RESUMO
Anthropogenic pollution by trace metals in aquatic environments in semiarid zones is a critical area of investigation. The objective of this study was to investigate the concentration and spatial distribution of trace metals in surface sediments in the Rosário reservoir, which is affected by the intensive aquaculture of Tilápia-do-Nilo (Oreochromis niloticus). Sediment samples were collected in three different areas, postculture (PCTV), cultivation (CTV) and control (CTRL) in the dry season in 2019. The granulometric composition, organic matter and concentrations of Fe, Mn, Zn, Cu, Cr, Cd, Pb and Ni metals were determined. Multivariate statistics were used. Geochemical and ecotoxicological indices and a comparison with sediment quality guidelines (SQG) were used. The sediment was characterized by silty clay loam with an average organic matter of 18.76 ± 4.27. The analytical merit figures demonstrated accuracy (metal recoveries in certified standards) between 89 to 99% and high precision (RSD < 5%). The concentration ranges for the metals were Fe: 0.11-0.85 (%), Mn: 14.46-86.91, Zn: 2.6-220.56, Cu: 26.89-98.75, Cr: 60.18-76.06, Cd: 0.38-0.59, Pb: 18.13-43.13, and Ni: 34.4-46.75, all in (mg/kg-1). The highest concentration values were found in the CTV areas (Fe: 40 ± 0.22, Mn: 66.48 ± 19.11, Zn: 114.83 ± 59.75 and Cr: 70.85 ± 2.62) and PCTV (Cd: 0.53 ± 0.04, Cu: 71.83 ± 21.20, Pb: 33.71 ± 4.34 and Ni: 44.60 ± 1.79). Pearson's correlation, hierarchical cluster analysis and principal component analysis confirmed the influence of fish farming on metals. Only Ni presented concentration values higher than the reference value established in the SQG. Thus, considering the probable geochemical and ecotoxicological effects, they comprise the two lowest levels of impact.
RESUMO
In recent decades, aquatic environment pollution has become a global challenge due to a rapid industrial growth. In this context, adsorption has become one of the most used methods, gaining importance especially in the last decades, given the growing concern over environmental damages caused by these pollutants. Additionally, its low cost and bioavailability are attractive. Therefore, the present study proposed to investigate the adsorption potential of A. indica seeds for Cu(II) and Pb(II) removal in synthetic solutions. Equilibrium studies were carried out via isothermal adsorption in batch systems. Kinetic studies were used to evaluate the lowest equilibrium time. The two evaluated ions were better suited to the Langmuir model and Freundlich model. When applying Langmuir's model on Neem seed powder adsorption, maximum adsorption capacities of 11.54 mg g-1 and 17.96 mg g-1, in the crude form and 11.41 mg g-1 and 19.80 mg g-1 in the alkaline form were obtained for Cu(II) and Pb(II) ions, respectively. The equilibrium time was approximately 80 and 100 min for both ions. The kinetic model best adjusted to the phenomena was the pseudo-second order (Ho Model), suggesting adsorption mainly has a chemical nature for both the studied metals. The results showed Neem seed powder may be a sustainable, efficient and low cost alternative for the removal of Cu(II) and Pb(II) metal cations present in effluents.
