基于水稳定同位素技术的生物炭对土壤持水性影响分析

Impact of Biochar Addition on Soil Water Retention Based on Water Stable Isotopes

以不同生物炭配比的土壤样品为研究对象,通过低温真空抽提和稳定同位素光谱技术,进行不同抽提时间下的土壤水稳定同位素分析,采用绘制土壤抽提曲线和计算抽提贡献率的方法,探讨生物炭对土壤持水性的影响。结果表明,低温真空抽提下,砂土的最短抽提时间(T_(min))为30 min,壤土为45 min,粘土为60 min。土壤持水性的变化会导致抽提过程中水稳定同位素值、T_(min)和抽提贡献率发生变化,通过分析不同生物炭配比下土壤的T_(min)、水稳定同位素分馏情况以及计算贡献率可得出,生物炭显著影响砂土持水性,且与生物炭添加量呈线性正相关;而对壤土和粘土的持水性有一定影响,但过量或过少则不明显,壤土对生物炭更为敏感。

Application of biochar in soil is being increasingly discussed as a mean to sequestrate carbon and improve chemical and physical properties for plant growth. Compared with the studies assessing the impact on water retention,little research has been published elucidating the mechanisms which were responsible for the change of water stable isotope extraction time. The impacts of biochar on water retention of three types soil（ sandy,loam and clay） with different biochar application rates were investigated by extraction timing curve and mean proportional contribution. The mixtures were extracted by cryogenic vacuum distillation and analyzed with isotope ratio infrared spectroscopy. The results showed that the minimum extraction time（ T_（min）） was 30 min for sandy soil,45 min for loam soil and 60 min for clay soil. The biochar application rates changed the T_（min）,as well as the water hydrogen isotope value and mean proportional contribution. The isotopic composition of extracted sandy soil water was more depleted in2 H with the increase of biochar application rates at T_（min）,while the extent of deviation to the standard values displayed peak for loam and clay soil water hydrogen isotope. The results indicated that biochar application rate was directly correlated to the water retention of sandy soil,and it was increased with the increase in water retention of loam and clay soils,but not all biochar application rates had the same impact. The loam soil was more sensitive than the clay soil to the biochar application.