ABSTRACT
The mangrove forest is an important transitional ecosystem consisted of terrestrial and marine environment located in tropical and subtropical regions with average temperatures above 20 °C. In Alagoas, the mangrove forests are found on the entire coastline from Maragogi to Piaçabuçu. In the last 20 years, due to the pollution of water resources, studies of coastal aquatic ecosystems have been developed. The objective of this study was to analyze the physicochemical properties and determine the levels of heavy metals in mangrove sediments of the Mundaú-Manguaba estuary lagoon complex (MMELC) and Meirim River in Alagoas. Zinc, copper, lead, cadmium and chromium were chosen due to their relationship with sewer, agricultural, and industrial wastes. 22 soil samples were collected in the MMELC and in the Meirim River. The samples were submitted to soil routine analyses of Embrapa. The heavy metals were extracted by the Mehlich-1 method and analyzed by atomic absorption spectrometry. The mean concentrations of these metals in thesediment samples followed the order Mn > Zn >Pb > Cr> Cu >Cd in MMELC and Zn > Mn >Pb > Cr> Cu >Cd in Meirim River. All proposed heavy metals were found in sediments, however, the cadmium levels were above the normal levels proposed by Environment National Council (CONAMA) and Canadian Council of Ministers of the Environment. The study shows that the analysis of sediment can contribute to environmental monitoring actions and development of public policies aimed to controlling the sustainable use of natural resources of the studied areas.
O manguezal é um importante ecossistema de transição entre o ambiente marinho e terrestre, localizado em regiões tropicais e subtropicais com temperaturas médias acima de 20°C. Em Alagoas podemos encontrar florestas de mangue em praticamente todo o litoral desde Maragogi até Piaçabuçu. Nosúltimos 20 anos, a poluição dos recursos hídricos tem levado ao estudo dos ecossistemas aquáticos costeiros, que são importantes para preservação e equilíbrio da vida. O objetivo deste trabalho foi analisar as propriedades físico-químicas e determinar os teores ambientalmente disponíveis de metais nos sedimentos do mangue existente na foz CELMM (e do rio Meirim em Alagoas. Foram escolhidos os metais zinco, cobre, chumbo, cádmio e crômio por estarem ligados aos despejos de esgotos, projetos agropecuários, e fontes industriais. Foram coletadas 22 amostras de solo nos estuários do CELMM e do rio Meirim. As amostras foram submetidas as análises de rotina para solos da Embrapa. As concentrações médias desses metais nas amostras de sedimento seguiram a ordem Mn > Zn >Pb > Cr> Cu >Cd in CELMM e Zn > Mn >Pb > Cr> Cu >Cd no Rio Meirim. Os metais foram extraídos pelo método Mehlich-1 e analisados por meio de espectrometria de absorção atômica. Foram encontrados nos sedimentos todos os metais propostos na pesquisa com destaque para os teores de cádmio detectados em valores absolutos acima de valores considerados normais pelo Conselho Nacional doMeio Ambiente e pelo Canadian Council of Ministers of the Environment em alguns pontos do estuário do rio Meirim. O estudo mostra que a análise dos sedimentos pode, portanto, contribuir para ações de monitoramento ambiental, subsidiando a implantação e desenvolvimento de políticas públicas que visem controlar o usoracional e sustentável dos recursos naturais das áreas do estudas.
Subject(s)
Metals, Heavy , Environmental Pollution , Wetlands , Biological AvailabilityABSTRACT
Abstract Mangroves are tropical and subtropical flooded forests that generally develop in estuarine areas over unstable sediments protected from the action of waves in the intertidal zone with an environment characterized by a great diversity of fauna and flora. Thus, the present study aimed to evaluate the levels of heavy metals that are absorbed by mangrove oysters, in estuarine systems in the Alagoas coast by determining the concentrations of Fe, Cu, Mn, Zn, Cd and Cr. Two areas, which consisted of both a collection during the rainy season and the dry season, were selected for sampling of mangrove oysters. In each collection, seven samples were collected, at seven different points, where each sample contained four oysters. In the laboratory the oysters were dried at 105°C for 72 hours and then macerated. It was then digested with 10 ml of a solution comprising a combination of 4:1 nitric acid and hydrochloric acid, initially in 1h at 40°C, followed by 3 hours at 140°C. In General, the medians followed the order Zn > Fe > Mn > Cu > Cr > Cd in MMELC and Zn > Cu > Fe > Mn > Cr > Cd in Meirim River. It is concluded that the Crassostrea rhizophorae oysters from the studied environments presented concentrations of all the metals proposed in the research and demonstrates its accumulating and bioindicator character.