BUSCADOR RECOLECTA

Electroactive bacterial biofilms can be produced on a polarized electrode by forcing its use as the final electron acceptor for bacterial respiration. This strategy offers the researcher the unique possibility to control the respiration process with extreme precision. The production of current, the accumulation of charge and the conducting properties of electroactive biofilms has been interrogated in this work through very basic electrochemical techniques including chronopotentiometry, chronoamperometry and cyclic voltammetry. Presented results indicate that charge can be accumulated in the biofilm conductive network, that network conductivity does not represent a limit for current production and that both the steady state current and the amount of accumulated charge depend on the redox state of cytochromes wiring the cells to the electrode. A model of biofilm conduction is presented as well.

Poly(amidoamine) (PAMAM) dendrimers are attracting great interest as a consequence of their unique properties as carriers of active molecules in aqueous media, as we expect their presence in the environment to be widespread in the future. In this article, we focus on the analytical methods to characterize and to determine these polymeric materials in waters and on their ecotoxicity for aquatic organisms. We review physical characterization techniques (e.g., light scattering, electron microscopy, atomic force microscopy) and analytical techniques, mainly based on liquid chromatography, so as to consider their main capabilities, advantages and drawbacks. We assessed the toxicity of certain PAMAM dendrimers for the green alga Pseudokirchneriella subcapitata by determining the EC50 and correlating it with the ζ-potential.

Mixed matrix membranes of H-ZSM-5 incorporated poly(vinyl alcohol) (PVA) membranes were prepared by solution casting method and crosslinked with glutaraldehyde. The prepared membranes were characterized by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy, differential scanning calorimeter and thermogravimetric analysis. Resulting membranes were tested for pervaporation (PV) separation of methanol–benzene mixture. Pervaporation separation characteristics of the zeolite incorporated membranes were tested at varying methanol feed compositions at different temperatures. It was observed that the mixed matrix membrane containing 5 wt.% of zeolite showed the highest selectivity value of 47 with 71.03 g/m2 h of flux at 20 wt.% methanol in feed mixture at 30 °C temperature. In comparison with higher (5 wt.%) zeolite content membrane, the less zeolite (1 wt.%) incorporated membrane shown the less selectivity along with moderate flux. The experimental studies explain that there is an increase in membrane performance such as swelling, permeation flux and methanol selectivity with H-ZSM-5 content in the membrane. In addition membrane swelling experiments with feed components were performed to understand the PV results.

The influence of iron species on amoxicillin (AMX) degradation, intermediate products generated and toxicity during the photo-Fenton process using a solar simulator were evaluated in this work. The AMX degradation was favored in the presence of the potassium ferrioxalate complex (FeOx) when compared to FeSO4. Total oxidation of AMX in the presence of FeOx was obtained after 5 min, while 15 min were necessary using FeSO4. The results obtained with Daphnia magna biossays showed that the toxicity decreased from 65 to 5% after 90 min of irradiation in the presence of FeSO4. However, it increased again to a maximum of 100% after 150 min, what indicates the generation of more toxic intermediates than AMX, reaching 45% after 240 min. However, using FeOx, the inhibition of mobility varied between 100 and 70% during treatment, probably due to the presence of oxalate, which is toxic to the neonates. After 240 min, between 73 and 81% TOC removal was observed. Different pathways of AMX degradation were suggested including the opening of the four-membered β-lactamic ring and further oxidations of the methyl group to aldehyde and/or hydroxylation of the benzoic ring, generating other intermediates after bound cleavage between different atoms and further oxidation to carboxylates such acetate, oxalate and propionate, besides the generation of nitrate and ammonium.

he annually reoccurring blooms that characterize the surface waters of the Baltic Sea are dominated by filamentous, heterocystous cyanobacteria such as Nodularia spumigena. In a previous study, we have demonstrated that N. spumigena strain AV1 differentiates heterocysts in the absence of detectable nitrogen fixation activity, an unusual physiological trait that is clearly distinct from other well-studied cyanobacteria. To further analyze the uncoupling between these two processes, we analyzed the gene expression and modification of the nitrogenase enzyme (the enzyme responsible for nitrogen fixation) in N. spumigena AV1, as well as in several other N. spumigena strains. Here, we demonstrate the occurrence of two nifH gene copies in N. spumigena strain AV1, only one of which is located in a complete nifHDK cluster and several NifH protein forms. Furthermore, we demonstrate the occurrence of a DNA rearrangement mechanism acting within the nifH gene copy located in the nifHDK cluster and present only in the strains exhibiting the previously reported uncoupling between heterocyst differentiation and nitrogen fixation processes. These data stress the existence of a distinct and complex regulatory circuit related to nitrogen fixation in this ecologically significant bloom-forming cyanobacterium.

The effect inter-row polyethylene mulch on the water use efficiency and crop productivity of furrow- and drip-irrigated maize (Zea mays L.) was evaluated in a field study. In contrast to the traditional ‘on ridge’ mulching, the inter-row polyethylene mulch was placed in such a way that it could be easily removed for reuse since the row of plants itself was not covered but the furrows were completely covered. Irrigation needs were computed by multiplying the cumulative Class A Pan evaporation between irrigations by a crop coefficient that changed through the growing season. Our results indicate that inter-row mulching induced earliness under both irrigation treatments. Seventy five percent of canopy density was attained in the mulched treatments contrasting with 45–61 % in the non-mulched treatments at 34 days after sowing. Throughout the growing period, shoot biomass was significantly higher for the mulched treatments that had as well higher root biomasses. The overall estimated evaporative losses from the non-mulched treatments were between 37 % and 39 % of the total water applied. The whole gross canopy water use efficiency in the furrow and drip mulched treatments was 64 % and 45 % higher than in the respective non-mulched treatments. These results indicate that inter-row polyethylene mulch is an efficient technique by which soil evaporation is reduced and plant productivity increased.

