M2 PM Non-Point Source Pollution and TMDLs
Monday, 14 November 2005: 1:50 PM - 5:30 PM in Ballroom 2

(ZHA-1117-780006) A Chemodynamic Sediment Flux Model in TMDLs Determination of PAHs in Patrick Bayou, Texas.

Kaulen, Mark¹, Zhang, Chunlong¹, ¹ University of Houston-Clear Lake, Houston, Texas, USA

ABSTRACT- Patrick Bayou, a shallow and tidal tributary of the Houston Ship Channel in Texas, receives treated industrial and municipal wastewater, and non-point source storm water from the surrounding area. It is currently listed as 303(d) impaired water due to sediment toxicity and is designated as a National Priorities List site under the federal Superfund program. Although sediment toxicity in Patrick Bayou remains "undefined" from several studies by local industries and partners, historical data strongly suggested heavy PAHs contamination in sediments. These contaminated sediments serve as a potential source for water column PAHs and can contribute to the overall budget and determination of Total Maximum Daily Loadings (TMDLs). In this study, a chemodynamic model based on resistance-in-series algorithm initially developed by Thibodeaux (1996) is extended and applied to estimate sediment flux under typical conditions of Patrick Bayou. By incorporating a series of compound- and site- specific parameters, this steady state model can estimate sediment flux as a function of several key parameters, such as porewater concentration, partition coefficient, molecular diffusivity, biodensity, water depth, and water flow rate. The model predicts that flux rates under typical conditions of Patrick Bayou are 87, 43, and 11 mg/m²*year for naphthalene, phenanthrene and pyrene, respectively. Converting these sediment flux rates into total mass of PAHs from Patrick Bayou water segment, the contaminated sediments are clearly shown to be a significant input relative to non-point sources that cannot be neglected in TMDLs formulation. The simplicity of this spreadsheet chemodynamic model may imply its utility as an approximate yet cost-effective water quality management tool, particularly for similar slow-moving, shallow waters overlying historically contaminated sediments where bioturbation and water-side mass transfer may become the predominant mechanisms at the water-sediment interface.

Key words: contaminated sediment, sediment flux, PAHs, TMDLs