Assessment of Heavy Metals in Suspended Sediments

Objective: This study aimed to assess the concentration of heavy metals in suspended sediments in the Coxim and Taquari Rivers, Mato Grosso do Sul, over a hydrological year. It observed variations in concentrations and their relationship with land use and cover in the watershed. Theoretical Framework: The research is based on the significance of suspended sediments as carriers of nutrients and pollutants in fluvial systems, as well as on the criteria established by CONAMA Resolution 454/2012 regarding sediment quality. Previous studies highlight the importance of fine particles in transporting heavy metals, such as Iron (Fe) and Aluminum (Al), due to their greater specific surface area. Method: Four sampling campaigns were conducted at points P1, P2, and P3, covering both flood and drought periods. Flow rates were measured using an acoustic Doppler meter (ADP M9) and sediments were collected using the Equal Width Increment (IIL) method. Acid digestion followed USEPA (1996) protocols, while granulometry was analyzed via laser diffraction (Mastersizer 2000). Results and Discussion: Net flow rates varied from 220 m³/s (P1) to 226.5 m³/s (P2), with sediment transport ranging from 1,708.56 t/day to 12,473.05 t/day. At point P2, loads of 405,873.6 kg/day of Al and 267,214.5 kg/day of Fe were reached. The metals Zn and Ni exceeded the limits set by CONAMA 454/2012, while Cu, Cr, Cd, and Pb remained at lower levels. The sediments consisted mainly of fine sand (60%), with smaller particles (17%) playing a significant role in metal transport. Research Implications: The results underscore the need for public policies focused on sustainable land management and siltation control, emphasizing the importance of sediment monitoring as an environmental indicator. Originality/Value: This study contributes by integrating data on metal transport with the physical characteristics of sediments, proposing the inclusion of parameters such as Fe and Al in environmental regulations for sediments.