Speciation, behavior, and bioavailability of copper downstream of a mine-impacted lake

• Published in: Environmental toxicology and chemistry Vol. 26; no. 12; pp. 2594 - 2603
• Main Authors: Martin, A.J, Goldblatt, R
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Periodicals, Inc 01-12-2007; Blackwell Publishing Ltd
• Subjects: animal reproduction; Animals; Aquaculture; Aquatic animals; aquatic arthropods; Bioavailability; Biological Assay; Biological Availability; Biota; Canada; Ceriodaphnia dubia; chemical speciation; Cladocera - drug effects; Copper; Copper - analysis; Copper - toxicity; Daphnia - drug effects; Diffusive gradients; diffusivity; Discharge; Dissolved organic carbon; Drainage; ecotoxicology; Environmental Monitoring; filtration; Lakes; Lethal Dose 50; Membranes, Artificial; Minerals; Mining; Reproducibility of Results; sediment contamination; sediments; Soils; solutions; Speciation; Specimen Handling; streams; sulfates; Surface Properties; Thin films; toxicity testing; Toxicity Tests, Acute; Water column; Water effect ratio; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - toxicity; Water pollution; Water quality; Ontario; Canada; Canada, Ontario, Prince Edward Cty., East L
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1897/07-038.1

A combination of Cu speciation analysis and toxicity testwork was conducted to assess the behavior, speciation, and bioavailability of Cu in a stream system rich in dissolved organic carbon (DOC) downstream of a mine‐impacted lake (East Lake, ON, Canada). Elevated levels (∼50 μg/L) of Cu exist in the lake due to the release of dissolved Cu to the water column from underlying sediments. Most of the Cu present in East Lake and downstream is present as filterable species that represent 74 to 100% of the total. Measurements of labile Cu as measured by diffusive gradients in thin films (DGT) suggest that most of the Cu is unavailable to aquatic biota. The DGT results indicate that 9 to 24% of Cu within the receiving environment is biologically available. Decreases in the labile Cu fraction with distance downstream of East Lake correlate well with increases in the concentration of DOC (r2 = 0.79–0.95), presumably due to the progressive importance of Cu‐organic complexes. The relationship between filterable Cu and SO2−4 downstream of East Lake was linear (r2 = 0.99) for all sampling periods, suggesting that decreases in filterable Cu concentration downstream of East Lake could be attributed solely to dilution (i.e., conservative behavior). Variations in the filterable Cu concentration resulting in 50% mortality (LC50 = 96–203 μg/L) and the concentration resulting in an inhibition of reproduction by 25% (IC25 = 75–156 μg/L) with respect to Ceriodaphnia dubia (7‐d incubation) in Cu‐spiked solutions could be explained by differences in labile‐Cu concentrations as determined by DGT. The considerable complexation capacity afforded by lake and stream waters can be attributed to complexation of Cu with abundant DOC (7–17 mg/L). The relevance of the toxicity data to water‐effect ratio testwork, and the associated development of site‐specific water quality objectives, are discussed.