Soil salinization caused by sea level rise threatens coastal agricultural soils and geochemically... more Soil salinization caused by sea level rise threatens coastal agricultural soils and geochemically important wetlands worldwide. The aim of this review is to outline expected changes in soil biological activity by discussing the combined effects of salt stress and flooding on plants productivity and soil microbial communities, which determine consequences on fluxes of C, N and P. Finally, it outlines the expected repercussions on greenhouse gases emissions. The prediction of outcomes is made difficult by the concomitant and sometimes contrasting actions of flooding and seawater intrusion on partly acclimated and non-acclimated environments. Non-salt acclimated plants suffer from osmotic stress, but also from reduced O2 solubility. Microbial biomass declines with increasing salinity and microbial communities shift in composition. Large concentrations of Cl− inhibit nitrification, but salinity stimulates N2O fluxes. Impacts on C mineralisation rates is variable but enhanced by the larg...
The aptness of the ∑SEM/AVS (Simultaneously Extracted Metals/Acid Volatile Sulfides) index to asc... more The aptness of the ∑SEM/AVS (Simultaneously Extracted Metals/Acid Volatile Sulfides) index to ascertain environmental risk from potentially toxic elements in calcareous saltmarsh soils was tested using Structural Equation Modelling. This technique allows to detect both direct and indirect relationships among AVS, SEM and other soil variables, representing results in a graphical view. The dataset included 90 soil samples from 21 different sites belonging to six different saltmarshes and featured a wide range of soil chemico-physical properties. Variables included in the a priori model were hydroperiod, pH, soil redox potential, labile organic carbon, carbonates, total Fe and total amount of potentially toxic elements (PTE). The best optimised model pointed out the main soil properties which affect AVS accumulation and SEM speciation in these soils. Effect plots of AVS and SEM calculated with the partial linear mixed-effects models included in the piecewise Structural Equation Modelling showed a significant and positive influence of pH and of carbonates on AVS and a highly significant effect of carbonates and labile organic carbon on SEM. Single SEM components were also considered separately in order to define potential contributions of labile organic carbon or carbonates as alternative binding phases. Simultaneously extracted Cu, Ni and Zn resulted preferentially bound to carbonates followed by labile organic carbon, whereas Pb and Cd were easily bound to labile organic carbon.
Purpose The use of eco-friendly and cost-effective adsorbent materials in the remediation of soil... more Purpose The use of eco-friendly and cost-effective adsorbent materials in the remediation of soils contaminated by potentially toxic elements (PTE) is a sustainable way of reducing the transfer of these elements into the food chain. However, an evaluation of the potential of natural zeolites to immobilize toxic elements in contaminated soils was required to enable their efficient use. Materials and methods The effect of natural zeolite (Stilbite-Stellerite) from the Munella area (Northern Albania), added at rates ranging from 1.25 to 10 % w/w on a contaminated soil was investigated in a greenhouse pot experiment with ryegrass (Lolium multiflorum L.) and by selective extractions. PTE availability for plants was assessed either as their accumulation in plant tissue or by DTPA-extraction. Oral bio-accessibility was estimated by the in vitro PBET method and the mobility and consequent potential risk of leaching by the USEPA TLCP method. The effect of zeolites on soil properties (pH, electrical conductivity-EC, organic C, and total N) was also investigated. A five steps sequential extraction procedure (SEP) was applied to investigate the immobilization mechanism. Results and discussion The addition of 2.5% w/w of natural zeolites caused a significant decrease of PTE mobility, but to observe a significant reduction of DTPA-extractable metals, it was necessary to reach 10% addition rate. In contrast, plant growth showed a gradual increase with addition rate and a corresponding decrease of concentration of PTE in plant tissue. Correlation between DTPA-extractable PTE and their concentration in both root and shoot plant tissue was rather poor. Human hazard due to soil ingestion (PBET method) changed only for Cu and Zn in the gastric phase with 1.25 and 5% addition rate respectively, whereas decreased for Cu and Zn at 5% rate in the Intestinal phase. The results of SEP support the hypothesis that the main mechanism involved in metals fixation are as follows: (1) insolubilization by pH rise, (2) adsorption on Fe/Mn oxides (3) increase of cation exchange retention, (4) organic complexation. Conclusions The results of this work suggest that the addition of natural zeolites from the Munella area (AL) is a sustainable practice to reduce the environmental impact of PTE contaminated soils, but an assessment on the longevity of their immobili-zation need to be evaluated in the long-term perspectives.
