Release Of Toxic Elements Research Articles

How does the coupled action of freeze - Thaw and acidification affect the release of toxic elements from indigenous Zn smelting slags?

Under complicated field conditions, such as the coupled effects of freeze - thaw cycles (FTs) and acidification, the leaching behavior of potentially toxic element (PTEs) from indigenous Zn smelting slags (ZSS) was intricately connected to the mineralogy (e.g., the composition, assemblage, microstructure of mineral particles). In this study, FTs tests were carried out to explore the interactions between PTEs release and ZSS mineralogy. Subsequently, advanced characterization techniques were adopted to quantify the mineralogy and microstructure of ZSS. The results indicated that ZSS were mainly composed of silicate minerals (e.g., quartz, biotite and chlorite) and secondary Fe (III) oxyhydroxides (e.g., magnetite and limonite), accounting for 67.48% and 24.23%, respectively. The occurrence mode analysis revealed that 81.95% of As, 21.31% of Pb and 7.77% of Zn were hosted in limonite. About 37.89%, 59.34% and 34.50% of Cd, Pb and Zn were associated with carbonate bound fractions. Under FTs interacting with different pH conditions, the leaching concentrations of As, Cd, Cu, Pb and Zn did not significantly increase with the increase in FTs and pH. The microstructure damage of mineral particles in ZSS with the higher porosity was caused by both FTs and proton corrosion. More importantly, the geochemical modeling results suggested that the precipitation of hematite and magnetite might have little impacts on PTEs release under FTs and FTs with acidification. This work would provide a deeper understanding of PTEs release from smelting waste slags under complex physicochemical interactions.

Manipulation of the leaching behaviour of high-alloyed steel EAF slags through the particle size modulation

The safe disposal of EAF slag have become crucial due the environmental and health protection regulations. Its direct reuse is hampered by the possible release of toxic elements into the surrounding environment over time. Specifically, EAF slag from high-alloyed steel production could potentially release toxic metals (e.g., Ba, Cr, Mo and V). Currently, the assessment of leaching behaviour is carried out according to the EN 12457:2002 standard, which generically specify that the material should not be finely ground, limiting the particle size as much as possible. However, no guidance is given on reducing particle size and handling fine fractions, which could lead to manipulation of data and variability of results. In this work six different fractions (from <4 mm to <63 μm) of EAF slag from high-alloyed steel production were investigated. X-Ray Diffraction, Scanning Electron Microscopy and selective C2S dissolution were used to correlate the leaching behaviour with particle size and identify which mineral can alters the release of specific toxic elements. The pH of the water was measured immediately after filtration, and the solution was analysed by Inductively Coupled Plasma-Optical Emission Spectrometry. In addition, five mixtures were prepared using different mass fractions of the six granular fractions with the aim of unbalancing the mixtures toward coarser or finer fractions, respectively. All the mixtures were subjected to leaching under the same previous conditions and analysed to evaluate the behaviour of the different blended fractions. To investigate the predictability of the leaching behaviour of the mixtures, the experimental results were compared with the values predicted by a theoretical model calibrated using the results obtained from the leaching results of the six particle size fractions. The investigation showed that the leaching behaviour is negatively affected by the particle size reduction, mainly due to the increase of surface-to-volume ratio, which increases the dissolution rate. Similarly, the mass fraction of the main crystalline phases that regulate leaching (unstable spinels, brownmillerite and larnite) is also correlated with the change in particle size. Consequently, the leaching results for the mixtures highlighted a critical aspect contained in the European standard. Even small changes in particle size can lead to different concentrations of toxic metals in leachates, which can then be manipulated to achieve the desired result.

