Determinação de metais (Al, Cu, Fe, e Mn) em sedimentos da Barragem de Massingir por FAAS

Abstract

The present study is part of the "MDSAR" project (Massingir Dam and Smallhoider Agricultural Rehabilitation), carried out by ARA-Sul (Regional Water Administration), financed by the AfDB (African Development Bank) and coordinated by the Department of Biological Sciences. , Eduardo Mondlane University. The metals Al, Cu, Fe and Mn were determined in sediments from the Massingir dam, in the Elefantes River, Massingir District in Gaza Province using "FAAS" in order to assess the environmental impact of these metals on the dam. Sediment samples were collected at 5 stations at maximum depths ranging from 4 to 20m. For validation of the spectrophotometric method, reference materials from sediments from the river SARM 46 and 52 from "MINTEK" (South Africa) were used to optimize the instrumental and analytical conditions. The %RSD values ​​for the reference materials and samples were very good, ranging between 3.94%, 5.05%, 3.15% and 0.44 respectively. The concentrations of studied metals Al, Cu, Fe and Mn in the sediments of the Massingir dam are in the ranges of 8.37-9.98%, 67-85ug/g, 5.39-7.23% and 518- 959ug/g respectively. Mozambican legislation does not provide for limits on concentrations of metals allowed in river sediments. For the assessment of the environmental impact, the limits of concentrations allowed in sediments were taken as a basis according to the norms of several countries and found in the reviewed literature. The Cu concentration (73ug/g) determined in the present study is lower than the limits of concentrations allowed in sediments in the South African (100ug/g) and UK (135ug/g) standards but higher than the limits of allowable Cu concentrations in sediments in the standards of Australia (60ug/g), Germany (60ug/g), Netherlands (36ug/g), United States of America (34ug/g), Switzerland (50ug/g are) and Canada (8ug/g). Taking the limit of South Africa as a reference, as it is in the same region as Mozambique, it can be said that the sediments of the Massingir dam are not being polluted with this metal. For Al, Fe and Mn not found in several studies and countries reported in the consulted literature are lower than those of the present study. Cd was determined at the SETPOINT laboratory in Pretoria and its concentration is <1ug/g; comparing with the levels in other parts of the world most also present values ​​of .1ug/g so this metal is polluting the sediments of the Massingir dam (TRADUÇÃO NOSSA)