Fitotrattamento di sedimenti di dragaggio debolmente contaminati

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Heavy metal distribution in a sediment phytoremediation system at pilot scale

The continuous stream of polluted sediments, dredged from harbors and water bodies in order to maintain the navigation, is a common practice, but the fate of these sediments is an issue recognized worldwide. This pilot case study evaluated the application of phytoremediation as sustainable management strategy for the decontamination of polluted dredged marine sediments. The synergic action of different plant species (Paspalum vaginatum; P. vaginatum + Spartium junceum and P. vaginatum + Tamarix gallica) and organic matter (compost) in removing both heavy metals (Cd, Ni, Zn, Pb and Cu) and total petroleum hydrocarbons, and in recovering the nutritive and biological sediment properties were evaluated. In addition to the detection of total metal removal efficiency, the chemical distribution of metals in the sediment phases (exchangeable, manganese and iron oxides, organic matter and residual minerals) was also measured in order to make a more realistic estimation of the phytoremediation efficiency for the sediment decontamination. Finally, a complete picture of the metal flux was obtained by investigating the metal mass-balance in the treated sediments. The results of metal content in the sediment phases showed that metal distribution was not uniform and each metal predominated in different fractions; the solubility of metals in the sediment in the decreasing order was: Cd>Zn>Cu>Pb>Ni. The higher proportion of Ni and Pb in the residual phase can be the reason of the lower translocation of these metals in the plant tissues. On the other hand, Cd, Zn and Cu were the metals most easily translocated in plant tissues, both aboveground and roots, confirming their higher availability for the plants. The results of mass balance indicated that, at the end of the experimentation, a high content of metals were still found in the sediment. The greatest contribution in metal removal was attributed to a phytostabilization process at rhizosphere level followed by gravel and sand absorption. The capacity of rhizophere to precipitate heavy metals, could be considered as an alternative option for reducing the metal availability and, consequently, the toxicity in contaminated sediments

Short communication: Biochemically active humic substances in contrasting agricultural managements

 Because their crucial role in several soil biochemical cycles and their fast response to changes in soil management, extracellular enzymes activities are widely used as sensitive indicators of ecological change and soil quality. The aim of this work was to determine the effects of soil management on the stable pool of soil carbon cycling enzymes as indicators of essential functions. For this, extracellular β-glucosidase enzymes bounded by humic acids (C higher than 104 Da) were used to compare four long-term contrasting agricultural managements in a rainfed olive orchard representative of semi-arid Mediterranean habitats. The study was conducted for 30 years by designing a random-block of four treatments (nude vs. covered soils) and four replicates. Maintaining cover crops through fall, winter and early spring provoked a more stable and active pool of extracellular β-glucosidase in soils only if spontaneous vegetation was managed with mechanical methods. When herbicides were used during 30 years, the pattern of the molecular composition and activity of humus β-glucosidase complexes were similar in covered and nude soils, although higher activity was retrieved in the former. Tillage management increased carbon mineralization and the level of humic substances and the activity of β-glucosidase humic-bound were quite lower than in the rest of treatments. Given the ecological role of extracellular soil carbon cycling enzymes, the characterization of humus β-glucosidase complexes could be an adequate indicator of sustainability of agricultural management systems

Synergic action of organic matter-microorganism-plant in soil bioremediation

Bioremediation is a natural process, which relies on bacteria, fungi, and plants to degrade, break down, transform, and/or essentially remove contaminants, ensuring the conservation of the ecosystem biophysical properties. Since microorganisms are the former agents for the degradation of organic contaminants in soil, the application of organic matter (such as compost, sewage sludge, etc.), which increases microbial density and also provides nutrients and readily degradable organic matter (bioenhancement-bioaugmentation) can be considered useful to accelerate the contaminant degradation. Moreover, the organic matter addition, by means of the increase of cation exchange capacity, soil porosity and water-holding capacity, enhances the soil health and provides a medium satisfactory for microorganism activity. Plants have been also recently used in soil reclamation strategy both for their ability to uptake, transform, and store the contaminants (Atagana et al., 2011), and to promote the degradation of contaminants by microbes at rhizosphere level. It is widely recognized that plant, through organic materials, nutrients and oxygen supply, produces a rich microenvironment capable of promoting microbial proliferation and activity

Enzyme activity as an indicator of soil quality changes indegraded cultivated acrisols as the mexican trans-volcanic belt.