ENVIRONMENTAL GEOCHEMICAL INVESTIGATION OF THE GEOGENIC POLLUTION POTENTIAL OF BIDA FORMATION, NORTHERN BIDA BASIN NIGERIA

The environmental geochemistry of sandstones of Bida formation around Doko, northern Bida Basin Nigeria was studied to assess the potential for the release of toxic elements into the environment. Eight representative samples were collected and analysed to determine the total elemental concentration using X-ray fluorescence spectrometry (XRF). Four sub-samples were analysed for their near-total concentration of selected metals using atomic absorption spectrometry (AAS). The results show that many of the elements are depleted with mean enrichment ratios of less than 1. Ce, W, Nb and Pb are the exceptions with ER values of 116.4, 122.9, 25.26 and 2.22 respectively. A similar pattern was found with Igeo, where W, Ce and Nb fall within strongly to extremely polluted and extremely polluted classes. High to very high partition coefficients (KDi) for four selected PTEs show that metals are strongly held within the sandstone matrix rather than dissolving. Because the elements are not soluble, they will not be readily available for uptake by plant roots, or will not be directly toxic to soil biota. The undissolved metal pool also reflects the sandstone metal fraction that is unsusceptible to leaching and could therefore not contaminate water. We conclude that there is no significant geogenic pollution risk associated with PTE release and uptake from the formation. It is however recommended that further research should be carried out to investigate the phases hosting Ce, W, Nb and Zr in the sandstone in Doko and its environs.

Possibility of Using Vitreous Enamel Waste in the Construction Industry as the Concept of Cleaner Production

Waste vitreous enamels from the heating device production process were used for partial replacement of cement in the mortar and concrete production industry. This waste, due to the high content of heavy metals, is classified as hazardous waste. At the same time, waste vitreous enamels possess pozzolanic activity and belong to class 15 (WEP—generated during the production process of heating devices, premix technology), that is 5 (WETM—generated during the production process of heating devices, classic technology) of pozzolanic materials. The purpose of this research was to develop new composites from these wastes to reduce the deposition of the toxic compounds and reduce their environmental impact. The chemical and physical-chemical characterization and pozzolanic activity of the raw waste materials were studied by a mixture of complementary methods, as well as physical-mechanical characterization and a leaching test of mortar and concrete composites. The results indicate that the replacement of cement with WEP up to 30%, or with WETM up to 20% does not significantly affect the quality of concrete in comparison to the quality of the reference concrete prepared with 100% cement. The leaching test showed no significant release of toxic elements for both obtained composites.

Experimental and Numerical Investigation of the Flexural Behavior of Mortar Beams Strengthened with Recycled Plastic Mesh

The generation of plastic waste is increasing all over the world at an alarming rate, therefore raising concerns related to its disposal. As space for landfilling is becoming scarce and as incinerating the plastic waste leads to the release of toxic elements into the environment, recycling becomes a viable and an attractive option in pursuit of sustainable development. This paper investigates the flexural behavior of mortar beams reinforced with recycled plastic mesh. To achieve this objective, 27 mortar beams were prepared, with 24 of them containing waste plastic mesh with different void ratios and effective widths. All beams were cured for 28 days and then tested using a three-point bending test. Mid-span deflection was measured for each increment of load to obtain the load deflection curve. Moreover, a numerical simulation was performed on all mortar specimens using finite element software ABAQUS and a comparison was made with the experimental analysis. Test results showed that the addition of plastic mesh increased the flexural toughness and ductility of mortar beams. Furthermore, it was noticed that as the effective width ratio increased from 0 to 0.58, the ultimate capacity and flexural toughness increased. Beyond this level, a decrease was observed. On the other hand, the ductility index was proportional to the flexural toughness for all mesh effective width ratios. Comparing the ultimate capacity, flexural toughness and ductility index between the experimental and numerical data, there was a difference of up to 7%. This indicates that the numerical output can be a good predictor of the performance of plastic inside the mortar. Hence, using recycled plastic mesh could be recommended for improving the flexural performance of mortar beams, creating a sustainable composite.

