中文摘要：

利用苔藓组织氮含量和氮稳定同位素研究了贵阳市大气氮沉降的来源、沉降和迁移。结果表明,贵阳地区苔藓氮含量的变化特征很好地指示了区内大气氮沉降的空间变化。贵阳市区苔藓氮同位素与郊区或农村地区差异明显,区内城市与农村有不同的氮源。苔藓氮同位素从市区往外逐渐偏正（-8.87‰～-2.48‰）,说明来自市区的铵在逐渐减少,而来自农村的铵的贡献逐渐增加。贵阳地区从市区往外苔藓氮含量随距离指数降低（y=1.5e-0.13x＋1.26）,而氮同位素随距离对数升高[y=2.54ln（x）-12.227],揭示了源自市区的大气铵（NHx）向周边的扩散迁移呈指数降低的变化规律。运用极限法求解苔藓氮含量和氮同位素组成随距离变化的函数,发现市区铵沉降的影响范围小于41 km,在17.2 km以外的地区,市区铵沉降低于背景农业铵沉降值。

英文摘要：

The sources of atmospheric N,atmospheric N deposition and N transport were studied in Guiyang area using tissue N contents and N isotope in epilithic mosses.The results indicated that tissue N contents in epilithic mosses can be used to show the spatial variation of atmospheric N deposition.The significant difference in nitrogen isotopic ratios between urban and suburban（or rural） epilithic mosses was suggestive of two atmospheric N sources.More positive δ15N values in epilithic mosses from urban to rural sites reflected the decrease of urban-derived N and the increase of agricultural-derived N.In Guiyang area,N contents in epilithic mosses exponentially decreased with the distance from the city center（y=1.5e-0.13x ＋ 1.26） while the δ15N values logarithmically increased with the distance [y=2.54ln（x）-12.227],suggesting that urban-derived NHx decreased with the distance during its transport.The above equation was resolved using a limitation method.The results showed that the distance influenced by urban-derived NHx was 41 km and agricultural-derived NHx turned to be more important than urban-derived NHx beyond the distance of 17.2 km.