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

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

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

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

“In situ” vermicomposting of biological sludges and impacts on soil quality

10 pages, 8 tables, 3 figures.A laboratory experiment was carried out to study soil quality amelioration through “in situ” vermicomposting of biological sludges. The experiment dealt with the stabilization, through the action of worms (Eisenia fetida), of five mixtures containing aerobic and anaerobic biological sludges spread on the soil surface. The results showed that by increasing the percentage of anaerobic sludge in the mixtures, the number of worms which left the sludge and chose the soil as their habitat increased. The chemico-structural changes of the sludges left on the soil surface by worms were evaluated through the technique of pyrolysis-gas chromatography, which showed that the degrees of mineralization and humification of organic matter were dependent on the composition of the sludge mixtures. When the amount of aerobic sludge in the mixtures was higher than 50%, a stimulation of soil microbial metabolism occurred, as demonstrated by the index of metabolic potential (defined by dehydrogenase/water soluble carbon ratio). All treatments increased the percentage of soil total shrinkage area, mostly due to the formation of cracks of small–medium size (<1000 μm), which represent a favourable site for microbiological and biochemical processes in the soil. A positive statistical correlation between soil dehydrogenase activity, C and N substrates, and cracks of small–medium size was found.Peer reviewe

Land use in relation to soil chemical and biochemical properties in a semiarid Mediterranean environment

Low organic matter levels and fragile structure of coarse textured soils from arid and semiarid environments can lead to progressive degradation of their quality and productivity. Our objective was to evaluate the effects of land use on soil organic matter quality and quantity and biochemical properties related to soil microbial activity that are involved in the cycling of nutrients and carbon. Four sandy soils under different agricultural practices and four adjacent soils under grass cover in a Mediterranean environment comprising the humid-temperature climate of centralwest Italy were characterised chemically and biochemically. A sensitivity index was calculated for each of the measured properties by dividing the values for uncultivated soils with their cultivated counterparts. A metabolic potential index was calculated as the ratio between dehydrogenase activity (DHase), and water-soluble carbon (WSC). There was a general decline of total organic carbon (TOC), extractable humic substances (HS), WSC, water-soluble carbohydrates (WSCH), DHase, urease, protease, phosphatase and β-glucosidase activities following the different agricultural practices with respect to soil under grass cover. DHase, urease and phosphatase activities were more sensitive and responded more frequently to land use than TOC and WSC and WSCH. DHase/WSC ratio confirmed the reduction of cultivated soils metabolism as consequence of management practices.Peer reviewe