Avaliação da contaminação de sedimentos e M. meretrix da Baia de Maputo por metais e risco à saúde humana

Abstract

Environmental contamination by metals has become a growing concern in the Bay of Maputo. In this study, the concentration of metals was evaluated in three areas of Maputo Bay namely: Matola Rio, Macaneta and Lingamo, through the determination of metal contents in sediments and tissues of M. meretrix 45 samples of clams were collected (15 per area), with individuals between 3.5 and 5 cm in length, according to a model adapted from studies ecological effects of bioaccumulation (Krizmanic et al., 2019; Silva et al., 2022). The samples of sediments (n = 6; two per area) were collected manually with a Teflon spoon in areas exposed intertidal areas, up to 10 cm deep, following USEPA protocols (2001), APHA (2017) and ISO 5667-12 (2017). All samples were analyzed in triplicate. A digestion of sediment samples was carried out according to the method adapted from Loring and Rantala (1992). The digestion of M. meretrix tissues followed the protocol of Nussey et al. (1999). Both matrices were analyzed by plasma optical emission spectroscopy inductively coupled (ICP-OES, model ICPE-9820, Shimadzu). Reference materials certificates (SARM 46 and ERM-BB422) were used for analytical validation. Were the metals Al, As, Cd, Pb, Cr, Cu, Fe, Mn and Zn were quantified, based on the limits of World Health Organization (WHO). To assess the risk to human health, calculated the Estimated Daily Consumption (CDE), the Target Risk Quotient (HQ) and the Risk Carcinogenic (CR). The Grubbs test was applied to eliminate outliers and the Kruskal-Wallis for statistical comparison between areas and matrices, in cases of difference significant, the Dunn test with Bonferroni correction was applied to identify the pairs of areas with statistical differences and the Student t test for one sample was used to compare the average concentrations observed with the maximum limits allowed by the WHO. The results indicated that Fe, Cu and As were the most abundant metals, while Pb, Mn and Cr showed the lowest concentrations in clams and sediments. In the sediments, the decreasing concentrations in the following order: Matola River: As> Fe> Pb> Zn> Cu> Cd> Mn> Cr. Macaneta: As> Fe> Pb> Zn> Cu> Cd> Cr> Mn and Lingamo: As> Fe> Pb> Zn> Cu> Cr> Cd> Mn and in M. meretrix tissues, concentrations decreased in the following order: Matola Rio: Fe> Al> Cu> Zn> Mn> As> Cd> Pb. Macaneta: Cu> Fe> Al> Zn> As> Cd> Mn> Pb and Lingamo: Fe> Al> Cu> Zn> As> Cd> Mn> Pb. The risk assessment indicated that although the CDE values were below the maximum tolerable limits, the HQ for As exceeded the value of 1 in all areas (Matola Rio: 2.36; Macaneta: 1.75; Lingamo: 1.94), indicating potential risk not carcinogenic. Additionally, the CR values for As were higher than the acceptable limit of 10⁻⁴, showing a significant carcinogenic risk. The risks associated with cadmium and lead, remained below critical limits.(Tradução nossa)