Monitoramento ambiental e avaliação da qualidade da água, sedimento e molusco Bivalve (sururu) na laguna Mundaú (Alagoas, Brasil)

Abstract

The Mundaú-Manguaba Estuarine Lagoon Complex (CELMM) is one of the most important ecosystems in Brazil, playing a significant role in maintaining microclimates in natural environments, enhancing the urban landscape of the cities in which it is located, as well as being a potential for the development of fishing, recreation and tourism. However, it is clear that it suffers from the unbridled and poorly planned urbanization process, which leads to the eutrophication of its water resources due to the discharge of effluents, resulting in the loss of its sanitary quality and the aesthetic aspect of its landscapes. Therefore, environmental monitoring studies in different environmental compartments are of theutmostimportance, including the monitoring of metals such as lead (Pb), as well as the monitoring of other metals , which are indicators of contamination by domestic and industrial sewage. The aim of this study was to monitor the lead content in samples of water, sediment and sururu from the Mundaú lagoon - Alagoas, Brazil. Sampling was carried outin 11 points using the following criteria: proximity to the chlorochemical center, high and low population density, sururu fishing sites and sewage outfalls. in situ analysis of the physical-chemical parameters pH, temperature, conductivity, total dissolved solids, dissolved oxygen and salinity) was carried out during the 7 collections. water samples were analyzed directly for dissolved Pbdissolved byAbsorption Spectrometry with Electrothermal(GF AAS). thesururu and water samples (for the quantification of the total levels of the analytes) were subjected to acid digestion with HNO3 and H2O2 in a microwave oven for subsequent analysis byCoupledSpectrometry (ICP OES) . In the sample treatment optimization stage, 3 digestion mixtures were evaluated (HNO3 + H2O2 + HF; HNO3 + H2O2; and HNO3 + HCl) and the best result was observed for the procedure with HNO3 and H2O2, which was then used in the other digestions of the sediment samples where the analyte levels were also analyzed by ICP OES. This study showed that the Pbdissolved content in the water samples above 10 µg L-1 for sample 6 (7.42 - 37.4 µg L-1 ) and 7 (5.42 - 20.1 µg L-1 ), the maximum limit allowed by Brazilian legislation (CONAMA 357/05). The levels oftotal Pb in the sururu samples were below the quantification limit (53.7 µg L-1 ). As for samples, all the samples showed lead concentrations below the maximum limit allowed by CONAMA Resolution 344/2004 (46.7 mg Kg-1 ). The high concentrations of the analytes K, Mg, Ba, V, Mn, Fe, Cr and Zn in the sediment and water indicate deposition over time, possibly as a result of inadequate domestic and industrial effluent disposal practices in some areas of the Mundaú Lagoon.