title: Preparation and characterization of nickel-spiked freshwater sediments for toxicity tests: toward more environmentally realistic nickel partitioning.
abstract: Two spiking methods were compared and nickel (Ni) partitioning was evaluated during a series of toxicity tests with 8 different freshwater sediments having a range of physicochemical characteristics. A 2-step spiking approach with immediate pH adjustment by addition of NaOH at a 2:1 molar ratio to the spiked Ni was effective in producing consistent pH and other chemical characteristics across a range of Ni spiking levels. When Ni was spiked into sediment having a high acid-volatile sulfide and organic matter content, a total equilibration period of at least 10 wk was needed to stabilize Ni partitioning. However, highest spiking levels evidently exceeded sediment binding capacities; therefore, a 7-d equilibration in toxicity test chambers and 8 volume-additions/d of aerobic overlying water were used to avoid unrealistic Ni partitioning during toxicity testing. The 7-d pretest equilibration allowed excess spiked Ni and other ions from pH adjustment to diffuse from sediment porewater and promoted development of an environmentally relevant, 0.5- to 1-cm oxic/suboxic sediment layer in the test chambers. Among the 8 different spiked sediments, the logarithm of sediment/porewater distribution coefficient values (log Kd ) for Ni during the toxicity tests ranged from 3.5 to 4.5. These Kd values closely match the range of values reported for various field Ni-contaminated sediments, indicating that testing conditions with our spiked sediments were environmentally realistic.
authors: US Geological Survey, Columbia Environmental Research Center, Columbia, Missouri, USA.
authors: William G
authors: WG
authors: Brumbaugh
authors: John M
authors: JM
authors: Besser
authors: Christopher G
authors: CG
authors: Ingersoll
authors: Thomas W
authors: TW
authors: May
authors: Chris D
authors: CD
authors: Ivey
authors: Christian E
authors: CE
authors: Schlekat
authors: Emily Rogevich
authors: ER
authors: Garman
mesh_terms: D000818:Animals; D005618:Fresh Water; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007313:Insecta / Q000187:drug effects; D009532:Nickel / Q000032:analysis* / Q000633:toxicity; D009835:Oligochaeta / Q000187:drug effects; D013440:Sulfides / Q000032:analysis; D036401:Toxicity Tests, Chronic / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000633:toxicity
chemical_list: D013440:Sulfides; D014874:Water Pollutants, Chemical; C022838:nickel chloride; D009532:Nickel
keywords: Acid-volatile sulfide; Distribution coefficient; Nickel; Spiked sediment; Toxicity testing