title: An evaluation of the bioavailability and aquatic toxicity attributed to ambient zinc concentrations in fresh surface waters from several parts of the world.
abstract: Ambient concentrations of metals in surface waters have become an important consideration when establishing water quality criteria and conducting risk assessments. This study sought to estimate amounts of zinc that may be released into freshwater considering ambient concentrations, toxicity thresholds, and bioavailability. Cumulative distribution functions of ambient zinc concentrations were compared statistically for streams and lakes in Europe, North America, and South America to identify differences among mean distribution variables (e.g., slopes, intercepts, and inflection points). Results illustrated that most of the distributions among sites differed significantly. These differences illustrate the variability in ambient zinc concentrations in surface waters because of geographic location, regional geology, and anthropogenic influence. Additionally, water quality data were used to estimate bioavailable zinc concentrations in ambient surface waters (based on predictions using biotic ligand models). The amount of dissolved metal that could be added to surface waters without exceeding toxicity thresholds was calculated by subtracting ambient surface water concentrations from chronic no observable effect concentrations (NOEC; reproduction for Daphnia magna) or 10% effective concentrations (EC10; growth rate for Pseudokirchneriella subcapitata). Because ambient dissolved-zinc concentrations were, on average, below predicted effects thresholds, an average of 57.1 +/- 175 microg/L (+/- SD) of zinc could be added before exceeding the D. magna chronic NOEC or the P. subcapitata chronic EC10. However, numerous sites (17%) were identified as having ambient zinc concentrations in excess of these toxicity thresholds. This article uses existing biotic ligand models for zinc to estimate the potential magnitudes and variabilities of bioavailable zinc concentrations in fresh surface waters from different regions of the world.
authors.affiliation: International Zinc Association, 1822 NC Highway 54 East, Suite 120, Durham, North Carolina 27713, USA. evangenderen@iza.com
authors.forename: Eric
authors.initials: E
authors.lastname: Van Genderen
authors.forename: William
authors.initials: W
authors.lastname: Adams
authors.forename: Rick
authors.initials: R
authors.lastname: Cardwell
authors.forename: Joe
authors.initials: J
authors.lastname: Volosin
authors.forename: Robert
authors.initials: R
authors.lastname: Santore
authors.forename: Patricio
authors.initials: P
authors.lastname: Rodriguez
mesh_terms: D000818:Animals; D001682:Biological Availability; D003621:Daphnia / Q000378:metabolism; D005060:Europe; D005618:Fresh Water / Q000737:chemistry*; D009656:North America; D013020:South America; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity*; D015032:Zinc / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D015032:Zinc