Assessing microbial activities in metal contaminated agricultural volcanic soils--An integrative approach.

Volcanic soils are unique naturally fertile resources, extensively used for agricultural purposes and with particular physicochemical properties that may result in accumulation of toxic substances, such as trace metals. Trace metal contaminated soils have significant effects on soil microbial activities and hence on soil quality. The aim of this study is to determine the soil microbial responses to metal contamination in volcanic soils under different agricultural land use practices (conventional, traditional and organic), based on a three-tier approach: Tier 1 - assess soil microbial activities, Tier 2 - link the microbial activity to soil trace metal contamination and, Tier 3 - integrate the microbial activity in an effect-based soil index (Integrative Biological Response) to score soil health status in metal contaminated agricultural soils. Our results showed that microbial biomass C levels and soil enzymes activities were decreased in all agricultural soils. Dehydrogenase and ß-glucosidase activities, soil basal respiration and microbial biomass C were the most sensitive responses to trace metal soil contamination. The Integrative Biological Response value indicated that soil health was ranked as: organic>traditional>conventional, highlighting the importance of integrative biomarker-based strategies for the development of the trace metal "footprint" in Andosols.

Electrochemical oxidation of imazapyr with BDD electrode in titanium substrate.

In this work we have studied the treatment of imazapyr by electrochemical oxidation with boron-doped diamond anode. Electrochemical degradation experiments were performed in a one-compartment cell containing 0.45 L of commercial formulations of herbicide in the pH range 3.0-10.0 by applying a density current between 10 and 150 mA cm(-2) and in the temperature range 25-45 °C. The maximum current efficiencies were obtained at lower current densities since the electrochemical system is under mass transfer control. The mineralization rate increased in acid medium and at higher temperatures. The treatment was able to completely degrade imazapyr in the range 4.6-100.0 mg L(-1), although the current charge required rises along with the increasing initial concentration of the herbicide. Toxicity analysis with the bioluminescent bacterium Vibrio fischeri showed that at higher pollutant concentrations the toxicity was reduced after the electrochemical treatment. To clarify the reaction pathway for imazapyr mineralization by OH radicals, LC-MS/MS analyses we performed together with a theoretical study. Ions analysis showed the formation of high levels of ammonium in the cathode. The main final products of the electrochemical oxidation of imazapyr with diamond thin film electrodes are formic, acetic and butyric acids.

A comparative study of the electrochemical oxidation of the herbicide tebuthiuron using boron-doped diamond electrodes.

The thiadiazolylurea derivative tebuthiuron (TBH) is commonly used as an herbicide even though it is highly toxic to humans. While various processes have been proposed for the removal of organic contaminants of this type from wastewater, electrochemical degradation has shown particular promise. The aim of the present study was to investigate the electrochemical degradation of TBH using anodes comprising boron-doped (5000 and 30,000 ppm) diamond (BDD) films deposited onto Ti substrates operated at current densities in the range 10-200 mA cm(-2). Both anodes removed TBH following a similar pseudo first-order reaction kinetics with k(app) close to 3.2 × 10(-2) min(-1). The maximum mineralization efficiency obtained was 80%. High-pressure liquid chromatography with UV-VIS detection established that both anodes degraded TBH via similar intermediates. Ion chromatography revealed that increasing concentrations of nitrate ions (up to 0.9 ppm) were formed with increasing current density, while the formation of nitrite ions was observed with both anodes at current densities ≥ 150 mA cm(-2). The BDD film prepared at the lower doping level (5000 ppm) was more efficient in degrading TBH than its more highly doped counterpart. This unexpected finding may be explained in terms of the quantity of impurities incorporated into the diamond lattice during chemical vapor deposition.

Anodic oxidation of wastewater containing the Reactive Orange 16 Dye using heavily boron-doped diamond electrodes.

Boron-doped diamond (BDD) films grown on the titanium substrate were used to study the electrochemical degradation of Reactive Orange (RO) 16 Dye. The films were produced by hot filament chemical vapor deposition (HFCVD) technique using two different boron concentrations. The growth parameters were controlled to obtain heavily doped diamond films. They were named as E1 and E2 electrodes, with acceptor concentrations of 4.0 and 8.0 × 10(21)atoms cm(-3), respectively. The boron levels were evaluated from Mott-Schottky plots also corroborated by Raman's spectra, which characterized the film quality as well as its physical property. Scanning Electron Microscopy showed well-defined microcrystalline grain morphologies with crystal orientation mixtures of (111) and (100). The electrode efficiencies were studied from the advanced oxidation process (AOP) to degrade electrochemically the Reactive Orange 16 azo-dye (RO16). The results were analyzed by UV/VIS spectroscopy, total organic carbon (TOC) and high-performance liquid chromatography (HPLC) techniques. From UV/VIS spectra the highest doped electrode (E2) showed the best efficiency for both, the aromaticity reduction and the azo group fracture. These tendencies were confirmed by the TOC and chromatographic measurements. Besides, the results showed a direct relationship among the BDD morphology, physical property, and its performance during the degradation process.

