Temporal trends of trace elements bioaccumulation by a vulnerable cetacean (Pontoporia blainvillei) before and after one of the largest mining disasters worldwide.

One of the largest environmental disasters worldwide occurred on November 5th, 2015, when the Fundão dam collapsed in Mariana (Minas Gerais State, Southeast Brazil). The tailing mud flooded the Doce River basin and reached the sea in the coast of Espírito Santo State (ES), Southeast Brazil. This coastal region is the habitat of the most isolated population of franciscana dolphins (Pontoporia blainvillei), with the lowest populational census and lowest genetic diversity in Franciscana Management Area Ia (FMA Ia) - 18° 25'S and 21° 17'S. This study aimed to assess the bioaccumulation of trace-elements (As, Cd, Cu, Fe, Hg, Mn, and Zn) in muscle, liver and kidney of franciscana dolphins collected near the Doce River's mouth before (n = 32) and after (n = 19) the tailing mud reached the sea. The Generalized Additive Model (GAM) showed increasing temporal trends of Hg and Zn in muscle and liver after the dam failure, probably related to higher concentrations and bioavailability in the water column and sediments from the Doce River. Declining trends were found for As and Cu muscular and hepatic concentrations and Fe concentrations in kidney due to their lower bioavailability after the disaster, caused by association with tailings mud trapped in the riverbanks and suspended particulate material. Additionally, higher As and Hg concentrations found in the first period of sampling may be due to historical contamination by mining activities. The full extent of the impacts caused by the Fundão dam failure is still unknown. However, due to their rapid increase and remobilization process, toxic effects can be induced in the biota by these elements. Elements' bioaccumulation in this study contributes to the knowledge of franciscana dolphins from FMA Ia. Considering the conservation concern regarding this franciscana population and its scarce knowledge, the impact of this disaster can be alarming for species conservation.

Study of the radio-opacity of base and liner dental materials using a digital radiography system.

OBJECTIVES: This study investigated the radio-opacity of commercially available glass ionomer cements (GICs), flowable resin composites (FRCs) and calcium hydroxide cements (CHCs) and compared this with the radio-opacity of enamel, dentine and aluminium stepwedge. 16 GICs, 8 FRCs and 4 CHCs were analysed. METHODS: Three sets of three samples were prepared: 1 mm, 2 mm and 3 mm thickness for GIC and FRC and 1 mm thickness for CHC. Specimens of enamel and dentine with the same thicknesses were obtained. As a control, an aluminium stepwedge was used. Radiographs were taken with a digital Kodak RVG 5000 (0.32 s, 30 cm). The images were analysed using the Image Tool(®) program (v. 2.00; The University of Texas Health Science Center, San Antonio, TV) to obtain the mean grey values. RESULTS: Analysis of variance was used to investigate the significance of differences among the groups. For pairwise comparisons, the Tukey test was applied (p < 0.05). The GICs Ionomaster (Wilcos, Petrópolis, Brazil), Maxxion (FGM, Joinville, Brazil), Bioglass R (Biodinâmica, Ibiporã, Brazil), Bioglass F (Biodinâmica), Vidrion R (SS White, Rio de Janerio, Brazil) and Vidrion F (SS White), presented radio-opacity lower than that of dentine. All FRCs and CHCs studied showed radio-opacity higher than that of dentine. Vitro Fil (DFL, Rio de Janeiro, Brazil), Magic Glass (Vigodent, Rio de Janeiro, Brazil), Vitrebond (3M, Sumaré SP, Brazil), Riva Self Cure (SDI, Victoria, Australia), Riva Light Cure (SDI), Fill Magic (Vigodent), Opallis (FGM, Joinville, Brazil), Surefil SDR (Dentsply, Milford, DE), Tetric N (Ivoclar Vivadent, Schaan, Lichtenstein), Tetric (Ivoclar Vivadent), Hydro C (Dentsply, Petrópolis, Brazil), Hydcal (Technew, Madalena, Portugal) and Liner (Vigodent) showed radio-opacity similar to or greater than that of enamel for all thicknesses. CONCLUSIONS: The increased thickness of the materials studied increases their radio-opacity. Some commercially available GICs used as a base and liner for restorations have a very low radio-opacity (Ionomaster, Maxxion, Bioglass R, Bioglass F, Vidrion R and Vidrion F).