Fig 2. Bland Altman plot for perfluorooctane sulfonate after transformation by the natural logarithm, stratified by season.

The first plot represents samples from the winter, while the second plot represents samples from the summer. The average lnPFOS is the average of the natural log-transformed concentrations of perfluorooctane sulfonate (PFOS) in the transported and delayed samples and the immediately processed samples. The difference is the difference between the two natural log-transformed concentrations.