Hydrogen isotope composition of soil water above and below the hardpan in a rainfed lowland rice field
Hydrogen isotope composition of soil water above and below the hardpan in a rainfed lowland rice field
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DOI：
10.1016/j.fcr.2005.09.011
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发表时间：
2006-04
影响因子：
5.8
通讯作者：
K. Yano;Nobuhito Sekiya;B. K. Samson;M. Mazid;A. Yamauchi;Y. Kono;L. Wade
中科院分区：
文献类型：
--
作者：
K. Yano;Nobuhito Sekiya;B. K. Samson;M. Mazid;A. Yamauchi;Y. Kono;L. Wade
在稻田中，发育中的硬土层对蓄水是重要的，但在干旱时，硬土层也限制了水分从硬土层以下的迁移。实验地点在孟加拉国西北部的拉杰沙希。在田间约0.2m土壤深度处已形成硬土层。用安装在田间的多孔杯非破坏性地收集来自硬土层上方或下方的土壤水。用同位素比值质谱仪测定了各水样的δD值。在采样期间，随着降雨事件的发生，农田表面从饱和状态向非饱和状态变化。虽然δD值受降雨影响而波动，但在硬土层上、下之间始终存在显著差异，表明硬土层中δ D值的异质性持续存在。在名古屋大学的一项实验室实验中，使用从稻田中收集的完整土柱进一步证实了硬土层对δD特征保留的影响。低地水稻田的天然δD特征可能有助于通过木质部汁液的δD分析来鉴定某些表现出从硬土层以下原位吸水能力的基因型。
In rainfed lowland rice fields, developing hardpan soil layers must be important to pool rainfall, but during drought that also restricts water movement from below it. We investigated whether the hardpan can maintain a contrast of deuterium/hydrogen isotopic composition (δD) in soil water under field condition. The experimental site was at Rajshahi in north-west Bangladesh. The hardpan soil layers had developed around 0.2m soil-depth in the field. Soil water from either above or below the hardpan was collected non-destructively with porous cups installed into the field. Using an isotopic ratio mass spectrometer, δD value of each water sample was determined. During the sampling period, the field surface varied from water-saturated to unsaturated status with rainfall event. While the δD values fluctuated by the influence of rainfall, significant differences in the δD values were always detected between above and below the hardpan, revealing heterogeneity in the δD values persisted with the hardpan. The effect of hardpan on retention of the δD signature was further confirmed in a laboratory experiment using intact soil columns collected from a paddy field at Nagoya University. The natural δD signature in rainfed lowland rice field may be useful to identify certain genotypes that demonstrate in situ capability of water acquisition from below the hardpan through δD analysis of the xylem sap.