M7 PM Metals in the Environment: Aquatic Biological Perspectives
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 327-329

(AAA-1117-802093) Nickel speciation and toxicity in spiked European surface waters.

De Schamphelaere, K¹, Van Laer, L², Smolders, E², Playle, R³, Muyssen, B¹, Klinck, J³, Janssen, C¹, ¹ Ghent University - Laboratory of Environmental Toxicology and Aquatic Ecology, Gent, Belgium² KU Leuven - Laboratory of Soil and Water Management, Leuven, Belgium³ Wilfried Laurier University - Biology Department, Waterloo, ON, Canada

ABSTRACT- Six natural surface waters varying in pH (6.1-8.1), water hardness (15-218 mg CaCO₃/L), DOC (3.2-25.9 mg/L), and total alkalinity (2.3-144 mg CaCO₃/L) were sampled. DOC was mainly of a terrestrial origin as indicated by McKnights fluorescence indexes of about 1.4. Those waters were spiked with a range of Ni concentrations and subsequently subjected to speciation measurements and acute and chronic toxicity tests with Ceriodaphnia dubia. Free Ni²⁺ concentrations were determined with a Donnan-membrane technique. Overall, the fractions of free Ni²⁺ (Ni²⁺/dissolved Ni)varied between 4 and 60% over the concentrations range investigated, i.e. 3 to 150 ug Ni/L . The fraction of free Ni²⁺ increased within increasing hardness and decreasing pH. The fraction free Ni²⁺ was unaffected by equilibration time after spiking (2 hours - 7 days). Toxicity experiments yielded 48h-LC50s between 35 and 183 ug Ni/L and reproductive 10d-EC50s between 4.9 and 68 ug Ni/L. Linear relations with DOC explained 86% and 82% of the variability in 48h-LC50s and 10d-EC50s, respectively. UV-absorbance properties of the DOC could not explain additional variability. This indicates the important role of DOC-concentration in reducing Ni toxicity at low Ni concentrations. Ratios of 48h-LC50s to 10d-EC50s were between 1.5 and 8.0 and significantly increased with increasing alkalinity. This is explained by an increased chronic toxicity at higher alkalinity levels. These results stress the importance taking into account the effects of parameters such as pH, hardness, DOC and alkalinity in aquatic risk assessment of Ni.

Key words: Ceriodaphnia dubia, nickel toxicity, speciation, WHAM