Papers by Margherita Silvetti
Ecotoxicology and Environmental Safety, 2019
In this study we evaluated the microbiological and biochemical impact of iron-based water treatme... more In this study we evaluated the microbiological and biochemical impact of iron-based water treatment residuals (Fe-WTRs) and municipal solid waste compost (MSWC), alone and combined, on three different soils co-contaminated with arsenic (As) and trace-metals (TM), i.e. Pb, Cu and Zn. Overall, all the amendments considered significantly increased the abundance of culturable heterotrophic bacteria, with MSWC showing the greatest impact across all soils (up to a 24% increase). In most of treated soils this was accompanied by a significant reduction of both the (culturable) fungal/bacterial ratio, and the proportion of culturable As(V)-and As(III)resistant bacteria with respect to total bacterial population. The catabolic potential and versatility of the resident microbial communities (assessed by community level physiological profile) was highly soil-dependent and substantial increases of both parameters were observed in the amended soils with the higher total As concentration (from approx. 749 to 22,600 mg kg −1). Moreover, both carbon source utilisation profile and 16S rRNA soil metagenome sequencing indicated a significant impact of MSWC and Fe-WTRs on the structure and diversity of soil microbial communities, with Proteobacteria, Actinobacteria and Firmicutes being the most affected taxa. The assessment of selected soil enzyme activities (dehydrogenase, urease and β-glucosidase) indicated an increase of metabolic functioning especially in soils treated with MSWC (e.g. dehydrogenase activity increased up to 19.5-fold in the most contaminated soil treated with MSWC). Finally, the microbial and biochemical features of treated (and untreated) contaminated soils (i.e. total bacterial counts, catabolic potential and versatility and soil enzyme activities) were highly correlated with the concentrations of labile As and TM in these latter soils and supported a clear role of the tested amendments (especially MSWC) as As-and TM-immobilising agents. − , HAsO 4 2−) or as neutral arsenite (H 3 AsO 3) (Fendorf et al., 2010). This has an apparent influence on the respective trace element mobility and bioavailability in soil, making difficult the selection of an effective sorbent for both TM and metalloids. For instance, adding biochar and green waste compost to a contaminated soil increased significantly (> 30 fold) the concentration of labile As while reduced that of Cd and Zn (Beesley et al., 2010). Likewise, phosphate addition increased As but not Pb phytoavailability in a soil contaminated with lead arsenate (Creger and Peryea, 1994). More recently, Ibrahim et al. (2016) showed that rice husk biochar, added at 1-5% rate to a multi-element polluted soil, reduced the concentration of available Cr, Cd, Pb and Zn while increasing
Group Analysis, 1979
Prof. Watkins is an analysand of Eduardo Weiss, himself a disciple of Paul Federn. Watkins propou... more Prof. Watkins is an analysand of Eduardo Weiss, himself a disciple of Paul Federn. Watkins propounds Federn’s theories of ego states and ego boundaries in a clear and easily comprehensible form. It is useful to have Federn’s original contributions once again-ibrought to our attention. Much of his work has passed over in a popular form to Eric Berne’s transactional analysis in a form of the parent/child/adult model. Federn’s theory is much more subtle and comprehensive than this reductive model. It is of considerable use to us in the understanding of states of depersonalisation, schizoid emptiness and body image disturbances. It is a model which lends itself to the understanding of dissociation and differing ego states, a model which I believe is regaining prominence through the study of the more severe neurotic and borderline states. Professor Watkins is an expert hypnotist and devotes a good deal of his text to the hypno-analytic exploration of a schizoid patient. It is unfortunate that the protocols of sessions under hypnosis always read like rather bad drama. From my own experience in hypnosis I know that this is the way that sessions develop. One easily obtains very rich material and quickly becomes caught up in fascinating regressive states. It comes very easy to use the language of dissociation and ego states to the patient under hypnosis. They seem readily to confirm one’s theoretical predilections. Readers must form their own opinion as to the relevance of these sections.
