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PM08 Sediment Quality Assessment
Exhibit Hall
8:00 AM - Monday

(PM121) Profiles of pollutants impacting Bayou Texar, Pensacola, FL.

Mohrherr, C1, Liebens, J1, Lepo, J1, Rao, K1, 1 University of West Florida, Pensacola, FL, USA

ABSTRACT- Bayou Texar is an urban bayou that connects to Pensacola Bay. It receives discharge from a creek, stormwater outfalls, nonpoint sources along its shores, and an aquifer. Past studies have shown the presence of fluoride, metals, PAHs, and pesticides in bayou sediments. Groundwater plumes originating from two superfund sites to the west are apparently transporting pollutants towards the bayou. We entered data from county, state, and federal studies on pollution of the bayou water, bayou sediments, and groundwater into a GIS database. This database allowed us to identify spatial and topical data gaps. We then sampled bayou sediments by ponar grabs and vibracores at strategic locations where information was lacking. The sediments were analyzed for fluoride, radium, PAHs, and metals. Bottom water was sampled with a Van Dorn sampler and analyzed for salinity and fluoride. Porewater samples for fluoride analysis were obtained from sampled sediment by centrifugation. State of Florida Sediment Quality Assessment Guideline Threshold effects levels (TEL) were exceeded for PAHs in the creek and bayou. Probable effects levels (PEL) were exceeded in the bayou for lead, mercury, copper and zinc, while arsenic and chromium reached concentrations between their TEL and PEL. The metal and PAH contamination was most concentrated in surficial sediments and was likely transported into the bayou by surface waters and sediments. The metal and PAH levels were highest in the northern part of the bayou because of increased input due to the large number of stormwater outfalls in that area or because of a diminished flushing effect of tides in this upper part of the bayou. Fluoride levels were also elevated in the northern part of the bayou. In sediment cores, fluoride levels were highest at the sediment/water interface where particle size is finest. In porewater, however, fluoride levels increased with depth. This indicates a groundwater origin for the porewater fluoride. Fluoride in bayou water was not related to salinity but reached a peak in the area where porewater fluoride was highest. This suggests that fluoride-rich porewater may be mixing with bayou water. Radium in sediments varied spatially but in general it was low. In the northern part of the bayou, the radium increased locally with depth. This depth trend suggests that a source of radium exists under the bayou and that it locally moves towards the surface. (Supported by EPA Cooperative Agreement X-97455002)

Key words: heavy metals, sediments, fluoride, GIS


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