PARENT SESSION
PT5 - Fate & Effects of Metals: Aquatic Biology
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P606) Bioavailability and toxicity of lead and zinc to Leptocheirus plumulosus and Hyalella azteca.

Farrar, John^*,1, Bridges, Todd¹, Lotufo, Guilherme¹, ¹ US Army Engineer Research and Development Center, Vicksburg, MS, USA

ABSTRACT- Metals are among the most commonly occurring contaminants encountered when conducting sediment evaluations. The SEM-AVS/foc equilibrium partitioning model has been proposed as a screening tool for assessing metal contaminated sediments. However, few studies have been conducted evaluating the predictive capacity of the model following chronic exposures. To address the paucity of chronic metal toxicity data and to further evaluate the SEM-AVS/foc model utilizing chronic exposures, lead and zinc spiked sediment studies were conducted with H. azteca and L. plumulosus, respectively. The exposures were conducted following standardized chronic exposure test methods. Clean sediment was spiked with increasing concentrations of zinc (0, 250, 500, 1000, 2000 and 4000 ppm) or lead (0, 800, 1500, 3000, 6000 and 8000 ppm). A LOEC value of 3000 ppm lead was observed for survival in H. azteca. No effects on growth were observed. The LOEC values for L. plumulsous survival and growth were 500 ppm and 250 ppm zinc, respectively. The L. plumulosus growth LOEC value of 250 ppm zinc corresponds to an SEM-AVS/foc model value of 35.1 moles/gram OC and falls within the range where effects would not be predicted (<150 moles/gram OC). The LOEC value of 3000 ppm lead for H. azteca corresponds to a SEM-AVS/foc model value of 153.8 moles/gram OC and falls within the range where toxic effects are possible (>150 moles/gram OC). The model would have accurately predicted the absence of toxicity in the H. azteca experiment but would have predicted absence of toxicity where toxicity was observed in the L. plumulosus study. Additional testing of the model is warranted before definitive statements regarding the uncertainties in its applicability to chronic exposures, such as model failure rate, can be made.

Key words: zinc, lead, AVS, bioavailability