PARENT SESSION
70 - Metal Pollution: From Exposure to Ecological Effects
8:00 AM to 6:30 PM, Wednesday, 15 May 2002
Exhibition Area

(70-43) A copper bioavailability model for the green alga Raphidocelis subcapitata.

De Schamphelaere, Karel^*,1, Heijerick, Dagobert¹, Janssen, Colin¹, ¹ Laboratory of Environmental Toxicology and Aquatic Ecology - Jozef Plateaustraat 22, Ghent, Belgium

ABSTRACT- In this study, the results of a series of 72 hour toxicity tests were used to establish a model aimed at predicting threshold concentrations of copper to the green alga Raphidocelis subcapitata. The combined effects of pH, water hardness and dissolved organic carbon (DOC) on the ecotoxicity of copper to this algal species was investigated in a multi-factorial, central composite test design. Natural dissolved organic matter (DOM) was collected at three sites (Bihain, Belgium; Ossenkolk, Netherlands and Ankeveen, Netherlands) using reverse osmosis. With these three DOMs, a total of 35 toxicity tests was conducted. Overall, 72-hour E_bC10s ranged from 14.2 to 176 g Cu L^-1 (factor 12) and E_bC50s from 26.9 to 507 g Cu L^-1 (factor 20). Where determined, 72-hour NOE_bCs ranged from 19.4 to 174 g Cu L^-1 (factor 9) and were in close agreement with 72-hour E_bC10s. Measurements of free copper ion activities during the experiments learned that (1) Bihain and Ossenkolk DOM could complex more copper than Ankeveen DOM, resulting in a larger copper protective effect and (2) significant linear relationships could be established pH and log(72-hour E_bC50_Cu2+) or log(72-hour E_bC10_Cu2+): log(72-hour E_bC50_Cu2+) = -1.401 x pH + 1.863 (R²=0.97), and log(72-hour E_bC10_Cu2+) = -1.225 x pH - 0.077 (R²=0.96). By linking the equations to the geochemical speciation program WHAM, accurate predictions (within factor 2) could be made of 72-hour E_bC50s and E_bC10s, not only for the 35 toxicity tests, but also for copper toxicity tests performed in 13 European surface waters.

Key words: Biotic Ligand Model, copper toxicity, natural dissolved organic matter, raphidocelis subcapitata (green alga)