Conclusions

The screening level ecological risk assessment for Nahant Marsh predicted lead poisoning and potential mortality in waterfowl receptors from the ingestion of spent lead shot in the marsh. The recovery of lead poisoned ducks and geese by natural resource personnel monitoring the site confirm the risks predicted for this exposure pathway.

The adversity of the predicted effects from other exposure pathways evaluated in the screening level ecological risk assessment has not been confirmed. However, there is adequate information in the screening level ecological risk assessment report to generally characterize ecological risks and help make risk management decisions for the site.

The uncertainties for the water toxicity and wetland sediment toxicity pathways may be resolved, if necessary, by collecting additional field data. The use of the additional field data will help increase the confidence and statistical power for the screening level risk calculations.

The remaining ecological risk pathways with uncertainties that were presented in the screening level ecological risk assessment include: 1) soil lead toxicity to plants and invertebrates, and 2) food chain lead hazards to avian receptors. The following risk questions were developed help resolve the uncertainties associated with the soil toxicity and food chain pathways. These risk questions may be used to help guide the development of further measures of effects and future site investigations, if deemed necessary.

Risk Questions:

1. What concentration of lead in the terrestrial soil represents a site-specific threshold for adverse effects to plants and soil dwelling invertebrates? Could this concentration be used as a preliminary clean up goal?

2. What is the long term impact to the meadow habitat in the lead shot fall zone from implementing the various risk management scenarios?

3. What is the site-specific earthworm bioaccumulation factor? Do the site- specific risk calculations for the avian food chain transfer models demonstrate the potential for adverse effects?