Differences in pathogen indicators between proximal urban and rural karst springs,Central Kentucky,USA |
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| Authors: | Thomas M Reed Alan E Fryar Gail M Brion James W Ward |
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| Institution: | (1) AMEC Earth and Environmental, 108 Esplanade Ave., Suite 310, Lexington, KY 40507, USA;(2) Department of Earth and Environmental Sciences, University of Kentucky, 101 Slone Building, Lexington, KY 40506-0053, USA;(3) Department of Civil Engineering, University of Kentucky, 161 Raymond Building, Lexington, KY 40506-0281, USA;(4) Department of Physics, Angelo State University, ASU Station #10904, San Angelo, TX 76909, USA; |
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| Abstract: | Because of their architecture, karst aquifers are susceptible to contamination by fecal-derived pathogens. Previous studies
have examined the behavior of bacterial indicators such as total coliforms (TC) and fecal coliforms (FC) in karst aquifers,
but simple techniques for discriminating between human and non-human inputs are still needed. This study examines concentrations
of TC, FC, atypical colonies (AC, which grow on the same media as TC), male-specific coliphage virus (MSP, an indicator of
human feces), and nitrate at two springs in the Inner Bluegrass region of Kentucky (USA). Blue Hole Spring primarily drains
the city of Versailles, whereas spring SP-2 drains pasture. Baseflow was monitored, usually biweekly, from December 2002 to
March 2004, while storm flow was monitored in September 2003 and March 2004. At each spring, bacterial concentrations were
highest in storm flow and lowest in “normal” baseflow (for which 72-h antecedent precipitation was negligible). Concentrations
in baseflow tended to be highest during late spring and summer and lowest during autumn and winter. FC concentrations exceeded
regulatory (contact) standards in storm-flow samples. For both storm flow and baseflow, AC concentrations were greater than
TC, which in turn were greater than FC. Median AC and TC concentrations were greater in baseflow at Blue Hole than at SP-2.
MSP was detected in most samples from Blue Hole but never at SP-2. The AC/TC ratio was typically <15 except for normal baseflow
samples at Blue Hole, which is probably impacted by leakage from sanitary sewers, as suggested by MSP and nitrate results.
Mobilization of sessile bacteria appears to reduce the AC/TC ratio during storm flow. Consequently, this ratio shows promise
as a screening tool to identify sewage inputs in karst groundwater basins under baseflow conditions. |
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