Research Article: DDT, Dioxins, and PCBs in Sediments in a Historically Polluted Estuary along the Gulf of Mexico

Abstract

This study assessed current profiles of organochlorine pollutants in sediment of Escambia Bay and River in northwest Florida, United States (US), which experienced catastrophic environmental collapse in the 1970s as a result of unregulated industrial and domestic sewage releases. Fifty-seven composite sediment samples were collected with a ponar grab sampler. Organochlorines were extracted with United States Environmental Protection Agency (USEPA) Method 3550 and concentrations were determined with USEPA Method 1668A for polychlorinated biphenyls (PCBs), USEPA Method1613B for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and USEPA Method 8081A for 4,4′-dichlorodiphenyltrichloroethane (DDT), 4,4′-Dichlorodiphenyldichloroethane (DDD), and 4,4′-Dichlorodiphenyldichloroethylene (DDE). For PCBs, 12 (21%) out of the 57 samples exceed the Florida threshold effects level (TEL) of 21.6 μg/kg and no sample exceeds the Florida probable effects level (PEL) of 189 μg/kg. The 17 PCDD/F congeners that are considered to have significant toxicity have a mean of 1.9 μg/kg and a range of 0.022–11 μg/kg. The mean total toxic equivalence value (TEQ) of PCDD/Fs and dioxin-like PCBs for the sediments is 2.6 ng/kg. About 56% of the samples exceed the US National Oceanic and Atmospheric Administration (NOAA) TEL for total TEQ, 23% of which also exceed the NOAA TEL, implying that these total TEQ toxicities can impact sediments adversely. DDT was detected in 25% of the samples. All but one of the detections were in the river and adjacent wetlands. The detected DDT concentrations exceed the Florida PEL (4.77 μg/kg) except for one sample that only exceeds the TEL (1.19 μg/kg). The common DDT degradation products, DDD and DDE, were not detected in the river and wetland sediments.

Acknowledgments

This study was supported by US Environmental Protection Agency Cooperative Agreement award X-9745502 to the Center for Environmental Diagnostics and Bioremediation at The University of West Florida. The authors are greatly indebted to Dr. K. Ranga Rao for his scientific and managerial contributions to the study. Kristal Flanders managed the spatial databases for the project. Jeffrey Jackson helped with the fieldwork and Michael Somerville assisted with some laboratory procedures.