Vertical Distribution and Correlation of Nutrients and Grain Sizes in Sediment Cores of Lake Fuxian

Based on the results of radionuclides (²¹⁰Pb_ex and ¹³⁷Cs) dating of three sediment cores respectively from northern, central and southern parts of Lake Fuxian, vertical distribution and correlation of nutrients (TOC, TN and TP) and grain sizes in the past 150 years were analyzed. The results showed that the TOC concentration varied from stable and slow states to rising in sediment cores. The vertical distribution of TN concentration showed a slight fluctuation characteristic. The variation trend of TP concentration was relatively complex, with the overall trend of dropping firstly and rising later. These variation characteristics were closely related to different levels of natural evolution and human activities in past periods. The C/N ratio in the sediment cores had the rising trend from north to south, indicating that the origin of organic matter in the sediments from Lake Fuxian gradually transited from bacteria and algae within the lake to the land plants. The vertical distribution of grain sizes in sediment cores was disordered, and the size order was central > northern > southern, which may be related to the density, length and sediment yield of rivers in the lake catchment. The correlation analysis of nutrients and grain sizes demonstrated that the size in range of 32-63 μm was significantly positively correlated with TOC concentration, while the size in range of 4-8 μm was significantly negatively correlated with TOC concentration. No correlation was found between TN concentration and grain sizes, and the size of below 2 μm was significantly positively correlated with TP concentration.