title: Toxicity of silver in water and sediment to the freshwater amphipod Hyalella azteca.
abstract: Hyalella azteca was exposed to Ag as AgNO3 over a 10-d period in water and two lake sediments that were selected on the basis of their differences in metal-binding properties. The median lethal concentrations (LC50s) for waterborne exposures were 5.4 and 4.9 microg/L for total and dissolved Ag, respectively. In the sediment containing a lesser quantity of total Ag-binding ligands (i.e., Bond Lake, Douglas County, WI, USA, sediment), an Ag-amended sediment toxicity test resulted in a 10-d LC50 of 0.084 g (i.e., 84,000 microg) Ag/kg dry sediment or 8.6 microg Ag/L of pore water (PW). The no-observed-effect concentration (NOEC) to lowest-observed-effect concentration (LOEC) range was 0.012 to 0.031 g Ag/kg dry sediment, or less than 5.0 to 6.0 microg Ag/L of PW. In the sediment with a greater quantity of total Ag-binding ligands (i.e., West Bearskin Lake, Cook County, MN, USA, sediment), the 10-d LC50 was 2.98 g Ag/kg dry sediment, and the NOEC to LOEC range was 2.15 to 4.31 g Ag/kg dry sediment. Because "dissolved" concentrations of Ag in PW were less than 5.0 microg/L at the critical exposures in the latter test, the bioavailable and toxic form of Ag may have been a weakly associated coprecipitate or colloidal complex with hydrous iron oxides that competitively partitioned to the surface of the gills.
authors.affiliation: Department of Natural & Applied Sciences, University of Dubuque, Dubuque, Iowa 52001, USA. dcall@dbq.edu
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Call
authors.forename: Christine N
authors.initials: CN
authors.lastname: Polkinghorne
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Markee
authors.forename: Larry T
authors.initials: LT
authors.lastname: Brooke
authors.forename: Dianne L
authors.initials: DL
authors.lastname: Geiger
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Gorsuch
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Robillard
mesh_terms: D033304:Amphipoda / Q000187:drug effects*; D000818:Animals; D018533:Biomass; D005618:Fresh Water / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D012834:Silver / Q000008:administration & dosage / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D012834:Silver