Evaluation of mercury levels in sediment and soil samples from Vila Nova river basin, in Amapa State, Brazil, using radiochemical neutron activation analysis

In the present work, results from a survey on mercury concentration in sedi ments and soils from a gold mining area along the Vila Nova river, in Amapa State, Brazil, are presented. These values were compared with those from t he Igarape: Pedra Preta basin, an area unaffected by mining activities. Tot al mercury contents were determined in the muddy (silt+clay) fraction of th e sediments and in the <2 mm fraction of the soils using radiochemical neut ron activation analysis (RNAA). The detection limit of the method was 54 mu g.kg(-1) for soils and 14 mu g.kg(-1) for sediments when 200 mg of sample were analysed. The Hg results obtained from a comparison between our curren t method (RNAA) and CV AAS are also presented. Mercury levels showed to be very high in the soils and sediments collected in the Vila Nova river (up t o 2 mg.kg(-1)) when compared to background values (0.3 mg.kg(-1)) for this region. An enrichment factor was calculated, using Al as a normalizing fact or. It showed values up to 8 in sediments of the Vila Nova river basin, ind icating a relatively high degree of pollution as compared to the values of about 1 for the samples of the Igarape Pedra Preta basin.