中文摘要：

根据2008年3～11月逐月对青木关北段地下河水质的监测，以及2010年6～11月逐月对青木关南段地下河水质的监测，利用15N同位素技术并结合水化学指标，分析地下河的水化学特征以及硝酸盐来源的时空变化特征。结果表明：在北段和南段地下河出口硝酸盐平均浓度分别为20．35mg／L和5．077mg／L，人13分别为3．20mg／L和0．842mg／L，两段的硝酸盐平均浓度在出口处均比入1：1处高6倍多。此外，通过分析青木关整个地下河流域的秽。N空间分布情况，可以得出：南段地下河水中N0f一6”N值较高，且变化显著，最高值37．825％。出现在9月21日丁家龙洞取样点，其硝酸盐来源可能是粪便和污水；而北段地下河水中NO3-15N值都比较低，变化幅度较小，均未超过10％o，说明北段地下河水中硝酸盐的主要来源是土壤有机氮或农业氮肥。

英文摘要：

Based on the monthly monitoring of the northern of the Qingmuguan undergroundwater from March, 2008 to October, 2008, and the monthly monitoring of the southern of the Qingmuguan groundwater from June, 2010 to October, 2010, using hydro-chemical and is N isotope techniques, variations of nitrate-ni- trogen and its possible sources were investigated. The results showed that the nitrate concentrations were 20.35 mg/L and 5. 077 mg/L at the outlet of the north and south underground river,and were 3.20 mg/L and 0. 842 mg/L at the inlet of the river. The outlet of the two parts were all 6 times more than the inlet of them. In addition,through analyzing the spatial distribution of 315N in the whole underground river basin,