Abstract

The measurement and analysis of inherent optical properties (IOPs) of the main water constituents are necessary for remote-sensing-based water quality estimation and other ecological studies of lakes. This study aimed to measure and analyze the absorption and backscattering coefficients of the main water constituents and, further, to analyze their relations to the water constituent concentrations in Poyang Lake, China. The concentrations and the absorption and backscattering coefficients of the main water constituents at 47 sampling sites were measured and analyzed as follows. (1) The concentrations of chlorophyll a (CCHL), dissolved organic carbon (CDOC), suspended particulate matter (CSPM), including suspended particulate inorganic matter (CSPIM) and suspended particulate organic matter (CSPOM), and the absorption coefficients of total particulate (ap), phytoplankton (aph), nonpigment particulate (ad), and colored/chromophoric dissolved organic matter (ag) were measured in the laboratory. (2) The total backscattering coefficients, including the contribution of pure water at six wavelengths of 420, 442, 470, 510, 590, and 700nm, were measured in the field with a HydroScat-6 backscattering sensor. (3) The backscattering coefficients without the contribution of pure water (bb) were then derived by subtracting the backscattering coefficients of pure water from the total backscattering coefficients. (4) The CCHL, CSPM, CSPIM, CSPOM, and CDOC of the 41 remaining water samples were statistically described and their correlations were analyzed. (5) The aph, ad, ap, ag, and bb were visualized and analyzed, and their relations to CCHL, CSPM, CSPIM, CSPOM, or CDOC were studied. Results showed the following. (1) Poyang Lake was a suspended particulate inorganic matter dominant lake with low phytoplankton concentration. (2) One salient aph absorption peak was found at 678nm, and it explained 72% of the variation of CCHL. (3) The ad and ap exponentially decreased with increasing wavelength, and they explained 74% of the variation of CSPIM and 71% variation of CSPM, respectively, at a wavelength of 440nm. (4) The ag also exponentially decreased with increasing wavelength, and it had no significant correlation to CDOC at a significance level of 0.05. (5) The bb decreased with increasing wavelength, and it had strong and positive correlations to CSPM, CSPIM and CSPOM, a strong and negative correlation to CCHL, and no correlation to CDOC at a significance level of 0.05. Such results will be helpful for the understanding of the IOPs of Poyang Lake. They, however, only represented the IOPs during the sampling time period, and more measurements and analyses in different seasons need to be carried out in the future to ensure a comprehensive understanding of the IOPs of Poyang Lake.

© 2011 Optical Society of America

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