Fish farming in Grado Lagoon: impacts and dynamics of two fishfarms

La vallicoltura è una pratica ampiamente diffusa nelle lagune dell’Alto Adriatico, legata alla loro particolare natura fisica e all’elevata disponibilità trofica. Nella laguna di Grado essa viene praticata in modo estensivo o parzialmente integrato, cioè subordinando, totalmente o quasi, l’accrescimento del prodotto ittico alla naturale produttività dell’habitat acquatico. Lo studio proposto è stato condotto con frequenza mensile nei mesi di luglio, novembre, dicembre 2004 e gennaio 2005 e, a cadenza quindicinnale, nei mesi di agosto, settembre ed ottobre 2004, febbraio e marzo 2005, in due valli, l’Ara Storta e la Noghera, tra loro molto diverse e in grado di fornire una buona rappresentatività dell’impatto di tale attività sull’ecosistema lagunare. Sono stati monitorati i principali nutrienti (NO2 –, NO3 –, NH4 +, PO4 – e SiO2), la temperatura e la salinità. Dal punto di vista biologico si è voluto focalizzare l’attenzione sulla componente fitoplanctonica, la cui importanza quale indicatore dello stato di qualità delle acque è stata recentemente ribadita dalla Direttiva 2000/60 della Comunità Europea. La parte di elaborazione statistica, avvalendosi anche dei dati ARPA-FVG relativi ai parametri chimico-fisici monitorati nelle stazioni lagunari esterne alle valli, è consistita nella classificazione gerarchica delle stazioni di campionamento e nell’analisi delle componenti principali (PCA) per l’ordinamento delle stesse.Fish farming is a widely diffused activity in Norther Adriatic lagoons, and it is related to their peculiar geomorfological characteristics and to the high trophic availability. In the Grado Lagoon, fish farming is carried out extensively or with partially integrated methods. This means that fish growing is totally or nearly totally subordinated to the natural productivity of the lagoonal environment. During this study, data collection was carried out once per month in July 2004 and in the period November-January 2005, and twice per month in the period August- October 2004 and February-March 2005. The study area was located in two fish farms, Ara Storta and Noghera. Such farms are characterised by very diverse conditions, and thus are particularly indicated to give a good range of potential impacts of fish farming activities on the lagoonal ecosystem. The main nutrients have been monitored (NO2 –, NO3 –, NH4 +, PO4 – e SiO2), together with temperature and salinity. The biological investigations were focused on the phytoplancton, whose relevance as an indicator of water quality has been recently recognised also by the EU Water Framework Directive 2000/60. The data obtained from the study sites and from ARPA-FVG chemical-physical data collected in several lagoonal sites out of the farms were hierarchically classified, and a PCA statistical analysis was performed in order to rank the different classes obtained

Environmental assisted cracking of pipeline steels in CO2 containing environment

Buried pipelines are susceptible to Environmental Assisted Cracking (EAC) in three different conditions: Stress Corrosion Cracking in the presence of Carbonate-Bicarbonate (CB-SCC), Near Neutral Stress Corrosion Cracking (NN-SCC) and Hydrogen Embrittlement (HE). Both CB-SCC and NN-SCC involve in their mechanism the presence of CO2 and/or its dissociated species dissolved in moisture under the coating, while the generic term of HE refers to the phenomena of brittle fracture taking place for entry of atomic hydrogen inside the metal lattice, owing to the applied cathodic protection. Historically the CB-SCC was the first established form of stress corrosion on pipelines in the 60s, while Trans Canada Pipeline published in 1985-86 the first case of NN-SCC. The initiation conditions and the mechanism of propagation of CB-SCC were well established by means of the works of Parkins in 70ths. Many studies were carried out on NN-SCC, but actually there is not an exhaustive understanding of the problem. This paper summarizes the results obtained by authors on pipeline steels in NN-SCC promoting environments. Constant load, constant deformation, slow strain rate, slow bending and corrosion fatigue tests were executed on different grades of pipeline steels. The obtained results pointed out the effect of continuously plastic deformation to observe the propagation of NN-SCC cracks. NN-SCC cracks are preferentially nucleated from localized attacks. Inside the pits, the decreasing of pH enhances the hydrogen ions reduction. The results of slow strain rate tests are in agreement with a hydrogen embrittlement mechanism for the NN-SCC cracks propagation. Electrochemical tests, potentiodynamic and cyclic voltammetry were also carried out in order to analyze the effect of temperature, pH, CO2 and bicarbonate concentration on the pitting initiation. A pre-corrosion procedure, using a solution with high concentration of bicarbonate ions saturated with CO2 and a great number of voltammetry cycles was developed to obtain localized attacks on the specimen surface, similar than those observed in the failure analysis of the cracked pipelines. The SSR and slow bending tests carried out on these pre-corroded specimens evidenced presence of cracks with the same morphology of NN-SCC. Finally some corrosion-fatigue tests carried out on linear elastic fracture mechanics specimens (Single Edge Notch three four point Bending specimens) evidenced the increasing of fatigue propagation crack growth in NN-SCC environment. In the range of traditional and innovative pipeline steels, the mechanical properties (ultimate tensile strength and yield strength) seem do not influence their NN-SCC resistance

