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Characterization Of Contaminant Migration Potential In The Vicinity Of An In-Place Sand Cap
Citation:
Merritt, K. A., R. Fimmen, B. Sass, E. Foote, M. A. MILLS, J. Leather, AND V. Magar. Characterization Of Contaminant Migration Potential In The Vicinity Of An In-Place Sand Cap. Journal of Soils and Sediments. Springer-Verlag, BERLIN-HEIDELBERG, Germany, 10(3):440-450, (2010).
Impact/Purpose:
To characterize the chemical transport potential of polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) in the vicinity of a sand cap placed in the nearshore zone of a tidal marine embayment.
Description:
This study characterized the chemical transport potential of polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) in the vicinity of a sand cap placed in the nearshore zone of a tidal marine embayment. Groundwater seepage was investigated along the perimeter and within the footprint of the sand cap, with results verifying the presence of significant freshwater upwelling shoreward of the sand cap boundary. The depth distribution of PAHs and TPHs was assessed in sediment cores collected from within the nearshore area, as well as from within the cap area footprint. The depth distribution of PAHs and TPHs demonstrated a spatial pattern of elevated chemical concentrations in the nearshore area relative to the capped area, consistent with the spatial pattern of elevated freshwater flux. Visual inspection of recovered cores confirmed the presence of a fine-grained, low conductivity sediment layer underlaying the sand cap, with material properties of this layer potentially suggesting compaction following placement of the sand cap. This fine-grained sediment layer was not evident in cores collected shoreward of the sand cap. The presence of the aquitard under the sand cap, coupled with the apparent erosion of this fine-grained layer in the higher energy shoreward zone suggests the potential for enhanced groundwater seepage in the shoreward zone of the sand cap. It is hypothesized that enhanced groundwater flux is responsible for the elevated concentrations of PAH and TPH observed in core profiles collected from the zone characterized by elevated freshwater seepage and tidal pumping.
