The absorption characteristics, composition, spatial variability, and relative contribution of optically active constituents over the range of photosynthetically active radiation (PAR, 400-700 nm) were analyzed from samples collected in the Yiluo and Huntai Rivers in May 2017 and 2013, respectively. Results demonstrated that the absorption curves of total suspended particulates[ap(λ)] were similar to those of non-algae particles[ad(λ)]. Significant correlations between ap(λ) and ad(λ) were obtained, especially at 440 nm, with r=0.968 in the Yiluo River and r=0.899 in the Huntai River. Meanwhile, positive correlations between ap(λ) and the absorption of phytoplankton[aph(λ)] were observed at 675 nm. ap(λ) in the two basins was dominated by ad(λ). Moreover, the composition of auxiliary pigments and chloropyhll a concentration[Chla] showed more significant spatial variations based on aph(440)/aph(675) in the Yiluo River than in the Huntai River. In addition, CDOM absorption slopes (SCDOM) indicated that CDOM composition in the Yiluo River was dominated by exogenous substances; in comparison, the Huntai River had more endogenous substances. SCDOM in the Yiluo River was lower than in the Huntai River, indicating that the CDOM composition of the Yiluo River was inclined towards high molecular weights. Furthermore, Mr[aCDOM(250)/aCDOM(365)] showed greater ranges and lower mean values in the Yiluo River than in the Huntai River, confirming that CDOM molecular weight varied greatly in the former. CDOM molecular weight in the Huntai River was also lower than in the Yiluo River, in accordance with SCDOM results.
Keywords: CDOM; Huntai River; Yiluo River; optical absorption characteristics; particulate matter; spatial difference.