Investigation of electrochemically-induced repassivation of Al 7075-T6 and Al 2024-T3 as a function of applied stress and galvanic corrosion

The repassivation behavior of Al alloys 7075-T6 and 2024-T3 was investigated by means of pitting scan (PS) technique (Fig. 1) (Trueba, Trasatti, 2015). The effect of mechanical load and galvanic coupling was estimated by considering principally the electrochemical characteristics of the reverse curve, namely the pit transition potential (Eptp), the associated current density (iptp) and the steepness. The load levels explored were mostly below the elastic limit, using four point bent-beam (4PBB) stress-corrosion test specimens (ASTM G39-99). CRES 304 or Ti6Al4V alloy were physically joined with Al sheet for simulating stress-induced galvanic corrosion. Different experimental variables (e.g. irev, [Cl-], pH, scan rate, etc.) were also considered. The study was complemented with corrosion morphology analysis. Please click Additional Files below to see the full abstract

The influence of process parameters on mechanical properties and corrosion behaviour of friction stir welded aluminum joints

Aim of this study is to analyse how the process parameters affect the mechanical properties and the corrosion behaviour of butt joints obtained by friction stir welding (FSW). The experimental study was performed by the friction stir welding of sheets having a thickness equal to 4 mm and made of three aluminum alloys, namely AA7075, AA6060 and AA2024, considering all the combinations among the three materials and varying the process parameters, namely rotational speed and feed rate. Tensile tests were performed orthogonally to the welding direction on specimens having the welding nugget placed in the middle of gage length, while micro-Vickers tests were carried out on each specimen moving from the joint axis until the hardness of the base material was reached. The best conditions in terms of mechanical strength were obtained using the "intermediate" values of rotational speed, and, in general, when the process parameters result in low values feed rate per unit revolution (F/S), that corresponds to the higher thermal contribution to the joint region. Since in many industrial applications the mechanical resistance is not sufficient for completely describing the joint reliability, further local corrosion potential measurements and four-point bending tests were performed to evaluate the corrosion behaviour and stress corrosion cracking susceptibility of FSW Joints. The tests were carried out on prismatic specimens obtained by FSW joints of the same alloy (7075-7075 and 2024-2024) and mixed joints (7075-2024). No specimens failed during the test. It was observed that the lower the hardness, the more anodic the corrosion potential. In these zones an intense localized attack takes place in the HAZ due to the presence of precipitates. No systematic correlations between the parameters and the resistance to corrosion were observed. The presence of preferential corrosion sites was confirmed also by means of long time immersion tests

Investigation of SCC of high strength aluminum alloys by means of slow strain rate test and cyclic anodic polarization in combination

The stress corrosion cracking (SCC) behavior of high strength 7075-T6 and 2024-T3 Al alloys in NaCl solutions is investigated by means of slow strain rate test (SSRT) and cyclic anodic polarization in combination. Smooth, dog-bone shaped flat tension test specimens, having gage section areas of 40 mm2 and 32 mm2, respectively, and 90 mm of gage length, were machined in the longitudinal (rolling) direction from the commercial wrought sheets (Aviometal Spa). The tensile test was performed at a constant strain rate (ἐ = 10-7, 10-6 or 10-5 s-1) from a pre-load of about 5 kN until fracture. The electrochemical system consisted in non-connected two Plexiglas cylindrical cells that were fixed at the middle of the opposite surfaces of the tensile specimen (working electrode, surface area at each side of 2 cm2). The variation of the open circuit potential (OCP) during straining was measured with respect to saturated calomel reference electrode (SCE) by connecting the two electrode system to a Gamry potentiostat. Contemporarily, the opposite surface was electrochemically perturbed by imposing consecutive cyclic anodic polarizations with open circuit potential measurements in between (OCP/polarization sequences), using an Ir-coated Ti auxiliary electrode, another SCE and a second Gamry potentiostat. At least two combined experiments for each test condition were carried out for repeatability check. Experiments with no OCP/polarization sequence during straining, and vice versa, were performed for reference purposes. The stress-strain curves of Al 7075-T6 (Fig. 1a) show that the ultimate strength and failure strain decrease in aggressive environment as the strain rate is lowered, regardless the electrochemical perturbation, being in agreement with reported data [1]. More interestingly, quasi-periodic stress relaxation/recovery events above the elastic region in correspondence with the dissolution/repassivation cycle were detected for ἐ ≤ 10-6 s-1 and 0.1667 mV/s of potential scan rate (n). The resolved negative spikes in the stress time derivative curve and the related polarization curves (as log | I | - t) for ἐ = 10-7 s-1, 0.6 M NaCl and n = 0.1667 mV/s are reported in Figure 1b. The spike pattern along the time axe was dependent on ἐ and NaCl concentration. The results from ongoing combined experiments with Al 2024-T3 for verification of the above findings will be presented altogether with empirical data analysis for a quantitative insight into the environmentally assisted failure mechanisms. Please click Additional Files below to see the full abstract

