Coupled hydrological and biogeochemical modelling of nitrogen transport in the karst critical zone.
Coupled hydrological and biogeochemical modelling of nitrogen transport in the karst critical zone.
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DOI：
10.1016/j.scitotenv.2020.138902
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
Zhicai Zhang;Xi Chen;Qinbo Cheng;Siliang Li;F. Yue;Tao Peng;S. Waldron;D. Oliver;C. Soulsby
中科院分区：
文献类型：
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作者：
Zhicai Zhang;Xi Chen;Qinbo Cheng;Siliang Li;F. Yue;Tao Peng;S. Waldron;D. Oliver;C. Soulsby
由于岩溶区水动力特性的显著不均匀性，岩溶区氮素运移比非岩溶区复杂。在这里，我们提出了一个新的，分布式的，耦合的水文-地球化学模型，可以模拟水和氮在岩溶流域的关键区的传输。利用贵州省后寨小流域的水文、水稳定同位素和氮-氮浓度数据对该模型进行了校正。水文动力学似乎控制研究集水区的氮负荷。流量和水稳定同位素的结合显著地限制了模型参数化，并减轻了参数对模拟结果的等效性影响。喀斯特地貌和土地利用对水文过程和氮素运移的时空变化具有功能性影响。在研究流域，农业肥料是最大的N输入源，占总量的86%。植物吸收消耗约45%的投入，主要是在低洼的谷底地区和平原覆盖相对较厚的土壤。因此，大量的N从土壤水库释放到表层岩溶（通过裂缝或天坑），然后输出到南部的石灰岩地区的地下通道。这种N排入地下水可能导致广泛的，潜在的长期污染的岩溶系统。因此，提高施肥和农业管理效率是减少氮素损失和污染风险的迫切需要。
Transport of nitrogen (N) in karst areas is more complex than in non-karst areas due to marked heterogeneity of hydrodynamic behaviour in the karst critical zone. Here, we present a novel, distributed, coupled hydrological-biogeochemical model that can simulate water and nitrogen transport in the critical zone of karst catchments. This new model was calibrated using integrated hydrometric, water stable isotope, and nitrogen-N concentration data at the outflow of Houzhai catchment in Guizhou province of Southwest China. Hydrological dynamics appears to control N load from the study catchment. Combining flow discharge and water stable isotopes significantly constrained model parameterisation and mitigate the equifinality effects of parameters on the simulated results. Karst geomorphology and land use have functional effects on spatiotemporal variations of hydrological processes and nitrogen transport. In the study catchment, agricultural fertilizer was the largest input source of N, accounting for 86% of the total. Plant uptake consumed about 45% of inputs, primarily in the low-lying valley bottom areas and the plain covered by relatively thick soils. Thus, a large amount of N released from soil reservoirs to the epikarst (via fractures or sinkholes) is then exported to the underground channel in the limestone area to the south. This N draining into groundwater could lead to extensive, potentially long-term contamination of the karst system. Therefore, improving the efficiency of fertilization and agricultural management in valleys/depressions is an urgent need to reduce N losses and contamination risk.