中文摘要：

为了分析黄土塬区土地利用变化对土壤中NO3^--N迁移规律的影响，在陕西长武黄土塬区沿东西方向设置6个样地，每个样地内均选择耕地、由耕地转变来的果龄10a和20a左右的苹果园（下称耕地、10a果园和20a果园）3种土地利用方式采集土壤样品，分析土地利用变化对NO3^--N迁移的影响，并初步评估其对地下水污染的潜在风险．结果表明：不同土地利用方式下土壤中NO^--N均出现累积现象，达到累积峰时的土层深度表现为果园〉耕地，NO3^--N最大累积量表现为20a果园〉10a果园〉耕地．耕地、10a果园和20a果园土壤w（NO3^--N）平均稳定深度分别为300、400和500cm，平均稳定值分别为2．4、2．5和2．6mg／kg．地下水中ρ（NO3^--）为15．3mg／L，而3种土地利用方式下土壤中ρ（可移动态NO3^--）分别为14．2、26．2和26．3mg／L，可见，与耕地相比，果园土壤中NO3^--N淋溶至地下水的风险更大．但由于土地利用变化导致的土壤水分运动和地下水补给存在差异，各土地利用方式对地下水中NO3^--N的贡献率尚需进一步量化．

英文摘要：

Land use change greatly impacts fertilizer application and soil water movement, which further influence nitrate nitrogen transfer and groundwater quality. Therefore, it is important to study the relationship between land use change and nitrogen migration. After analyzing soil samples from farmland over 10-year and 20-year-old apple orchards from six sites on the Changwu Loess Plateau, the characteristics of nitrate nitrogen accumulation and leaching were evaluated and the relationship between them and groundwater pollution was investigated. The results showed that nitrate nitrogen accumulation occurred for different land use types, and the depth of the accumulation peaks was orchards 〉 farmland. The content of accumulation peaks was 20-year-old apple orchard 〉 10-year-old apple orchgrd 〉 farmland. The average depth of stabilized nitrate concentration was 300, 400 and 500 cm, and the average concentrations were 2.4, 2.5 and 2.6 mg/kg for farmland, 10-year and 20-year-old apple orchard, respectively. The nitrate concentration of groundwater was 15.3mg/L; however, those in the deep soil were 14.2, 26.2 and 26.3 rag/L, respectively. Apple orchards had greater threat to groundwater pollution compared with farmland. Due to the difference between soil moisture movement and groundwater recharge, the contribution of nitrate under different land uses to groundwater pollution should he further quantified.