Many groundwater remediation designs for contaminant plume containment are developed using mathematically based groundwater now models. These mathematical models are most eiTective as predictive tools when the parameters that govern groundwater flow are known with a high degree of certainty. The hydraulic conductivity of an aquifer, however, is uncertain, and so remediation designs developed lIsing models employing one realization of the hydraulic conductivity field have an associated risk of failure of plume containment. To account for model uncertainty attributable to hydraulic conductivity in detennining an optimal groundwater remediation deSign for plume containment, a method of optimization called robust optimization is utilized, This method of optimization is a multi scenario approach whereby mUltiple hydraulic conductivity fields are examined simultaneously. By examining these fields simultaneously, the variability of the uncertainty is included in the model. To increase the efficiency of the robust optimization approach, a sampling technique i.' > developed that allows the modeler to determine the minimum number of field realizations necessary to achievc a reliable remediation design.

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Endocrine-disrupting compounds (EDCs), including 17α-ethinyl estradiol (EE2) and 4-nonylphenol (4-NP), enter coastal environments primarily in effluents of wastewater treatment facilities and have become ubiquitous in marine surface waters, sediments, and biota. Although EE2 and 4-NP have been detected in marine shellfish, the kinetics of bioconcentration and their tissue distribution have not been thoroughly investigated. The authors performed bioconcentration and depuration experiments in the blue mussel, Mytilus edulis, with 3.37 nM EE2 (0.999 μg/L) and 454 nM 4-NP (100.138 µg/L). Mussels and seawater were sampled throughout a 38-d exposure and a 35-d depuration period, and 6 tissues were individually assayed. Uptake of EE2 and 4-NP was curvilinear throughout exposure and followed a similar uptake pattern: digestive gland > gill ≥ remaining viscera > gonad > adductor > plasma. Depuration varied, however, with half-lives ranging from 2.7 d (plasma) to 92 d (gill) for EE2 and 15 d (plasma) to 57 d (gill) for 4-NP. An innovative modeling approach, with 3 coupled mathematical models, was developed to differentiate the unique roles of the gill and plasma in distributing the EDCs to internal tissues. Plasma appears pivotal in regulating EDC uptake and depuration within the whole mussel.