Pacifico Ruggiero

Short-term effects of municipal solid waste compost amendments on soil carbon and nitrogen content, some enzyme activities and genetic diversity

Abstract. Municipal solid waste (MSW) composts have been frequently used as N and C amendments to improve soil quality and to support plant growth, with the additional benefit of reducing waste disposal costs. However, attention has been paid to the risks of MSW use for the soil environment. The presence of heavy metals in MSW composts can affect some microbiological characteristics of soil such as the structure of the soil microbiota, which are responsible for the transformations making nutrients available to plants. The effects of MSW compost and mineral-N amendments in a 2-year field trial on some physical-chemical properties, some enzyme activities and the genetic diversity of cropped plots (sugar beet-wheat rotation) and uncropped plots were investigated. Variations of pH were not statistically related to MSW compost and mineral-N amendments, or to the presence of the crop. Amendment with MSW compost increased the organic C and total N contents, and dehydrogenase and nitrate reductase activities of soil. In cropped plots amended with MSW compost, dehydrogenase activity was positively correlated with β-glucosidase activity, and both enzyme activities with organic C content. No MSW compost dosage effect was detected. No effects were observed on denaturing gradient gel electrophoresis and amplified rDNA restriction analysis patterns, indicating that no significant change in the bacterial community occurred as a consequence of MSW amendment.

Zinc distribution and speciation within rocket plants (Eruca vesicaria L. Cavalieri) grown on a polluted soil amended with compost as determined by XRF microtomography and Micro-Xanes

Zinc distribution and speciation within different organs (root, petiole, and leaf) of the edible plant Eruca vesicaria L. Cavalieri were determined using synchrotron microbeam X-ray techniques (XRF microtomography and mu-XANES) for plants grown in polluted soil with or without compost amendment. Data on soil derived from different extraction procedures and using mu-XANES analyses on rhizospheric soil indicated that compost amendment did not significantly influence the Zn speciation and availability in soil. However, major differences were observed within the plants. Plants grown in the presence of compost were able to partly block zinc immediately outside the root endodermis in the form of zinc-phytate, while a smaller Zn fraction was allowed to xylem transport as zinc-citrate. In the leaves, zinc was largely excluded from leaf cells, and about approximately 50% was in the form of phosphate precipitates, and the other 50% was complexed by cysteine and histidine residues. The reported data provide new information concerning the mechanisms of zinc tolerance in E. vesicaria L. Cavalieri, a very common edible plant in Mediterranean regions, and on the role of compost in influencing the molecular strategies involved in zinc uptake and detoxification.

Effects of conventional tillage on biochemical properties of soils

Abstract Modification of soil environment by different farming practices can significantly affect crop growth. Tillage causes soil disturbance, altering the vertical distribution of soil organic matter and plant nutrient supplies in the soil surface, and it may affect the enzyme activity and microbial biomass which are responsible for transformation and cycling of organic matter and plant nutrients. In this study, the influence of three conventional tillage systems (shallow plowing, deep plowing and scarification) at different depths on the distribution and activity of enzymes, microbial biomass and nucleic acids in a cropped soil was investigated. Analysis of variance for depth and tillage showed the influence of the different tillage practices on the activity of some enzymes and on the nucleic acids. Glucosidase, galactosidase, nitrate reductase and dehydrogenase activity were significantly affected by the three tillage modalities. Activity in the upper layer (0–20 cm) was higher in the plots tilled by shallow plowing and scarification than in those tilled by deep plowing. Positive relationships were observed between the soil enzymes themselves, with the exception of urease and pyrophosphatase activity. Moreover, significant correlations were found between DNA and β-galactosidase, and between RNA and β-glucosidase, β-galactosidase, alkaline phosphatase and phosphodiesterase. α-Glucosidase, β-galactosidase, alkaline phosphatase and phosphodiesterase were highly correlated with biomass C determined by the fumigation-extraction method.

Fractionation of sugar beet pulp into pectin, cellulose, and arabinose by arabinases combined with ultrafiltration

Incubation of beet pulp with two arabinases (alpha-L-arabinofuranosidase and endo-arabinase), used singularly or in combination at different units of activity per gram of beet pulp, caused the hydrolysis of arabinan, which produced a hydrolyzate consisting mainly of arabinose. Pectin and a residue enriched with cellulose were subsequently separated from the incubation mixture. The best enzymatic hydrolysis results were obtained when 100 U/g of beet pulp of each enzyme worked synergistically with yields of 100% arabinose and 91.7% pectin. These yields were higher than those obtained with traditional chemical hydrolysis. The pectin fraction showed a low content of neutral sugar content and the cellulose residue contained only a small amount of pentoses. Semicontinuous hydrolysis with enzyme recycling in an ultrafiltration unit was also carried out to separate arabinose, pectin, and cellulose from beet pulp in 7 cycles of hydrolysis followed by ultrafiltration. The yields of separation were similar to those obtained in batch experiments, with an enzyme consumption reduced by 3.5 times and some significant advantages over batch processes.

