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Glass Fiber Filter 1.5 u m vs. 0.7 u m pore size. 44 samples collected in Virginia Tributaries for May through July 2000 Filtered samples through Whatman GF/F (0.7 u m) and Whatman 934-AH (1.5 u m). 1.5 u m filters provided to ODU from DCLS
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Glass Fiber Filter1.5 um vs. 0.7 um pore size • 44 samples collected in Virginia Tributaries for May through July 2000 • Filtered samples through Whatman GF/F (0.7 um) and Whatman 934-AH (1.5 um). • 1.5 um filters provided to ODU from DCLS • Volume filtered determined by how quickly and easily samples passed through the filter pad.
Paired Comparisons P < .05 so significant difference between TSS values from different pore size filters
Plot difference versus the mean + 2 STD Mean - 2 STD
Mean values Difference = 3.26 mg/L 47.3 50.6
Conclusions • Significant difference in TSS concentrations measured using different filter sizes. • 1.5 um pore size filter biased lower than 0.7 um pore size filter. • Mean difference in concentration between filters is about 3.3 mg/L. • Bias observed in split samples results is probably explained by the results of this study. • Changing filters could affect trend analysis results.