the surrounding areas. In this study, the potential use of Helichrysum microphyllum subsp. tyrrhenicum for phytostabilization was evaluated in ex situ conditions. Ninety specimens were randomly selected and were planted in three substrates (reference substrate, mine waste materials, and mine wastes with compost). Mineralogical compositions of substrates, rhizosphere, and roots were assessed through X-ray diffraction (XRD). Zn, Pb, and Cd concentrations of substrates, rhizosphere, soil pore waters, and plant tissues were determined. The phytostabilization potential was determined through the application of biological accumulation coefficient (BAC), biological concentration factor (BCF), and translocation factor (TF). Moreover, survival and biometric parameters were assessed on plant specimens. The polluted substrates and related rhizosphere materials were mainly composed of dolomite, quartz, pyrite, and phyllosilicate. Zn was the most abundant metal in substrates, rhizosphere, and soil pore waters. XRD analysis on roots showed the presence of amorphous cellulose and quartz and Zn was the most abundant metal in plant tissues. H. microphyllum subsp. tyrrhenicum restricts the accumulation of the metals into roots limiting their translocation in aereal parts, indicating its potential use as phytostabilizer (BCF, BAC, TF < 1). Survival and growth data showed a great adaptability to different substrates, with an evident positive effect of the implementation of compost which increased the plant survival and decreased the metals uptake into roots.