Evaluation of Heavy Metals In Mangrove Soil of the Graciosa River In Bahia, Brazil.

Mangrove soils are developed from marine and fluvial sediments and are predominantly characterized by high salt and organic matter concentrations. They are distributed along coastal areas with smooth topography and under constant influence of both, marine and fresh waters. Mangrove soils have specific physical, chemical and biological properties, as well as some heavy metals that in high concentrations become toxic to the environment. This work aimed to characterize a mangrove soil in South Bahia, Brazil, with focus on heavy metals. Samples of 5 layers from a profile (125 cm depth) were evaluated. In a first phase it was done the characterization of soil samples collected in a deforested (anthropic) riverine area, in 2002. For the superficial layer C1 (0-20 cm) samples of an adjacent and non impacted area (under natural conditions) had been also collected. Secondarily, data from both superficial layer samples (natural and anthropic) were compared, considering samples of 2002 (deforested situation) and 2007 (regenerated situation). Heavy metals concentration on the samples of 2002 were significantly different among the layers and exhibited, in general, low levels in relation to those found in no polluted soils, except for Cd and Pb that presented intermediate level. In the period between 2002 and 2007, for the superficial layers, natural and anthropic, a decrease in metals concentrations was observed, except to Ni.

Key Words: Gleysol; Soil properties; Trace elements.