ASSESSMENT OF AQUATIC ECOSYSTEM HEALTH AT THE PIKE HILL COPPER MINE SUPERFUND SITE, VERMONT
The sediment environment also indicates regions of impairment. On the basis of probable effects concentrations, sediment impairment was dominated by elevated Cu, and localized elevated Cd and Zn. Uncertain toxic effects were predicted throughout both brooks on the basis of equilibrium-partitioning sediment benchmarks, with one downstream exception that indicated no toxic effects. Laboratory toxicity testing on sediment indicated chronic toxicity to the amphipod Hyalella azteca and the midge Chironomus dilutus at some sites in both streams. Interestingly, toxicity was not indicated for either species in sediment from the most acidic metal-rich location, likely due to the low lability of Cu remaining in the sediment. Depositional habitat invertebrate richness and abundance data generally agreed with sediment toxicity and other ecosystem-health indicators.
In general, degraded surface-water and sediment quality, particularly from Cu, appears to be the dominant cause of toxicity. The biological community begins to recover at the most downstream locations in both brooks.