Enumerating Microorganism Surrogates for Groundwater Transport Studies Using Solid-Phase Cytometry

• Published in: Water, air, and soil pollution air, and soil pollution, 2014, Vol.225 (2), p.1827-10, Article 1827
• Main Authors: Stevenson, Margaret E, Blaschke, A. Paul, Schauer, Sonja, Zessner, Matthias, Sommer, Regina, Farnleitner, Andreas H, Kirschner, Alexander K. T
• Format: Article
• Language: English
• Subjects: Aquatic resources; Atmospheric Protection/Air Quality Control/Air Pollution; Bacteria; Climate Change/Climate Change Impacts; detection limit; Detection limits; Drinking water; Earth and Environmental Science; Enumeration; Environment; Environmental monitoring; Environmental studies; Experiments; Flow cytometry; Fluorescence; Groundwater; groundwater contamination; groundwater flow; Groundwater pollution; Health aspects; Health risks; Hydrogeology; Laboratories; Microorganisms; Microscopy; Microspheres; Natural products; Natural waters; Pollution dispersion; risk; Soil Science & Conservation; Spheres; Surface water; Tracers (Chemistry); Water pollution; Water Quality/Water Pollution; Water resources; Water, Underground
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-013-1827-3

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.