With a certain nitrate input at the land surface, different nitrate levels in the unsaturated zone can act as a direct proxy of an aquifer vulnerable to nitrate. Improved understanding of different nitrate distribution characteristics in the unsaturated zone and its formation mechanism is important to evaluate nitrate vulnerable of an aquifer and protect groundwater from nitrate pollution. This paper collects data of nitrate content of the only two existing unsaturated profiles in North China, summarizes the differences in nitrate distribution in the profiles, points out that infiltrate rate and denitrification potential are two keys to the differences. Furthermore, future developments in the unsaturated zone, which is quantification of denitrifcaiton potential using isotope techniques are proposed.%在地表等量氮输入条件下,包气带中硝酸盐含量分布是其抗污染能力的直接表征.阐明不同包气带中硝酸盐分布的差异并分析其成因对于评价下覆含水层的硝酸盐污染脆弱性、保护地下水资源免遭硝酸盐污染,具有重要意义.本文基于太行山山前冲洪积扇上栾城和正定两个16m深包气带硝酸盐含量数据,指出两个剖面上包气带中硝酸盐分布特征的差异性.分析研究区的施肥历史、大气降水的人渗补给强度及土壤有机质含量,认为包气带水分运移速度和反硝化能力是导致包气带硝酸盐分布差异的两个关键因素.在分析N同位素测试技术进步的基础上,指出利用同位素技术对包气带中的反硝化能力的定量化研究有望取得新进展.
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