ROLE OF SUSPENDED SEDIMENT IN FACILITATING PATHOGEN TRANSPORT IN INNER BLUEGRASS KARST AQUIFERS

In karst terrains, suspended sediment carried into the subsurface or remobilized within conduits may facilitate the transport of pathogens via adhesion. We are studying the relationship between suspended sediment and pathogen indicators at two springs in the Inner Bluegrass region of Kentucky. Blue Hole spring (BH) drains much of downtown Versailles (2000 population 7,511), while SP2, located at the University of Kentucky Animal Research Center (ARC), drains primarily pasture. At both sites, electrical conductivity (EC), temperature (T), and turbidity are continuously monitored, and the pathogen indicators fecal coliform (FC), total coliform (TC), atypical colonies (AC), and male-specific coliphage (MSP) have been sampled biweekly since December 2002. Stream stage is also continuously monitored and correlated to flow at BH, while flow is continuously gaged via a weir downstream of SP2. Trends in EC, T, turbidity, and microbial data have been examined relative to precipitation from the ARC. Peaks in turbidity and EC minima appear to coincide with individual storms. T also responds to rainfall > 1.0 cm in a 24-hour period. Results of microbial analyses reflect the differences in land use between the sites. AC/TC ratios were < 10 for SP2 and > 10 for the majority of the BH samples. The lowest AC/TC ratios at BH coincided with rainfall, as did the highest MSP values. MSP, an indicator of human fecal contamination, was detected in the majority of the BH samples but in none of the SP2 samples. Experiments to examine the properties that dictate E. coli attachment to and detachment from the silt-sized fraction of the bed sediment at SP2 are underway. Finally, the relationship between turbidity and total suspended solids will be examined by manual sampling during storm flow, and suspended sediment loads will be estimated.