The interaction between hexavalent chromium Cr(VI), as K(2)CrO(4), and standard humic acids (HAs)... more The interaction between hexavalent chromium Cr(VI), as K(2)CrO(4), and standard humic acids (HAs) in bulk solution was studied using three complementary analytical methods: UV-Visible spectroscopy, X-ray absorption spectroscopy and differential pulse stripping voltammetry. The observed UV-Vis and X-ray absorption spectra showed that, under our experimental conditions, HAs did not induce reduction of Cr(VI) to its trivalent chemical form. The interaction between Cr(VI) and HAs has rather led to the formation of Cr(VI)-HAs micelles via supramolecular chemical processes. The reported results could contribute towards explaining the relative persistence of ecotoxic hexavalent chromium in soils.
The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been u... more The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been utilised to estimate the potential microbial activity of soil freshly amended with a wide range of organic amendments and compared to the size and activity of soil microflora, measured by the microbial biomass C (B C ) and CO 2 evolution, respectively. Three different composting mixtures at different phases of the composting process were added to a semi-arid soil and incubated for 2 months under laboratory conditions. The addition of the organic amendment immediately increased B C and both measures of microbial activity (FDA and CO 2 evolution). Highly significant correlations were found between FDA hydrolysis and B C for soil amended with the three composting mixtures (r=0.81-0.96; P<0.01), regardless of the origin, composition and degree of stability of the organic amendments. FDA hydrolysis, conversely to CO 2 evolution, was unaffected by the disturbance caused by the soil amendment, indicating that the two parameters probably reflect different aspects of soil microbial activity. FDA hydrolysis could serve as an alternative estimation of the microbial biomass in freshly amended soils, despite the disturbance caused by the exogenous organic matter.
We studied the long-term effects (12 years) of municipal refuse compost addition on the total org... more We studied the long-term effects (12 years) of municipal refuse compost addition on the total organic carbon (TOC), the amount and activity of the microbial biomass (soil microbial biomass C, B C and metabolic quotient qCO 2 ) and heavy metal bioavaiability in soils as compared to manuring with mineral fertilizers (NPK) and farmyard manure (FYM). In addition, we studied the relationships between among the available fraction [Diethylenetriaminopentacetic acid (DTPA) extractable] of heavy metals and their total content, TOC and B C . After 12 years of repeated treatments, the TOC and B C of control and mineral fertilized plots did not differ. Soils treated with FYM and composts showed a significant increase in TOC and B C in response to the increasing amounts of organic C added. Values of the B C /TOC ratio ranged from 1.4 to 2, without any significative differences among soil treatments. The qCO 2 increased in the organic-amended soil and may have indicated microbial stress. The total amounts of metals in treated soils were lower than the levels permitted by the European Union in agricultural soils. DTPA-extractable metals increased in amended soils in response to organic C. A multiple regression analysis with stepwise selection of variables was carried out in order to discriminate between the influence exerted on DTPA-extractable metals by their total content, TOC and B C . Results showed that each metal behaved quite differently, suggesting that different mechanisms might be involved in metal bioavailability Key words Organic fertilization 7 Soil microbial biomass carbon 7 Metabolic quotient 7 Bioavailability 7 Heavy metals
We studied the long-term effects (12 years) of municipal refuse compost addition on the total org... more We studied the long-term effects (12 years) of municipal refuse compost addition on the total organic carbon (TOC), the amount and activity of the microbial biomass (soil microbial biomass C, B C and metabolic quotient qCO 2 ) and heavy metal bioavaiability in soils as compared to manuring with mineral fertilizers (NPK) and farmyard manure (FYM). In addition, we studied the relationships between among the available fraction [Diethylenetriaminopentacetic acid (DTPA) extractable] of heavy metals and their total content, TOC and B C . After 12 years of repeated treatments, the TOC and B C of control and mineral fertilized plots did not differ. Soils treated with FYM and composts showed a significant increase in TOC and B C in response to the increasing amounts of organic C added. Values of the B C /TOC ratio ranged from 1.4 to 2, without any significative differences