Combined bioreduction and volatilization of SeVI by Stenotrophomonas bentonitica: Formation of trigonal selenium nanorods and methylated species

Nowadays, metal pollution due to the huge release of toxic elements to the environment has become one of the world's biggest problems. Bioremediation is a promising tool for reducing the mobility and toxicity of these contaminants (e.g. selenium), being an efficient, environmentally friendly, and inexpensive strategy. The present study describes the capacity of Stenotrophomonas bentonitica to biotransform SeVI through enzymatic reduction and volatilization processes. HAADF-STEM analysis showed the bacterium to effectively reduce SeVI (200 mM) into intra- and extracellular crystalline Se0 nanorods, made mainly of two different Se allotropes: monoclinic (m-Se) and trigonal (t-Se). XAS analysis appears to indicate a Se crystallization process based on the biotransformation of amorphous Se0 into stable t-Se nanorods. In addition, results from headspace analysis by gas chromatography-mass spectometry (GC–MS) revealed the formation of methylated volatile Se species such as DMSe (dimethyl selenide), DMDSe (dimethyl diselenide), and DMSeS (dimethyl selenenyl sulphide). The biotransformation pathways and tolerance are remarkably different from those reported with this bacterium in the presence of SeIV. The formation of crystalline Se0 nanorods could have positive environmental implications (e.g. bioremediation) through the production of Se of lower toxicity and higher settleability with potential industrial applications.

Application of the Hazardous Waste Vitreous Enamel Generated in the Production Process of Heating Devices as a Partial Replacement for Cement

Solving problems with hazardous waste materials is of crucial importance today. In the presented study, the application of waste vitreous enamel as a cement replacement up to 30% in mortar and concrete production was investigated. The chemical and physical-chemical characterization of the starting material was performed, as well as a leaching test and physical-mechanical characterization of mortar and concrete mixes. Obtained results showed that, due to its chemical composition, the vitreous enamel used must be classified as hazardous waste. At the same time, it possesses pozzolanic properties and satisfies minimal criteria for use as a cement replacement. Testing mortars and concrete mixes indicate that waste vitreous enamel can be applied as a construction material for cement replacement in the maximal amount of 20%. The leaching test was performed in accordance with international standard EN 12457-2 on hardened mortar with a maximal cement replacement of 20%. The results showed that there was no significant release of toxic elements, i.e., that the practical application of hazardous waste vitreous enamel in the construction industry may be fully in line with environmental standards.

Use of recycled sand as a corrective material for soil acidity in soybean crops

Acidity is one of the main factors capable of reducing the productive potential of Brazilian soils, as it promotes the release of toxic elements for plants and reduces the availability of nutrients. Recycled civil construction and demolition waste (R-CCW class A) is a major environmental problem in Brazilian cities, especially in terms of its illegitimate disposal, causing floods, clogging of galleries and silting of channels, in addition to the proliferation of vectors and pollution. The objective of this study was to evaluate the potential of recycled sand (R-CCW) as a corrective of soil acidity, through soybean cultivation, in an experiment installed in PVA1 yellow-reddish with sandy/medium texture, acid and of low fertility with doses of 10, 20 and 40% of R-CCW, by mass, in Fernandópolis/SP. Variables related to soil fertility and to plants that were subjected to analysis of variance by F and comparison of averages by the Skott-Knott test at 5% probability were evaluated. The results obtained allowed us to conclude that recycled sand from civil construction R-CCW class A has favorable effects in terms of its ability to neutralize H+ ions in the soil solution and those adsorbed to negative soil charges, important effects as an acidity corrective, in addition to providing increases in the contents of Ca, Mg, SB, CEC and V%, greater development of soybean plants, which indicates that this use is an environmentally correct alternative for the disposal of these residues.

Reusable Water Bottles: Release of Inorganic Elements, Phthalates, and Bisphenol A in a “Real Use” Simulation Experiment

Reusable water bottles are growing in popularity; thus, possible chemical release from the internal surface into water should be carefully considered to control related health risks. We experimentally evaluated the release into deionized water of 40 elements, six phthalates, and bisphenol-A for 20 different reusable bottles by simulating the use in real world scenario. The 20 bottles, identified as those most purchased in Italy, were made of various materials (stainless steel, aluminum, plastic, and silicone). The experiment was carried out for four consecutive weeks in duplicate for each type of bottle. Our results showed the release, to various extents, of inorganic elements from all 20 bottles, while the release of phthalates and bisphenol-A was never found. The elements most frequently released were Al, Sr, Mo, and Cr, while the highest concentrations were for Ca, K, Mg, and Na; the release of toxic elements (such as Pb, Cd, Ni, Sb) also occurred. The comparison of our results with regulatory limits on drinking water quality revealed no exceeding values except for Al. However, these releases represent a further intake, and the related risks cannot be neglected, especially for highly susceptible populations. Thus, it is essential to correctly inform consumers both with dedicated interventions and exhaustive labelling.

