RADIOCARBON SIGNATURE OF THE RIVERINE PARTICIPATE ORGANIC CARBON: THE ZENGJIANG RIVER EXAMPLE

摘要

Measurements of particulate organic carbon (POC) content and radiocarbon (~(14)C) signature in the riverine suspended sediments were made for one hydrological year in the Zengjiang River of southern China in an attempt to detect the effects of grain-size of the riverine suspended sediment and hydrological condition on the nature of the riverine POC. The POC content in the fine-fraction riverine suspended sediment is constantly larger than that in the coarse-fraction sediment for all the samples collected. Radiocarbon analysis by accelerator mass spectrometry suggested that the apparent ~(14)C ages ranged from 310 a BP to 1980 a BP for the coarse-fraction, and from 220 a BP to 1400 a BP for the fine-fraction POC. The apparent ~(14)C age of riverine suspended sediment is older during the former-flood season than that in other months. Our results showed that riverine POC inventories and its radiocarbon signature were constrained by the grain-size of the riverine suspended sediment and by the hydrological conditions within the drainage basin. The sources diversity of the riverine POC and the soil erosion intensity within drainage basin can be identified by radiocarbon signature.