Abstract

This study was undertaken to evaluate the heavy metals contamination of copper, zinc, manganese, iron, chromium, nickel, lead and cadmium, to assess the environment quality of the coastal area from town activities. Nickel, lead and cadmium are used in different kind of current accumulators and they are dangerous for sea wild life and for human food resources. The five others metals are usual and at a high concentration they are able to threat environment system.  Six samples had been choice at two town of Madagascar north-western coast: Nosy Be and Mahajanga, in February, 2007. These sampling points stand in front of each mean sewage mouths in each locality. Table 1 and 2 give us same descriptions of each sampling points. These two sampling area are among the principal fishing area of Madagascar. Three kinds of analytical method were used for metals determination and quantification: flame spectrophotometer atomic absorption, UV spectrophotometer, and voltammeter method. The flame spectrophotometer atomic absorption gives the best result by testing with certified reference materiel.  Our data suggested that Mahajanga’s stations have higher values of cadmium (1 mg/kg) and lead (91 mg/kg) than the non-contaminated sediments. However, the concentrations of other metals such as copper, zinc, manganese, iron and chromium in Nosy Be sediments, were twice as higher than in those of Mahajanga. In compiling our data obtained at the same stations in the vertical water column, we would like to confirm the growing order of potential absorption between metals and sediments, nickel, copper, cadmium and lead.  According to the results of determinations, we suggested that more determination should have done in open sea to assess metals in a wide scale.

Key words: Marine pollution, heavy metals, coastal sediments, toxicity, Nosy Be, Mahajanga, Madagascar