Fig. 4.

Production of ${\mathrm{O}}_2^{\mathrm{\cdot -}}$ in particulate organic matter suspension. a A dramatic decrease in the SPR absorbance of the AgNPs suspension in the presence of 150 U SOD mL⁻¹, produced by the reduction of 0.93 mM silver ions (Ag⁺) with 143.2 mg C L⁻¹ particulate organic matter (POM) at pH 8.6 under simulated sunlight for 24 h. b EPR spectra of the DMPO adduct with ${\mathrm{O}}_2^{\mathrm{\cdot -}}$ in POM suspension at different pHs after incubation of the samples under simulated sunlight for 1 h