On Describing and Estimating the Fate of Stranded Oil

Abstract

ABSTRACT The prediction of stranded oil fate and natural removal rates is essential to the selection of environmentally appropriate shoreline cleanup techniques, environmental priorities and tradeoffs. Our experience is that monitoring and describing stranded oil fate and persistence is not an exact science. Interpretation of data requires a careful and experienced approach. The need for a consistent long-term data set and appropriate methodology is stressed. A review of the different data and indices leads to the conclusion that length of oiled shoreline is unsuitable as a detailed measure of the degree of oiling and of changes in shoreline oiling. Length (and width) data are more appropriate for scoping estimates and qualitative uses. On coarse or mixed sediment beaches, quantitative oil penetration and concentration data are very difficult to obtain and interpret, affecting the calculation of oil volumes or oiled sediment volumes. Equivalent Area (EA) oiled appears to be the most appropriate and practical all-round index for the degree of shoreline oiling and for comparing temporal changes. Surface oil cover data become less representative of subsurface oil over time due to differential removal rates. Indices of change of beached oil and data sets generated from various spill monitoring programs are examined. Long-term data from the Baffin Island Oil Spill Project provide information on rates of change that can be applied to projections for real-world spills, by representing one worse-case boundary condition for coarse sediment beaches.