Abstract:Water samples were collected at 15 well distributed sites and three depths in the Meiliang Bay of Lake Taihu on 16 and 17 August 2006. From these samples three water quality parameters (CDOM, detritus and phytoplankton) were determined using a photometer and the quantitative filtering technology (QFT). The spectral absorption characteristics of these in-water constituents were then analyzed, with regional models established for each of them. Spectral absorption models of CDOM were established in four bands, UV-C (250-290nm), UV-B (290-320nm), UV-A (320-400nm), and blue band (400-500nm). It was found that a close quadratic relationship exists between the slope gradient of the absorption curve S and absorption coefficient at 440nm. The R2 value is as high as 0.958 and 0.835 in, respectively, the ultraviolet and blue bands. Spectral absorption curves of total suspended sediments are similar at different depths at certain sites, but vary with depth at other sites as a result of the variability in the vertical distribution of organic and inorganic matters and total suspended sediments concentrations. The slope coefficient of the regressed spectral absorption of detritus S ranges from 0.0056 to 0.0090 nm-1, with a mean of (0.0070±0.0008)nm-1. The regression models at all sampling sites have an R2 value over 0.91. Over the visible light spectral range, the relative contribution of all in-water constituents to total absorption has a sequence of phytoplankton > detritus > CDOM. As the main contributor, phytoplankton always contributes more than half in the blue, green and red bands, in contrast to the mean corresponding contribution rates of 0350±0.145, 0.412±0.162 and 0.232±0.125 for detritus. The average contribution rates for CDOM are even lower at, respectively, 0.121±0.052, 0.088±0.059 and 0.050±0.038.