Optical property of dissolved organic matter and its correlation with heavy metals in surface water around metal mines to be exploited in southern Anhui Province, China

In this study, we aimed to clarify the optical characteristics of dissolved organic matter (DOM) in the surface water around the metal mine to be exploited and its relationship with heavy metals. In total 11 pond water samples and 21 river water samples were collected around the typical to be exploited metal mine in southern Anhui Province, China. The optical properties of DOM in surface water were studied using ultraviolet-visible (UV-Vis) spectroscopy and excitation-emission matrix (EEM) spectroscopy. Co-occurrence network analysis revealed the intrinsic relationship among UV-Vis spectral parameters, fluorescent components, and heavy metals. The results showed that the DOM in the river had higher content, but its molecular weight was smaller than in the pond. EEM coupled with parallel factor analysis (EEM-PARAFAC) revealed humic-like components (C1 and C2) and protein-like components (C3), and the average content of each fluorescent component in the river was higher than that in the pond. However, except for As, the average content of other heavy metals (Cr, Cu, Cd, Pb, and Zn) in ponds was more significant than in rivers. The co-occurrence network analysis result revealed that there might be different relationships between heavy metals and the DOM due to the various land use.