新型沙漠土壤水分真空抽提装置的研制与应用
A New Vacuum-distilled Extraction Apparatus for Desert Soil Water and Its Application
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摘要: 稳定同位素分析技术是解译干旱-半干旱区沙漠土壤水分运动信息的较好工具。该技术难点不是同位素测试本身,而是用于同位素分析的土壤水分抽提。针对这一难点,本研究对传统抽提装置进行改进。改进型土壤水分抽提装置为支路并联玻璃管路结构,采用真空抽提和液氮冷凝结合收集土壤水分。新装置工作时真空度高且稳定,由实验室原装置的5 Pa提高到0.5 Pa,水分抽提回收率接近100%;其样品装载最多可达600 g,水分收集最大容量为15 mL,显著优于国外典型装置。条件实验显示,相应水分同位素δ值的标准偏差<1‰,表明新装置性能良好,满足测试要求;105℃条件下沙漠水分真空蒸馏抽提时间最少只需要20 min,就能保证水分的充分收集及其同位素没有明显分馏。新型装置的显著特点是适合不同湿度类型、不同质量的样品抽提,且水分抽提回收率高,还具有造价低廉、操作灵活及易维护等特点,与实验室原装置相比,工作效率提高了一倍。野外沙样土壤水分抽提实验及其同位素分析进一步证实了改进型新装置在同位素水文研究中具有重要的应用价值。Abstract: The stable isotopic technique is a good tool to trace information on soil water movement in arid and semi-arid regions. Soil water extraction, rather than isotopic measurement, is the bottleneck in this technique. To solve this problem, a new device has been developed, based on the conventional vacuum extraction in our laboratory. The new device is mostly composed of glass tubes with two parallel connections. The combination of vacuum extraction and liquid nitrogen condensation was applied to collect soil water and the working vacuum was improved to around 0.5 Pa from 5 Pa. For this new device, which is better than other devices, the maximum load capacity of the soil sample and the maximum collection volume of soil water were 600 g and 15 mL respectively. A series of experiments show that the standard deviation of δD and δ18O are both less than 1‰, indicating a good quality for this new device. These experiments also demonstrate that it takes only 20 min to completely extract soil water from desert sand at 105℃ without significant mass fractionation. This new device is more flexible for various extractions of samples with different weights and moistures with a good water recovery, and is also characterized by a low cost, simple operation and cheap maintenance. Compared with the conventional device, the work efficiency of the new device has been doubled. In addition, the extractions of field samples and isotopic investigations further demonstrate the importance of the new device in the study of isotope hydrology.
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Keywords:
- vacuum /
- extraction /
- apparatus /
- optimization /
- stable
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