Figure 1.
Daily variation of water level in Lake Taihu in 2010.
Figure 2.
Temporal changes in total dissolved nitrogen concentration (TDN), total dissolved phosphorus concentration (TDP), and the ratio of TDN to TDP, for WDA (a–c) and PDA (d–f) CDOM samples exposed to natural solar radiation.
Except for the initial value (0d), each measurement is an average of three samples (true replicates). Error bars indicate standard deviation.
Figure 3.
Temporal changes in CDOM absorption coefficients a(254) (a), and the first-order kinetics fitting of a(254) vs UV radiation cumulative value (b), of WDA and PDA CDOM samples.
Error bars indicate standard deviations
Figure 4.
Temporal changes in three parameters of CDOM composition: molecular size (MS), spectral slope (S), and spectral slope ratio (SR) of WDA (a, c, e) and PDA (b, d, f) CDOM samples.
Figure 5.
Correlations between CDOM absorption coefficient a(254) and molecular size MS, spectral slope ratio SR, and spectral slope S, for WDA CDOM (a–c) and PDA CDOM (d–f).
Figure 6.
Examples of EEMs for days 0 and 9 for WDA CDOM (a, b), and for PDA CDOM (c, d), (b, d: data pooled for three parallel samples).
Fluorescence is in QSU units. Peaks A and C represent terrestrial humic acids fluorescence, and peak T represents tyrosine fluorescence.
Figure 7.
The PARAFAC model output showing fluorescence signatures of the three fluorescent components for the WDA (a–c) and PDA CDOM (g–i), and the contour plots presenting the spectral shapes of excitation and emission for the WDA (d–f) and PDA (j–l) CDOM.
The line plots present split-half validation results; excitation (left) and emission (right) spectra were estimated from two independent halves of the dataset (red and green lines), and the complete dataset (black lines). A perfect validation is obtained if loadings from the two halves are identical.
Table 1.
Spectral characteristics of excitation and emission maxima of the three fluorescent components identified for the WDA and PDA CDOM by PARAFAC modeling, compared with those from previously identified sources.
Figure 8.
Temporal variations in intensity of CDOM fluorescence components for WDA (a–c) and PDA (d–f) CDOM samples.
For comparison, the control samples (CK5d, CK7d) after 5d and 7d for the WDA experiment are shown. Error bars indicate standard deviation.
Figure 9.
Linear relationships between CDOM absorption coefficient a(254) and total dissolved nitrogen concentration (TDN), total dissolved phosphorus concentration (TNP), and the TDN∶TDP ratio, for WDA (a–c) and PDA (d–f) CDOM.
Figure 10.
Linear relationships between the CDOM absorption coefficient a(254) and the fluorescence intensity for three fluorescence components for WDA (a–c) and PDA (d–f) CDOM.