真空蒸馏提取与原位采集对土壤水氢氧稳定同位素值比值的影响

为了研究不同采样方法对采集的土壤水氢氧稳定同位素比值的影响,设计了室内降水入渗模拟试验,收集土柱底部出流水、土壤溶液采样器原位采集10cm、40cm、70cm、100cm处的土壤水,在相同层位采集土壤样品并采用真空蒸馏法提取土壤水。通过样品的氢氧稳定同位素比值对比分析可知,降水入渗干燥的土壤过程中土颗粒优先吸附轻同位素,第一个收集的水分具有最正的氢氧稳定同位素比值;真空蒸馏法提取的土壤水是土壤吸湿水和入渗水分的混合,土壤溶液采样器原位采集的土壤水代表土壤中流动的水分,此水分是土壤中可被有效利用的水分。

Effects of vacuum distillation extraction and in-situ collection methods on the ratio of hydrogen and oxygen isotope of soil water

To study the effects of different collection methods on hydrogen and oxygen isotope values of soil water, a laboratory experiment is designed to model the rainfall infiltration behavior, and the water outflow from the bottom of the soil column is collected. In this experiment, soil waters at depths of 10 cm, 40 cm, 70 cm and 100 cm are collected and this collection method is termed as in-situ collection method. On the other hand, soil samples at the same depths are taken out with the soil waters being collected using vacuum distillation extraction method. The comparison results between D and ¹⁸O values show that during the process of rainfall infiltration in the dry soil sample, the light isotopes are preferentially adsorbed by soil particles, and the outflow water collected first has the most positive hydrogen and oxygen isotope values. The soil water extracted by the vacuum distillation method is composed of moisture-absorbing water of the air-dried soil and the water infiltrated into the unsaturated zone. The soil water collected by the in-situ soil solution sampler represents the water flowing in the soil and could be effectively used.