USING A TRIAD APPROACH IN THE ASSESSMENT OF HAZARDOUS-WASTE SITE LEACHING FROM A SUPERFUND SITE TO AN ADJACENT STREAM

A triad approach was used in the evaluation of sediment in the Wolf Ri ver adjacent to the North Hollywood Dump, a federally listed superfund site. Chemical analyses were done for 18 organochlorine pesticides, 2 1 polychlorinated biphenyl (PCB) congeners, and 10 metals. Sediment to xicity was evaluated with freshwater invertebrates, Chironomus tentans and Hyalella azteca. Benthic macroinvertebrate diversity and abundanc e were assessed with a family-level biotic index. Mean Al, Ba, Cd, Cu, Fe, Ni, Pb, and Zn concentrations were significantly higher in sedime nts collected in the spring. Both spring and fall sediments exhibited toxicity downstream from, adjacent to, and upstream from the dump, wit h toxicity significantly higher in fall sediments; however, a consiste nt trend was not observed. Toxicity was typically greater in the fall, and metal concentrations were typically higher in spring sediments, s uggesting that metals were not responsible for the toxicity. Sediment- associated organochlorine pesticide and PCB congener concentrations we re all below detectable limits, suggesting that these potential contam inants are not contributing to the observed toxicity. No differences w ere found in benthic macroinvertebrate community structure, which was composed of predominantly pollution-tolerant families, among seasons o r river reaches, which appear to be limited by the physical characteri stics of the river (e.g., substrate instability, low total organic car bon (<0.6%), and water velocity). Sediments in urban reaches of the Wo lf River appear to be degraded; the North Hollywood Dump cannot be iso lated as a source of toxicity in this study. In situ testing, sediment toxicity identification and evaluation testing, acid-volatile sulfide analyses, or artificial substrate work would be appropriate to follow .