Chromophoric dissolved organic matter optical characteristics and spatial distribution in the lakes of the middle reaches of the Yangtze River

Abstract

Chromophoric dissolved organic matter (CDOM) is the colored fraction of the dissolved organic carbon (DOC) pool. According to investigations and filed measurements in Lake Honghu, Lake Donghu, Lake Liangzi in September and October of 2007, optical characteristics and spatial distribution of CDOM in these lakes are analyzed. Results show that CDOM absorption coefficient in Lake Honghu is the highest, with the mean value of the CDOM absorption coefficient at 400nm (a g (400)) is 1.45m-1 , while the lowest is in Lake Liangzi, with the mean value of the CDOM absorption coefficient at 400nm is 0.68m-1. A significantly positive correlation between CDOM absorption coefficient and suspended sediment concentration is found in Lake Honghu. In Lake Liangzi, CDOM absorption coefficient is positive correlated with chlorophyll concentration, which means CDOM in the lake is mainly contributed by Phytoplankton degradation. The slope (S) in the exponential correlation function does not vary much in Lake Honghu and Lake Donghu. Fulivc acid is the dominated constituent of CDOM in Lake Liangzi, and the absorption coefficient of CDOM vary extremely. There is a negative correlation relationship (-0.9) between S and a g (400) in Lake Liangzi.

A Floating Optical Buoy (FOBY) for Direct Measurement of Water‐Leaving Radiance Based on the Skylight‐Blocked Approach (SBA): An Experiment in Honghu Lake, China

“…The spectral slope of CDOM between 300 and 350 nm varied from 0.015 to 0.026 nm −1 . These results show good agreement with previous studies (Chen et al, 2009;Zhou et al, 2017). Figure 5 shows the self-shading corrected R rs spectra between 368 and 881 nm from FOBY for all stations.…”