Occurrence and source analysis of heavy metals and dissolved organic matter in Nanyi Lake

Abstract

Nanyi Lake is a tributary in the lower reaches of the Yangtze River and the largest freshwater lake in southern Anhui. Anthropogenic activities have significantly affected the lake with the rapid development of the surrounding economy in recent years. This study collected a total of 39×2 water samples of surface water and overlying water, detected the heavy metal content (As, Cr, Cu, Mn, Ni, Pb, Sb, Zn, Fe, Cd), and analyzed the spectral characteristics of the dissolved organic matter (DOM). The results demonstrated that the content of heavy metals As, Cr, Cu, Ni, Pb, Zn, and Cd in the surface water and overlying water of Nanyi Lake was lower than the class III limits of the environmental quality standard for surface water (GB3838–2002). However, the heavy metals Fe, Mn, and Sb in the overlying and surface water have sites that exceed the limit of class III. The contour map of spatial distribution demonstrated different degrees of heavy metals (except Zn) enrichment near the Langchuan River in the East Lake District. Parallel factor analysis showed that the main components of DOM in Nanyi Lake were tryptophan-like, fulvic acid-like, and tyrosine-like, and the dissolved organic matter was primarily derived from autogenous endogenous sources. The principal component and correlation analysis showed that the heavy metals in Nanyi Lake were primarily derived from the production wastewater discharged by the surrounding industrial and mining enterprises through the rivers input, followed by the non-point source runoff input of the surrounding agricultural production and lake aquaculture.