G. W. Suter II
Date Issued--May 1991
This assessment provides guidance for monitoring the environment off the Department of Energy (DOE) Oak Ridge Reservation for the purpose of estimating risks to the nonhuman environment. It is a companion to the screening assessment for human health effects (Hoffman, et al., 1991). The approach taken in both assessments was to screen contaminant chemicals into categories that reflect the need for monitoring. In this ecological assessment, the upper screening criterion is a level that indicates acute lethality or other severe effects. The intermediate screening criterion indicates a level of exposure that would be expected to cause low levels of effect in chronic exposures. The lower screening criterion is a ``safe'' concentration that is based on the intermediate criterion divided by a safety factor. The safety factors are based on consideration of the distribution of sensitivity among species, population and ecosystem processes that con amplify organism-level effects, and the appropriateness of the measures of exposure.
Screening criteria were developed for aquatic organisms, benthic organisms, and piscivorous wildlife and were applied to contaminant concentrations in water, sediment, and fish flesh. The criteria for aquatic and benthic organisms were based on national water quality criteria (NWQC) for protection of aquatic life or equivalent toxicity data. Because there are no sediment quality criteria and no suitable body of sediment toxicity data, the screening criteria for aquatic organisms were compared to estimated concentrations of organic chemicals in interstitial water and concentrations of metals in whole sediment. In addition, bioaccumulation factors were applied to concentrations in fish flesh to estimate water concentrations to which fish had been exposed, and these were compared to the screening criteria. The screening criteria for piscivorous wildlife were developed for this assessment from the best available data.
The exposure data were categorized into ten reaches: Melton Hill Reservoir (MHR), the portion of the Clinch River most influenced by White Oak Creek (WOCC), the Poplar Creek embayment (PCE), the portion of the Clinch River most influenced by Poplar Creek (PCC), Watts Bar Reservoir (WBR), Norris Reservoir (NR), Poplar Creek (PC), East Fork Poplar Creek (EF), Tennessee River (TN), and White Oak Lake (WOL). The off-site reaches most influenced by the operations at Oak Ridge facilities are MHR, WOCC, PCE, PCC, and WBR. Negative reference reaches, those that are not influenced by DOE facilities are NR and TR. Positive reference reaches, those that are on-site and heavily influenced by Oak Ridge facilities, are PC, EF, and WOL.
The reported maximum aqueous concentrations of aluminum, arsenic, boron, calcium, cadmium, chromium, copper, cyanide, lead, lithium, mercury, nickel, silver, sodium, uranium, and zinc exceeded upper or intermediate criteria (acute or chronic NWQC or estimated equivalent values) in off-site reaches that are influenced by Oak Ridge operations (MHR, WOCC, PCE, PCC). In addition, the maximum aqueous concentration of pentachlorophenol exceeded the upper criterion and PCB and phthalate ester concentrations exceeded the intermediate criterion in the PCE. Application of bioaccumulation factors to concentrations of arsenic, cadmium, copper, lead, selenium, and silver in fish tissues appears to confirm that exposures to high aqueous concentrations have occurred. However, concentrations of chromium, mercury, nickel, zinc, and PCBs in fish tissues suggest exposure concentrations that are lower that NWQC. Taken together, these results suggest that toxic effects have occurred in these waters. The magnitude and extent of these effects cannot be estimated because the form of the chemicals and their temporal and spatial distributions are undefined. Because the measurements may include biologically unavailable forms of the chemicals, the effects may be much smaller than these results suggest.
The available sediment concentrations for metals other than mercury are uninterpretable. Estimated pore-water concentrations of mercury exceed the intermediate criterion, suggesting that benthic organisms are affected. Intermediate criteria were also exceeded by the maximum estimated pore-water concentrations of Bis(2-exthlhexyl)phthalate in PCE and of phenanthrene in PCE and PCC. The detection limits for many other organic chemicals would result in pore-water concentrations that greatly exceed criteria.
Fish tissue concentrations of mercury are sufficient to cause toxic effects in piscivorous wildlife in all measured reaches including TR, but particularly in PCE and PCC. Selenium in fish from PCC and thallium in fish from MHR may be toxic to wildlife. DDT in the most contaminated fish from MHR and WOCC is sufficient to cause eggshell thinning in piscivorous birds. Mean PCB concentrations in fish are sufficient to cause reproductive failure in mink in all measured reaches but MHR and TR, and mean fish concentrations in those reaches are barely below the observed effects level. These results indicate that piscivorous wildlife along the Clinch River are at risk.
Although this screening assessment was intended primarily to eliminate chemicals from further consideration, it has eliminated relatively few. Metals in general cannot be eliminated because of the inability to interpret sediment concentrations and the high concentrations of several metals in water, sediment, and fish flesh, discussed above. Most of the organic chemicals measured in water were undetected and below screening criteria. However, only chloroform, bromodichloromethane, phenols, and total PCBs were measured in any reach other than the PCE, and they were measured only in WOCC. Therefore, organics in water cannot be eliminated. Most priority organics were measured in sediments from MHR, WOCC, PCE, PCC, and NR. Most were undetected, and some can be eliminated because the estimated pore-water concentration is below the lower criterion, but many are not eliminated. Most priority organics were measured in fish flesh from MHR, WOCC, and PCE, but not from reference reaches. Most were undetected, and many can be eliminated, but it is not possible to determine whether concentrations are elevated or what the sources are because of the absence of reference values. Finally, the occurrence of several chemicals in multiple media at potentially toxic concentrations raises the issue of combined toxic effects that are greater than those induced by any single chemical. Given these results, it is advisable to deemphasize measurement of sources of exposure relative to the measurement of biological indicators of exposure and effects.