Propylene glycol-specific dehydrogenases as functional biomarkers for monitoring biodegradation in sites contaminated by de-icing chemicals

The area under study at Gardermoen airport (Oslo, Norway) is a glacial contact formation with sand and gravels dominating near the ground surface. Due to the northern climate, every winter large amounts of de-icing chemicals, i.e. propylene glycol (PG) and potassium formate, are commonly used in the airport for the removal of snow and ice from airplanes and runways, respectively. Even though these contaminants are easily degradable by biotic or abiotic factors, they may still threaten groundwater, due to the system overloading. The present study, performed within the FPVII European research project: “SoilCAM - Soil Contamination: Advanced integrated characterisation and time-lapse Monitoring”, deals with the physic-chemical and microbiological characterization of the site and the development of suitable methods for monitoring PG biodegradation on site under reclamation. For this purpose, functional biomarkers were selected to evaluate their potential use in Real Time quantitative PCR (q-PCR) experiments directly on soil DNA. The soils are highly leached, with low biological and biochemical activities. Therefore, pollutant transfer to the groundwater occurs quickly and is virtually unhindered. Bacterial strains isolated from the soil were able to degrade PG in aerobic conditions at 4, 15 and 30 °C. The PG-degrading population was mainly composed by different species of Pseudomonas, as shown by denaturing gradient gel electrophoresis (DGGE) analysis on soil DNA. Gene probes for PG-specific alcohol dehydrogenase (ADH-IIG) detected the presence of such genes in the isolates. The deduced amino acid sequence of representative strains presented over 92% identities with PG-specific dehydrogenase-related proteins. ADH-IIG detected in soil DNA indicated that PG-degrading strains were present along the soil profile from 0 to 100 cm. The application of q-PCR analysis on DNA from soil mesocosm experiments will confirm the suitability of ADH-IIG as biomarker for monitoring PG biodegradation in soil systems

Evaluation of the Thermal Effects in Tilting Pad Bearing

The analysis of thermal effects is of expressive importance in the context of rotordynamics to evaluate the behavior of hydrodynamic bearings because these effects can influence their dynamic characteristics under specific operational conditions. For this reason, a thermohydrodynamic model is developed in this work, in which the pressure distribution in the oil film and the temperature distribution are calculated together. From the pressure distribution, the velocity distribution field is determined, as well as the viscous dissipation, and consequently, the temperature distribution. The finite volume method is applied to solve the Reynolds equation and the energy equation in the thermohydrodynamic model (THD). The results show that the temperature is higher as the rotational speed increases due to the shear rate of the oil film. The maximum temperature in the bearing occurs in the overloaded pad, near the outlet boundary. The experimental tests were performed in a tilting pad journal bearing operating in a steam turbine to validate the model. The comparison between the experimental and numerical results provides a good correlation. The thermohydrodynamic lubrication developed in this assignment is promising to consistently evaluate the behavior of the tilting pad journal bearing operating in relatively high rotational speeds

A comparison of flexible coupling models for updating in rotating machinery response

This paper analyzes the effects of the mathematical models of flexible couplings in rotating mechanical systems in terms of their vibrational behavior. The residual unbalance of the coupled shafts is considered to be the main source of vibration in the rotating system. The moments and the frequencies of the forces, which result from these effects, are close to the natural frequencies of the mechanical system. Since the coupling is considered to be a flexible component in the power transmission system, it introduces a certain amount of mass, damping and stiffness to the system, influencing its natural frequencies. The present work shows the modeling of a mechanical rotor-bearing-coupling system, through the finite element method, used in this case to analyze the transverse vibrations of the system. Different modeling techniques were taken into account for this purpose. Such models are recommended for flexible couplings to analyze their influence on the natural frequencies of the system and on the unbalance response of the system. Afterwards, a model updating was carried out to fit the coupling stiffness and damping coefficients, using the minimum quadratic technique. Some sensitivity of the proposed models was observed in relation to the coupling parameters.235246Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Experimental validation of a bearing wear model using the directional response of the rotor-bearing system

