• 关键词：氮素淋失  氮素形态  浅层地下水  红壤丘陵区  土地利用  亚热带

• 基金项目：国家科技支撑计划项目(No.2014BAD14B02);国家自然科学基金(No.41171396,41201220)

• 焦军霞
• 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125

• 杨文
• 1. 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125;2. 湖南师范大学 资源与环境科学学院, 长沙 410081

• 王美慧
• 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125

• 孟岑
• 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125

• 王毅
• 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125

• 李裕元
• 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125

• 周脚根
• 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125

• 尹娟
• 湖南省湘西自治州气象局, 吉首 416000

• 张满意
• 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125

• 吴金水
• 中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125

• 摘要：土壤养分累积引起的氮素(N)淋失是导致农区地下水污染的重要原因,也是农业面源污染的重要形式.本文以湖南省长沙县典型亚热带红壤丘陵流域为研究对象,通过连续定位观测,研究了林地、稻田、菜地和茶园4种代表性土地利用类型浅层(130~150 cm)地下水中N浓度的逐月动态变化特征.连续3年(2010—2013年)的观测结果表明:4种土地利用类型下浅层地下水总氮(TN)平均浓度差异显著(p<0.05),其中,林地最低(0.85 mg·L^-1),茶园最高(7.64 mg·L^-1);从N的形态构成来看,林地、菜地和茶园浅层地下水中N形态以硝态氮(NO₃^--N)为主,分别占TN的46.7%、70.2%和72.8%,而稻田浅层地下水N形态则以铵态氮(NH₄⁺-N)为主,占TN 43.5%,表明土壤淹水条件是影响地下水N淋失形态的关键因子.地下水各形态N浓度的动态变化在不同土地利用下也迥然不同:林地地下水各形态N的含量低、变幅小,而稻田、菜地和茶园地下水N浓度变幅较大;采用单因子方法对不同土地利用下地下水的水质进行评价,结果表明:研究区浅层地下水中TN和NO₃^--N无显著污染,NH₄⁺-N污染较为严重,而综合指数法(F值法)进一步表明研究区浅层地下水污染主要出现在稻田和茶园,因此,控制稻田和茶园N肥的施用量是预防亚热带红壤丘陵区地下水N污染的关键.

• Abstract：Nitrogen (N) leaching, resulted from soil nutrient accumulation, is an important factor for groundwater pollution in rural area. A continuous in-situ observation of N concentrations in shallow groundwater (130~150 cm) under four representative land-use types was conducted in a typical hilly red soil watershed in Changsha County, China. The land use patterns included forest (F), paddy field (PF), vegetable land (V) and tea plantation (T). Result of 3-year observation (2010—2013) showed that there were significant differences in monthly-mean total nitrogen (TN) concentrations in shallow groundwater under the four land-use types (p<0.05), with the lowest concentration value for F (0.85 mg·L^-1) and the highest for T (7.64 mg·L^-1). With respect to the chemical composition of TN, the proportions of the nitrate (NO₃^--N) were 46.7%, 70.2% and 72.8% under F, V and T, respectively, and the proportion of ammonium nitrogen (NH₄⁺-N) reached 43.5% for PF. This result suggests that water logging condition plays a key role on the N chemical composition in the shallow groundwater. The concentration dynamics of different N forms under the four land-use types were significantly different. The N concentrations under F were relatively low and stable, while the changes in the N concentrations were more significant under PF, V and T. The assessment of water quality using single-factor method showed that shallow groundwater was slightly polluted by TN and NO₃^--N, while it was seriously polluted by NH₄⁺-N in the study area. Moreover, the result of water quality assessment using synthetic index method showed that the pollution under PF and T was more frequent than V and F. Therefore, to prevent N pollution in the shallow groundwater in the hilly red soil region in subtropics, controlling N fertilizer application rates in farmland, in particular in PF and T, should be of top priority.

• Key words：nitrogen leaching  nitrogen chemical composition  shallow groundwater  hilly red soil region  land use  subtropics

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