title: Tracing fecal pollution sources in karst groundwater by Bacteroidales genetic biomarkers, bacterial indicators, and environmental variables.
abstract: Fecal contamination in Midwestern karst regions was evaluated by simultaneously measuring traditional bacterial indicators (coliforms and Escherichia coli), Bacteroidales-based biomarkers, and environmental variables. Water samples from springs and wells were collected from karst regions in Illinois (IL), Wisconsin (WI), Kentucky (KY), and Missouri (MO). Quantitative PCR (Q-PCR) with seven primer sets targeting different members of Bacteroidales was used to determine the origin of fecal contamination (i.e., from human waste, livestock waste, or both). Most samples were contaminated by both human and animal waste, with a few samples showing pollution solely by one or the other. Spring water tended to have higher levels of contamination than well water, and higher concentrations of fecal biomarkers were detected in urban springs compared to rural spring systems. However, there were discrepancies on contamination profile determined by Bacteroidales-based biomarkers and by traditional bacterial indicators. Among all the environmental parameters examined, E. coli, sulfate, total dissolved solids (TDS), and silicon were significantly correlated (p<0.05) with the level of Bacteroidales-based fecal indicators. A rapid screening method using total nitrogen (TN) and chloride (Cl(-)) concentrations to determine fecal contamination was shown to be effective and correlated well with Bacteroidales-based MST. The results suggest that human and livestock feces co-contaminated a large portion of karst groundwater systems in Midwestern regions, and the inclusion of traditional bacterial indicators, environmental variables, and Bacteroidales-based MST is an effective approach for identifying fecal contamination in karst regions.
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana Champaign, United States.
authors.forename: Ya
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Illinois State Water Survey, Prairie Research Institute, University of Illinois at Urbana Champaign, United States.
authors.forename: Walton R
authors.initials: WR
authors.lastname: Kelly
authors.affiliation: Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana Champaign, United States.
authors.forename: Samuel V
authors.initials: SV
authors.lastname: Panno
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana Champaign, United States. Electronic address: wtliu@illinois.edu.
authors.forename: Wen-Tso
authors.initials: WT
authors.lastname: Liu
mesh_terms: D041963:Bacteroidetes / Q000235:genetics* / Q000254:growth & development; D015415:Biomarkers / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D005243:Feces / Q000382:microbiology; D005819:Genetic Markers; D060587:Groundwater / Q000382:microbiology*; D007087:Illinois; D014871:Water Microbiology; D014876:Water Pollution / Q000032:analysis*
chemical_list: D015415:Biomarkers; D005819:Genetic Markers
keywords: Bacterial indicators; Bacteroidales-based microbial source tracking; Environmental variables; Fecal contamination; Karst