Andrea Baglieri

Microbial Response to Na2SO4 Additions in a Volcanic Soil

We studied the effects of increased electrical conductivity (EC) of a soil on the activity and structure of its microbial community. Dry soil samples were added with 0, 11, 22, and 45 g kg−1 of Na2SO4 and left to incubate for 40 d before microbial respiration, microbial biomass C (MBC), microbial biomass N (MBN), K2SO4-extractable C (Ext-C), K2SO4-extractable N (Ext-N), and potentially mineralizable N (PMN) were determined. Amplified ribosomal DNA restriction analysis (ARDRA) and denaturing gradient gel electrophoresis (DGGE) were applied on α-, β-proteobacterial, and actinomycete 16S rDNA fragments amplified by PCR from total DNA in order to better understand the effect of osmotic stress on the soil microbial communities. The increase in EC significantly reduced respiratory activity of the microbial biomass and lowered microbial C; moreover, it increased the soluble fraction of both C and N. Greater N mineralization was found in soils to which 11 and 22 g kg−1 of Na2SO4 had been added as compared with both the untreated soil, and that receiving 45 g kg−1 of Na2SO4. The two former soils were also richer in aerobic bacteria (107 CFU g−1 soil) than the other two soils (106 CFU g−1 soil), and the ARDRA and DGGE analyses showed an activation of the α-proteobacteria. No significant differences were found in the ARDRA and DGGE patterns of the β-proteobacteria and actinomyces groups, suggesting a no-detectable response of these microorganisms to the Na2SO4 addition within the concentration range in this study.

Processed vs. non-processed biowastes for agriculture: effects of post-harvest tomato plants and biochar on radish growth, chlorophyll content and protein production.

The aim of this work was to address the issue of processed vs. non-processed biowastes for agriculture, by comparing materials widely differing for the amount of process energy consumption. Thus, residual post harvest tomato plants (TP), the TP hydrolysates obtained at pH 13 and 60 °C, and two known biochar products obtained by 650 °C pyrolysis were prepared. All products were characterized and used in a cultivation of radish plants. The chemical composition and molecular nature of the materials was investigated by solid state 13C NMR spectrometry, elemental analysis and potentiometric titration. The plants were analysed for growth and content of chlorophyll, carotenoids and soluble proteins. The results show that the TP and the alkaline hydrolysates contain lignin, hemicellulose, protein, peptide and/or amino acids moieties, and several mineral elements. The biochar samples contain also similar mineral elements, but the organic fraction is characterized mainly by fused aromatic rings. All materials had a positive effect on radish growth, mainly on the diameter of roots. The best performances in terms of plant growth were given by miscanthus originated biochar and TP. The most significant effect was the enhancement of soluble protein content in the plants treated with the lowest energy consumption non processed TP. The significance of these findings for agriculture and the environment is discussed.

Effects of organoclays on soil eubacterial community assessed by molecular approaches

The aim of this study was to evaluate the effects of the commercial organoclays, CLOISITE 30B, NANOFIL 804 and DELLITE 26C on soil eubacterial community. An enrichment test was carried out on Nutrient Broth containing the organoclay and the microorganisms previously isolated from soil. Four transfers were made, each after 7 days incubation. The molecular analyses on the eubacterial community were performed before treatment and 7 days after each transfer. DNA was extracted, amplified with eubacterial primers, finally analysed by amplified ribosomal DNA restriction analysis (ARDRA) and denaturing gradient gel electrophoresis (DGGE). The profiles of the samples treated with each organoclay showed the absence, the appearance and an increase in the intensity of some bands. These bands were excised from the gels, and the related microorganisms were identified by DNA sequencing, as Pseudomonas putida, Alcaligenes xylosoxidans, Pseudomonas monteilii and Pseudomonas aeruginosa. NAN804 treatment did not have any influence on soil eubacterial community, CLO30B had a slight toxic effect only on P. putida, instead the DEL26C treatment had a stronger toxic effect on P. putida and a slight toxic effect on P. monteilii. Finally, all the tested organoclays stimulated the growth of both A. xylosoxidans and P. aeruginosa.

Behavior of fenhexamid in soil and water.

A study was conducted to investigate fenhexamid (FEX) behavior in soil and in water. FEX proved to be rather stable at acid pH but showed slight degradation at neutral and alkaline pH. After 101 days of FEX spiking of a soil sample, 94% at pH 4, 12% at pH 7 and 23% at pH 9 of the active ingredient was still present. In natural water the rate of FEX disappearance appeared to be slow which may be due to abiotic rather than biotic processes. The soil degradation tests showed low persistence of the active ingredient if a good microflora activity is guaranteed (DT50 about 1 day). Moreover, in absence of microorganisms, FEX proved to be stable. Humidities of 25 and 50% of Water Holding Capacity (WHC) influenced in equal measure the rate of degradation. From the same soil, a bacterium was isolated and identified as Bacillus megaterium, which was able to metabolize FEX with the hydroxylation of the cyclohexane ring. Moreover, FEX showed an elevated affinity for humic acid (73%), smectite (31%), and ferrihydrite(20%) and low affinity for vermiculite (11%) and kaolinite (7%).

Degradation of Pyrimethanil in Soil: Influence of Light, Oxygen, and Microbial Activity

The research was carried out in order to verify the influence that light, oxygen, and microbial activity have on the degradability of pyrimethanil (PYR) in soil. The products of degradation were also identified and their evolution in time evaluated. The results indicate that the molecule is more persistent in the absence of light, oxygen, and microbial activity. The order of importance of these three factors is as follows: light < microbial activity < oxygen. The following products of degradation were identified: (1) benzoic acid, (2) cis,cis-muconic acid, (3) hydroxyl-4,6-dimethyl-2-pirimidinamine, (4) N′-ethyl-N-hydroxyformamidine, and (5) 4,6-dimethyl-2-piridinamine, which appeared different from those reported in literature for the degradation of PYR in abiotic conditions. This result suggests that the degradation in soil is mainly biotic.

