DISTRIBUIÇÃO E FRACIONAMENTO DE METAIS EM SEDIMENTOS DE MANGUE DO RIO TIBIRI NA ILHA DO MARANHÃO

Abstract

Although they are found at trace levels in the environment, the metals Cd, Ni, Cr, Zn, Cu and Pb have received numerous studies due to the toxic potential. Some of them have no known biological function such as Pb and Hg. However, these metals, at certain concentrations, offer risk for aquatic organisms. This risk, Beyond to the total concentration of them, is associated with their mobility in environmental matrices. To assess the risk of trace metals in sediments from mangrove Tibiri River, located on the Maranhão island, This study used the guide values developed by environmental agencies based on the total concentration of these elements. The results showed that the levels were below the metal TEL (Threshold effect level) and ERL (Effect low range), ranges associated with occasional adverse biological effects for aquatic life. The concentrations of trace metals found in sediments are the same order of magnitude of the background prescribed by the National Oceanic and Atmospheric Administration (NOAA). The order of mobility (considering the sum of the first three most mobile fractions) was: Ni (24%)> Zn (20.6%)> Cu (14.5%)> Pb (1.9%)> Cd = Cr (not detected). The low mobility values contribute to minimizing the environmental risk of trace metals.