PCBs and PCDD/Fs in a historically polluted estuary along the northern Gulf of Mexico

Liebens, Johan (author)
Mohrherr, Carl (author)

39th Annual NAEP Conference, St. Petersburg, Florida

2014

Escambia Bay is a large shallow estuary in northwest Florida, US. It receives most of its waters from the Escambia River which originates to the north in Alabama. Starting in the 1950’s several industrial facilities were constructed on the bay and river. Prior to the 1970’s there were unregulated releases from these facilities and from domestic sewage facilities that lead to a catastrophic environmental collapse of the system in the early 1970s. The present study assesses the current profiles of PCBs and PCDD/Fs in sediment of Escambia Bay and River and examines the concentrations, spatial patterns, and potential origin of these pollutants relative to environmental and human health concerns. Fifty-seven composite samples were collected with a ponar grab sampler. PCBs and PCDD/Fs were extracted with USEPA Method 3550. USEPA Method 1668A was employed to detect the concentrations of the 209 PCB congeners and USEPA 1613B was used to detect PCDD/Fs. Sediment PCBs have a mean concentration of 15.6 ug/kg and a range from 1.0 to 93.3 ug/kg. Twelve (21%) out of the 57 samples exceed the FDEP TEL of 21.6 ug/kg and no sample exceeds the FDEP PEL of 189 ug/kg. In spite of these relatively low concentrations, bioaccumulation of PCBs in seafood from the bay has resulted in advisories for seafood consumption. The 17 PCDD/F congeners that are considered to have significant toxicity have a mean of 1.9 ug/kg and a range of 0.022-11.0 ug/kg. The mean total TEQ of PCDD/Fs and dioxin-like PCBs combined is 2.6 ng/kg. PCDD/Fs contribute about 92% and PCBs about 8% of the total TEQ. About 33% of the samples exceed the NOAA TEL for total TEQ but not the AET and an additional 23% of the samples exceed the AET. This implies that about 56% of samples exhibit total TEQ toxicities that could impact sediments adversely. The current PCB profile most closely resembles Aroclor 1254 produced prior to 1972. This is consistent with the composition of a spill on the Escambia River in 1969 and suggests that the PCBs have persisted in the sediments for at least 40 years with only moderate degradation of the original profile. An overall decline of 3% in the chlorination of the PCBs is associated with a shift to the lesser-chlorinated congeners, however, the total TEQ did not decline. The PCDD/F congener profile is similar to what has been observed in local bayous in that octachlorodibenzop-dioxin (OCDD) is the dominant congener in the sediment but does not unequivocally point to a specific source.

dioxins
furans
PCBs
TEQ
Escambia Bay

uwf:23168