Evaluation of soil contamination due to crude E-waste recycling activities in the capital city of India

Unempirical E-waste urban mining is beleaguered as a potential threat to the environment and human health. India is intensely imperiled as a chaotic region for approximately 95 % of immature E-waste recycling among which Delhi is the foremost hub. A field study at active E-waste recycling sites in Delhi was carried out to estimate the soil contamination due to the release of toxic elements in the vicinity areas. The geoaccumulation index, contamination factor, and ecological risk indicated that the soil was contaminated with the metals like Pb (1569.9), Cd (2.41), Zn (675.89), Ni (61.02), Cu (3846.8), & Al (9864.2) mg/kg, and Pb (2627.94), Al (8123.6 Cu (4108.7), Zn (354.18), & Cd (3.56) mg/kg which exceeded the threshold limit of WHO, respectively at both the acid leaching and open burning areas of E-waste recycling sites. For effective E-waste management at the informal E-waste recycling sites requires a cost-effective and environment-friendly treatment method. The results of the present study show the higher soil contamination due to the presence of heavy metals. Hence, there is a dire need for taking immediate actions and control measures by the policymakers and decision-makers and adopt scientific methods toward restricting the migration of metals into the surroundings. Phytoremediation and bioremediation are highly recommended to curb the accumulation of hazardous materials at the contaminated sites.

Electrodialytic treatment of secondary mining resources for raw materials extraction: Reactor design assessment

The sustainability of mining activities is compromised due to the high amounts of mining residues generated that have to be disposed of, often in open dams, that may cause environmental deterioration, e.g. release of toxic elements to water supplies. These residues are, however, secondary resources of raw materials. In the case of Panasqueira mine, they even are a source of tungsten, considered a critical raw material. The present work aims to assess the electrodialytic process efficiency for raw materials extraction from Panasqueira mine residues. Experiments were performed with 2 and 3-compartment electrodialytic reactors, applying current intensities between 50 and 100 mA, from 4 to 14 days, and sample suspensions enhanced with NaCl or effluent. Additionally, control experiments with no current application were carried out. The results showed that a 3-compartment reactor operating at 100 mA, with NaCl as supporting electrolyte, presented the highest extraction of copper (13%), tin (10%), tungsten (13%) and arsenic (63%).

Release of wood extractable elements in experimental spirit model: Health risk assessment of the wood species generated in Balkan cooperage

This work investigates the release of toxic elements from wood into the experimental spirit models and the safety risks for consumers. The spirit models were prepared as ethanolic extracts using the procedure which reproduces maturation of spirits. Investigation included staves of wood species commonly used in Balkan cooperage: mulberry, Myrobalan plum, black locust, wild cherry, and various oaks. Potassium was the most abundant element, except in the wild cherry extract where calcium was dominant, and the Myrobalan plum extract where phosphorus was the most abundant. The parameters for the health risk assessment, such as hazard index (HI) and hazard quotient (HQ) were calculated for potentially toxic elements and indicated that all wood extracts would be safe for human consumption. Owing to the proven abundance of phenolics in the investigated wood extracts, relations among elements and phenolics were also studied and conclusions were made based on the statistically significant correlations.

Hydroxyapatite/hydroxyapatite-magnesium double-layer coatings as potential candidates for surface modification of 316 LVM stainless steel implants

Various methods are being used for surface modification of orthopedic and dental implants such as deposition of biocompatible coatings on implant surfaces. In this study, hydroxyapatite/hydroxyapatite-Mg double-layer coatings applied on 316 LVM stainless steel are investigated. The applied coatings consist of a dense layer of plasma-sprayed hydroxyapatite and a top layer of cold-sprayed hydroxyapatite-magnesium composite coating (Mg = 10 and 30 wt%). The coated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) tests. The biological behaviors of the coated samples were evaluated by immersing the samples in a simulated body fluid (SBF) followed by inductively coupled plasma (ICP) spectroscopy, MTT and electrochemical tests. Microstructural studies of the coated samples after corrosion tests showed that the magnesium component of the top layer degraded in SBF solution and formed porosities, which are potential sites for bone tissue growth. Results of ICP spectroscopy analysis indicated that the applied double-layer coating systems prevent the release of toxic elements in the substrate such as nickel. Results of MTT and SBF immersion tests showed that the double-layer coating system improves the biocompatibility and bioactivity of 316 LVM stainless steel.

