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

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

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

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

Stabilisation and mineralisation of sludge in reed bed system after 10-20 years of operation

Sludge stabilisation and mineralisation occurring in the sludge residue within the sludge treatment reed bed systems during periods of operation between 10 - 21 years in three different systems receiving sludge from urban wastewater treatment plants situated in Denmark. Samples were taken in the sludge residues along the entire profiles, in order to compare the effectiveness of the sludge stabilisation process in the three systems. Particular attention was given to the stabilisation process occurring within the reed beds; in fact, parameters correlated to biochemical properties of organic sludge matter have been determined. Statistical procedures were used to evaluate how the biochemical processes influence the quality of sludge organic matter in the three systems. The level of total organic carbon and total nitrogen had a similar trend along the profile: their concentration decreased with increasing depth, reaching very low levels at the deepest layers. The same trend was also observed for the water soluble carbon, N-NH3, b-glucosidase and urease activities, hydrolytic enzymes linked to C and N cycles, respectively: their values decreased dramatically with increasing depth, meaning that the level of mineralisation of the organic matter was higher in the deepest layers. The determination of extracellular enzymes bound to humic substances and humic carbon permitted to evaluate the stabilisation of organic sludge matter, and also allowed to individuate in which ways the sludge was stabilised, in terms of mineralisation and humification of the organic matter

Decontamination and functional reclamation of dredged brackish sediments

The continuous stream of sediment dredged from harbors and channels to provide shipping traffic efficiency is a considerable and ongoing problem worldwide recognized. In this study (European Project AGRIPORT) phytoremediation has been considered as a sustainable reclamation technology for bringing slightly polluted brackish sediments into productive use. The experimentation has been carried out in containers of about 1 m3 filled with contaminated (heavy metals and hydrocarbons) brackish sediments. The fine particles granulometric composition made necessary a bio-physical pre-conditioning of sediments by mixing them with an agronomic structured soil (30% v/v). Moreover, a high quality compost was mixed with the sediment-soil matrix at surface level (40t/ha) with the aim of favouring the initial adaptation of the selected vegetal species. Different plant treatments were chosen: i) Paspalum vaginatum, ii) Phragmites australis, iii) Spartium junceum + Paspalum vaginatum, iv) Nerium oleander+ Paspalum vaginatum, v) Tamarix gallica+ Paspalum vaginatum, and vi) No plants used as control. After one year from the beginning of the experimentation all the plant species were still in healthy condition and well developed. During the time, increasing values of nitrate were generally observed in the planted sediments, suggesting an improvement of the chemico-physical conditions for microorganisms and plants. The stimulation of the microbial activity in the planted sediment with respect to control has been confirmed by the increase of the dehydrogenase activity. Concerning the organic and inorganic contaminant concentrations, decreased values were detected, despite the short period passed, indicating the efficiency and success of this technology for brackish sediments reclamation

Vermicomposted olive oil wastewaters in horticultural practices

The aim of this study was to evaluate the effect of a vermicompost (obtained from olive mill wastewaters and cellulose materials) on soil quality and fertility, and on the yield of different horticultural species (Allium porrum L.; Cichorium intybus L., Brassica oleracea). The results showed an improvement in the chemical (increase in total and soluble nutrients) and biological (increase in enzyme activities) soil fertility also with respect to a soil treated with traditional municipal solid waste compost. Moreover, in vermicompost treatments a higher yield (Allium porrum L.; and Brassica oleracea) or equal (Cichorium intybus L.,) to the traditional compost was observed

Recupero e Valorizzazione di sedimenti di dragaggio per un riutilizzo in campo agronomico/ambientale

Not availabl