Estimation of Kd(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 (Kd(PAR)) and light absorption is an imperative requirement to retrieve Kd(PAR) from remote sensing data for aquatic environments. The spatial distributions of the Kd(PAR) and light absorption of optically active components (aOACs) were routinely estimated in China lakes and reservoirs. Spatial Kd(PAR) was relatively dependent on the inorganic particles (average relative contribution of 57.95%). The aOACs could explain 70-87% of Kd(PAR) variations. A linear model is used to predict Kd(PAR), as a function of light absorption coefficient of phytoplankton (aphy), colored dissolved organic matter (aCDOM), and inorganic particles (aNAP): Kd(PAR) = 0.41 + 0.57 × aCDOM + 0.96 × aNAP + 0.57 × aphy (R2 = 0.87, n = 741, p < 0.001). In the lakes with low TSM concentration and non-eutrophic lakes with high TSM, aCDOM was the most powerful predicting factor on Kd(PAR). In eutrophic lakes with high TSM, aNAP had the most significant impact on Kd(PAR). This study allowed Kd(PAR) to be predicted from aOACs values in the inland waters.