[Estimation of the optically active substances in case II water of the lower Jinjiang River based on the bio-optical...

The water's Inherent Optical Properties (IOPs), including absorption and scattering coefficients of water components, are the essential parameters for bio-optical model and retrieval of water quality using the semi-analytical method. Nevertheless, the application of the bio-optical model in river water studies is still very rare. Therefore, taking the lower Jinjiang River of Fujian, SE China as an example, this study measured and calculated the bio-optical properties of river water and concentrations of optically active substances based on in situ water samples collected from river in 2007. It shows that R(0(-))753, R(0(-))702/R(0(-))680 and R(0(-))670/R(0(-))423 can be used to estimate total suspended solids (TSS) concentration, phytoplankton pigment (PP) concentration and the CDOM absorption at 440 nm, respectively. The determination coefficients (R2) of the retrieval model of TSS, PP and CDOM are 0.953, 0.8205 and 0.6213, respectively. The corresponding relative errors of the models (RE) are 6.1%, 21.87% and 22.18%. The results show that the model for estimating TSS can achieve the highest accuracy, the PP-estimating model has the second highest accuracy and the CDOM-estimating model has the lowest. The relatively lower concentration of phytoplankton pigments, narrow characterized spectral range of CDOM and influence of CDOM's R(0(-)) by TSS and PP within this spectral range contributed to their relatively lower accuracy.