Mangrove forests are characteristic of tropical and subtropical coastal areas, which are subject to anthropic disturbances, acting as a bioaccumulator of trace metals, removing essential mineral elements from the soil for their development. These metals after absorption by the roots can result in toxicological effects, which activate detoxification mechanisms in the plant, such as the production of phytochelatins, which are a family of metal-complexing peptides, which are part of the phytoremediation technique. Therefore, the objective is to evaluate the impact of metal contamination on mangrove vegetation in an old steelworks tailings area, located in Saco do Engenho, Baía de Sepetiba, RJ. Root, stem and leaf samples were collected from the fern Nephrolepis biserrata beside the tailings pile, while flowers, leaves and branches were collected from the mangrove species Rhizophora mangle in Saco do Engenho (6 points) and parallel channel (4 points). The obtained metal extracts were used to determine the total content of the elements by ICP-MS and for phytochelatin determination it was performed by SEC-HPLC-ICP-MS. The highest concentration of As (34.81 mg kg -¹) was detected in leaves of the fern sample, which can be attributed to the ability to accumulate and tolerate As in its biomass. While Zn reached 287.91 mg kg-¹ in root, and Cd that did not exceed 3 mg kg-¹ in the plant compartments. The highest concentrations of As in mangrove vegetation were reported only in flowers (6.1 mg kg-¹) in S. Engenho 6, remaining <1.3 mg kg-¹ along the sampling points. In relation to Zn, it can be observed that the levels remained high, with an increasing tendency towards greater accumulation in branches and leaves. On the other hand, the channel showed opposite patterns in Zn concentrations, with high levels in leaves (58.8 mg kg-¹) and flowers (52.9 mg kg-¹). The concentrations reported by the present work allow us to infer that trace metals present in Saco do engenho tend to have a higher content in the innermost area close to the courtyard of the former Cia Mercantil Ingá, diluting towards the mouth. In the channel, the highest concentrations of Fe and Mn are related to the influence of drainage from the ore and coal terminal. In the fern species, the biomolecule analyzes show the existence of 2 chemical species of As in the plant structure, while for the mangrove 3 chemical species were found in the leaves and 2 in the flowers and branches. Therefore, it is necessary to carry out further studies to identify the chemical species of As in the Saco do Engenho mangrove.
Keywords: chemical oceanography; effluent; trace metals; phytochelatin; Sepetiba bay.
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