HR: 0800h
AN: B51B-0363    [Abstracts]
TI: Data quality assessment of direct counts of virus-sized microsphere in water samples by epifluorescence microscopy
AU: * Chae, G
EM: gtchae@kigam.re.kr
AF: KIGAM, Korea Institute of Geoscience and Mineral Resources, 30 Gajeong-dong, Yuseong- gu, Daejeon, 305-350, Korea, Republic of
AU: Stimson, J
EM: jrstimso@sciborg.uwaterloo.ca
AF: University of Waterloo, Department of Earth Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada
AU: Emelko, M B
EM: mbemelko@civmail.uwaterloo.ca
AF: University of Waterloo, Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada
AU: Blowes, D W
EM: blowes@sciborg.uwaterloo.ca
AF: University of Waterloo, Department of Earth Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada
AU: Ptacek, C J
EM: ptacek@sciborg.uwaterloo.ca
AF: University of Waterloo, Department of Earth Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada
AU: Mesquita, M M
EM: mmesquit@engmail.uwaterloo.ca
AF: University of Waterloo, Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada
AB: Fluorescent microsphere has been used as pathogen surrogates in pathogen transport studies. A common technique, direct counting by epifluorescence microscopy, for the enumeration of virus- and bacteria-sized microsphere has been applied in laboratory and field studies. However, few studies have focused on factors ensuring precise and accurate measures. Factorial experiment and two-way ANOVA with repeated measures performed to investigate the factors affecting the data quality. The evaluated factors were 1) the density of microspheres in each field and 2) the total number of counts in an enumeration. Two parameters, relative standard deviation and percent error, were used to assess methodological precision and accuracy. In addition, two water compositions with different ionic strength, i.e., calcite-saturated artificial groundwater (AGW) and deionized water (DIW) was used for assessing the effect of ionic strength and presence of precipitates. A standard method was used to prepare slides and enumerate microspheres, with particular care to randomly select fields for counting. As a result of visual observations of the slides, undulation in the filter membrane, bubble entrained in the mounting medium, and the presence of precipitates that form in AGW create biases in microsphere enumeration. As result of statistical assessment, microsphere density was found to be critical for ensuring methodological precision, whereas the total number of microspheres counted was essential to ensuring methodological accuracy. The results suggested that to minimize variability using the field approach, the enumeration of at least 350 microspheres and 25–40 microspheres field-1 is necessary.
DE: 0424 Biosignatures and proxies
DE: 0448 Geomicrobiology
DE: 4809 Colloids
SC: Biogeosciences [B]
MN: 2007 Fall Meeting