Figure 3. Comparison on measurements in freeze/thaw treatments and controls.

Concentrations of SARS-CoV-2 RNA targets (N, S, ORF1a, left column) and PMMoV RNA (middle column), as well as their ratios (right column) as measured in settled solids in controls (darker bars) and treatments (lighter bars) and total errors as reported by the digital PCR instrument, or in the case of the ratios, the errors were propagated. Units are copies per gram dry weight (cp/g) for SARS-CoV-2 and PMMoV RNA targets, and there are no units for the ratio. Asterisks denote measurements or calculated ratios for which the errors on the treatments and controls do not overlap and indicate the measurements were different. Top row shows experiments where solids were stored at −20 °C for 2–3 days while the bottom row shows experiments where dewatered solids were stored at −80 °C for 35–122 days (see Table 1).