The present work gives continuity in the analysis of the wear influence on cylindrical hydrodynamic bearings by presenting an experimental validation of the wear model previously proposed by the authors. This validation is carried on using the frequency response of the rotor-bearings system in directional coordinates. For this purpose, a test rig was assembled in order to evaluate the behavior of the rotating system when supported by hydrodynamic bearings with different wear patterns. The experimental measurements are used to validate the wear model, comparing the anisotropy influence on the experimental and numerical responses. The simulated directional frequency responses showed a good agreement with the experimental ones, demonstrating the potential of the proposed wear model in satisfactorily represent its influence on the rotor-bearings system response in the frequency range where the numerical model was validated884CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPNão temNão temNão te

In situ interface engineering for probing the limit of quantum dot photovoltaic devices.

Quantum dot (QD) photovoltaic devices are attractive for their low-cost synthesis, tunable band gap and potentially high power conversion efficiency (PCE). However, the experimentally achieved efficiency to date remains far from ideal. Here, we report an in-situ fabrication and investigation of single TiO2-nanowire/CdSe-QD heterojunction solar cell (QDHSC) using a custom-designed photoelectric transmission electron microscope (TEM) holder. A mobile counter electrode is used to precisely tune the interface area for in situ photoelectrical measurements, which reveals a strong interface area dependent PCE. Theoretical simulations show that the simplified single nanowire solar cell structure can minimize the interface area and associated charge scattering to enable an efficient charge collection. Additionally, the optical antenna effect of nanowire-based QDHSCs can further enhance the absorption and boost the PCE. This study establishes a robust 'nanolab' platform in a TEM for in situ photoelectrical studies and provides valuable insight into the interfacial effects in nanoscale solar cells

Rice plant growth-promoting rhizobacteria: a focus on phosphate solubilization

The application of microbial inoculants is an innovative biotechnology to preserve the productivity and sustainability of rice cultivation. Plant growth-promoting rhizobacteria (PGPR) can be applied directly to the soil by seed inoculation, plant tissue treatments or soil applications, to increase the crop biomass growth and to control several plant pathogens, thus avoiding or reducing chemical control. In particular, PGPR able to release soluble phosphorous (P) ions from insoluble mineral or organic forms is drawing attention, also in consideration of severe depletion of raw materials for phosphate fertilizer manufacturing. In the present work, 299 bacterial strains isolated from rhizosphere compartments of rice were characterized for different PGP activities. ACC deaminase activity, phytate mineralization and N2 fixation were the most represented PGP traits. Twenty-one strains possessing most of the tested PGP activities were inoculated in growth pouches experiments to determine in vivo the ability to promote seed germination. Four PGPR identified as Pseudomonas koreensis, Priestia aryabhattai and Bacillus zanthoxyli showed a major significant promotion of biomass growth. Pot experiments with Green Fluorescent Protein- transformed Pseudomonas koreensis strain are ongoing to evaluate plant colonization and rice growth promotion under different levels of bioavailable phosphate

Influence of water management on the active root-associated microbiota involved in arsenic, iron and sulfur cycles in rice paddies

In recent years, the role of microorganisms inhabiting rice rhizosphere in promoting arsenic contamination has emerged. However, little is known concerning the species and metabolic properties involved in this phenomenon. In this study, the influence of water management on the rhizosphere microbiota in relation to arsenic dissolution in soil solution was tested. Rice plants were cultivated in macrocosms under different water regimes: continuous flooding, continuous flooding with a 2 weeks-period drainage before flowering and dry soil watered every 10 days. The active bacterial communities in rhizosphere soil and in rhizoplane were characterized by 16S rRNA pyrosequencing. An in-depth analysis of microbial taxa with direct or indirect effects on arsenic speciation was performed and related contribution was evaluated. Continuous flooding promoted high diversity in the rhizosphere, with the plant strongly determining species richness and evenness. On the contrary, under watering the communities were uniform, with little differences between rhizosphere soil and rhizoplane. Arsenic-releasing and arsenite-methylating bacteria were selected by continuous flooding, where they represented 8 % of the total. On the contrary, bacteria decreasing arsenic solubility were more abundant under watering, with relative abundance of 10 %. These values reflected arsenic concentrations in soil solution, respectively 135 \ub5g L-1 and negligible in continuous flooding and under watering. When short-term drainage was applied before flowering, intermediate conditions were achieved. This evidence strongly indicates an active role of the rhizosphere microbiota in driving arsenic biogeochemistry in rice paddies, influenced by water management, explaining amounts and speciation of arsenic often found in rice grains