A novel procedure to obtain nanocrystalline diamond/porous silicon composite by chemical vapor deposition/infiltration processes.

Nanocrystalline diamond (NCD) films were formed on porous silicon (PS) substrate by Chemical Vapor Deposition/Infiltration (CVD/CVI) process using a hot filament reactor. This innovative procedure is determinant to grow a controlled three-dimensional diamond structure with diamond grains formation in the pores, covering uniformly the different growth planes. In this CVI process, a piece of reticulated vitreous carbon (RVC) was used, under de PS substrate, as an additional solid source of hydrocarbon that ensures the production of pertinent carbon growth species directly on PS and into its pores. PS substrates were obtained by anodization etching process of n-type silicon wafer in a hydrofluoric acid (HF) solution containing acetonitrile (CH3CN) which result in an uniform and well controlled porous distribution and size when compared with the usual ethanol solution. Depositions were performed using Ar-H2-CH4 where the methane concentration varied from 0 up to 1.0 vol%, to analyze the influence of RVC use as an additional carbon source on growth mechanism. Scanning Electron Microscopy (SEM) and Field Emission Gun (FEG) were used to investigate PS and NCD film morphology. SEM images of NCD showed faceted nanograins with average size from 5 to 16 nm and uniform surface texture covering all the supports among the pores resulting in an apparent micro honeycomb structure. Raman spectra confirmed the existence of sp2-bonded carbon at the grain boundaries. The spectra showed a peak that may be deconvoluted in two components at 1332 cm(-1) (diamond) and 1345 cm(-1) (D band). Two shoulders at 1150 and 1490 cm(-1) also appear and are assigned to transpolyacetylene (TPA) segments at the grain boundaries of NCD surfaces. In addition, X-ray diffraction analyses of all films presented characteristic diamond diffraction peaks corresponding to (111), (220) and (311).

Serial study of the complement fractions C3, C4 and C3PA in allergic children.

The C3, C4 and C3PA complement fractions were dosed by radial immunodiffusion in the serum of 25 children with ages from 4 to 9 years in a non symptomatic period comprehending 10 atopic asthmas (40,0% of the cases) 8 non atopic asthmas (32.0%) and 7 urticarias (28,0%). The quantitative dosage of the studied fractions was carried out in a serial form 7, 14, 30 and 45 days after the first determination, what made a total of 116 dosages of C3, 112 of C4 and 114 of C3PA. Globally, no differences were verified in the averages and standard deviations of the complement fractions studied in the various pathological situations considered. The complement anomaly more frequently observed was the C4 increase in 37,8% of the assays in patients with atopic asthma, 16,2% of the assays in patients with non-atopic asthma and in 33,3% of the assays in urticaria cases. The other complement fractions studied showed inconstant variations in some cases. The serial study demonstrated in the same patient, variations larger than 2 standard deviations in 25,8% of the assays for C3, 25,0% for C4 and 27,2% for C3PA, what may possibly indicate the great instability of the complement system which depends on a function, consumption or activation and synthesis relation, having to be taken into consideration in those assays comprehending the quantitative study of the seric complement fractions.

IgE and complement in allergic children.

The following measurements were made using radial immunodiffusion with commercial M-Partigen plaques (Behringwerke, Marburg): Global-IgE in the serum of 29 children (17 atopic asthmas, 3 non atopic asthmas and 9 acute urticarias); C3 and C4 complement fractions in 56 patients (27 atopic asthmas, 11 non atopic asthmas and 18 acute urticarias); C3PA complement fraction in 41 patients (18 atopic asthmas, 9 non atopic asthmas and 14 acute urticarias). High IgE serum levels were observed chiefly in the cases of atopic asthma with polysensitization and in urticarias. The anomaly of the complement system most often found in children was an increase of C4 (23,2% of the cases), not related to the clinical form or duration of the disease. An increase of the C3 fraction (14,6% of the cases) was also observed together with an increase of these two fractions in all the cases where an increase of C3PA was observed. Only in 11,1% of atopic asthmas was a decrease of the serum concentration values of C3 observed.