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

• Published in: Environmental toxicology and chemistry Vol. 38; no. 7; pp. 1476 - 1485
• Main Authors: Cervi, Eduardo Cimino, Hudson, Michelle, Rentschler, Alison, Burton, G. Allen
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.07.2019
• Subjects: Acid‐volatile sulfide; Acute toxicity; Amphipoda - drug effects; Amphipoda - growth & development; Animals; Bioavailability; Brazil; Chronic toxicity; Computer simulation; Daphnia - drug effects; Daphnia - growth & development; Daphnia magna; Deoxygenation; Environmental protection; Exposure; Geologic Sediments - chemistry; Heavy metals; Humans; Hydrogen-Ion Concentration; Iron; Iron - toxicity; Lakes - chemistry; Manganese; Manganese - toxicity; Metal bioavailability; Metals - toxicity; Oxidation; Reproduction - drug effects; Sediment toxicity; Sediments; Storage reservoirs; Toxicity; Tropical ecotoxicology; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - toxicity; Water Quality; Water quality criteria; Zinc; Zinc - toxicity; Zooplankton; Brazil; Metal bioavailability; Tropical ecotoxicology; Sediment toxicity; Acid-volatile sulfide; Water quality criteria
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.4434

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 Conceptual model of metal (Me) speciation under different sediment redox states. During bedded conditions (A) metals are mainly bounded as insoluble sulfides or associated with organic carbon (OC). When resuspended (B), sulfide species are oxidized, mobilizing metals (such as Zn) into the overlying water (OW). However, the mobilized metal is scavenged by OC and freshly‐precipitated FexOx. As particles redeposit (C), and are returned to the benthic environment, further oxidation can occur in the aerobic sediment layer releasing Fe. High dissolved Fe concentrations in OW caused acute and chronic toxicity to D. magna. Ingestion of Zn caused growth inhibition and mortality to H. azteca.