Relationships between the elution characteristics and spectrophotometric properties of water-soluble organic matter from a mor-type O horizon
2008
Satou, T.(National Inst. of Advanced Industrial Science and Technology Tsukuba, Ibaraki (Japan)) | Higashi, T.
Relationships between the elution characteristics and the spectrophotometric properties of water-soluble organic matter (WSOM) were investigated to understand the processes that leach dissolved organic matter (DOM) from the O horizon of a Haplorthod under an evergreen coniferous forest. In the present study undisturbed mor-type O horizon samples (900-square cm basal area) were collected to exclude the additional yields of WSOM caused by physical disturbance. The WSOM was sequentially eluted from the samples by dripping ultra-pure water with a novel elution device to obtain sufficient amounts of WSOM powder for spectrophotometric characterization. The drip rate of the ultra-pure water and the elution time were kept constant at 150 mL/min and 1 h, respectively, and this elution of WSOM was repeated five times every hour. Based on the present methods, following elution the characteristics and spectrophotometric properties of WSOM demonstrated that: (1) the yields of WSOM obtained during five elution times were proportional to the carbon mass of the O horizon calculated on a unit area basis, (2) the presence of two different fractions in WSOM with different spectrophotmetric properties was clearly indicated by the elution characteristics where the fraction with low aromaticity, rich in carboxyl groups, was eluted faster than the fraction with relatively higher aromaticity, (3) the relative contribution of the Oi subhorizon to the intact O horizon in terms of the amount of eluted WSOM was small compared to the Oe and Oa subhorizons, (4) the Oa subhorizon appeared to be an important source of WSOM with relatively higher aromaticity than the Oe subhorizon.
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