Effect of selected metal ions on the photocatalytic degradation of bog lake water natural organic matter

Herein we report the photocatalytic degradation of natural organic matter from a bog lake (Lake Hohloh, Black Forest, Germany) in the presence of 0, 5, and 10 μmol L−1 of added Cu2+, Mn2+, Zn2+ and Fe3+. The reactions were followed by size exclusion chromatography with organic carbon detection (SEC-DOC) and by measurements of low molecular weight organic acids. Addition of Cu2+ had the largest effect of all four studied metals, leading to a retardation in the molecular size changes in NOM: degradation of the larger molecular weight fraction was inhibited leading to reduced production of smaller molecular weight metabolites. Similarly, addition of Cu2+ reduced the production of formic and oxalic acids, and reduced the bioavailability of the partially degraded NOM.