MULTI-PROXY CHARACTERIZATION OF WATER QUALITY IN KARST SPRINGS OF EUREKA SPRINGS, AR

Founded in 1879, Eureka Springs is located in an area of karst terrain on the Ozark Plateau of northern Arkansas. More than 100 springs lie within the city limits. These springs and the karst hydrologic system are highly vulnerable to urban land use; many of the springs have shown contamination by various compounds and by indicator bacteria. In a collaborative effort to further characterize impact and potentially accrue information on sources, the U. S. Geological Survey, City of Eureka Springs, and Arkansas Department of Environmental Quality joined forces September 2009 to collect a representative sample of springs and streams in the area. These low-flow samples were analyzed for Organic Wastewater Constituents (OWC’s), indicator bacteria (E. Coli, and Fecal Coliform) and general geochemical water quality parameters.

Of the 62 OWC’s analyzed, 12 were found in at least one of the sampling sites. Eleven of the 14 total detections were found at a single site located downstream from a wastewater treatment facility. The most common OWC’s detected were flame-retardants, and synthetic musks. The presence of OWC’s in drinking water is cause for concerns of abnormal physiological processes, reproductive impairment, increased incidences of cancer, and development of antibiotic resistant bacteria.

Indicator bacteria colony counts ranged from 2 (estimated(e)) to 500 (e) with an average of 115 per 100 mL for E. Coli, and from 8 (e) to 130 with an average of 59 per 100 mL for Fecal Coliform. The presence of these indicator species suggests fecal contamination and the potential occurrence of harmful bacteria.

Geochemical water analysis revealed several parameters above background levels. All nitrate values were above the natural level of < 0.5 mg/L ranging from 1.08 to 4.36 mg/L. Only the sample taken from below the wastewater treatment plant exceeded the EPA recommended total phosphorous level of < 0.1 mg/L at a level of 3.19 mg/L. Lead was detected above EPA action levels at a spring site at 1.84 mg/L.

These data show the impact of urban land use on water quality in the springs, highlighting the vulnerable character of the karst hydrologic system. Future plans for in the study include nitrate and water isotope analyses, consideration of sewage effluent indicator species, optical brightener tracing and a high-flow OWC sampling event.