Bioavailability models for predicting acute and chronic toxicity of zinc to algae, daphnids, and fish in natural surface waters.
Bioavailability models predicting acute and/or chronic zinc toxicity to a green alga (Pseudokirchneriella subcapitata), a crustacean (Daphnia magna), and a fish (Oncorhynchus mykiss) were evaluated in a series of experiments with spiked natural surface waters. The eight selected freshwater samples had varying levels of bioavailability modifying parameters: pH (5.7-8.4), dissolved organic carbon (DOC, 2.48-22.9 mg/L), Ca (1.5-80 mg/L), Mg (0.79-18 mg/L), and Na (3.8-120 mg/L). In those waters, chronic zinc toxicity (expressed as 10% effective concentrations [EC10]) varied up to 20-fold for the alga (72-h EC10 from 27.3 to 563 microg Zn/L), and approximately sixfold for the crustacean (21-d EC10 from 59.2 to 387 microg Zn/L), and fivefold for the fish (30-d LC10, lethal concentration for 10% of the organisms, from 185 to 902 microg Zn/L). For P. subcapitata a refined bioavailability model was developed by linking an empirical equation, which predicts toxicity expressed as free Zn2+ activity as a function of pH, to the geochemical speciation model WHAM/Model V. This model and previously developed acute and/or chronic biotic ligand models for D. magna and 0. mykiss generally predicted most effect concentrations by an error of less than a factor of two. In waters with pH > 8, however, chronic toxicity to D. magna was underestimated by a factor 3 to 4. Based on the results of this validation exercise and earlier research, we determined applicability ranges for pH (6-8) and Ca (5-160 mg/L) in which all three developed models are valid. Within these ranges, all three models may be considered useful tools for taking into account bioavailability in regulatory assessments of zinc.
De Schamphelaere
Karel A C
KA
Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, Jozef Plateaustraat 22, B-9000 Gent, Belgium. karel.deschamphelaere@ugent.be
Lofts
Stephen
S
Janssen
Colin R
CR
D000818:Animals; D001682:Biological Availability; D003621:Daphnia / Q000187:drug effects* / Q000378:metabolism; D056890:Eukaryota / Q000187:drug effects* / Q000378:metabolism; D005399:Fishes / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D018570:Risk Assessment; D023382:Toxicity Tests, Acute / Q000379:methods; D036401:Toxicity Tests, Chronic / Q000379:methods; D014867:Water / Q000737:chemistry*; D014873:Water Pollutants / Q000633:toxicity; D015032:Zinc / Q000633:toxicity*
D014873:Water Pollutants; D014867:Water; D015032:Zinc