Environmental Science and Pollution Research
Soil Biology and Biochemistry
Journal of Environmental Management, 2017
In this study we report on the interactions between the water-soluble fraction (WSF) of two munic... more In this study we report on the interactions between the water-soluble fraction (WSF) of two municipal solid waste composts (C1- and C2-WSF) with Pb(II) and Cu(II) ions at pH 4.5. The Me(II) addition to the compost-WSFs led to the formation of soluble Me(II)-organic complexes (as highlighted by FT-IR spectroscopy), and to a decrease of the trace metals' solubility, which was greater for Pb(II) than Cu(II). This was due to the formation of insoluble Me(II) complexes involving the water-soluble organic carbon (WSOC) and the inorganic anions within both WSFs [1.10 and 0.62 mmol L(-1) and 2.06 and 0.42 mmol L(-1) of Pb(II) and Cu(II) precipitated from C1- and C2-WSF respectively, when 6.4 mmol L(-1) Me(II) was added]. A loss of WSOC from both WSFs, i.e. ∼13% and <5%, was detected in the systems containing 6.4 mmol L(-1) Pb(II) and Cu(II) respectively. A significant contribution in the formation of Pb(II) precipitates was also due to phosphate, chloride and sulphate anions, since their concentrations in the WSF decreased of 80, 25 and 90%, respectively, after the addition of 6.4 mmol L(-1) Pb(II). A decrease of phosphate anions in both WSFs (∼30%) was found in the systems containing Cu(II).
Bioresource Technology, 2017
The ability of two municipal solid waste composts (MSW-C) to sorb As(V) in the presence of Pb(II)... more The ability of two municipal solid waste composts (MSW-C) to sorb As(V) in the presence of Pb(II) and in acidic conditions was investigated. Sorption isotherms and kinetics showed that both MSW-C were able to sorb As(V) in a similar way (∼0.24mmolg(-1) MSW-C), but only when Pb(II) was present (0.45mmolL(-1)). The concomitant sorption of Pb(II) by both MSW-C (∼0.40mmolg(-1)) suggested that the metal cation was likely acting as bridging element between the negatively charged functional groups of composts and As(V). SEM-EDX analysis of the MSW-C+Pb(II)+As(V) systems supported the association between Pb(II) and As(V), while sequential extraction procedures and organic acids treatment showed that As(V) was strongly retained by MSW-C+Pb(II) and suggested the presence of different interaction types between As(V) and Pb(II). Plant growth experiments highlighted the key role of Pb(II) in the reduction of As(V)-phytotoxicity for triticale plants (×Triticosecale Wittm.) in the presence of MSW-C.
CLEAN - Soil, Air, Water, 2016
Fresenius Environmental Bulletin, 2012
Water, Air, & Soil Pollution, 2015
The aim of this thesis was to study the interaction mechanisms between an inorganic sorbent, red ... more The aim of this thesis was to study the interaction mechanisms between an inorganic sorbent, red mud (RM), and two different anions, arsenate and phosphate. Adsorption isotherms and sequential extraction procedures were firstly used to investigate these interactions. Sorption isotherms of arsenate and phosphate on RM, at pH 4.0, 7.0 and 10.0, were obtained while a sequential extraction procedure using H2O, (NH4)2SO4, NH4H2PO4, NH4 +-oxalate and NH4 +- oxalate + ascorbic acid, was applied to saturated RM samples to determine the interaction strength between respective anions and sorbent. Moreover, a physical, chemical and mineralogical characterization of not treated RM (alumina industry by-product) and RM exchanged with anions was carried out using spectroscopic techniques (FT–IR spectroscopy and X-Ray diffraction) and thermal analysis (TG and DTG) to evaluate the general suitability of RM as sorbent of phosphate and arsenate. Results showed that the RM was an effective sorbent of b...