among soil treatments. The qCO 2 increased in the organic-amended soil and may have indicated microbial stress. The total amounts of metals in treated soils were lower than the levels permitted by the European Union in agricultural soils. DTPA-extractable metals increased in amended soils in response to organic C. A multiple regression analysis with stepwise selection of variables was carried out in order to discriminate between the influence exerted on DTPA-extractable metals by their total content, TOC and B C . Results showed that each metal behaved quite differently, suggesting that different mechanisms might be involved in metal bioavailability Key words Organic fertilization 7 Soil microbial biomass carbon 7 Metabolic quotient 7 Bioavailability 7 Heavy metals
The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been u... more The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been utilised to estimate the potential microbial activity of soil freshly amended with a wide range of organic amendments and compared to the size and activity of soil microflora, measured by the microbial biomass C (B C ) and CO 2 evolution, respectively. Three different composting mixtures at different phases of the composting process were added to a semi-arid soil and incubated for 2 months under laboratory conditions. The addition of the organic amendment immediately increased B C and both measures of microbial activity (FDA and CO 2 evolution). Highly significant correlations were found between FDA hydrolysis and B C for soil amended with the three composting mixtures (r=0.81-0.96; P<0.01), regardless of the origin, composition and degree of stability of the organic amendments. FDA hydrolysis, conversely to CO 2 evolution, was unaffected by the disturbance caused by the soil amendment, indicating that the two parameters probably reflect different aspects of soil microbial activity. FDA hydrolysis could serve as an alternative estimation of the microbial biomass in freshly amended soils, despite the disturbance caused by the exogenous organic matter.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Soil salinization caused by sea level rise threatens coastal agricultural soils and geochemically... more Soil salinization caused by sea level rise threatens coastal agricultural soils and geochemically important wetlands worldwide. The aim of this review is to outline expected changes in soil biological activity by discussing the combined effects of salt stress and flooding on plants productivity and soil microbial communities, which determine consequences on fluxes of C, N and P. Finally, it outlines the expected repercussions on greenhouse gases emissions. The prediction of outcomes is made difficult by the concomitant and sometimes contrasting actions of flooding and seawater intrusion on partly acclimated and non-acclimated environments. Non-salt acclimated plants suffer from osmotic stress, but also from reduced O2 solubility. Microbial biomass declines with increasing salinity and microbial communities shift in composition. Large concentrations of Cl− inhibit nitrification, but salinity stimulates N2O fluxes. Impacts on C mineralisation rates is variable but enhanced by the larg...
The aptness of the ∑SEM/AVS (Simultaneously Extracted Metals/Acid Volatile Sulfides) index to asc... more The aptness of the ∑SEM/AVS (Simultaneously Extracted Metals/Acid Volatile Sulfides) index to ascertain environmental risk from potentially toxic elements in calcareous saltmarsh soils was tested using Structural Equation Modelling. This technique allows to detect both direct and indirect relationships among AVS, SEM and other soil variables, representing results in a graphical view. The dataset included 90 soil samples from 21 different sites belonging to six different saltmarshes and featured a wide range of soil chemico-physical properties. Variables included in the a priori model were hydroperiod, pH, soil redox potential, labile organic carbon, carbonates, total Fe and total amount of potentially toxic elements (PTE). The best optimised model pointed out the main soil properties which affect AVS accumulation and SEM speciation in these soils. Effect plots of AVS and SEM calculated with the partial linear mixed-effects models included in the piecewise Structural Equation Modelling showed a significant and positive influence of pH and of carbonates on AVS and a highly significant effect of carbonates and labile organic carbon on SEM. Single SEM components were also considered separately in order to define potential contributions of labile organic carbon or carbonates as alternative binding phases. Simultaneously extracted Cu, Ni and Zn resulted preferentially bound to carbonates followed by labile organic carbon, whereas Pb and Cd were easily bound to labile organic carbon.
