title: Enumerating Microorganism Surrogates for Groundwater Transport Studies Using Solid-Phase Cytometry.
abstract: Investigations on the pollution of groundwater with pathogenic microorganisms, e.g. tracer studies for groundwater transport, are constrained by their potential health risk. Thus, microspheres are often used in groundwater transport studies as non-hazardous surrogates for pathogenic microorganisms. Even though pathogenic microorganisms occur at low concentrations in groundwater, current detection methods of microspheres (spectrofluorimetry, flow cytometry and epifluorescence microscopy) have rather high detection limits and are unable to detect rare events. Solid-phase cytometry (SPC) offers the unique capability of reliably quantifying extremely low concentrations of fluorescently labelled microorganisms or microspheres in natural waters, including groundwater. Until now, microspheres have been used in combination with SPC only for instrument calibration purposes and not for environmental applications. In this study, we explored the limits of the SPC methodology for its applicability to groundwater transport studies. The SPC approach proved to be a highly sensitive and reliable enumeration system for microorganism surrogates down to a minimum size of 0.5 μm, in up to 500 ml of groundwater, and 0.75 μm, in up to 1 ml of turbid surface water. Hence, SPC is proposed to be a useful method for enumerating microspheres for groundwater transport studies in the laboratory, as well as in the field when non-toxic, natural products are used.
authors.affiliation: Centre for Water Resource Systems, Vienna University of Technology, Karlsplatz 13, 1040 Vienna, Austria.
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Stevenson
authors.affiliation: Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13, 1040 Vienna, Austria ; Interuniversity Cooperation Centre Water and Health (ICC), www.waterandhealth.at, Vienna, Austria.
authors.forename: A Paul
authors.initials: AP
authors.lastname: Blaschke
authors.affiliation: Institute for Hygiene and Applied Immunology, Medical University of Vienna, Kinderspitalgasse 15, 1090 Vienna, Austria.
authors.forename: Sonja
authors.initials: S
authors.lastname: Schauer
authors.affiliation: Institute for Water Quality, Resource and Waste Management, Vienna University of Technology, Karlsplatz 13, 1040 Vienna, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Zessner
authors.affiliation: Institute for Hygiene and Applied Immunology, Medical University of Vienna, Kinderspitalgasse 15, 1090 Vienna, Austria ; Interuniversity Cooperation Centre Water and Health (ICC), www.waterandhealth.at, Vienna, Austria.
authors.forename: Regina
authors.initials: R
authors.lastname: Sommer
authors.affiliation: Institute of Chemical Engineering, Research Group Environmental Microbiology and Molecular Ecology, Vienna University of Technology, Gumpendorfer Straße 1a, 1060 Vienna, Austria ; Interuniversity Cooperation Centre Water and Health (ICC), www.waterandhealth.at, Vienna, Austria.
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Farnleitner
authors.affiliation: Institute for Hygiene and Applied Immunology, Medical University of Vienna, Kinderspitalgasse 15, 1090 Vienna, Austria ; Interuniversity Cooperation Centre Water and Health (ICC), www.waterandhealth.at, Vienna, Austria.
authors.forename: Alexander K T
authors.initials: AK
authors.lastname: Kirschner
keywords: ChemScan™ RDI; Drinking water resources; Groundwater; Microspheres; Pathogen surrogates; Solid-phase cytometry