Earl Hayter

Chapter 21 Fine sediment resuspension and nutrient transport in Newnans Lake, FL

Abstract The nature of fine sediment resuspension and nutrient transport was examined for Newnans Lake in north-central Florida. Physical and water quality parameters were monitored over a period of 8 months in the lake and the inflow and outflow streams. Suspended-sediment concentration (SSC) response to wind was found to occur over a wide frequency band, with spectral peaks that seemingly correlate with lunar motion. On a time-mean basis, wind energy maintains the particulate matter as a benthic suspended-sediment layer with a mean height of about 0.80 m and SSC of about 70 mg/L. The suspended-sediment mass per unit bed area is less than 1 mm thick bed layer, indicating that there is little interaction between the ≈ 2 m thick muck in the lake and the water column. Nutrient balance is simplified because dissolved nutrient loads are close or nearly equal to total loads, with minor contributions from the suspended matter. Mass balances for phosphorus and nitrogen indicate periods of days over which the lake acts both as a net exporter and a net importer of these nutrients.

Comparison of Chemical Bioaccumulation Models to Assist in Model Selection for Ecological Assessments and TMDL Development

This paper describes a recent EPA-sponsored study (Imhoff et al., 2004) that analyzed and compared the capabilities of advanced chemical bioaccumulation models that are currently available to support the evaluation of ecological effects in aquatic ecosystems. These models are commonly used to establish the linkage of a variety of water quality targets and sources, and to provide a means for comparing various watershed and waterbody management strategies. EPAs Office of Research and Development (ORD), National Environmental Research Laboratory (NERL), Ecosystem Research Division (ERD), is currently supporting EPAs Office of Emergency Response and Remediation (OERR) by addressing priority research needs related to assessing the fate and transport of pollutants via contaminated sediment and bioaccumulation. The results of the first support effort by ERD, an evaluation of currently available numerical models useful for assessing fate and transport of contaminated sediments (Imhoff et al., 2003), were presented at the fall 2003 WEF TMDL Conference (Imhoff, 2003). The work effort presented in this paper constitutes the second element of the support effort by ERD, a parallel evaluation of currently available numerical models useful for assessing chemical bioaccumulation. Eight models were identified that were judged superior to all others in their promise as tools for chemical bioaccumulation analysis. To provide ERD with a basis on