Sources of Uncertainty in the Application of the Equilibrium Partitioning Approach to Sediment Quality Assessment

One widely discussed method to assess biological impact of contaminated sediments is through the application of the equilibrium partitioning model. The partitioning model can be used to develop normalized chemical concentrations that can be correlated to biological effects resulting from sediment contamination. The application of the equilibrium partitioning model requires the measurement or estimation of several model variables. However, the combined uncertainties in the determination of these variables may limit the usefulness of this approach. Uncertainty in estimated pore water effects concentrations and analytical variability of three chemical measurements was investigated using Monte Carlo simulation. Results of Monte Carlo simulations indicated that the levels of analytical uncertainties in the study were acceptable. However, the results also revealed that analytical variability can significantly impair interpretation of the data and should be considered in the choice among different analytical methods. Investigation of duplicate field samples collected in the study indicated an additional source of uncertainty from the occurrence of spatially heterogeneous contaminant distributions.