Inherent Optical Properties of Highly Turbid Eutrophic Waters, Taihu Lake, China

Phytoplankton, suspended matter and yellow substance are the three main optically active substances in inland waters and their optical properties play a important role in determining both the penetration depth of light and the radiant energy for vegetation photosynthesis. The spectral light absorption and backscattering are essential in the development of analytical, reflectance model and multi-spectral algorithms on water quality monitoring. With regard to the increasing use of analytical reflectance model in the interpretation of remote sensing data, it seems timely to investigate the relationship of the specific absorption and the specific back scattersing coefficients and their respective concentrations for chlorophyll-a, suspended sediments and yellow substances in complex inland waters of different trophic states. Variability in the specific absorption coefficients and specific backscattering coefficients of living phytoplankton, suspended sediments and yellow substances was analyzed using a dataset of 42 spectra in Taihu Lake, which were determined from 400 nm to 750 nm with 1 nm increment in wavelength. Based on the quantitative relationship between inherent optical properties and constituents´ concentrations, a reflectance model was established, which is consistent with in situ reflectance spectra in correlation profiles with the three optically active substances. Advancements in mapping the inherent optical properties in the high turbid eutrophic inland waters will underlie the research program of the water quality monitoring, and facilitate the environmental monitoring using remote sensing data.