FATE AND TRANSPORT MODELING OF PCBS IN THE HOUSTON SHIP CHANNEL ESTUARY

摘要

The Houston Ship Channel (HSC) is a highly industrialized corridor both for commercial shipping and petrochemical activities. As is the case with many such industrialized areas, there are high concentrations of persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs). This study brings together PCB data from five separate sampling events between 2002 and 2009 in several media (bed sediment, water, and tissue) to develop a hydrodynamic water quality model using Environmental Fluid Dynamics Code (EFDC). The model incorporates specific known PCB sources from industry, urban runoff, and Superfund sediment sites to quantify external loads and internal PCB contaminant transport. Two specific research objectives were in view concerning the model's development. The first is to understand the role of the bed sediment in the overall contaminant picture. It is fairly clear that a large repository of PCBs exists throughout the HSC, some in areas that are highly localized and others over a larger sediment region spanning an entire reach of the estuary. But, due to complex pathways for the movement of bed sediment and the bioavailability of PCBs in the bed sediment, it is not as clear how important bed sediment is with regards to overall PCB loading and risk as compared with other sources. The second research objective is to evaluate temporal trends in water and sediment PCB contamination in the HSC, especially with regard to the area of the HSC upstream of the San Jacinto River, which contains the highest concentration of industrial activities. Though PCB contamination generally seemed to be decreasing from 2002-2008, the concentrations increased from 2008-2009. Unusually long dry periods and Hurricane Ike are possible explanations for the increase.