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The State of the Bay Galveston Bay Area Project

Chlorinated Organic Compounds in Galveston Bay Sediments

 

Contamination of water, sediment, and tissue with chlorinated organic compounds can come from many sources. Contamination of surface waters and sediments may come from point sources (identifiable sources at specific locations such as wastewater outfalls) or nonpoint sources (multiple sources located across a relatively large area such as urban runoff). Whereas nonpoint sources are often associated with bacterial contamination and excess nutrient runoff, point sources are typically associated with chlorinated organic compounds such as polychlorinated biphenyls (PCBs) and dioxins. Given that Galveston Bay has had large industrial complexes such as those along the Houston Ship Channel and in Texas City operating along its shore for more than 50 years; it should come as no surprise that some areas of the Lower Galveston Bay watershed have problems with contamination of chlorinated organic compounds. This type of contamination is often associated with high intensity land use. High intensity development is defined as having impervious surfaces account for 80 to 100 percent of the total cover and is representative of large industrial and commercial complexes.

As with metals, samples of chlorinated organic compounds are typically collected in the sediments rather than directly from the water column. In the case of these compounds, even better information may be obtained by analyzing concentrations in tissue of living organisms. Concentrations of chlorinated organic compounds in fish tissue are discussed in Seafood Safety - Toxics.

Industrial organic compounds are primarily sampled in sediments of the Houston Ship Channel where much of the bay’s industrial activity takes place. An indicator comparing sediment samples of these compounds to TCEQ (2008) screening levels was initially developed by the Galveston Bay Indicators Project (Lester and Gonzalez 2005). As seen in the indicator below, most areas of Galveston Bay, with the exception of the Houston Ship Channel, do not appear to have large problems with toxic organics in sediment. However, samples collected from the Houston Ship Channel show elevated concentrations of PCBs and semivolatile organics, including polycyclic aromatic hydrocarbons (PAHs). Some PAHs are manufactured, but most are created through the incomplete combustion of organic compounds. Two samples of lindane and chlordane collected in the year 2000 in West Bay exceeded the TCEQ screening levels. Samples were collected from 1973-2009.

 

organics indicator

 

Literature Cited:

Lester, L. J., and L. A. Gonzalez. 2005. Galveston Bay Indicators Project Final Report. Webster, Texas: Texas Commission on Environmental Quality (TCEQ), Galveston Bay Estuary Program (GBEP).

TCEQ. 2008. Guidance for assessing and reporting surface water quality in Texas. Austin, Texas: Texas Commission on Environmental Quality.

 

 
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