Effectiveness of various sorbents and biological oxidation in the removal of arsenic species from groundwater

The AsIII and AsV adsorption capacity of biochar, chabazite, ferritin-based material, goethite and nano zerovalent iron was evaluated in artificial systems at autoequilibrium pH (i.e. MilliQ water without adjusting the pH) and at approximately neutral pH (i.e. TRIS-HCl, pH 7.2). At autoequilibrium pH, iron-based sorbents removed 200 ug L-1 As highly efficiently whereas biochar and chabazite were ineffective. At approximately neutral pH, sorbents were capable of removing between 17 and 100% of AsIII and between 3 and 100% of AsV in the following order: biochar,chabazite,ferritin-based material,goethite,nano zero-valent iron. Chabazite, ferritin-based material and nano zero-valent iron oxidised AsIII to AsV and ferritin-based material was able to reduce AsV to AsIII. When tested in naturally As-contaminated groundwater, a marked decrease in the removal effectiveness occurred, due to possible competition with phosphate and manganese. A biological oxidation step was then introduced in a one-phase process (AsIII bio-oxidation in conjunction with AsV adsorption) and in a two-phase process (AsIII bio-oxidation followed by AsV adsorption). Arsenite oxidation was performed by resting cells of Aliihoeflea sp. strain 2WW, and arsenic adsorption by goethite. The one-phase process decreased As in groundwater to 85 %, whereas the two-phase process removed up to 95%As, leaving in solution 6 ugL-1 As, thus meeting the World Health Organization limit (10 ug L-1). These results can be used in the scaling up of a twophase treatment, with bacterial oxidation of As combined to goethite adsorption

Dihydrogen (H2) pulses for possible application in groundwater bioremediation from chloroethenes

Groundwater contamination by chloroethenes (PCE, TCE, DCE, VC) poses a global challenge, affecting groundwater quality and availability. Microbial dechlorination through organohalide respiration (OHR) represents a sustainable solution to eliminate such contaminants. Only a few bacterial genera are known to perform anaerobic OHR, including Chloroflexi, Firmicutes, and Proteobacteria. Since microbial dechlorination rate is limited by the amount of electron donors available to bacteria, dihydrogen (H2) pulse is studied to implement bioremediation interventions. The present study aims to investigate at a microcosm-scale level the effect of H2 pulses on OHR process in a real-case groundwater contaminated by chloroethenes (150-300 mg/L) from landfill leachate. Thesis comprised: 1) natural attenuation, 2) H2 pulse, 3) H2 + nutrient and vitamin B supplementation, 4) abiotic control. After two months of incubation, an average decrease of 50%, 84%, and 40% was observed for PCE, TCE, and 1,2-DCE, although the addition of H2 or H2 and nutrients did not highlight any significant differences with respect to natural attenuation. After an initial increase (from 120,000 to 160,000 μg/L), a decrement of VC was detected after two months. Bacterial populations increased significantly during the first month of incubation in all thesis (Tukey’s test p<0.05). H2 pulse caused a significant (Tukey’s test p<0.05) increase of Dehalococcoides from 5.89^02 to 2.87^03 gene copies/mL. Other functional biomarkers involved in OHR highlighted a small but not significant increase during the incubation time. Chemical and microbiological data evidenced that a natural attenuation process was active in the studied groundwater. H2 pulses could represent a possible strategy to enhance OHR, although analyses at successive incubation times will provide more exhaustive conclusions on the dehalogenation process. Acknowledgements: Agritech National Research Center - European Union Next-Generation EU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) - MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 - D.D. 1032 17/06/2022, CN00000022)