Different species of mercury in the livers of tropical dolphins

Four kinds of mercury species (inorganic mercury (Hg-inorg), methylmercury (MeHg), total organic mercury (Sigma Hg-org), and insoluble mercury, deemed to be mercuric selenide (HgSe), were determined in the livers of dolphins from the Brazilian coast. The MeHg was identified and quantified in the toluene layer on a Gas Chromatograph with an Electron Capture Detector (GC-ECD). The Sigma Hg-org was isolated by acid leaching (H2SO4-KBr-CuSO4) and then extracted into CH2Cl2. The Sigma Hg-org and Hg-inorg were determined by Cold-Vapor Atomic Absorption Spectroscopy (CV-AAS). The MeHg was the smallest fraction of Hg-tot, with a median of 9%, whereas the highest fraction of the Hgtot was as HgSe, corresponding to 53%. The fractions of Hg-inorg and Sigma Hg-org corresponded to 30% and 39%, respectively. The lowest fraction of MeHg and the highest fraction of HgSe in the liver of all animals are related to different capacities or strategies of detoxification of methylmercury in this organ.