Abstract
Abstract Estuaries receive daily inputs of chemical elements which can impact the quality of water and sediment, as well as the health of biota. In addition to the sediment, bivalve mollusks have been used in the chemical monitoring of these systems. This study investigated the presence and contents of As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in superficial sediment and in bivalves (Crassostrea gasar, C. rhizophorae and Mytella guyanensis) from estuaries in the south / extreme south of Bahia State, northeast Brazil. The samples were evaluated with inductively coupled plasma optical emission spectrometry (ICP-OES, Varian 710). Except for Cd, all other elements were found in the samples, being that Co was exclusive in the sediment. The estuaries equivalent to sampling stations #1 - Valença, #2 - Taperoá, #3 - Ilhéus and #4 - Belmonte showed levels of metals compatibles with those established by the Brazilian legislation, however, the #5 - Santa Cruz Cabrália, in addition to the presence of As, presented a high level of Pb and Cu in C. gasar, which was attributed to the impacts of nautical activities in that locality.
Highlights
Estuaries and mangroves receive daily discharges of chemical elements, like heavy metals
The results of the present study showed that the chemical element levels in the superficial sediment of the mangroves corresponding to the sampling stations #1-Valença, #2-Taperoá, #3-Ilhéus and #4-Belmonte were compatible with the maximum limits recommended by Resolution CONAMA nr. 420 (Brasil, 2009) with regard to the elements Ba, Co, Cr, Cu, Ni, Pb and Zn
The CONAMA legislation establishes a maximum limit of 60 mg kg-1 for Cu in soils (Brasil, 2009)
Summary
Estuaries and mangroves receive daily discharges of chemical elements, like heavy metals This input being the partial result of natural processes, whose substances are usually leached from their place of origin and transported by river waters to their final destination, represented almost always by estuarine sediments (Liu et al, 2020). Human activities, such as the discharge of industrial and domestic effluents into water bodies, are the most accountable for the increase in chemical levels in these systems (Bakshi et al, 2017; Charry et al, 2018).
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