The Effects of Rainfall on Carbon Isotopes of POC in the Teshio River, Northern Japan

Abstract

During a rainfall event in early September 2006, the transport behavior of particulate organic carbon (POC) in a small river (Teshio River, northern Japan) with alluvial plain and forest characteristics was investigated chiefly with carbon isotopes. The radiocarbon (∆14C value) of POC varied widely from -56‰ at the beginning of the rain event to -10‰ at peak rainfall. The ∆14C values have a positive correlation with C/N ratios and a negative correlation with δ13C values except for the data from when both turbidity and water level were at their maximums due to rainfall. These results indicate that the sources of organic matter in the river come from the surface layer of soil as the water level rises during a rainfall event.