Release of toxic elements in fishpond sediments under dynamic redox conditions: Assessing the potential environmental risk for a safe management of fisheries systems and degraded waterlogged sediments

Waterlogged soils and sediments contaminated with potentially toxic elements (PTEs) constitute a complicated case of degraded areas; their management requires understanding of the dynamic redox-driven PTE mobilization. Such studies about PTE redox-induced dynamics in fishpond sediments are still scarce, but of great importance concerning environmental and human health risk. We studied the redox potential (EH)-induced impacts on the solubility of As, Co, Cu, Mo, Ni, Se, V, and Zn in the sediments of a fish farm in the Nile Delta, Egypt, using an automated apparatus of biogeochemical microcosm. We assessed the fate of elements as affected by the EH-induced changes in pH, Fe, Mn, SO42−, Cl−, and the dissolved aliphatic (DOC) and aromatic (DAC) organic carbon. Sediment redox ranged from −480 mV to +264 mV. Flooding the sediments caused a significant decrease in pH from 8.2 to 5.7. Dissolved concentrations of As, Co, Ni, Se, and Zn, as well as DOC, Fe, and Mn increased under the reducing acidic conditions. The release of As, Co, Ni, Se, and Zn could be attributed to the decrease of EH and the subsequent decrease of pH, as well as to the increase of DOC, and/or the dissolution of Fe–Mn oxides caused by redox reactions. Dissolved concentrations of Cu, Mo, and V increased under oxic conditions and were significantly positive correlated with EH, pH, DAC, and SO42−. This enhancement might be caused by the EH-dependent increase of pH under oxic conditions (particularly for Mo and V), which also led to DAC increase. Sulfide oxidation and the release of the associated elements may have also had a contribution, particularly in the release of Cu. Therefore, the release dynamics of dissolved Cu, Mo, and V in the sediments were controlled, to a certain extent, by the changes of EH/pH, DAC, and sulfur chemistry. We conclude that the biogeochemical differences in the behaviour of the studied elements under variable redox regimes substantially affected the fishponds via possible enhancement of PTE mobilization. Our work shows that the potential environmental risks related to PTE mobilization and fish food security should be taken into consideration for the management of degraded aquaculture systems and waterlogged soils and sediments.

A release of toxic elements from military shooting range soils as affected by pH and treatment with compost

A screening part of this study examined soil enrichment in 7 potentially toxic elements: Cd, Cr, Cu, Ni, Pb, Sb and Zn, in two complexes of military shooting ranges situated in SW Poland. For those elements that pose a real threat to the environment, their release into pore water was examined more thoroughly. The highest values of geoaccumulation index Igeo, with the median values above 1.5, were found for Sb, Pb and Cu, therefore further release-oriented experiments focused on these three elements. Their maximum concentrations in soils were: 89.6, 48,400 and 1230 mg kg−1, respectively. A 140-day incubation experiment was carried out with 5 strongly enriched soils treated with acid, lime and commercial green-waste compost, to illustrate the effects of pH and exogenous organic matter on the release of Sb, Pb and Cu into soil pore water. The treatment with lime and/or compost is usually believed to immobilize metals, while various authors reported contradictory effects of soil amendment with organic matter on the solubility of Sb. The present work indicated that liming can induce a release of Sb and Cu into soil pore water, and the treatment with compost can result in increased Cu and Pb solubility in alkaline conditions. The effect of immobilization observed in acid- and lime-treated soils after a prolonged incubation, was in the case of Pb and Cu explained by simple buffering rather than by aging. Long incubation with compost ensured immobilization of Pb, but not necessarily of Sb and Cu. The overall effects of soil treatment with moderately mature compost on the release of Sb, Pb and Cu into pore water of shooting range soils are ambiguous, and for this reason, each case of planned application of compost to polluted soils should be preceded by a thorough experimental examination.

