Influence of Irrigated Paddy Fields on the Fluorescence Properties of Fluvial Dissolved Organic Matter

This study investigated seasonal and geographical variation in the fluorescence properties of dissolved organic matter (DOM) in a river system that includes rice paddy fields in its watershed. The river system covers a northern area of the main island of Japan, and between 6 and 45% the watershed ar...

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Bibliographic Details
Published in:Journal of environmental quality 2011-07, Vol.40 (4), p.1266-1272
Main Authors: Abe, Youichiro, Maie, Nagamitsu, Shima, Eikichi
Format: Article
Language:English
Subjects:
Agriculture
Biogeochemistry
Cereal crops
Cultivation
Dissolved organic matter
Factor analysis
Factor Analysis, Statistical
Fluorescence
Grain cultivation
Humic Substances - analysis
Japan
Land use
Oryza - growth & development
Rice
Rice fields
Rivers
Seasonal variations
Seasons
Spectrometry, Fluorescence
Tributaries
Water analysis
Water Pollution, Chemical - analysis
Water sampling
Water Supply
Watershed management
Watersheds
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Summary:This study investigated seasonal and geographical variation in the fluorescence properties of dissolved organic matter (DOM) in a river system that includes rice paddy fields in its watershed. The river system covers a northern area of the main island of Japan, and between 6 and 45% the watershed area of the tributaries is paddy fields. Water samples were collected monthly from eight tributaries for 1 yr, and the fluorescence properties of DOM were monitored by combined excitation‐emission matrix (EEM) and parallel factor analysis. The EEM was statistically decomposed into six fluorescence components with different environmental dynamics. The relative proportion of these components varied with season and geographic location, the former having a greater effect than the latter. Seasonal variation is largely attributed to changes in the source of DOM associated with irrigated rice cultivation practice. The fluorescence component composition showed a stronger autochthonous signature, which varied over a wider range during off‐cropping period (October–April) than cropping period (May–September). During the cropping period, a large amount of allochthonous DOM with relatively similar quality was transported into river water from flooded paddy fields and masked the variability in the quality of DOM among tributaries. Therefore, irrigated rice cropping practices are considered to be one of major factors that influence seasonal and geographical variation of fluvial DOM composition.
ISSN:0047-2425
1537-2537
DOI:10.2134/jeq2010.0374