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[AHW17-06] Carbon isotope composition of riverine particulate organic matter in the Kumaki River system with forest and paddy field in Noto Peninsula, Japan
Keywords:Radiocarbon, stable carbon isotope, suspended solids, terrestrial organic matter
delta13C values range from –28.5 to –24.8‰ for the organic matter in riverine suspended solids and river bottom sediments. The capitaldelta14C values are 86 to 97‰ at the headwater site, –5 to 34‰ at the upper site and –18 to –64‰ at the middle site. The capitaldelta14C of POC decreases from the headwater to the middle sites at the Kumaki River. POC content is 3.9 to 21%, and C/N ratio ranges from 9 to 19. These parameters also show downward decreasing trend in the river line. Similar downward variations were found in the Nishiyachi River but little bit different correlation with delta13C and capitaldelta14C. Land-use pattern in the Kumaki River watershed is occupied by forest in the upper area and by paddy field along the middle and lower river area. These results indicate that paddy field in the middle and lower watershed area in the Kumaki River system has main sources of POM exported to the coastal marine environments.