Purpose The use of eco-friendly and cost-effective adsorbent materials in the remediation of soil... more Purpose The use of eco-friendly and cost-effective adsorbent materials in the remediation of soils contaminated by potentially toxic elements (PTE) is a sustainable way of reducing the transfer of these elements into the food chain. However, an evaluation of the potential of natural zeolites to immobilize toxic elements in contaminated soils was required to enable their efficient use. Materials and methods The effect of natural zeolite (Stilbite-Stellerite) from the Munella area (Northern Albania), added at rates ranging from 1.25 to 10 % w/w on a contaminated soil was investigated in a greenhouse pot experiment with ryegrass (Lolium multiflorum L.) and by selective extractions. PTE availability for plants was assessed either as their accumulation in plant tissue or by DTPA-extraction. Oral bio-accessibility was estimated by the in vitro PBET method and the mobility and consequent potential risk of leaching by the USEPA TLCP method. The effect of zeolites on soil properties (pH, electrical conductivity-EC, organic C, and total N) was also investigated. A five steps sequential extraction procedure (SEP) was applied to investigate the immobilization mechanism. Results and discussion The addition of 2.5% w/w of natural zeolites caused a significant decrease of PTE mobility, but to observe a significant reduction of DTPA-extractable metals, it was necessary to reach 10% addition rate. In contrast, plant growth showed a gradual increase with addition rate and a corresponding decrease of concentration of PTE in plant tissue. Correlation between DTPA-extractable PTE and their concentration in both root and shoot plant tissue was rather poor. Human hazard due to soil ingestion (PBET method) changed only for Cu and Zn in the gastric phase with 1.25 and 5% addition rate respectively, whereas decreased for Cu and Zn at 5% rate in the Intestinal phase. The results of SEP support the hypothesis that the main mechanism involved in metals fixation are as follows: (1) insolubilization by pH rise, (2) adsorption on Fe/Mn oxides (3) increase of cation exchange retention, (4) organic complexation. Conclusions The results of this work suggest that the addition of natural zeolites from the Munella area (AL) is a sustainable practice to reduce the environmental impact of PTE contaminated soils, but an assessment on the longevity of their immobili-zation need to be evaluated in the long-term perspectives.
The interaction between hexavalent chromium Cr(VI), as K(2)CrO(4), and standard humic acids (HAs)... more The interaction between hexavalent chromium Cr(VI), as K(2)CrO(4), and standard humic acids (HAs) in bulk solution was studied using three complementary analytical methods: UV-Visible spectroscopy, X-ray absorption spectroscopy and differential pulse stripping voltammetry. The observed UV-Vis and X-ray absorption spectra showed that, under our experimental conditions, HAs did not induce reduction of Cr(VI) to its trivalent chemical form. The interaction between Cr(VI) and HAs has rather led to the formation of Cr(VI)-HAs micelles via supramolecular chemical processes. The reported results could contribute towards explaining the relative persistence of ecotoxic hexavalent chromium in soils.
The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been u... more The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been utilised to estimate the potential microbial activity of soil freshly amended with a wide range of organic amendments and compared to the size and activity of soil microflora, measured by the microbial biomass C (B C ) and CO 2 evolution, respectively. Three different composting mixtures at different phases of the composting process were added to a semi-arid soil and incubated for 2 months under laboratory conditions. The addition of the organic amendment immediately increased B C and both measures of microbial activity (FDA and CO 2 evolution). Highly significant correlations were found between FDA hydrolysis and B C for soil amended with the three composting mixtures (r=0.81-0.96; P<0.01), regardless of the origin, composition and degree of stability of the organic amendments. FDA hydrolysis, conversely to CO 2 evolution, was unaffected by the disturbance caused by the soil amendment, indicating that the two parameters probably reflect different aspects of soil microbial activity. FDA hydrolysis could serve as an alternative estimation of the microbial biomass in freshly amended soils, despite the disturbance caused by the exogenous organic matter.
