Chronology and nutrients change in recent sediment of Taihu Lake, lower Changjiang River Basin, east China

Abstract

Two short sediment cores named ZS and THS dated by the 210 Pb or 137 Cs method were collected from the northwest and southwest of Taihu Lake respectivly, and total organic carbon (TOC) and nutrients including total nitrogen (TN) and total phosphorus (TP) were determined to analyze the chronology and nutrients change in recent sediment. The results show that 137 Cs activities are low (less than 15 Bq/kg) in the two cores, attributed to the 137 Cs migration. Based on 210 Pb constant rate of supply (CRS) model, the sedimentation accumulation rates range from 0.13 g/(cm 2 •yr) to 0.76 g/(cm 2 •yr) in the ZS core, and from 0.10 g/(cm 2 •yr) to 0.56 g/(cm 2 •yr) in the THS core. A remarkable increase in organic matter and nutrients has occurred in the two dated cores since the mid-1980s. The historical changes of organic matter and nutrients in the two cores are consisitent with the monitoring data for surface sediment after the 1960s. The TP accumulation rates after the early 1980s are 0.97 and 0.92 times higher than those from the 1950s to the 1980s in ZS and THS cores, respectively. Higher TP concentrations in the past two-decade deposits of Taihu Lake are due to both diagenetic factors and human activities.