| 长江上游典型山地农业小流域浅层地下水硝态氮时空变异特征及影响因素 |
| 摘要点击 1904 全文点击 813 投稿时间：2019-12-23 修订日期：2020-04-07 |
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| 中文关键词 浅层地下水 硝态氮 时空变异特征 影响因素 农业小流域 |
| 英文关键词 shallow groundwater nitrate temporal and spatial variation characteristic regulators small agricultural watershed |
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| 中文摘要 |
| 长江上游山区以浅层地下水作为主要供水水源，但其极易受到农业生产等活动所导致的硝态氮（NO3--N）污染.本文选取长江上游典型山区农业小流域作为研究对象，对土地利用与管理强度和水文地质条件等进行了野外调查，阐明其浅层地下水NO3--N时空变异特征并分析其影响因素.结果表明，研究小流域地下水中NO3--N质量浓度变化范围为0.40~12.51 mg ·L-1，超标率近30%.受降雨和管理强度影响，丰水期降雨量和施肥量增加，土壤中氮素在降雨驱动下淋溶流失进入浅层地下水，呈现出丰水期NO3--N质量浓度（6.73 mg ·L-1）高于枯水期NO3--N质量浓度（6.28 mg ·L-1）的时间变异特征.在空间上，小流域地下水中NO3--N质量浓度呈现坡耕地和居民区集中分布的截留和大兴子流域中地下水NO3--N质量浓度（截留子流域：6.58mg ·L-1；大兴子流域：6.34 mg ·L-1）高于苏荣子流域（5.20 mg ·L-1）的特征，主要由不同子流域地下水埋深和土地利用类型的空间分异特征导致.此外，浅层地下水NO3--N质量浓度与Cl-、NH4+-N、DOC和SO42-质量浓度呈正相关，而与pH值呈负相关，表明地下水化学因子亦是其不可忽略的影响因素.因此，加强山地农业小流域浅层地下水NO3--N时空变异特征及其影响因素研究对防控山区农村浅层地下水硝态氮污染和保障饮用水安全十分必要. |
| 英文摘要 |
| Shallow groundwater is the main drinking water supply for the mountainous area in the upper reaches of the Yangtze River, while its quality is often degraded by nitrate (NO3--N) pollution due to intensive agricultural production activities. In the present study, we selected a mountainous agricultural watershed in the upper reaches of the Yangtze River to investigate the land use, management, and hydrogeological conditions, aiming to clarify the spatial-temporal variations in NO3--N concentration of shallow groundwater, thereby exploring the key regulators. The results showed that the NO3--N concentrations of the groundwater ranged from 0.40 to 12.51 mg ·L-1in the study area, and the exceeding ratio was nearly 30%. On an average, NO3--N concentrations for the wet season were higher than that for the dry season, indicating great variations in NO3--N concentration across different seasons. In addition, the spatial variations of NO3--N concentration in groundwater were also significant among different sub-catchment, which was mainly due to variations in the groundwater table depth and land uses. Furthermore, the significant correlations between the NO3--N concentrations and concentrations of Cl-, NH4+-N, DOC, and SO42- in the shallow groundwater were also explored in this study, suggesting that the NO3--N concentrations were likely to depend on the chemical factors of the shallow groundwater in the study area. Overall, our current study highlights that the characterization of spatial-temporal variations of NO3--N status in shallow groundwater and illustration of key regulators are essential to mitigate NO3--N pollution and prevent quality degradation of shallow groundwater in mountainous rural areas of the upper Yangtze River watershed. |
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