Removal of fenhexamid and pyrimethanil from aqueous solutions by clays and organoclays.

The ability of a sodium montmorillonite (CLONa) and two commercial available organoclays having interlayer organic cations possessing different functional groups (CLO20A and CLO30B) was investigated for adsorbing two pesticides namely fenexamid (FEX) and pyrimethanyl (PMT). The two organoclays displayed a higher affinity with the pesticides than the unmodified clay, but the improvement in adsorption capacity varied according to the characteristics of the pesticide and the interlayer organic cation. FEX was adsorbed to a greater extent than PMT by both organoclays, which may be due to the higher hydrophobicity of FEX thereby indicating considerable hydrophobic interaction between the adsorbent/adsorbate systems. Our findings may find application in the removal of water-soluble pesticides from aquifers.

Use of model soil colloids to evaluate adsorption of phenanthrene and its mobilization by different solutions

The effects of cyanobacteria aqueous extracts containing Microcystin-LR (MC-LR) on the seed germination and growth of Pisum sativum, Lens esculenta, Zea mays and Triticum durum were investigated. Experiments were carried out on a range of doses of the extract (equivalent to 0, 1.6, 2.9, 5.8, 8.7 and 11.6 mu g MC-LR/mL). The results confirm that these plants were sensitive to cell-free extracts of a toxic Microcystis and that germination inhibition was dose dependent. One-way analysis of variance (ANOVA) showed that P. sativum is the most sensitive tested species with a 97% germination rate reduction and L. esculenta was the most resistant. At the 8th day, the exposure to the microcystins (MC) resulted in a significant decrease of plant epicotyls length, roots length and a net inhibition of lateral root formation. It is concluded that MC could affect also terrestrial plants seedling germination and growth. Therefore, the use of water for irrigation contaminated by MC could exert negative biochemical effects on seed and plant metabolism which might influence the agricultural crops.

Organo-clays and nanosponges for acquifer bioremediation: Adsorption and degradation of triclopyr

To avoid the problem of groundwater contamination, mitigation techniques have been proposed that consist of creating barriers made of suitable materials that can facilitate the adsorption and degradation of the pollutants. This study aims at evaluating the capacity of two organo-clays (Dellite 67 G and Dellite 43 B) and one nanosponge to adsorb the herbicide, triclopyr. Triclopyr was chosen because it is a good example of a moderately mobile, leacheable molecule. The rate of degradation of the molecule in the soil, both with and without the presence of the materials under examination, was also determined. Both the organo-clays adsorbed more than 90% of the herbicide. The nanosponge and the soil adsorbed less than 10% triclopyr. When the soil was added with the two organoclays, adsorption increased to 92%. When added to the soil, the materials accelerated the degradation of triclopyr. The half-life in soil was 30 days, whereas in soil with Dellite 67 G and Dellite 43 B it was 10 and 6 days respectively. The addition of the nanosponge to the soil decreased the half life by 50%. These results lead us to suggest that they be used in creating reactive barriers for the remediation of soils and aquifers.

Organically modified clays as binders of fumonisins in feedstocks.

This study reports an investigation on the ability of organically modified clays to bind mycotoxins, fumonisins B1 (FB1) and B2 (FB2). Organically modified clays are commercia materials prepared from natural clays, generally montmorillonite, by exchanging the inorganic cation with an ammonium organic cation. A screening experiment conducted on 13 organically modified clays and 3 nonmodified clays, used as controls, has confirmed that the presence of an organic cation in the clay interlayer promoted the adsorption of both fumonisins. On the basis of the results of the screening test, four modified clays and a Na-montmorillonite were selected for the determination of the adsorption kinetics and isotherms. On all the tested materials adsorption took place within one hour of contact with fumonisins solutions. Adsorption isotherms have pointed out that the modified clays exhibited a higher adsorptive capacity than the unmodified clay. It was also demonstrated that, notwithstanding the reduced structural difference between FB1 and FB2, they were differently adsorbed on the modified clays. Addition of 2% modified clays to contaminated maize allowed a reduction of more than 70% and 60% of the amount of FB1and FB2 released in solution. Although in vivo experiments are required to confirm the effectiveness of the organically modified clays, these preliminary results suggest that these materials are promising as fumonisins binders.

Comparison between the humic acids characteristics of two andisols of different age by: FT-IR and 1H-NMR spectroscopy and py-FIMS

Mt Etna (Italy) is the highest, active volcano in Europe. Thanks to the availability of descriptive documents and maps, it is possible to date the formation of several Etna soils. We evaluated the effect of soil formation age on the composition of the soil organic matter (SOM) and humic acids (HAs) from two Etna andisols of different ages but having the same vegetation (Castanea saliva) and pedogenetic substrate (tephra). The characterization of the SOM and the HAs was carried out by elementary and functional group analysis, UV-visible spectrophotometry, Fourier Transform InfraRed (FT-IR) and 1H-Nuclear Magnetic Resonance (1H-NMR) spectroscopies, and Pyrolysis-Field Ionization Mass Spectrometry (py-FIMS). Data showed that the age of the soil cannot be considered as influencing the chemical composition of the SOM. However higher volatilisation temperatures, for some compound classes, indicate the presence of more thermally-stable, organic molecules, therefore a more mature organic matter, or an organic component more greatly bound to the mineral component in the older soil. Finally the HA extracted from old soil contains a lower quantity of aliphatic compounds and a greater quantity of carbohydrate and aromatic molecules than the HA extracted from young soil.