Characterization and pollution evaluation of TOC, TN and TP in sediments of Caohai Lake, Guizhou Province, China

Little is known about the distribution and risk levels of biological elements and nutrients in surface sediment of a closed, shallow, and eutrophication lake in a karst plateau wetland. Sediment/soil samples in Caohai lake, Guizhou Province, China and adjacent upland lakeshore were collected. The abundances of total organic carbon (TOC), total nitrogen (TN), TOC:TN, TOC: total phosphorus (TP), and TN:TP in the lake sediments were significantly higher than those in the surrounding lakeshore soils. 42.86% of the surface sediments exhibited TOC and TN concentrations above the severe effect level, whereas all selected TP concentrations fell between the lowest effect and severe effect levels. Sediment-bound TOC and TN were mainly derived from the endogenous residues, while TP was primary deposited in the form of inorganic phosphorus. Targeted measures should be implemented to reduce the levels of sediment-bound TOC and TN in Caohai Lake.