Abstract
The analyses of specific ultraviolet absorbance (SUVA) and excitation emission matrix (EEM) were applied to characterize algogenic organic matter (AOM) produced by Microcystis aeruginosa at low nutrient concentrations and at three different N/P ratios. The production of dissolved organic carbon (DOC) during stationary phase was 3.6-5.8 times as much as that during exponential phase at any N/P ratios, while the components with ultraviolet absorbance at 260nm (E260) were remarkably released during the exponential phase at N/P=20. The ΔE260/ΔDOC value during the exponential phase at N/P=20 was 5.1 l·Abs·mgC-1·m-1, which was significantly higher than the reported values for AOMs. Six peaks of fluorescence intensity on EEM maps were identified and one of them (called “Pα” at 230 nm/430 nm (excitation/emission)) had never been reported as a fluorescence peak before. Peak profiles of AOMs on EEM maps were characterized by 1) the presence of Pα, 2) the absence of P3, 3) the relatively high fluorescence intensities at P1 and P2, and 4) the higher fluorescence intensity at P4 than at P6. EEM maps were divided into four zones according to the position of important peaks. The presence of unidentified peaks was discussed based on the relationship between fluorescence peak intensity and the integral value of fluorescence within each zone.
