降雨および農業イベント時に水田から流出する溶存有機炭素の生分解性と流出量  [in Japanese] Quantity and Biodegradability of Dissolved Organic Carbon from paddy fields during rainfall and agricultural events  [in Japanese]

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Abstract

The aim of this study is to quantify and characterize dissolved organic carbon (DOC) in effluents (i. e. surface and drain flow) from a paddy field. Water samplings were taken from four paddy fields in Tottori, Japan, during rainfall and agricultural events between April and September 2003, including irrigation and non-irrigation periods, and then DOC concentration was measured. DOC concentration after 50 days incubation was also measured to determine biodegradability. In addition, EMCs (Event Mean Concentration) and Tank model were applied to quantify DOC loadings from the paddy fields. As a result, DOC concentrations of surface flow were between 1.1 and 10.1 mgC/l. The highest concentration was seen in the beginning of rainfall-runoff in non-irrigation period in April. However, the variation of DOC concentration did not always correspond to rainfall. It seems that it varied depending on agricultural event, i.e. decreasing DOC concentration was found during irrigation period. As a result of calculation by Tank model and EMC, the yearly DOC loading and non-biodegradable DOC from a paddy field were estimated 190-296 kg/ha/year and 153-241kg/ha/year, respectively. More than 80 % of the total DOC was non-biodegradable. Especially, the large amount of non-biodegradable DOC was discharged from Shirokaki event in May and from drain in non-irrigation period.

Journal

  • ENVIRONMENTAL ENGINEERING RESEARCH

    ENVIRONMENTAL ENGINEERING RESEARCH (42), 137-143, 2005

    Japan Society of Civil Engineers

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