Risk Assessment as a Decision-Making Tool for Treatment of Emissions at a New Aluminum Smelter in Iceland: 3. Ecological Assessment

ABSTRACT

Predictive ecological risk assessment was used to determine whether any risk-reduction benefit would result from the installation and operation of wet scrubbers at an aluminum smelter in East Iceland. Sulfur dioxide and hydrogen fluoride exposure will not result in any appreciable risk to mosses, lichens, lodgepole pine, and heather/heath grassland communities beyond the dilution zone without scrubbers. With scrubbers, exceedances of plant criteria may occur beyond the dilution zone. Critical concentrations of polycyclic aromatic hydrocarbons (PAHs) and hydrogen fluoride (HF) in terrestrial wildlife food items were converted to critical air concentrations, which were then compared to modeled air concentrations. Terrestrial wildlife species are not expected to be exposed to PAH concentrations that result in appreciable risk. If wildlife species are assumed to consume only grasses, predicted HF exposures will not result in exceedance of toxicity thresholds. However, if wildlife species are assumed to consume only heather, thresholds are exceeded at some locations for the rock ptarmigan and wood mouse. Results of population modeling indicate no potential for population impacts to rock ptarmigan outside the facility boundary. Impacts to wood mouse carrying capacity are expected to extend beyond the dilution zone with scrubbers, but not without.

Key Words:

• ecological risk assessment
• aluminum smelter
• sulfur dioxide
• hydrogen fluoride
• polycyclic aromatic hydrocarbons
• population model

Acknowledgments

The authors thank Melanie Edwards for technical assistance in statistical analyses, as well as Chris Shirley and Rick Nelson for technical editing, and Jason Pope for improving the graphical presentation of the data. Joe Scire and Irene Lee provided air and deposition modeling estimates used throughout the risk assessment. The authors also thank the anonymous reviewers whose comments and feedback significantly improved this article.

The authors received funding for this risk assessment from Alcoa. The opinions expressed are the independent scientific views of the authors.

Notes

^a Mean or median adult body weight, females;

^b Food ingestion rate (Rodentia) = 0.332 BW^0.774;

^c Food ingestion rate (Galliformes) = 0.088 BW^0.891;

^d Food ingestion rate (Herbivores) = 0.859 BW^0.628;

^e Value is for meadow vole;

^f Value is for wild turkey;

^g Yearly average for sheep, pasture as only feed source.

^a Values derived from Horntvedt (1997);

^b Senescence period derived from NZDC (1995).

^a Values derived from data provided by WMO (2005);

^b Based on an assumed growth season of April 1 to September 30.

^a Bengston et al. (1989);

^b Developed from observations reported in Bengston et al. (1989).