Avaliação do risco ecológico de elementos potencialmente tóxicos em solos de manguezais na Baía de Todos Santos, Bahia, Brasil

Abstract

The mangroves are under constant anthropic pressure, characterized by the advance of urbanization, industrialization, deforestation, which contributes to the contamination of the ecosystem. Among the contaminants, Potentially Toxic Elements (EPTs) stand out, which are characterized by high toxicity, bioaccumulation, becoming a global problem. Given the above, this study aimed to evaluate the ecological risk of EPTs in mangrove soils under maritime influence in Baía de Todos os Santos (BTS). The mangroves of Ponta Grossa (PG), Cacha Pregos (CP), Saubara (SB) and Ilha de Maré (ILM) were selected to obtain soil samples. In each location, a 25m² grid was demarcated and the respective sampling points according to the flood gradient: ZA, BF, BB1, BB2. In the laboratory, the samples were air-dried, crushed and sieved to obtain the Fine Air Dry Earth (TFSA). EPTs (As, Cd, Cr, Ni, Pb, Zn) were determined using the BCR method. With the results in hand, the following were evaluated: Contamination Factor (FC); the Global Contamination Factor (GFC); the Ecological Risk (ER); Potential Ecological Risk Index (IPRE); Risk Assessment Code (RAC). In all mangroves there were concentrations of As, Cd, Cr, Ni, Pb and Zn in F1 and F2. In Saubara, As, Ni and Pb were superior to the legislation (NOOA, 2008) in F3 and F4. The PERI of CP indicated low contamination and the RAC high risk for As and Zn. In Ilha de Maré, the RAC for As, Cd, Cr, Ni, Pb and Zn indicated medium to very high risk. In Ponta Grossa, the PERI indicated a low risk of contamination and the RAC for As, Ni and Zn was moderate to very high. In Saubara, the PERI was moderate and the RAC for As, Cr and Zn moderate to high. Cacha Pregos, Ponta Grossa, Ilha de Maré and Saubara require monitoring due to the availability of some EPTs and activities that take place in their surroundings.