Influence of environmental factors on absorption characteristics of suspended particulate matter and CDOM in Liaohe River watershed, northeast China

Abstract

Absorption characteristics of optically active substances, including non-algal particles, phytoplankton, and chromophoric dissolved organic matter (CDOM), were measured in conjunction with environmental factors in five rivers within the Liaohe River watershed. Spectral absorption of non-algal particles [a _NAP(λ)] was similar to that of total particles for most samples, suggesting that the absorption of the total particles [a _p(λ)] was dominated by a _NAP(λ). The CDOM absorption spectra [a _CDOM(λ)] of West Liaohe and Taizihe rivers were easily distinguished from those of Hunhe, Liaohe, and East Liaohe rivers. Redundancy analysis indicated that absorption by optically active substances and anthropogenic nutrient disturbances probably resulted in the diversity of water quality parameters. The environmental variables including dissolved organic carbon, total alkalinity (TAlk), and total nitrogen (TN) had a significant correlation with CDOM absorption at 440 nm [a _CDOM(440)]. There was almost no correlation between a _p(λ) and chlorophyll a, TN, total phosphorus, and TAlk. Moreover, total copper ion concentration and mercury ion concentration had a strong correlation with a _p(440), a _p(675), a _NAP(440), and a _NAP(675). The concentration of total aluminum ions exhibited a positive correlation with a _p(675) and a _NAP(675) (p < 0.05), and a significant correlation was observed between total arsenic concentration and a _CDOM(440). Furthermore, the interaction between metal ions and optically active substances provided an insight into particulates and CDOM properties linked to water quality characteristics for rivers in semiarid areas.

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