The present work shows the results of X-ray diffraction (XRD), Fourier transform infrared (FT-IR)... more The present work shows the results of X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and thermal analysis of untreated (RM nt) and acid-treated red mud (RM a), a bauxite oreprocessing waste, exchanged with Pb 2+ , Cd 2+ , and Zn 2+ cations. These studies were performed in order to investigate the changes in the sorbent structure caused by the exchange with metals of different ionic radii. The XRD pattern of RM nt , analyzed according to the Rietveld method, showed a mixture of eight different phases. However, just three phases made up 78 wt.% of the RM nt : cancrinite (33 wt.%), hematite (29 wt.%), and sodalite (16 wt.%). X-ray diffraction patterns of RM nt exchanged with Pb 2+ and Cd 2+ cations revealed two additional phases, namely hydrocerussite [Pb 3 (CO 3) 2 (OH) 2 (10 wt.%)] and octavite [CdCO 3 (8 wt.%)]. These two phases probably originated from the carbonate precipitation processes which were due to the decarbonation of cancrinite. Hydrocerussite and octavite were not found in the case of acid-treated red mud samples. In the FT-IR spectra, the introduction of cations caused a distinct shift to higher wavenumbers in the peak at~1100 cm À1 , which is attributed to the asymmetric stretch of SiÀOÀAl. This effect may be associated with the Pb 2+ , Cd 2+ , and Zn 2+ adsorbed by the red muds which caused a deformation of the initial structure. Thermal analysis data of the red mud samples were obtained by thermogravimetric/differential thermogravimetric analysis, and these methods were employed to evaluate the desorption behavior of water and to clarify the thermal stability of the chemical phases of the different red mud samples. The loss of metal-bound water in the red mud samples was found to depend on the size of non-framework cations and water loss consistently followed the order: Zn 2+ >Cd 2+ >Pb 2+ .
Fresenius Environmental Bulletin
Journal of Hazardous Materials, 2010
In this study we evaluated the arsenate adsorption capacity of red muds (RM), wastes tailing from... more In this study we evaluated the arsenate adsorption capacity of red muds (RM), wastes tailing from the alumina production, at different pH values (4, 7, and 10). RM samples were artificially enriched in batch tests with solutions containing increasing concentrations of As(V). The pH of the solution significantly affected the adsorption, which increased with the decrease of pH. Moreover a sequential extraction procedure [H 2 O; (NH 4) 2 SO 4 ; NH 4 H 2 PO 4 ; NH 4 +-oxalate; NH 4 +-oxalate + ascorbic acid] was applied to RM samples exchanged with arsenate. Using this approach it was shown that low concentrations of arsenate sorbed in RM were present as water soluble and exchangeable fractions, while NH 4 +-oxalate and NH 4 +oxalate + ascorbic acid extracted most of the adsorbed arsenate from RM at different pH values. Besides, FT-IR spectroscopy was used to better understand the nature of RM surface configuration after As(V) sorption. In the FT-IR spectra the presence of As(V) species was highlighted by a well resolved band at 865 cm −1. The intensity and broadness of this band increased at the decreasing of pH. This band could be related to (As-O) vibration of an inner-sphere Al-O-As complex and/or due to As-O bonds of the adsorbed As(V) species on Fe oxides of RM samples.
Journal of Hazardous Materials, 2006
The ability of manganese oxide coated zeolite (MOCZ) to adsorb copper and lead ions in single-(no... more The ability of manganese oxide coated zeolite (MOCZ) to adsorb copper and lead ions in single-(non-competitive) and binary-(competitive) component sorption systems was studied in fixed-bed column. The experiments were applied to quantify particle size, bed length, influent flow rate and influent metal concentration on breakthrough time during the removal of copper and lead ions from aqueous solutions using MOCZ column. Results of fixed-bed adsorption showed that the breakthrough time appeared to increase with increase of the bed length and decrease of influent metal concentration, but decreased with increase of the flow rate. The Thomas model was applied to adsorption of copper and lead ions at bed length, MOCZ particle size, different flow rate and different initial concentration to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. The model was found suitable for describing the adsorption process of the dynamic behavior of the MOCZ column. The total adsorbed quantities, equilibrium uptakes and total removal percents of Cu(II) and Pb(II) related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different conditions. The results suggested that MOCZ could be used as an adsorbent for an efficient removal of copper and lead ions from aqueous solution. The removal of metal ion was decreased when other additional heavy metal ion was added, but the total saturation capacity of MOCZ for copper and lead ions was not significantly decreased. This competitive adsorption also showed that adsorption of lead ions was decreased insignificantly when copper ions was added to the influent, whereas a dramatic decrease was observed on the adsorption of copper ions by the presence of lead ions. The removal of copper and lead ion by MOCZ columns followed the descending order: Pb(II) > Cu(II). The adsorbed copper and lead ions were easily desorbed from MOCZ with 0.5 mol l −1 HNO 3 solution.