Assessment of groundwater suitability for irrigation in a gold mine surrounding area, NE Iran

The Kouh-e Zar mining area with iron oxide-rich types of Cu–Au (IOCG)-type gold mineralization is located in a fractured zone between two main “Darouneh” and “Taknar” faults in 35 km northwest of Torbat-e Heydarieh. In this study, the hydrogeochemistry and water quality of groundwater were examined for irrigation uses. Totally, 11 groundwater samples were collected in semi-arid area surrounding the mine. According to the irrigation water quality indices such as sodium absorption ratio, sodium percentage, residual sodium carbonate, residual sodium bicarbonate, potential salinity, salinity index, salinity hazard, permeability index and magnesium hazard, the water resources were appraised suitable to unsuitable. Na+ was a dominant cation and HCO3− was a dominant anion in the water samples. Fortunately, SO42− content is low (< 250 mg/L) in the water samples because of low-sulfide content mineralization in this mine. Water–rock interaction was defined as the controlling process on groundwater chemistry based on the Gibbs diagram. Calculated saturation indices revealed that the anion and cations in groundwater originated from dissolution of minerals and evaporation process. In the case of dominant Ca2+ and Mg2+, they were originated by dissolution of carbonate minerals such as calcite, dolomite and aragonite. Na+ was likely originated by plagioclase weathering in the brecciated volcanic rocks. Though the sulfidic mineralization is not so high in the Kouh-e Zar area, however, considering the existence of metalogenic mineralization in the Kouh-e Zar area, there is also a risk potential of release of toxic elements into the groundwater on which further deep investigation is ongoing in the area.

Rapid Escherichia coli inactivation in visible light by Fe/Zn-α-NiMoO4 nanorod

The microwave hydrothermal synthesized Fe and Zn doped α-NiMoO4 nanorod was characterized by various techniques. The doping of metal ions into the lattice of α-NiMoO4 was verified by HRTEM, SAED, and EDS analysis. The Fe and Zn doped α-NiMoO4 photocatalyst completely inactivated the Escherichia coli in aqueous medium under visible light irradiation within 30 min and 45 min, respectively. The extending of absorption towards the visible light region or reduce in band gap, formation of new energy level in valance band and conduction band, trapping of generation of electron-hole pairs, oxygen vacancy, and efficient separation of electron-hole make the enhancement of photocatalytic disinfection by doped photocatalyst. Furthermore, the TEM images suggest the destruction of bacteria cell. The TEM elemental mapping of bacteria reveals that there is no release of toxic elements into the bacteria cell from the photocatalyst. So, these results demonstrated that the doped efficient photocatalyst can be applied for rapid inactivation of pathogens in infected waste water.

Photochemical oxidation and dissolution of arsenopyrite in acidic solutions

Arsenopyrite (FeAsS) is the most common iron sulfide mineral in the nature, and its oxidation causes arsenic (As) release and thus environmental pollution. Sunlight participates in the oxidative dissolution of sulfide minerals in supergene environments, affecting the release of toxic elements. In this work, we investigated the oxidative dissolution process of arsenopyrite in acidic solution under ultraviolet (UV) irradiation. The effects of pH, oxygen partial pressure and waveband of incident light on the dissolution and release of As were further investigated. The results showed that UV irradiation can promote the oxidative dissolution of arsenopyrite and the release of As. As(V), Fe(II) and SO42− were the major forms of the released As, Fe and S, respectively. Reactive oxygen species (ROS) including O2−/HO2, OH and H2O2 were generated through the oxidation of As(III) by oxygen under far-UV irradiation, photo-Fenton reaction of Fe(II)/FeOH2+ and conversion of OH/O2−, which play important roles in arsenopyrite oxidation. A small amount of OH and H2O2 was generated from the decomposition of H2O induced by Fe(III) at the sulfur-deficient sites on arsenopyrite surface. Oxygen accelerated the formation of ROS, which facilitated the oxidative dissolution of arsenopyrite and the release of As. At initial pH 3.0, the released As mainly existed in the form of ions in the solution. With initial pH increasing to 5.0, the formation of ferric arsenate precipitate and goethite contributed to the adsorption and fixation of released As. This work reveals the release mechanism of As in the photochemical oxidation process of arsenopyrite, and expands the understanding about the geochemical cycling of As.