Studies for the application of boron neutron capture therapy to the treatment of differentiated thyroid cancer

The aim of these studies was to evaluate the possibility of treating differentiated thyroid cancer by BNCT. These carcinomas are well controlled with surgery followed by therapy with 131I; however, some patients do not respond to this treatment. BPA uptake was analyzed both in vitro and in nude mice implanted with cell lines of differentiated thyroid carcinoma. The boron intracellular concentration in the different cell lines and the biodistribution studies showed the selectivity of the BPA uptake by this kind of tumor.Fil: Dagrosa, María Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Carpano, Marina. Comisión Nacional de Energía Atómica; ArgentinaFil: Perona, Marina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Thomasz, Lisa. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Nievas, S.. Comisión Nacional de Energía Atómica; ArgentinaFil: Cabrini, R.. Comisión Nacional de Energía Atómica; ArgentinaFil: Juvenal, Guillermo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Pisarev, Mario Alberto. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Chemical, Electrochemical, and Surface Morphological Studies of the Corrosion Behavior of the AZ31 Alloy in Simulated Body Fluid: Effect of NaOH and H2O2Surface Pretreatments on the Corrosion Resistance Property

Magnesium and its alloys have attracted attention for biomedical implant materials in dental and orthopedic applications because of their biodegradability and similar properties to human bones. The very high rate of degradation in the physiological systems is, however, a major setback to their utilization. Chemical modification is one of the approaches adopted to enhance the corrosion resistance property of Mg and its alloys. In this work, NaOH and H2O2were used as a pretreatment procedure to improve the corrosion resistance of the AZ31 Mg alloy in simulated body fluid (SBF). Advanced techniques such as dynamic electrochemical impedance spectroscopy (dynamic-EIS), atomic force microscopy, and optical profilometry were used in addition to the classical mass loss, hydrogen evolution, EIS, and polarization techniques to study the corrosion resistance property of the alloy in SBF for 30 h. Results obtained show that the surface treatment significantly enhanced the corrosion resistance property of the alloy. From dynamic-EIS at 30 h, the charge transfer resistance of the untreated AZ31 Mg alloy is 432.6 ω cm2, whereas 822.7 and 2617.3 ω cm2are recorded for NaOH- and H2O2-treated surfaces, respectively. H2O2is a better treatment reagent than NaOH. The mechanism of corrosion of both untreated and treated samples in the studied corrosive medium has been discussed. © 2022 American Chemical Society. All rights reserved

Understanding the Corrosion Behavior of the AZ91D Alloy in Simulated Body Fluid through the Use of Dynamic EIS

Dynamic electrochemical impedance spectroscopy (dynamic EIS) has the capacity to track changes on surfaces in a changing corrosive system, an advantage it holds over classical EIS. We used the dynamic EIS approach to provide insight into the corrosion behavior of the AZ91D Mg alloy in simulated body fluid for 30 h at 25 °C. The results reveal that the impedance response of the alloy is influenced by the immersion time. Between 0 and 7 h, impedance with three time constants was obtained, whereas two-time-constant impedance spectra were obtained between 8 and 30 h of immersion. The results confirm the breakdown of the corrosion product at longer immersion times

Assessment of the corrosion behaviour of untreated and chemically treated pure magnesium in simulated body fluid

The corrosion behaviour of pure Mg in simulated body fluid (SBF) and the effect of chemical treatment on the corrosion resistance property were investigated using DEIS (dynamic electrochemical impedance spectroscopy), EIS (electrochemical impedance spectroscopy), PDP (potentiodynamic polarization), SEM (scanning electron microscopy), AFM (atomic force microscope), and pH measurement techniques for 30 h. NaOH or H2O2 were utilized for the chemical treatment. The DEIS was used for the first time in the investigation of Mg corrosion in SBF. Results obtained disclosed that the chemical treatment benefitted the anticorrosion property immensely. Results from both the electrochemical and surface analysis techniques are consistent