9 P.Soils located at the Mexican Trans-volcanic Belt (MTB) have a worrying degree of degradation due to inappropriate management practices. Early indicators of soil changes are very useful to alert about negative impacts of wrong managements on these volcanic soils. The aim of this work was to evaluate the short-term effects (4 years) of different agricultural practices on soil organic matter (SOM) quality and to validate the potential of the selected biochemical properties as optimal early indicators of soil quality in Mexican cultivated Acrisols. During 2002–2005 four agronomic management systems: conventional (Tc); improved conventional (Ti); organic (To) and fallow (Tf) were assayed in plots located at the MTB. An uncultivated soil under grass cover (Sg) was used as reference. Soil samples were collected at 0–10 cm depth and were analysed chemically (soil organic C, total N, water-soluble C and humic C), and biochemically (total and extra-cellular enzyme activity). After 4 years, soil organic C, total N, water-soluble C and dehydrogenase activity had higher values in To, followed by Ti treatment. A similar response pattern was observed in the extra-cellular enzyme activity. The highest total enzyme activity was found in Sg, followed by Ti and To treatments, and the lowest values appeared in Tc and Tf. To and Ti increased SOM contents of the degraded Acrisols studied, while Tc and Tf managements decreased the quality of these soils. The results showed that the assayed soil enzymes can be used as indicators of quality changes of these Mexican volcanic soils.The authors thank the European Union for supporting the REVOLSO Project (INCO-DEV Program) and the Spanish Ministry of Education & Science. Thanks are also due to C. I. Hidalgo (Colegio de Postgraduados de Montecillo, Mexico) for the mineralogical identification of soil clays analysis and J. Padilla (Colegio de Postgraduados de Montecillo, Mexico), C. Macci, S. Doni and laboratory technicians from the Istituto per lo Studio degli Ecosistemi (CNR, Italy) for theirs lab assistance.Peer reviewe

Sperimentazione di una tecnica naturale di decontaminazione di sedimenti marini di dragaggio per il riutilizzo come terreno agrario

The proposed technique is based on the use of natural plants (paspalum v., tamarix g.,spartium j.), and organic amendment, with the aim of reaching the following objectives: (1) sediment decontamination; (2) physical, chemical and biological amelioration of sediments. Good results were obtained in terms of adaptation of the plants used, decrease in contamination (about 20% for metals and 70% for hydrocarbons) and increase in nutrient content and microbial activity. Moreover, the proper monitoring of irrigation has permitted to reset the volume of leachate, ensuring, however, the field capacity and the decrease of salinity in the medium. The experiment was carried out at pilot-scale, treating 80 m3 of sediment with AGRIPORT technology

A real-scale soil Phytoremediation

In the present investigation, a phytoremediation process with a combination of different plant species (Populus nigra (var.italica), Paulownia tomentosa and Cytisus scoparius) has been proposed at real-scale to bioremediate and functionally recover a soil historically contaminated by heavy metals and organic contaminants. In the attempts to assess both effectiveness and evolution of the remediation system toward a natural soil ecosystem, besides the pollution parameters, also parameters describing the efficiency of the microbiological components (enzyme activities), were investigated. In three years the total content of hydrocarbons and heavy metals in soil decreased with time (50% and 10-30%, respectively), in particular at surface level. The reduction in pollutants was probably the reason of the increase over the time of the ?-glucosidase and phosphatase activity, enzymes related to C and P cycles, respectively. However, this trend was obviously due also to the greater availability of substrates. Dehydrogenase activity, widely used as an indicator of overall microbial activity, showed a great variability among sampling points. Moreover, a phytotest carried out with Lepidium sativum and Raphanus sativus, showed after three years a significant increase in percentage of plant growth, confirming a reduction in soil toxicity and an improvement in soil nutritional state. At the moment the evaluation of the soil protein pattern (SDS-page), are in progress, in order to identify a correlation between the organic contamination and the soil protein expression. Therefore, this biological system seems very promising to perform both decontamination and to functionally recover a polluted soil also at real-scale level

Assessment of overgrazing on degradation of sloping soil

Overgrazing, particularly on slopes, can cause significant alterations in soil quality, determining a greater vulnerability to soil erosion. The aim of this work was to assess the influence of horse overgrazing on sloping (20%) soil properties. Chemical and biochemical parameters have been determined in order to evaluate soil quality. A significant decrease in nutrients was observed after one year. The trend of enzyme activities highlighted a reduction of metabolic processes. However, after one year of resting land, an improvement of soil quality could be noticed by the restoration of the initial level of enzymatic activities