Inland impacts of atmospheric river and tropical cyclone extremes on nitrate transport and stable isotope measurements
Inland impacts of atmospheric river and tropical cyclone extremes on nitrate transport and stable isotope measurements
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DOI：
10.1007/s12665-018-8018-x
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发表时间：
2019-01
影响因子：
2.8
通讯作者：
A. Husic;J. Fox;E. Adams;J. Backus;E. Pollock;W. Ford;C. Agouridis
中科院分区：
文献类型：
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作者：
A. Husic;J. Fox;E. Adams;J. Backus;E. Pollock;W. Ford;C. Agouridis
大气河流和热带气旋起源于热带地区，可以将大量降雨输送到内陆温带地区。本研究的目的是调查硝酸盐（NO3−）途径、浓度峰值和稳定同位素（δ 15 NNO 3、δ 18 ONO 3、δ 2 HH 2 O、δ 18 OH 2 O和δ 13 CDIC）测量对这些极端事件的响应。2017年，热带气旋和大气河流分别在美国肯塔基州以成熟喀斯特地形为特征的流域产生了排名第一和第四的事件。从两个事件的水文响应是不同的，由于降雨特性与热带气旋产生的春季过程线和更大的径流产生的地表流相比，大气河流的陡峭上升的分支。比电导、δ 2 HH 2 O、δ 18 OH 2 O和δ 13 CDIC的局部最小值和最大值与两次事件的过程线峰值相吻合。NO3−、δ 15 NNO 3、δ 18 ONO 3和温度的最小值和最大值滞后于两次事件的过程线峰值，并且在过程线衰退期间，这些值继续受到扩散补给的影响。快速流动途径占总NO3−产量的不到20%，而中间（30%）和缓慢流动（50%）途径构成了剩余的负荷。然而，将过程线分为快速、中间和慢速流动路径无法预测NO3−浓度峰值的时间。相反，中间流路径被概念化为经历孔隙度的变化，与表层岩溶大孔隙和裂缝到土壤微孔的变化相关，来自后者的水的到来可能会导致NO3-浓度在春季达到峰值。我们的研究结果表明，可能需要一个更离散化的概念模型的途径，以预测峰值养分浓度的河流排水岩溶地形。
Atmospheric rivers and tropical cyclones originate in the tropics and can transport high rainfall amounts to inland temperate regions. The purpose of this study was to investigate the response of nitrate (NO3−) pathways, concentration peaks, and stable isotope (δ15NNO3,δ18ONO3,δ2HH2O,δ18OH2O, andδ13CDIC) measurements to these extreme events. A tropical cyclone and atmospheric river produced the number one and four ranked events in 2017, respectively, at a Kentucky USA watershed characterized by mature karst topography. Hydrologic responses from the two events were different due to rainfall characteristics with the tropical cyclone producing a steeper rising limb of the spring hydrograph and greater runoff generation to the surface stream compared to the atmospheric river. Local minima and maxima of specific conductance,δ2HH2O,δ18OH2O, andδ13CDICcoincided with hydrograph peaks for both events. Minima and maxima of NO3−,δ15NNO3,δ18ONO3, and temperature lagged behind the hydrograph peak for both events, and the values continued to be impacted by diffuse recharge during hydrograph recession. Quick-flow pathways accounted for less than 20% of the total NO3−yield, while intermediate (30%) and slow-flow (50%) pathways composed the remaining load. However, hydrograph separation into quick-, intermediate-, and slow-flow pathways was not able to predict the timing of NO3−concentration peaks. Rather, the intermediate-flow pathway is conceptualized to experience a shift in porosity, associated with a change from epikarst macropores and fissures to soil micropores, with the arrival of water from the latter component likely causing peak NO3−concentration at the spring. Our results suggest that a more discretized conceptual model of pathways may be needed to predict peak nutrient concentration in rivers draining karst topography.