Estimation of K d (PAR) in inland waters across China in relation to the light absorption of optically active components.

The comprehensive analysis of the relationships between the attenuation of photosynthetic active radiation (K _d (PAR)) and light absorption is an imperative requirement to retrieve K _d (PAR) from remote sensing data for aquatic environments. The spatial distributions of the K _d (PAR) and light absorption of optically active components (a _OACs ) were routinely estimated in China lakes and reservoirs. Spatial K _d (PAR) was relatively dependent on the inorganic particles (average relative contribution of 57.95%). The a _OACs could explain 70-87% of K _d (PAR) variations. A linear model is used to predict K _d (PAR), as a function of light absorption coefficient of phytoplankton (a _phy ), colored dissolved organic matter (a _CDOM ), and inorganic particles (a _NAP ): K _d (PAR) = 0.41 + 0.57 × a _CDOM + 0.96 × a _NAP + 0.57 × a _phy (R ² = 0.87, n = 741, p < 0.001). In the lakes with low TSM concentration and non-eutrophic lakes with high TSM, a _CDOM was the most powerful predicting factor on K _d (PAR). In eutrophic lakes with high TSM, a _NAP had the most significant impact on K _d (PAR). This study allowed K _d (PAR) to be predicted from a _OACs values in the inland waters.