Abstract
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 (NO 3 − ) pathways, concentration peaks, and stable isotope (δ 15 N NO3 , δ 18 O NO3 , δ 2 H H2O , δ 18 O H2O , and δ 13 C DIC ) 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, δ 2 H H2O , δ 18 O H2O , and δ 13 C DIC coincided with hydrograph peaks for both events. Minima and maxima of NO 3 − , δ 15 N NO3 , δ 18 O NO3 , 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 NO 3 − 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 NO 3 − 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 NO 3 − 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.
| Original language | English |
|---|---|
| Article number | 36 |
| Journal | Environmental Earth Sciences |
| Volume | 78 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 1 2019 |
Bibliographical note
Publisher Copyright:© 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
Funding
Acknowledgements The authors would like to thank the thematic issue guest editor Zexuan Xu and two anonymous reviewers for their insightful comments, which helped to greatly improve the quality of the manuscript. The authors would like to acknowledge the researchers and staff at the Kentucky Geological Survey, in particular, Chuck Taylor and James Currens, and the University of Arkansas Stable Isotope Laboratory. We also thank the Department of Civil Engineering at the University of Kentucky for partial funding of students involved with this research study. Finally, we gratefully acknowledge the financial support of this research under National Science Foundation Award 1632888. Data will be stored and publicly available at the following link: https://figshare.com/articles/EES_TI_Karst_Extremes/7170347.
| Funders | Funder number |
|---|---|
| Civil Engineering Department | |
| National Science Foundation (NSF) | 1632888 |
| University of Kentucky |
Keywords
- Contaminant transport
- Extreme events
- Karst
- Nitrate
- Pathways
ASJC Scopus subject areas
- Global and Planetary Change
- Environmental Chemistry
- Water Science and Technology
- Soil Science
- Pollution
- Geology
- Earth-Surface Processes