Solving mercury (Hg) speciation in soil samples by synchrotron X-ray microspectroscopic techniques

Direct mercury (Hg) speciation was assessed for soil samples with a Hg concentration ranging from 7 up to 240 mg kg(-1). Hg chemical forms were identified and quantified by sequential extractions and bulk- and micro-analytical techniques exploiting synchrotron generated X-rays. In particular, microspectroscopic techniques such as mu-XRF, mu-XRD and mu-XANES were necessary to solve bulk Hg speciation, in both soil fractions <2 mm and <2 microm. The main Hg-species found in the soil samples were metacinnabar (beta-HgS), cinnabar (alpha-HgS), corderoite (Hg(3)S(2)Cl(2)), and an amorphous phase containing Hg bound to chlorine and sulfur. The amount of metacinnabar and amorphous phases increased in the fraction <2 microm. No interaction among Hg-species and soil components was observed. All the observed Hg-species originated from the slow weathering of an inert Hg-containing waste material (K106, U.S. EPA) dumped in the area several years ago, which is changing into a relatively more dangerous source of pollution.

Molecular approaches to investigate herbicide-induced bacterial community changes in soil microcosms

Abstract. Since biochemical and microbiological methods used to study microbial community changes induced by anthropogenic activities can be biased, the impact of two herbicides on soil microorganisms was investigated by culture-independent molecular techniques. The effect of three different amounts (the recommended field dose, tenfold, and 100-fold the dose) of propanil or prometryne on the bacterial community of a clay soil, two modalities of incubation (soil moisture at 70% of the field capacity and a soil-herbicide suspension, 1:10, w:v), and time of incubation were investigated by denaturing gradient gel electrophoresis (DGGE) and amplified rDNA restriction analysis (ARDRA). Two sets of primers for 16S rDNA were used to amplify total soil DNA. Sterile and non-sterile samples were used to determine, by HPLC, the amounts of herbicides adsorbed on soil and transformed by soil microorganisms. Prometryne persisted in soil longer than propanil. Propanil was removed significantly more by non-sterile than by sterile samples, while for prometryne, slight differences were observed. 3,4-Dichloroaniline, a product of propanil hydrolysis, was detected in non-sterile samples and increased with incubation time. Propanil did not affect soil bacteria significantly as indicated by DGGE and ARDRA, with the only exception being the soil-herbicide suspension. Despite a lower utilization of prometryne by soil microorganisms, DGGE analysis showed a more diverse banding than with propanil. Some bands were also detected in the DNA sample extracted from the soil-prometryne suspension, and could be representative of bacterial species utilizing the herbicide as a carbon source, in two very different soil microcosms.

Bioaccessibility, bioavailability and ecotoxicity of pentachlorophenol in compost amended soils

The influence of compost on the bioaccessibility, bioavailability and ecotoxicity of pentachlorophenol (PCP) as a function of time was studied by means of different chemical and ecotoxicological methods. Experiments were conducted in both sterile and non-sterile microcosms and samplings carried out at 20, 60 and 120d from initial contamination. PCP bioaccessibility, assessed by means of Porapak resin extraction, was around 75% of the applied dose with no aging or compost effects. Two different methods were applied to assess the bioavailability of PCP, respectively, to bacteria and earthworms and linked to ecotoxicological assays (biosensor and earthworm coelomocytes assays). Water extraction was applied to assess the bioavailability to bacteria: results showed that this fraction was always below 50%, with significant decreases as a result of aging processes and compost addition. In non-sterile microcosms, compost amendment increased the amount of PCP biodegraded, while the ecotoxicological assay with the biosensor Pseudomonas fluorescens pUCD607 indicated a higher toxicity in the most degraded samples, thus suggesting the formation of more toxic metabolites. Earthworm body accumulation results were rather in accordance with water extractions data, with decreasing bioavailable amounts as a result of time and compost addition. No compost or aging effects were instead detected by coelomocytes assay. Results indicate how different methods must be applied altogether to assess the bioavailability and ecotoxicity of xenobiotics such as PCP in soil. The addition of compost was also proven as an effective strategy for the remediation of PCP contaminated soils, although issues related to the possible formation of toxic metabolites must be taken into account.

