A comparison of Shoreline Cleanup Assessment Technique (SCAT) visual observations of oiling and measured soil and sediment chemical concentrations following the 2010 Deepwater Horizon accident.

Abstract

Abstract This study examines the Deepwater Horizon SCAT results in comparison to measured chemical concentrations in shoreline sediments. Surface and subsurface oiling levels were grouped into oiling categories from Very Light to Heavy as per SCAT protocol. Discrete sediment and soil sample locations from the shoreline and immediate nearshore from 27 separate NRDA studies were separated into the SCAT oiling category zones. Measurements of chemical constituents associated with petroleum (i.e., PAH, saturated hydrocarbons, petroleum biomarkers) were used to evaluate the concentration and composition of petroleum present in samples. Hydrocarbon source interpretation (“fingerprinting”) was used to identify and exclude samples which were conclusively not DWH oil. Analysis of the chemical distributions in shoreline sediments shows that the oil character varied greatly in time and space, often over very small distances. Average PAH and alkane concentration data tend to agree with the SCAT designations, however, the concentration of petroleum chemicals in any individual sample could not be predicted by SCAT category alone. The results suggest limited predictive ability in specific locations; however, they are useful to estimate the average conditions within the landscape setting in the northern Gulf of Mexico and in the design of injury studies.