Pollution in an Urban Bayou: Magnitude, Spatial Distribution and Origin

Abstract

Bayou Texar in Pensacola, FL, receives pollutants from a variety of sources, presumably including two USEPA's Priorities List sites. To evaluate the potential negative impacts of pollution in this type of setting, we determined the level and distribution of some of the pollutants in the bayou and identified the most likely sources for them. Results show that fluoride, a tracer for a contaminated groundwater plume from one of the Priorities List sites, enters sediments in the northern part of the bayou and migrates into the water. Radium in the bayou most likely also emanates from the contaminated groundwater plume. However, 228 Ra/ 226 Ra isotope ratios indicate that the radium enters the plume from the aquifer matrix, and thus does not originate directly at the Priorities List site. PAHs of creosote origin are known to have been released by the second Priorities List site but apparently they do not affect the sediments of the bayou because ratios of individual PAHs show that they are derived from combustion. The concentrations of the PAHs are slightly higher in the northern part of the bayou. Unlike other pollutants, most metals exceed their probable effects level (PEL) in many places in the bayou. The highest concentrations are observed in the northern part of the bayou. Low metal concentrations in monitoring wells and in deep sediments in the bayou suggest that the metals do not come from the groundwater plume. Sediment transport analysis shows that sediments are trapped in the northern part of the bayou. Consequently, long term accumulation explains the observed high concentrations of heavy metals, and other sediment bound pollutants, in the northern part of Bayou Texar. Pollutant concentrations vary greatly spatially, demonstrating the importance of geographical analysis for this type of environmental research.

Trace metal assessment in soils in a small city and its rural surroundings, Pensacola, FL, USA

“…This relatively small size implies that the trace metal pollution has spread only by local processes, such as potentially, short range atmospheric transport or surface runoff. The spatial concurrence of the hot spot and the industrial corridor does not necessarily represent a causal relationship, but given the well-documented pollution history in the industrial corridor (Geraghty and Miller 1992;Liebens et al 2006), it seems reasonable to assume that this previously undocumented trace metal hot spot is due to the local (former) industry. The former industry included a wood treatment facility, a fertilizer manufacturing plant, and a scrap metal facility.…”