THE ROLE OF ACID VOLATILE SULFIDE AND INTERSTITIAL WATER METAL CONCENTRATIONS IN DETERMINING BIOAVAILABILITY OF CADMIUM AND NICKEL FROM CONTAMINATED SEDIMENTS TO THE MARINE POLYCHAETE NEANTHES ARENACEODENTATA

This study investigated the influence of acid-volatile sulfide (AVS) a nd interstitial water (IW) metal concentrations on bioavailability and toxicity of Cd and Ni to an infaunal sediment-ingesting marine worm, Neanthes arenaceodentata. Ten-d exposures were conducted with sediment s, contaminated primarily with Cd and Ni, from Foundry Cove (Hudson Ri ver, NY), and with uncontaminated sediments spiked with Cd or Ni. Mola r ratios of simultaneously extracted metal (SEM)/AVS ranged from <0.02 to 44 for Cd-spiked, 0.02 to 241 for Ni-spiked, and <0.06 to 125 for Foundry Cove sediments. In all experiments, significant mortality was not observed when SEM/AVS ratios were <1.0 and interstitial water toxi c units (IWTU) were <1.0 (toxic unit = IW metal concentration/LC50 val ue of water-only exposure). In the Cd and Ni-spiked experiments, when SEM/AVS ratios or IWTUs were >1.0, sediments were either lethal or wor ms did not burrow. Mortality of worms in Foundry Cove sediments was le ss than or equal to 20%, and worms burrowed in all these sediments. Ho wever, IW contained <1.0 TU (Ni + Cd) in all Foundry Cove sediments ex cept one (IWTU = 1.69). Metal concentrations in worms generally increa sed with increases in sediment metal concentration, SEM/AVS molar rati o, and IW metal concentration. The presence of metal in worms from sed iments with SEM/AVS ratios <1.0 may be evidence of release of Cd or Ni from oxidized metal sulfide (a result of burrowing), uptake of metal from ingested sediment, or adsorption to body surfaces. These results support the hypothesis that when the concentration of AVS in sediments exceeds that of divalent metals (Cd, Cu, Hg, Ni, Pb, Zn) sediments wi ll not be acutely toxic. However, a greater number of sediments was co rrectly predicted to be nontoxic when interstitial water metal concent ration of <1.0 TU was used.