中文摘要：

选取我国西北干旱区敦煌地区6种不同类型的典型土壤为研究对象,通过测定各土壤剖面Cl^-和NO3^-浓度,探究Cl^-和NO3^-的空间分布特征以及NO3^-的富集程度.结果表明,NO3^-与Cl^-的分布特征基本一致,并与水分含量具有良好的相关性,随包气带埋深的增加呈现波动递减的变化趋势.强烈的蒸散发作用和微生物的硝化作用使土壤表层的NO3^-含量较高,植物根系对NO3^-和水分的吸收降低了NO3^-浓度,并导致NO3^-与Cl^-的分布特征存在不同程度的差异性.不同类型土壤中的NO3^-含量不同,盐碱地〉林地〉农田〉草地〉戈壁〉沙漠.沙土可促进NO3^-的淋溶,无植被生长的戈壁沙漠中较高的NO3^-/Cl^-伴随较低的Cl^-含量说明硝态氮的富集主要发生在干旱阶段,蓝藻菌的固氮作用活跃,而农田土壤中硝态氮的富集受人为源影响显著.

英文摘要：

By measuring the concentrations of Cl^-and NO3^- in six typical soils collected from Dunhuang in northwest China,this study explored the spatial distribution characteristics of Cl^-and NO3^- and accumulation of NO3^-. The results indicated that the distribution characteristic of NO3^-was similar to that of Cl^-,and both of them correlated well with the soil moisture. With the increase in the depth of the unsaturated zone,the concentration of NO3^-displayed a decreasing trend of volatility. The intense evaporation and microbial nitrification resulted in relatively high NO3^-content in the soil surface,while water and nutrition uptake by plant roots reduced the concentration of NO3^-in the root zone. This process caused some differences in the vertical distributions between NO3^- and Cl^-. The concentration of NO3^- showed significant difference among different soils,with an order of saline〉 forest〉 farmland 〉grassland 〉gobi 〉desert. Because NO3^-can easily leach out in sand soil,the lower level of Cl^-and high level of NO3^-/ Cl^-in gobi and desert indicated that nitrate enrichment mainly occurs in the arid phase and nitrogen fixation of cyanobacteria is active.However,nitrate enrichment in farmland soil was significantly affected by anthropogenic activities.