Journal of Hazardous Materials, 2011
In this study we evaluated the efficiency of red muds (RM, a bauxite residue) to immobilize the a... more In this study we evaluated the efficiency of red muds (RM, a bauxite residue) to immobilize the arsenic present in a polluted sub-acidic soil (UP-soil; total As 2428 mg kg(-1)) and to influence some chemical, biochemical and microbiological properties after 2 years since RM addition. The RM addition caused a pH increase, a striking decrease of total organic carbon and a significant increase of water-soluble C, N and P. The analysis of As mobility through sequential extraction showed a reduction of the water-soluble arsenic in the RM-soil compared to the UP-soil (3.44% and 5.59% of the total As respectively) and a remarkable increase of the residual (non extractable) arsenic fraction in the RM-soil (>300% compared to UP-soil). RM addition increased significantly the microbial abundance and the activity of selected enzymes (dehydrogenase, urease) with respect to UP-soil while had a major influence on the structure of soil microbial communities as evaluated by the Biolog Community Level Physiological Profile. The reduced As mobility, together with an increase of C, N and P labile-pool (likely originating from a "de-structuring effect" of RM on the soil organic matter) were identified as the key factors affecting the biological activity in the RM-treated soil.
Journal of Hazardous Materials, 2010
In the present work we investigated the interactions established between red mud (RM) and phospha... more In the present work we investigated the interactions established between red mud (RM) and phosphate anions (P) at pH 4.0, 7.0 and 10.0. The amount of P sorbed by RM (P-RM) increased as the pH decreased being equal to 4.871 mmol g(-1) at pH 4.0, 0.924 mmol g(-1) at pH 7.0, and 0.266 mmol g(-1) at pH 10.0. Sequential extractions' data of P-RM equilibrated at pH 4.0 and 7.0, suggested that the phosphate sorption at these pH values was mainly regulated by two different mechanisms that gave rise to a chemical adsorption on RM phases, and to the formation of metal phosphate precipitates. By contrast, at pH 10.0 the P-sorption was regulated by a chemisorption mechanism on Fe-Al phases of RM. These findings were supported by FT-IR analysis, which showed a broad band at 1114 and 1105 cm(-1) in P-RM spectra at pH 4.0 and 7.0 respectively, attributable to P-O(H) stretching nu(3)-modes associated to inner-sphere complexes of phosphate on Fe-Al phases, or alternatively to stretching vibrations of PO(4)(3-) tetrahedra, arising from a precipitate of aluminium phosphate. Importantly, the FT-IR spectroscopy showed a phosphate-promoted dissolution of tectosilicates, notably cancrinite and sodalite, in RM exchanged with phosphate at pH 4.0 and 7.0.
Journal of Environment Quality, 2013
The mobility and bioavailability of As in the soil-plant system can be affected by a number of or... more The mobility and bioavailability of As in the soil-plant system can be affected by a number of organic acids that originate from the activity of plants and microorganisms. In this study we evaluated the ability of citrate and malate anions to mobilize As in a polluted subacidic soil (UP soil) treated with red mud (RM soil). Both anions promoted the mobilization of As from UP and RM soils, with citrate being more effective than malate. The RM treatment induced a greater mobility of As. The amounts of As released in RM and UP soils treated with 3.0 mmol L citric acid solution were 2.78 and 1.83 μmol g respectively, whereas an amount equal to 1.73 and 1.06 μmol g was found after the treatment with a 3.0 mmol L malic acid solution. The release of As in both soils increased with increasing concentration of organic acids, and the co-release of Al and Fe in solution also increased. The sequential extraction showed that Fe/Al (oxi)hydroxides in RM were the main phases involved in As binding in RM soil. Two possible mechanisms could be responsible for As solubilization: (i) competition of the organic anions for As adsorption sites and (ii) partial dissolution of the adsorbents (e.g., dissolution of iron and aluminum oxi-hydroxides) induced by citrate or malate and formation of complexes between dissolved Fe and Al and organic anions. This is the first report on the effect of malate and citrate on the As mobility in a polluted soil treated with RM.
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Papers by Margherita Silvetti