RESUMO
The main objective of this work was to propose and evaluate a methodology for shielding-gas selection in additive manufacturing assisted by wire arc additive manufacturing (WAAM) with an austenitic stainless steel as feedstock. To validate the proposed methodology, the impact of multi-component gases was valued using three different Ar-based blends recommended as shielding gas for GMA (gas metal arc) of the target material, using CMT (cold metal transfer) as the process version. This assessment considered features that potentially affect the building of the case study of thin walls, such as metal transfer regularity, deposition time, and geometrical and metallurgical characteristics. Different settings of wire-feed speeds were conceived to maintain a similar mean current (first constraint for comparison's sake) among the three gas blends. This approach implied different mean wire-feed speeds and simultaneously forced a change in the deposition speed to maintain the same amount of material deposited per unit of length (second comparison constraint). The composition of the gases affects the operational performance of the shielding gases. It was concluded that by following this methodology, shielding-gas selection decision-making is possible based on the perceived characteristics of the different commercial blends.
RESUMO
Heavy metal pollution in soil has emerged as a major environmental concern. This can be attributed to human activities such as mining, modern agriculture, and industrialization. This study was conducted to determine how heavy metals spread from mine tailings to surrounding farmland. Metal absorption and accumulation were also investigated in the root and shoot biomass of tapioca crops grown in those farmlands. Metal concentrations in MTAS1 were 85.3 ± 1.2, 45.8 ± 1.5, 134.8 ± 1.7, 92.4 ± 2.2, and 78.95 ± 1.4 mg kg-1, respectively. Heavy metal concentrations in MTAS2 and MTAS3 were found to be 79.62 ± 1.6, 75.4 ± 1.5, 41.31 ± 1.1, 47.8 ± 1.6, 142.5 ± 2.1, 128.4 ± 1.4, 86.2 ± 1.9, 79.5 ± 1.3, and 83.4 ± 1.2 mg kg-1, respectively. Tapioca crop shoot and root biomass grown at these metal polluted sites absorbed and accumulated significant amounts of Cd, Cu, Zn, Pb, Ni, and Mn. Notably, the metal content of the tapioca crop's root and shoot biomass exceeded national standards.
Assuntos
Biomassa , Metais Pesados , Mineração , Raízes de Plantas , Brotos de Planta , Poluentes do Solo , Metais Pesados/análise , Metais Pesados/metabolismo , Poluentes do Solo/análise , Poluentes do Solo/metabolismo , Raízes de Plantas/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Brotos de Planta/crescimento & desenvolvimento , Manihot/crescimento & desenvolvimento , Manihot/metabolismo , Manihot/química , Agricultura/métodos , Monitoramento AmbientalRESUMO
Metal contamination has never been assessed in Ampullae of Lorenzini. This study employed Rhizoprionodon lalandii, as an ecotoxicological model to investigate potential metal accumulation in Ampullae of Lorenzini jelly. No differences between sexes were observed regarding jelly metal concentrations at Rio das Ostras (RJ) or Santos (SP). Statistically significant correlations were noted between total lengths (TL) and condition factors and several metals at both sampling sites, demonstrating the potential for Chondrichthyan sensory capacity disruption and possible effects on foraging success. Maternal metal transfer to Ampullae jelly was confirmed. Rhizoprionodon lalandii is thus, a good model to assess Ampullae of Lorenzini contamination, as this electrosensory organ seems to be highly vulnerable to metal contamination.
Assuntos
Metaloides , Tubarões , Animais , Brasil , Ecotoxicologia , Metais , Alimentos MarinhosRESUMO
Metal concentrations (Cu, Pb, Zn and Cd) were determined in muscle, gills, soft tissues and eggs in male, non-ovigerous and ovigerous female Callinectes sp. specimens from a reference site in Southeastern Brazil. Metallothionein (MT) and reduced glutathione (GSH) levels were also determined. Results demonstrate that sex has a significant influence on metal, MT and GSH concentrations. Significant maternal transfer of Pb and Zn from ovigerous females to eggs was verified, while female crabs, both ovigerous and non-ovigerous, showed elevated GSH and MT in viscera when compared to males, indicating possible MT role in excreting metals to eggs in ovigerous females of this species. Several strong statistical correlations between metals and MT indicate MTs role in detoxification of both toxic and essential elements in different organs. Pb and Zn were significantly correlated to GSH, indicating oxidative stress caused by the former and a direct link between Zn and GSH in maintaining homeostasis. Regarding human consumption, metal concentrations were lower than the maximum permissible levels established by international and Brazilian regulatory agencies, indicating that this species is safe for human consumption concerning this parameter. The presence of metals in Callinectes sp., however, is still of importance considering that this is a key species within the studied ecosystem and, therefore, plays a major role in the transference of pollutants to higher trophic levels. In addition, the presence of significant metal concentrations found in eggs must be considered in this context, since crab eggs are eaten by several other species, such as shorebirds, seabirds, and fish. Also, to the best of our knowledge, this is the first study regarding both MT and GSH levels in Callinectes sp. eggs and is of interest in the investigation of molecular mechanisms regarding metal exposure in these crustaceans. Data reported in this study support the conclusions from previous reports, provide mechanistic insights regarding metal exposure, metallothionein and oxidative stress induction in this species and also present novel data regarding eggs.