Spatial and temporal variation of polychlorinated biphenyls in the Houston Ship Channel

An on-going study in the Houston Ship Channel (HSC) characterized polychlorinated biphenyl (PCB) levels in sediment, water, and tissue in 2002-2003 and 2008. The observed PCB concentration ranges in all media were higher than those measured in other PCB-impacted water bodies in the world, with the highest concentrations occurring within the industrialized segments. Contrary to polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/PCDF) observations, the PCB concentrations in the dissolved phase were greater than the suspended phase. Possible explanations include passage of colloids, competition for adsorption sites from other hydrophobic contaminants, and continuing current sources. The PCB homologue distributions were similar for suspended water, sediment and tissue with the profile normalized around penta-chlorobiphenyls, while the dissolved phase profile normalized around tri-chlorobiphenyls. PCB-209 was detected in the suspended water phase and in sediment (10%) prompting interest into its sources to the HSC since PCB-209 was present only in rare commercial mixtures and is a byproduct in very few manufacturing processes. Inter-media analyses showed a significant correlation and transfer of PCBs. Dioxin-like PCBs contributed significant toxicity to total equivalent in tissue (33%), while they were insignificant in water (<10%) and sediment (<5%). The PCB concentrations over time showed a significant decrease in suspended water, sediment and tissue, while dissolved water concentrations showed insignificant change. The homolog distribution, however, showed a significant change in dissolved water and fish, a minor change in sediment and insignificant change in suspended water. Furthermore, an analysis for six representative congeners showed that they were accurate in predicting the total PCB concentrations and could be thus used as indicator PCBs.