Metal Toxicity During Short‐Term Sediment Resuspension and Redeposition in a Tropical Reservoir

Abstract

Billings Complex is the largest water‐storage reservoir in São Paulo, Brazil, and has been contaminated since the 1960s. Periodically, Billings sediments are subjected to currents causing resuspension and subsequent release of metals. A short‐term (4‐h) resuspension was simulated using sediment flux exposure chambers (SeFECs) to better understand the fate, bioavailability, and transport of iron (Fe), manganese (Mn), and zinc (Zn) during these events, as well as possible organism toxicity. Daphnia magna and Hyalella azteca were exposed during the 4‐h resuspension, and were monitored after exposure for survival, growth, and reproduction. Resuspension rapidly deoxygenated the overlying water, decreased the pH, and resulted in elevated dissolved Zn above the US Environmental Protection Agency's (2002) criteria for acute toxicity (120 µg L–1). However, Zn was scavenged (after 20 h) from solution as new sorption sites formed. Dissolved Mn increased during and after resuspension, with maximum values at 20 h post exposure. An initial release of Fe occurred, likely associated with oxidation of acid‐volatile sulfides, but decreased after 1 h of resuspension. The Fe decrease is likely due to precipitation as oxyhydroxides. No acute toxicity was observed during resuspension; however, mortality of D. magna and H. azteca occurred during the postexposure period. Daphnia magna also exhibited chronic toxicity, with decreased neonate production after exposure. This sublethal effect could lead to decreased zooplankton populations over a longer period in the reservoir. Environ Toxicol Chem 2019;38:1476–1485. © 2019 SETAC

Phytotoxicological assessment and its relationship with environmental variables of Rio Grande Reservoir waters (São Paulo State, Brazil)

“…It is known that sediments have a high potential for accumulation, functioning as a record of environmental information in seasonal and spatial aspects (Franklin, 2010). However, sediment resuspension is not a constant threat, but it is a common one and can be an important stressor for organisms (Cervi et al, 2019). The resuspension acts on the dynamics of nutrients and contaminants that have been stored in the sediment layers of the water body over time, causing negative impacts on the water quality.…”

“…One of the possibilities for monitoring is ecotoxicological tests which aim to predict and understand whether the contaminants' effects are likely to cause damage to organisms exposed to toxic agents (Silva and Mattiolo, 2011). The tests were carried out with aquatic species, such as the Daphnia magna, the Desmodesmus subspicatus and the Hyalella azteca, which are widely used in scientific studies (Paula, 2016;Cervi et al, 2019), and regulated by the competent agencies Phytotoxicological assessment and its relationship with environmental variables……”

Has the Rio Doce “time bomb” been defused? Using a weight‐of‐evidence approach to determine sediment quality

“…A short‐term (4 h) resuspension was simulated using the Sediment Flux Exposure Chamber (SeFEC) system to better understand the fate, bioavailability, and transport of metals during these events, as well as possible organism toxicity. The SeFEC design (Cervi et al, 2019; Fetters et al, 2016) allows a more representative metal exposure and associated toxicological effects under environmentally realistic conditions (0.2–1.0 g L −1 of suspended particulate matter; Figure 3).…”

“…The experimental design for resuspension tests was conducted according to Cervi et al (2019). The release of metals was studied using freshwater and estuarine sediment and/or tailings‐like layers from the Rio Doce and offshore exposed to mineral and artificial brackish water (5 and 35 ppt of sodium chloride; Figure 4).…”

Modified Red Muds and Slag Based Hydraulic Binders for Zn Removal: A Matrix-Spiking Approach Applied on Clayey Sediments

“…It is mostly approached from the angle of suspension/re-deposition mechanisms [29,30] with a focus on the biological effects of its speciation [31]. Indeed, physical (vibrations, gravity disturbances) as well as biological (bioturbation, heterotrophic activities) turbid episodes may alter Zn redox states and have detrimental impacts on benthic communities [32][33][34][35].…”