Fig. 5

HO^• yield of preconditioned fibers and ferrithydrite measured by the DMPO/HO^•-EPR signal intensity. The signal is expressed as a precentage of the HO^• yield of pristine fibers, which was analyzed at every measuring session as a reference. Panel a.) HO^• yield of DFOB-altered fibers + 0, 3, 30 and 300 μmol g⁻¹ Fe, and 3 mg ferrihydrite; Panel b.) HO^• yield of blank-altered fibers + 0, 3, 30 and 300 μmol g^− 1 Fe and 3 mg ferrihydrite. The letters indicate significantly different HO^• yields as identified by the Tukey post-hoc test following an ANOVA. The results illustrate an increase in HO^• yield upon addition of Fe to DFOB-altered fibers, yet the HO^• yield of blank-altered fibers was not reached. Error bars indicate standard deviations (n = 4)