Decoupled ammonia nitrogen and total nitrogen exports under hydroclimatic variability in an alpine headwater catchment of the central Qinghai-Tibet Plateau

IF 7.3 1区地球科学 Q1 ENGINEERING, CIVIL

Journal of Hydrology Pub Date : 2026-10-28 DOI:10.1016/j.jhydrol.2026.136695

Xueping Wang, Xiaolin Shui, Yujie Zhang, Xiaohong Zhao, Zhoufeng Wang, Bo Hu, Haixia Zhu

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引用次数: 0

Abstract

As the “Asian Water Tower” with a fragile alpine ecosystem, nitrogen loading in the Qinghai-Tibet Plateau (QTP) is critical to the water security of the downstream Yangtze River. This study elucidated the spatiotemporal dynamics and potential factors of nitrogen export in the Tongtian River through long-term monitoring (2015–2024) and seasonal sampling, coupled with Optimal Parameters-based Geographical Detector (OPGD) analysis. The results revealed a distinct temporal decoupling between ammonia nitrogen (NH3-N) and total nitrogen (TN). TN concentration and flux exhibited a persistent upward trend (p < 0.001) over the decade·NH3-N concentration showed no significant trend (p > 0.05), whereas its flux exhibited a significant upward trend (p < 0.01), a signal captured only after controlling for intra-annual variability. TN concentrations were highest in the spring campaign (1.71 mg/L), while the NH3-N campaign mean was highest in summer (0.26 mg/L) and close to the autumn and winter means. OPGD identified cropland as the factor with the highest explanatory power for NH3-N concentration (q = 0.54) and pH as the primary explanatory factor for TN concentration (q = 0.53). Suspended sediment concentration had the highest explanatory power for NH3-N flux (q = 0.56), whereas TN flux was predominantly associated with pH and suspended sediment concentration (q = 0.74 and 0.71, p < 0.001). Interaction analysis further indicated joint associations of land-use, hydro-meteorological, and suspended sediment variables with temporal variability in nitrogen export. The contrasting nitrogen patterns may reflect differences in catchment inputs, hydrological transport, and temperature-dependent transformations. Therefore, management strategies must shift from passive concentration monitoring to actively decoupling anthropogenic practice from peak hydro-sedimentary windows

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青藏高原中部高寒水源集水区水文气候变率下氨氮和总氮输出解耦

青藏高原作为脆弱的高寒生态系统的“亚洲水塔”，其氮负荷对长江下游的水安全至关重要。本研究通过长期监测（2015-2024年）和季节性采样，结合基于最优参数的地理探测器（OPGD）分析，阐明通天河氮素输出的时空动态及其影响因素。结果表明，氨氮（NH3-N）与总氮（TN）之间存在明显的时间解耦关系。10年间，TN浓度和通量呈持续上升趋势（p <； 0.001）。NH3-N浓度无显著上升趋势（p >； 0.05），而其通量呈显著上升趋势（p <； 0.01），这一信号只有在控制年内变率后才能捕捉到。TN浓度在春季最高（1.71 mg/L）， NH3-N均值在夏季最高（0.26 mg/L），接近秋冬均值。OPGD发现农田是NH3-N浓度解释力最大的因子（q = 0.54），pH是TN浓度的主要解释因子（q = 0.53）。悬沙浓度对NH3-N通量的解释能力最强（q = 0.56），而TN通量主要与pH和悬沙浓度相关（q = 0.74和0.71,p <； 0.001）。交互作用分析进一步表明，土地利用、水文气象和悬沙变量与氮输出的时间变异有共同的关联。不同的氮模式可能反映了流域输入、水文运输和温度依赖转化的差异。因此，管理策略必须从被动的浓度监测转向主动地将人为活动与峰值水沉积窗口分离

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来源期刊

Journal of Hydrology 地学-地球科学综合

CiteScore

11.00

自引率

12.50%

发文量

1309

审稿时长

7.5 months

期刊介绍： The Journal of Hydrology publishes original research papers and comprehensive reviews in all the subfields of the hydrological sciences including water based management and policy issues that impact on economics and society. These comprise, but are not limited to the physical, chemical, biogeochemical, stochastic and systems aspects of surface and groundwater hydrology, hydrometeorology and hydrogeology. Relevant topics incorporating the insights and methodologies of disciplines such as climatology, water resource systems, hydraulics, agrohydrology, geomorphology, soil science, instrumentation and remote sensing, civil and environmental engineering are included. Social science perspectives on hydrological problems such as resource and ecological economics, environmental sociology, psychology and behavioural science, management and policy analysis are also invited. Multi-and interdisciplinary analyses of hydrological problems are within scope. The science published in the Journal of Hydrology is relevant to catchment scales rather than exclusively to a local scale or site.