The Development of Comparative Information Yield Curves for Application to Subsurface Characterization.

Defining rational and effective hydrogeological data acquisition strategies is of crucial importance in subsurface contamination as such efforts are always resource limited. Usually strategies are developed with the goal of reducing uncertainty, but less often they are developed in the context of their impacts on uncertainty. This work presents an approach for determining subsurface site characterization needs based on human health risk. The main challenge is in striking a balance between reduction in uncertainty in hydrogeological, behavioral and physiological parameters. Striking this balance can provide clear guidance on setting priorities for data acquisition and for better estimating adverse health effects in humans. This challenge is addressed through theoretical developments and numerical simulation. A wide range of factors that affect site characterization needs are investigated, including the dimensions of the contaminant plume and additional length scales that characterize the transport problem, as well as the model of human health risk. With the proposed approach, conditions are investigated where reduction of uncertainties from flow physics, human physiology and exposure related parameters might contribute to a better understanding of human health risk assessment. The concept of comparative information yield curves is used for investigating the relative impact of hydrogeological and health-related parameters in risk. Results show that characterization needs are dependent on the ratios between flow and transport scales within a risk-driven context. Additionally these results indicate that human health risk becomes less sensitive to hydrogeological measurements for large plumes. This indicates that under near-ergodic conditions, uncertainty reduction in human health risk may benefit from better understanding of the physiological component as opposed to a more detailed hydrogeological characterization. Other results show that the worth of hydrogeological characterization in human health risk depends on the interplay between the characteristic time the contaminant plume takes to cross an environmentally sensitive target and on the exposure duration of the population. Finally, the role of geostatistical model uncertainty in defining sampling networks and its relevance in human health risk is also addressed.