Bioacumulação de metais presentes no material particulado atmosférico sedimentável em tilápia-do-Nilo (Oreochromis niloticus)

Abstract

The occurrence of sedimentary atmospheric particulate matter (MPAS) containing metals and metallic nanoparticles has increased in the world, causing the contamination of aquatic environments, as is the case for Espírito Santo, southeast region of Brazil. MPAS was collected in Vitória’s bay surroundigs, ES, to evaluate the bioaccumulation pattern of metals in Oreochromis niloticus and its possible effects on the gills. The metal profile of MPAS was analyzed and, subsequently, specimens of Nile tilapia, Oreochromis niloticus were exposed to MPAS (1g/L) in a semi-static system, for 30 days, with daily sampling of water for physicochemical parameters analysis and chemical profiling of the dissolved metals. Every 3 days, specimens of tilapia were picked for analysis of bioaccumulation (Total: 11 sample collection) of metals in the viscera and fillet, and every 6 days specimens were picked for histological analysis and determination of the metallothionein concentration in gills (Total: 6 sample collection). For the multi-element analysis, the samples were prepared by acid digestion method and the concentration of metals determined by ICP-MS (Inductively coupled plasma mass spectrometry). The following metals were identified and quantified: B, Al, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Rb, Sr, Ag, Cd, Pb, Hg, Ba, Bi, W, Ti, Zr, Y, La, Nb, Ce in the MPAS. Ta has been identified but not quantified. Six metals (Cu, Fe, Al, Zn, Mn, Pb) were chosen/picked for analysis in the fish’s viscera and fillet based on the following criteria: higher concentration in MPAS and limits determined by Brazilian and USA legislation. The concentration of Cu in water was higher than the limits established for freshwater from day 3 to day 15 and on day 24. The concentration of Fe was higher from day 3 to day 12. Al concentration was higher on all days, except on the 18th day. Pb’s concentration only exceeded the limit on the 6th day. The determined bioconcentration factor (BCF) was >1 for all metals analyzed, confirming their bioaccumulation in tilapia. Some metals such as Al, Fe, Mn and Pb showed similar accumulation patterns with significant increase in concentration in the first days until reaching a peak, followed by the subsequent decrease. Cu and Zn showed different bioaccumulation pattern with several peaks and persistence of a high concentration throughout the exposure. There was preferential bioaccumulation of those metals in the viscera compared to the fillet. The analysis of histopathology and the concentration of metallothionein in the gills showed no significant alteration after exposure to MPAS. Exposure to higher concentrations of MPAS may trigger more severe responses.