Characteristics, distribution and source of dissolved organic matter and its implications for antimony contamination in Zijiang River basin

Dissolved organic matter (DOM) is critical to affecting heavy metal migration and transformation in water. Zijiang River, the third largest tributary of Dongting Lake in Hunan Province, has a high level of antimony (Sb) mass concentration due to the rapid development of the antimony mining and smelting. Excitation-emission matrix spectroscopy (EEMs) and parallel factor analysis (PARAFA)were used to analyze the source and characteristics of DOM in Zijiang River and its indicative significance on antimony migration. The results show that the mass concentration of antimony in the river water in Zijiang River ranges from 1.50 to 62.20 μg/L, with an average of 7.26 μg/L, of which 55.56% exceed the antimony minimum limit of 5 μg/L. DOM of Zijiang River consists of three different components (C1, C2, and C3), which are terrestrial sources, humic-like substance, and the quinone-like humic substance used as electron transport tool, respectively. DOM is mainly composed of C1 and C2. Antimony migration and transformation are influenced by DOM in two ways: The quinone-like humic component, as an electron transfer tools, participates in the reduction of DOM and iron oxide; the complexation of fulvic acid with antimony results in the formation of DOM-Sb complex. The two approaches synergistically enhance the enrichment and transport capabilities of antimony in the Zijiang River. This study will provide a new direction and theoretical basis for the source and prevention of river water antimony pollution in the Zijiang River.