Use of stable isotopes in the studies on cycling of water and ions in ecosystem.

针对土壤中氘水（HDO）示踪剂的使用问题，进行了以下研究：1)tcd -气相色谱法测定纯净水样品中HDO浓度的准确性；2)分离纯化分析水样的方法；3)海洋和陆地水域（包括土壤水）中HDO的天然丰度及其波动。1)以轻水电解得到的低HD载气（HDO conc）为原料，tcd -气相色谱法测定HDO浓度的标准误差小于+2 ppm。= 11ppm)。2)建立了一种在田间采集土壤溶液样品进行DHO测定的张力渗湿法。土壤吸水量小于250cmH20时，提取过程中同位素效应较弱。结果表明，当土壤吸水性大于300cmH20时，张力渗滤法的提取效果较差。③土壤中HDO的自然丰度在135 ~ 150 ppm之间。为了获得HDO作为水示踪剂在田间条件下应用的附加信息，进行了一些田间试验。在利用双环式入渗仪测定入渗能力时，注意到入渗水量分布极不均匀。与土中大孔体系的尺度相比，柱体的尺度还不够大。在田间试验中，添加的HDO被迅速稀释，几乎无法追踪，特别是在土壤湿度高的情况下，如泥炭土。

To solve the problems concerning to the tracer use of deuterium water(HDO) in soils, following studies were conducted : 1) Accuracy of the determination of HDO concentration in purified water samples by using a TCD-gaschromatography, 2) methods to separate and purify the water samples for the analysis, 3)natural abundance of HDO and its fluctuation in marine and terrestrial waters, including soil water.1) The standard error of the determination of HDO concentration by the TCD-gaschromatography was less than +2 ppm when the low HD carrier gas obtained by electrolysis of light water(HDO conc.=11 ppm) was used. 2) A tension lysimeter method was developed to collect the samples of soil solution for the DHO determination in the field. The isotope effect during the extraction was slight when soil water suction was less than 250cmH20. It is concluded that the extraction by the tension lysimeter method is hardly applicable when soil water suction is higher than 300cmH20. 3) Natural abundance of HDO in soils was in the range from 135 to 150 ppm.Some field experiments were conducted to obtain additional information on the application of HDO as a tracer of water under the field condition. During the determination of infiltration capacity by using the double ring infiltrometer, extremely uneven distribution of infiltrated water was noticed. It was concluded that the scale of cylinder was not sufficiently large in comparison with the scale of macropore systems in soils. In field experiments the added HDO was diluted rapidly and was hardly traceable, especially when the soil wetness was high, as in the case of peat soils.