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

Integrating Bioremediation and Phytoremediation to Clean up Polychlorinated Biphenyls Contaminated Soils

Abstract-This work involved the use of phytoremediation to remediate an aged soil contaminated with polychlorinated biphenyls (PCBs). At microcosm scale, tests were prepared using soil samples that have been collected in an industrial area with a total PCBs concentration of about 250 µg kg -1 . Medicago sativa and Lolium italicum were the species selected in this study that is used as "feasibility test" for full scale remediation. The experiment was carried out with the addition of a mixture of randomly methylatedbeta-cyclodextrins (RAMEB). At the end of the experiment analysis of soil samples showed that in general the presence of plants has led to a higher degradation of most congeners with respect to not vegetated soil. The two plant species efficiencies were comparable and improved by RAMEB addition with a final reduction of total PCBs near to 50%. With increasing the chlorination of the congeners the removal percentage of PCBs progressively decreased

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

Effects of conventional and alternative management systems on soil phosphorus content, soil structure, and corn yield

Conventional management practices have been associated with increased soil erosion and organic matter loss and the contamination of surface and ground water. Alternative agriculture systems which minimize external chemical inputs and degradation of soil and water resources represent alternatives to conventional management practices. Four different management practices were compared on an alluvial silty loam soil cultivated to grow corn (Zea mays L.). The effects of conventional and reduced tillage and of different chemical inputs on the distribution of phosphorus (P) concentration and on soil porosity were investigated. Results showed that the highest P content was detected in the topsoil (0–10 cm) of the minimum tilled plots even though the amount of P fertilizer added was much lower than the amount added in the conventionally tilled plots. The total porosity was significantly higher in the minimum tilled soil and was related only to the tillage technique. Since the higher porosity was mainly due to the higher proportion of elongated and regular pores, the minimum tilled soil appeared to be more resistant to physical stresses and characterized by a higher biological activity

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

Enhanced Bioavailable Contaminant Stripping (EBCS): metal bioavailability for evaluation of phytoextraction success

Phytoextraction may be applied at field scale when the removal of bioavailable metals is the specific target of the technology. Residual metals in soil can be considered substantially inert or to be evaluated by site specific risk analysis

Assisted phytoremediation of a multi-contaminated soil: Investigation on arsenic and lead combined mobilization and removal

The removal of contaminants from an earthy matrix by phytoremediation requires the selection of appropriate plant species and a suitable strategy to be effective. In order to set up an assisted phytoremediation intervention related to a disused industrial site affected by an arsenic and lead complex contamination, an extensive experimental investigation on micro and mesocosm scale has been conducted. Particular attention was given to the choice of plant species: using crop plants (Lupinus albus, Helianthus annuus and Brassica juncea) a series of parallel test campaigns have been realized to investigate different scenarios for the reclamation. With regard to the arsenic contamination, which is certainly the most worrying, the possibility of employing a hyper-accumulator species (Pteris vittata) has also been investigated, highlighting advantages and difficulties associated with such an approach. The application of various mobilizing agents in different concentrations was tested, in order to maximize the extraction efficiency of plants in respect of both contaminants, showing the necessity of a chemically assisted approach to promote their uptake and translocation in the shoots. Phosphate addition appears to produce the desired results, positively affecting As phyto-extraction for both hyper-accumulator and crop plants, while minimizing its toxic effects at the investigated concentrations. With regard to Pb, although tests with EDDS have been encouraging, EDTA should be preferred at present due to lower uncertainties about its effectiveness. The performed tests also improved the addition of mobilizing agents, allowing the simultaneous removal of the two metals despite their great diversity (which in general discourages such approach), with significant saving of time and an obvious improvement of the overall process