Mercury speciation in the colloidal fraction of a soil polluted by a chlor-alkali plant: a case study in the South of Italy.

Mercury (Hg) speciation in different size fractions of a soil sample collected near an industrial area located in the South of Italy, which had been polluted by the dumping of Hg-containing wastes from a chlor-alkali plant, was investigated by XANES spectroscopy. In particular, a special procedure has been developed to study the soil colloidal fraction, both for sample preparation and for XANES data collection. In this soil, Hg was speciated in quite insoluble inorganic forms such as cinnabar (alpha-HgS), metacinnabar (beta-HgS), corderoite (Hg(3)S(2)Cl(2)), and some amorphous Hg, S and Cl-containing species, all derived from the land-disposal of K106 Hg-containing wastes. The contribution of the above-mentioned chemical forms to Hg speciation changed as a function of particle size. For the fraction <2 mm the speciation was: amorphous Hg-S-Cl (34%) > corderoite (26%) > cinnabar (20%) = metacinnabar (20%); for the fraction <2 microm: amorphous Hg-S-Cl (40%) > metacinnabar (24%) > corderoite (20%) > cinnabar (16%); and for the fraction 430-650 nm, where most of the colloidal Hg was concentrated: amorphous Hg-S-Cl (56%) > metacinnabar (33%) > corderoite (6%) > cinnabar (5%). From these data it emerged that, even if Hg was speciated in quite insoluble forms, the colloidal fraction, which is the most mobile and thus the most dangerous, was enriched in relatively more soluble species (i.e. amorphous Hg-S-Cl and metacinnabar), as compared with cinnabar. This aspect should be seriously taken into account when planning environmental risk assessment, since the small particle size in which Hg is concentrated and the changing speciation passing from millimetre to nanometre size could turn apparently safe conditions into more hazardous ones.

Characterization of wheat o-diphenolase isoenzyme

Abstract A highly purified isoenzyme of wheat o-diphenolase was characterized. The isoenzyme had a MW of ca 115 000, as determined by Sephadex G-100 gel filtration. The copper content was 0.20%, and the amino acid composition was determined. Two subunits (MWs ca 30 000 and 23 500) were detected by SDS gel electrophoresis. The Km was found to be 5.1 mM for 4-methylcatechol and kinetic analysis showed that the isoenzyme exhibited substrate inhibition. The isoenzyme was characterized by its response to some inhibitors.

Isoenzymes of wheat o-diphenolase revealed by column isoelectric focusing

ZusammenfassungWeichweizen-o-Diphenoloxydasen verschiedener Reinigungsstufen wurden über eine Säule isoelektrisch focussiert. Das durch Calciumphosphatgel gereinigte Enzym (Fraktion C) zeigt 4 multiple Formen, focussiert bei pI 3,60; 4,65; 6,80 und 9,60. Die Aktivität und der Reinheitszustand von diesen vier Formen wurden berechnet. Die Fraktion C wurde durch Chromatographie über Cellulose weiter gereinigt. Die in größeren Mengen gewonnene Fraktion zeigte beim isoelektrischen Focussieren keine multiple Formen mehr, nur eine Trennung von enzymatisch inaktiven Proteinen beim pH-Gradienten. Das enzymatisch aktive Protein, focussiert bei pI 9,60, zeigte einen 1753 mal besseren Reinheitszustand als das Rohenzym. Die Anwendung dieser Technik erlaubt die Charakterisierung der Weichweizen-o-Diphenoloxydasen und ihre Gewinnung in einem hochgereinigten Zustand.SummaryCommon wheat o-diphenolase at different purification steps has been submitted to column isoelectric focusing electrophoresis. The fraction purified with calcium phosphate gel shows multiple forms focused at pI 3.60, 4.95, 6.80, and 9.60. The enzyme activity and the purification degree of the four enzymatic components obtained have been calculated. The major fraction recovered after purification by chromatography on DEAE-cellulose does not display other multiple forms; however, it has some enzymatically inactive proteins well separated in the pH-gradient. The enzymatic protein, focused at pI 9.60, thus achieves a 1753-fold purification over the crude extract. The application of the technique allows a characterization of the wheat o-diphenolase and its recovery in highly purified form.