Longitudinal estimates of sediment-water diffusive flux of PCB congeners in the Houston Ship Channel

Abstract

Sediment-water diffusive exchange fluxes were estimated for PCB congeners between 2002 and 2012 for the Houston Ship Channel in Texas. These estimations were determined for four different sampling periods representing a unique effort to quantify fluxes, their magnitudes and variability, over a longer time period than similar studies. Total PCB fluxes, on the order of 0.10–250 μg/m2-yr, were most dependent on bulk sediment and total water concentrations and the partitioning models used. Diffusive flux directions were highly variable on a single-PCB analyte basis though they were generally sediment-to-water or indeterminate. Sediment concentrations from after Hurricane Ike (September 2008) were highly elevated (median increase 360%) from immediately before the event leading to much higher diffusive flux estimates. Lastly, sediment-water diffusive flux was 2–3 orders of magnitude less than net deposition and associated desorption fluxes leading to the possibility that burial would eventually lower the sediment impact to the estuary. This is, however, uncertain because depositing sediment still had elevated PCB concentrations.