Spectral characterization of colored dissolved organic matter for productive inland waters and its source analysis

This study examined the spatiotemporal dynamics of colored dissolved organic matter (CDOM) and spectral slope ( S ), and further to analyze its sources in three productive water supplies (Eagle Creek, Geist and Morse reservoirs) from Indiana, USA. The results showed that he absorption coefficient a CDOM (440) ranged from 0.37 m –1 to 3.93 m –1 with an average of 1.89 ± 0.76 m –1 (±SD) for the aggregated dataset, and S varied from 0.0048 nm –1 to 0.0239 nm –1 with an average of 0.0108 ± 0.0040 nm –1 . A significant relationship between S and a CDOM (440) can be fitted with a power equation ( S = 0.013 × a CDOM (440) –0.42 , R 2 = 0.612), excluding data from Geist Reservoir during high flow (12 April 2010) and the Morse Reservoir on 25 June 2010 due to a T-storm achieves even higher determination coefficient ( R 2 = 0.842). Correlation analysis indicated that a CDOM (440) has strong association with inorganic suspended matter (ISM) concentration (0.231 < R 2 < 0.786) for each of the field surveys, and this trend followed the aggregated datasets ( R 2 = 0.447, p < 0.001). In contrast, chlorophyll-a was only correlated with a CDOM (440) in summer and autumn (0.081 < R 2 < 0.763), indicating that CDOM is mainly from terrigenous sources in early spring and that phytoplankton contributed during the algal blooming season. The S value was used to characterize CDOM origin. The results indicate that the CDOM source is mainly controlled by hydrological variations, while phytoplankton originated organic matter also closely linked with CDOM dynamics in three productive reservoirs.