Application of DART® Technology in the Delineation of Hydrocarbon Impacted Sediments

The delineation of hydrocarbons in sediments can be a difficult and expensive process typically requiring the sampling of sediments over a large area. This paper discusses an alternative approach utilizing DART technology, which utilizes the physical property of petroleum hydrocarbon fluorescence to delineate the presence of polyaromatic hydrocarbons in sediments. Specifically, the DART sampler is comprised of solid rods made from or coated with solid phase extraction (SPE) media. Upon insertion into the subsurface, the PAHs present in the sediment will adsorb onto the DART sampler in response to the high affinity of the SPE material. Upon migration of the PAHs into the DART samplers, they are held within the SPE matrix and remain trapped almost indefinitely. The DART samplers are then retrieved and analyzed using the Laser-Induced Fluorescence (LIF) technology.  Hence, a vertical profile of the PAH concentration in sediment is reflected along the length of the DART sampler.

DART samplers were utilized to delineate hydrocarbon sediments in an area off-shore of a former sludge impoundment associated with a petroleum hydrocarbon facility. The off-shore sediments were composed of clays and silts. The DART samplers were utilized after the application of MIP technology proved to have limited success. In contrast, the response of the DART samplers provided a clear image of the presence of hydrocarbons in the sediments. Moreover, the response was calibrated to TPH analyses from sediment samples collected from retrieved cores. Utilizing the calibration, a semi-quantitative analysis of the relative hydrocarbon impacts could be made both horizontally and vertically throughout the shoreline area.