This article presents a dose-response study of the effects of two types of third-generation (G3) and fourth-generation poly(amidoamine) (PAMAM) dendrimers on two cell lines (RTG-2 and H4IIE) by in vitro cytotoxicity assays with 3-(4,5-dimethylthizol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), neutral red uptake (NRU), and lactate dehydrogenase (LDH) assays. We particularly investigated the potential cytotoxic effect of positive surface charge, which a cationic amino-terminated PAMAM dendrimer can display, on the marked ability of PAMAM dendrimers to cross the cell membrane compared with PAMAM dendrimers functionalized with chains of N-(2-hydroxydodecyl). Quantification of dose-response effects was performed by use of mass spectrometry analysis. The analytical method using liquid chromatography-hybrid quadrupole/time-of-flight mass spectrometry that we developed allowed characterization of defective dendrimers instead of "ideal structures." Identification was based on accurate mass measurement, assignment of elemental composition, and the fully resolved (13)C/(12)C isotopic clusters of the multiply charged ions of PAMAM dendrimers. Validation of the liquid chromatography-mass spectrometry method made possible reliable and reproducible quantification of the extracellular and intracellular concentration of dendrimers at a micromolar level (limits of detection from 0.14 to 1.34 μM and from 0.43 to 1.82 μM in standard and culture medium, respectively). A higher cytotoxicity was found with the H4IIE cell line for surface-modified PAMAM dendrimers. The LDH assay was significantly more sensitive than the MTT and NRU assays, with half-maximal inhibitory concentrations (IC(50)) of 12.96 and 38.31 μg mL(-1) for surface-modified G3 and G4 dendrimers, respectively. No cytotoxic effects, in terms of IC(50), of amino-terminated PAMAM dendrimers were observed on both H4IIE and RTG-2 cells when the concentration was below 500 μg mL(-1) for G3 and G4 dendrimers.

This work summarized all results obtained during almost two-years of a monitoring programme carried out in five municipal sewage treatment plants (STPs) located in the north, centre and south-east of Spain. The study evaluated the occurrence and persistence of a group of 100 organic compounds belonging to several chemical groups (pharmaceuticals, personal care products, pesticides and metabolites). The average removal efficiencies of the STPs studied varied from 20% (erythromycin) to 99% (acetaminophen). In analysed samples, we identified a large number of compounds at mean range concentrations between 7-59,495 ng/L and 5-32,720 ng/L for influent and effluent samples, respectively. This study also identified 20 of the mostly detected and persistent compounds in wastewater effluent, of which hydrochlorothiazide, atenolol, gemfibrozil, galaxolide and three metabolites (fenofibric acid, 4-AAA and 4-FAA), presented the highest average contribution percentages, in relation to the total load of contaminants for the different STPs effluent studied.

A new approach for the analysis of pharmaceuticals (target and non-target) in water by LC–QTOF-MS is described in this work. The study has been designed to assess the performance of the simultaneous quantitative screening of target compounds, and the qualitative analysis of non-target analytes, in just one run. The features of accurate mass full scan mass spectrometry together with high MS/MS spectral acquisition rates – by means of information dependent acquisition (IDA) – have demonstrated their potential application in this work. Applying this analytical strategy, an identification procedure is presented based on library searching for compounds which were not included a priori in the analytical method as target compounds, thus allowing their characterization by data processing of accurate mass measurements in MS and MS/MS mode. The non-target compounds identified in river water samples were ketorolac, trazodone, fluconazole, metformin and venlafaxine. Simultaneously, this strategy allowed for the identification of other compounds which were not included in the library by screening the highest intensity peaks detected in the samples and by analysis of the full scan TOF-MS, isotope pattern and MS/MS spectra – the example of loratadine (histaminergic) is described. The group of drugs of abuse selected as target compounds for evaluation included analgesics, opioids and psychostimulants. Satisfactory results regarding sensitivity and linearity of the developed method were obtained. Limits of detection for the selected target compounds were from 0.003 to 0.01 μg/L and 0.01 to 0.5 μg/L, in MS and MS/MS mode, respectively – by direct sample injection of 100 μL.

Volatile organic compounds (VOCs) are of prime concern due to their toxicity and persistence in the environment. We focus on sample-preparation methods, instruments used and concentrations reported in the determination of VOCs in aquatic matrices (e.g., seawater, river water, groundwater and drinking water). We pay special attention to sample-enrichment methods and mention the application of different detectors with respective sensitivities. We note that, among the sample-pre-concentration methods, purge-and-trap and solid-phase microextraction were the most chosen methods, which enabled excellent recoveries for a wide range of VOCs. Among the detectors, the mass-selective detector was unchallenged, due to the remarkable sensitivity and detection based on mass. Tandem mass spectrometry is still emerging for determining VOCs, since not many papers have been published on it. The compounds detected most were the halogenated volatiles [e.g., dichloroethane, trichloroethane, bromodichloromethane and dibromochloromethane (DBCM)], followed by benzene, toluene, ethylbenzene and xylene (BTEX). Trihalomethanes have also been reported as a result of water-disinfection byproducts. Finally, the VOC levels detected most were the trihalo-alkanes (trichloromethane: 1900 ng/L in estuary surface water; tribromomethane: 147–762 ng/L in drinking water; and, DBCM: 92–399 ng/L in drinking water), and among BTEX were benzene (3.9–141.7 ng/L in seawater) and xylene (4.3–332 ng/L in seawater). We also note the need for quality assurance and mention the European Union Directive regarding VOCs.