Development of Bio-Compatible Beta Ti Alloy Powders for Additive Manufacturing for Application in Patient-Specific Orthopedic Implants

The use and application of alloys as biomedical alloys have increased over the past few years owing to their excellent biocompatibility, corrosion resistance, high mechanical and fatigue resistance, low density, adequate wear resistance, and low elastic modulus. Orthopedic implant materials are exposed to high mechanical loading. Conventional materials based on Ti-6Al-4V, stainless steel or cobalt-chromium alloys demonstrate good mechanical strength, but also some toxicological concerns due to release of toxic elements which may result in inflammatory reactions. Metal alloys based on titanium, zirconium, tantalum and niobium represent higher biocompatibility with appropriate mechanical properties for avoiding stress-shielding and consecutive implant loosening. Application of specifically designed spherical β-titanium alloy powders in additive manufacturing, such as selective laser melting (SLM) or electron beam melting (EBM); enable the production of components with a high degree in freedom of design. Accordingly, SLM or EBM of Ti/Nb (/Ta) alloys offer the possibility to fabricate patient-specific orthopedic implants. The present paper describes development of β-titanium alloys powders designed for application in additive manufacturing technologies. TiNbZrTa (TNZT)-based 3D structures were successfully manufactured and mechanically tested.

Identification of a phenoloxidase- and melanin-dependent defence mechanism in Achatina fulica infected with Angiostrongylus vasorum

BackgroundAngiostrongylus vasorum has different freshwater aquatic and terrestrial gastropod molluscs as an intermediate host, e.g. Arion spp. The mollusc Achatina fulica is a danger to public health, given the large diversity of nematodes utilizing it as an intermediate host, such as the parasites of the genus Angiostrongylus, of importance in human and veterinary medicine. Achatina fulica has been shown to have an excellent capacity for maintaining outbreaks and natural infections with A. cantonensis in Asia. Within the mollusc, the nematode parasites activate haemocytes and/or haemolymph factors and in some invertebrates, phenoloxidase (PO), that induces the release of toxic elements and eliminates the parasites. Despite the importance of A. fulica in the life-cycle of nematodes, little is known regarding the defence mechanisms involving PO in molluscs infected with nematodes. Here, the presence of PO and nitric oxide (NO) in the haemolymph and haemocytes of A. fulica infected with first-stage (L1) larvae of Angiostrongylus vasorum was evaluated, together with the presence of melanin in the cephalopod mollusc tissue.ResultsAn increase in PO at one day post infection (dpi), in comparison with the control using the substrates L-tyrosine (F(4,90) = 6.73, P = 0.00006), L-DOPA (F(4,90) = 22.67, P = 0.02) and p-phenylenediamine (PPD) (F(4,90) = 27.58, P = 0.0019), was observed. PO increase coincided with the presence of melanin in the cephalopodal tissue. At 8 dpi, PO activity, compared to L-DOPA (F(4,90) = 22.67, P = 0.00002) and PPD (F(4,90) = 27.58, P = 0.079) decreased, while melanin increased. At 13 dpi, PO decreased with PPD (F(4,90) = 27.58, P = 0.000015) and also the amount of melanin observed in histology. At 30 dpi, PO increased along with the substrates L-DOPA and PPD, while melanin decreased. NO levels increased until 8 dpi, and decreased after 13 dpi.ConclusionsTo our knowledge, this is the first study that illustrates PO activity in a helminth-infected A. fulica and provides the first observation of an L-tyrosine dependent PO activity in molluscs infected with A. vasorum. This work suggests that PO pathway may help to control A. vasorum infection in A. fulica.