Lw. Hall et al., ACUTE AND CHRONIC TOXICITY OF COPPER TO THE ESTUARINE COPEPOD EURYTEMORA-AFFINIS - INFLUENCE OF ORGANIC COMPLEXATION AND SPECIATION, Chemosphere, 35(7), 1997, pp. 1567-1597
The objectives of this study were to conduct acute (48 and 96h) and ch
ronic (8d) copper toxicity tests with the estuarine zooplankter, Euryt
emora affinis and develop an acute-to-chronic ratio (ACR) for this spe
cies. Dissolved copper, copper speciation and organic complexation wer
e measured on selected samples during these toxicity tests. Organic co
mplexation measurements were critical to determine the bioavailability
of copper to the test species. Concentrations of dissolved copper at
selected test conditions displayed a loss of 20 to 35% over the course
of the acute and chronic experiments with the most significant loss o
ccurring during the first 48 hours. Due to the loss of dissolved coppe
r during exposures, a decay model was developed to calculate the adjus
ted dissolved copper concentrations that were used to determine the fi
nal toxicity values. The 48h LC50, 96h LC50 and 8d chronic values were
83.0, 69.4 and 64 mu g/L dissolved copper, respectively, using the ad
justed dissolved copper concentrations. An acute-to-chronic ratio of 1
.3 was calculated using the 48 h and 8 d toxicity values. Voltammetric
analysis of selected samples indicated greater than 99% complexation
of copper in all samples with complexing capacity increasing with both
time and copper concentration. The non-complexed inorganic copper con
centration was therefore a very small fraction ofthe total copper adde
d during these experiments. Non-complexed inorganic copper (II) specia
tion predicted by a model identified seven significant species of copp
er. Of these seven species, CuCO3 was the dominant species accounting
for approximately 78% of the total copper. The free cupric ion (Cu2+)
accounted for only 8% of the dissolved non-complexed inorganic fractio
n, or less than 0.2% ofthe total copper in solution. (C) 1997 Elsevier
Science Ltd.