Abstract: Particulate organic matter (POM) transportation from land to river is important in the global carbon cycling. Its sources, transportation and sinks are still not well known. Previous studies have shown that snow-melt may increase organic materials runoff. But the transportation behavior of POM is obscure because of lack of information on characteristics and sources. This study applied accelerator mass spectroscopy to analysis 14C which is a tracer of sources, turn over times and sinks as well as transportation of POM. We selected the Ishikari River at snow-melt season in this study. The Ishikari River flows through the low agricultural land to the east part of the Hokkaido Island in Japan which is covered by snow from January to April and has a catchments area of 14430 km2 and 268 km in length (the second largest in Japan). Snow-melt begins from first of April and completes mostly in middle of May. Water discharge increases in this period by 3-4 times more than other seasons. Water samples were collected once a month at Iwamizawa Bridge from April to September in 2004. Turbidity decreased from 468 mg/l in April to 23 mg/l in June. POC concentrations increased from 1.8% in April to 5.4% in June and decreased from 3.8% in July to 2.5% in September. D14C increased from -364‰ in April to -103‰ in June and decreased from -169‰ in July to -227‰ in September. There is a positive correlation between POC and D14C values (r=0.76). The minimum values for POC and D 14C were found in April at snow-melt season. The lowest amount of older POM was transported by a large amount of snow-melt water with much of inorganic materials from watershed. The relationship between POC and D14C indicates that the older POM was mixed with newly produced and younger organic matter from the watershed.
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See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)