W4 PM Sediment Quality Assessment
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in Ballroom 4

(BEC-1117-849406) Field evaluation of chromium toxicity in sediments of the Hackensack River, New Jersey.

Becker, D.¹, Proctor, D.¹, Ginn, T.¹, ¹ Exponent, Inc., Bellevue, WA, USA

ABSTRACT- Recent studies by USGS and EPA have evaluated the potential toxicity of chromium in freshwater and marine sediments, primarily in laboratory experiments in which clean sediments were spiked with known amounts of chromium. Results of the two studies indicate that chromium is largely insoluble and nontoxic when it is in the form of Cr(III), as opposed to the more soluble and toxic form of Cr(VI). EPA also evaluated field sediments collected from a marine site and found that chromium concentrations as high as 1,780-3,070 mg/kg did not result in elevated mortality in the 10-d sediment toxicity test with the marine amphipod Ampelisca abdita. These results indicate that chromium may not be toxic, even when concentrations are considerably greater than existing sediment quality values, all of which are less than 400 mg/kg. In this study, we evaluate the toxicity of chromium in sediments from the Hackensack River near a former chromite ore processing facility. The primary objective was to determine site-specific no-effect levels using both short-term and chronic sediment toxicity tests (i.e., the 10-d test with Ampelisca abdita and the 28-d test with the estuarine amphipod Leptocheirus plumulosus, respectively). Percent survival was a toxicity endpoint for both tests and biomass was an additional endpoint for the 28-d test. Evaluations were also conducted of chromium speciation and chromium-bearing phases in the test sediments (i.e., using electron microprobe analysis). Results of this study generally agree with those of USGS and EPA in showing that chromium can be present in sediments at highly elevated concentrations without resulting in sediment toxicity. Concentrations of total chromium as high as 1,310-1,490 mg/kg did not result in sediment toxicity in sediments from the Hackensack River. Nearly all chromium was present in the relatively nontoxic form of Cr(III). In addition, most chromium was present as the mineral chromite or sorbed to iron oxide, and chromium in both of those phases has limited bioavailability. The results of this study indicate that existing sediment quality values for chromium should not be used as pass/fail criteria for identifying the presence of sediment toxicity in site-specific cases where the bioavailability and toxicity of chromium may be limited.

Key words: sediment toxicity, chromium, bioavailability, amphipod tests