Phytoremediation has been proposed as an economic alternative for remediation of metal contaminated soils. It can be applied over extended surfaces and hilly areas, and targets the “bioavailable” soil fraction of heavy metals, which is the most relevant fraction from an environmental risk assessment perspective. The most important drawback is the long remediation period required (from years to decades). In these condition, the goal is to create a vegetative cap using native and naturalized woody plants in order to 1) prevent wind and water erosion of soil, 2) stabilize metal contaminants in the rooting zone, and 3) encourage epigeous uptake of metal contaminant. The use of shrub and trees species induce a gradual removal of the contaminant at diverse soil deep, making available biomasses for the production of renewable energy. This study was designed to analyze the ability of native and naturalized plant species found in a Pb contaminated area in La Spezia, located in the North of Italy, as candidate species to manage and mitigate environmental contaminant health risks. The polluted site, a little hill close to a factory that produces PbO since 1922, presents soil Pb concentration ranging from 170,5 to 4500,5 mg•kg-1. Plants able to survive in the presence of out-range levels of lead respect to the threshold limit (DM 152/2006) were identified, including trees (pine and Ailanthus sp.) and shrubs (Arbutus unedo L., Erica arborea L., Myrtus communis L., Ilex aquifolium L., Laurus nobilis L. and Pteridium aquilinum (L.) Khun). The content of lead in plant tissues was determined by ICP in ashed samples obtained from roots, stems + branches and leaves. A clear species peculiarity in the accumulation of Pb metal in the vegetative organs was revealed and to investigate Pb uptake capacity of selected woody species, a nine months long pot experiment was performed. Tree of Heaven, Bay Laurel and Common Myrtle plants were grown in soils with 312,4 mg Pb Kg-1 (Pb-) and 4344,5 mg Pb Kg-1 (Pb+), collected from two different sites within the contaminated area, without addition of organic fertilizer or treatments with EDTA. The Pb plant accumulation (550, 787, 1300 mg Kg-1s.s.) increased in Laurus nobilis, Ailanthus sp. and Myrtus communis, respectively, cultivated into 4500 mg Kg-1 Pb soil. Ailanthus plants accumulated larger Pb metal quantities compared to two shrub species, as a large part of lead was translocated from roots to epigeous parts (47). All the species included in this study might be considered as Pb tolerant plants and may be cultivated in soils presenting a medium or high lead contamination. Their different ability to accumulate lead in epigeous and ipogeous organs suggests the potential use for phytoextraction and/or phytostabilization. They were also discussed for the biomass production capacity, the possibilities for an economical exploitation and the phytostabilization efficiency in order to reduce the mobilization of Pb.
Lead Accumulation in Native and Naturalized Woody Species Grown on a Pb-contaminated Site
CINELLI, FABRIZIO;TOFFANIN, ANNITA;
2010-01-01
Abstract
Phytoremediation has been proposed as an economic alternative for remediation of metal contaminated soils. It can be applied over extended surfaces and hilly areas, and targets the “bioavailable” soil fraction of heavy metals, which is the most relevant fraction from an environmental risk assessment perspective. The most important drawback is the long remediation period required (from years to decades). In these condition, the goal is to create a vegetative cap using native and naturalized woody plants in order to 1) prevent wind and water erosion of soil, 2) stabilize metal contaminants in the rooting zone, and 3) encourage epigeous uptake of metal contaminant. The use of shrub and trees species induce a gradual removal of the contaminant at diverse soil deep, making available biomasses for the production of renewable energy. This study was designed to analyze the ability of native and naturalized plant species found in a Pb contaminated area in La Spezia, located in the North of Italy, as candidate species to manage and mitigate environmental contaminant health risks. The polluted site, a little hill close to a factory that produces PbO since 1922, presents soil Pb concentration ranging from 170,5 to 4500,5 mg•kg-1. Plants able to survive in the presence of out-range levels of lead respect to the threshold limit (DM 152/2006) were identified, including trees (pine and Ailanthus sp.) and shrubs (Arbutus unedo L., Erica arborea L., Myrtus communis L., Ilex aquifolium L., Laurus nobilis L. and Pteridium aquilinum (L.) Khun). The content of lead in plant tissues was determined by ICP in ashed samples obtained from roots, stems + branches and leaves. A clear species peculiarity in the accumulation of Pb metal in the vegetative organs was revealed and to investigate Pb uptake capacity of selected woody species, a nine months long pot experiment was performed. Tree of Heaven, Bay Laurel and Common Myrtle plants were grown in soils with 312,4 mg Pb Kg-1 (Pb-) and 4344,5 mg Pb Kg-1 (Pb+), collected from two different sites within the contaminated area, without addition of organic fertilizer or treatments with EDTA. The Pb plant accumulation (550, 787, 1300 mg Kg-1s.s.) increased in Laurus nobilis, Ailanthus sp. and Myrtus communis, respectively, cultivated into 4500 mg Kg-1 Pb soil. Ailanthus plants accumulated larger Pb metal quantities compared to two shrub species, as a large part of lead was translocated from roots to epigeous parts (47). All the species included in this study might be considered as Pb tolerant plants and may be cultivated in soils presenting a medium or high lead contamination. Their different ability to accumulate lead in epigeous and ipogeous organs suggests the potential use for phytoextraction and/or phytostabilization. They were also discussed for the biomass production capacity, the possibilities for an economical exploitation and the phytostabilization efficiency in order to reduce the mobilization of Pb.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
