Suspended Sediment Dynamics and Light Attenuation Characteristics in Peoria Lake, Illinois: Can Submersed Macrophyte Communities Improve Water Quality in this Shallow System.

摘要

We examined sediment resuspension dynamics and light availability in relation to the potential for macrophytes to improve water quality conditions in Peoria Lake, Illinois. The lake exhibited high total suspended sediment (TSS) loading and retention of predominantly fine-grained particles during 2000. Large fetches along the prevailing wind rose, coupled with shallow morphometry and sediment particles composed of > 90 percent silt and clay, resulted in frequent periods of sediment resuspension in September. The tau(sub c) of sediment in the vicinity of the resuspension monitoring station, determined experimentally using a particle entrainment simulator, was 2.3 dynes/sq cm. This value was in close agreement with tau(sub c), determined by direct examination of variations in in situ turbidity as a function of tau, calculated using wave theory, at the resuspension monitoring station during the month of September. As calculated tau increased above tau(sub c), turbidity increased substantially at the resuspension monitoring station during the month of September. Net TSS resuspension was very high in relation to TSS loading from the Illinois River during September. The settling velocity of particles in the water column was estimated as 0.004 cm/sec, based on analysis of five particle-size fractions ranging between 62.5 micrometers. Using a resuspension model, we reasonably predicted resuspension events that occurred in September at the resuspension station. Model explorations suggested that establishment of submersed aquatic macrophytes could substantially reduce sediment resuspension in Peoria Lake. However, K(sub d) was very high, while Secchi transparency was low at in-lake stations, and the silt fraction (i.e., 1.95 micrometers) strongly influenced K(sub d). Thus, in order to establish a persistent macrohpyte population in the lake to control resuspension, the underwater light regime must initially improve quite dramatically.