1. Dept. of Envir. Health Sci., Univ. of South Carolina, Columbia, SC 29208.
2. Dept. of Envir. Health Sci. and Marine Sci. Prog., Univ. of South Carolina, Columbia, SC (corresponding author). E-mail aelionm@sc.edu
3. Dept. of Civ. and Envir. Engrg. Virginia Polytechnic Inst. and State Univ., Blacksburg, VA 24061-0105.