Figure 6.

Hydroxyl radical generation as a function of particle loadings. Mineral particles (roughly 1–100 microns in diameter) were incubated with 10 μM APF and 50 mM phosphate pH 7.40 buffer for 24 hours followed by filtration (0.45 μm) and fluorescence measurements. The National Institute of Standards and Technology (NIST) samples used here are a low metal-content soil, San Joaquin soil (2709), and a high metal-content soil, Montana 1 (2710). The hROS reactivity values can be compared to the reported fluorescence intensity values shown on the other figures by dividing hROS reactivity by ten.