We studied the long-term effects (12 years) of municipal refuse compost addition on the total org... more We studied the long-term effects (12 years) of municipal refuse compost addition on the total organic carbon (TOC), the amount and activity of the microbial biomass (soil microbial biomass C, B C and metabolic quotient qCO 2 ) and heavy metal bioavaiability in soils as compared to manuring with mineral fertilizers (NPK) and farmyard manure (FYM). In addition, we studied the relationships between among the available fraction [Diethylenetriaminopentacetic acid (DTPA) extractable] of heavy metals and their total content, TOC and B C . After 12 years of repeated treatments, the TOC and B C of control and mineral fertilized plots did not differ. Soils treated with FYM and composts showed a significant increase in TOC and B C in response to the increasing amounts of organic C added. Values of the B C /TOC ratio ranged from 1.4 to 2, without any significative differences among soil treatments. The qCO 2 increased in the organic-amended soil and may have indicated microbial stress. The total amounts of metals in treated soils were lower than the levels permitted by the European Union in agricultural soils. DTPA-extractable metals increased in amended soils in response to organic C. A multiple regression analysis with stepwise selection of variables was carried out in order to discriminate between the influence exerted on DTPA-extractable metals by their total content, TOC and B C . Results showed that each metal behaved quite differently, suggesting that different mechanisms might be involved in metal bioavailability Key words Organic fertilization 7 Soil microbial biomass carbon 7 Metabolic quotient 7 Bioavailability 7 Heavy metals
We studied the long-term effects (12 years) of municipal refuse compost addition on the total org... more We studied the long-term effects (12 years) of municipal refuse compost addition on the total organic carbon (TOC), the amount and activity of the microbial biomass (soil microbial biomass C, B C and metabolic quotient qCO 2 ) and heavy metal bioavaiability in soils as compared to manuring with mineral fertilizers (NPK) and farmyard manure (FYM). In addition, we studied the relationships between among the available fraction [Diethylenetriaminopentacetic acid (DTPA) extractable] of heavy metals and their total content, TOC and B C . After 12 years of repeated treatments, the TOC and B C of control and mineral fertilized plots did not differ. Soils treated with FYM and composts showed a significant increase in TOC and B C in response to the increasing amounts of organic C added. Values of the B C /TOC ratio ranged from 1.4 to 2, without any significative differences among soil treatments. The qCO 2 increased in the organic-amended soil and may have indicated microbial stress. The total amounts of metals in treated soils were lower than the levels permitted by the European Union in agricultural soils. DTPA-extractable metals increased in amended soils in response to organic C. A multiple regression analysis with stepwise selection of variables was carried out in order to discriminate between the influence exerted on DTPA-extractable metals by their total content, TOC and B C . Results showed that each metal behaved quite differently, suggesting that different mechanisms might be involved in metal bioavailability Key words Organic fertilization 7 Soil microbial biomass carbon 7 Metabolic quotient 7 Bioavailability 7 Heavy metals
The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been u... more The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been utilised to estimate the potential microbial activity of soil freshly amended with a wide range of organic amendments and compared to the size and activity of soil microflora, measured by the microbial biomass C (B C ) and CO 2 evolution, respectively. Three different composting mixtures at different phases of the composting process were added to a semi-arid soil and incubated for 2 months under laboratory conditions. The addition of the organic amendment immediately increased B C and both measures of microbial activity (FDA and CO 2 evolution). Highly significant correlations were found between FDA hydrolysis and B C for soil amended with the three composting mixtures (r=0.81-0.96; P<0.01), regardless of the origin, composition and degree of stability of the organic amendments. FDA hydrolysis, conversely to CO 2 evolution, was unaffected by the disturbance caused by the soil amendment, indicating that the two parameters probably reflect different aspects of soil microbial activity. FDA hydrolysis could serve as an alternative estimation of the microbial biomass in freshly amended soils, despite the disturbance caused by the exogenous organic matter.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Uploads
Papers by MARCO CONTIN