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Abstract Relative to their limited areal extent, riparian ecosystems are disproportionately important in regulating inorganic solute export from agricultural landscapes. We investigated spatial patterns of solute concentrations in surface and ground waters of stream corridors to infer the dominant hydrologic transport and biogeochemical pathways that influence riparian nitrate and sulfate processing from uplands to streams. We selected three reaches of stream corridors draining an agricultural landscape that vary in hydrologic connection with upland aquifers. Non‐irrigated crop production dominates land use in the study area and influences the quality of upland groundwater draining to the stream corridors. We interpret patterns in solute concentrations of riparian groundwater and stream water relative to upland groundwater to infer the influences of biogeochemical processing and hydrologic connectivity. Excess nitrate from cultivated soils is evident in upland groundwater concentrations that consistently exceed the U.S. Environmental Protection Agency public drinking water standard. Nitrate and oxygen concentrations in riparian groundwaters were consistently lower than in terrace groundwater and adjacent stream waters, suggesting rapid consumption of oxygen and influence of anaerobic metabolic reduction processes in subsurface flow. Sulfate concentrations in streams were higher than in terrace groundwater, likely due to weathering of shale‐derived substrate in riparian aquifers. The degree of solute mitigation or augmentation by riparian biogeochemical processes depended on the geomorphic context that controlled the fraction of upland water passing through the riparian substrate. Observed net nitrate losses with net sulfate gains from uplands to stream channels reflect flow paths through a complex distribution of redox conditions throughout the riparian areas, emphasizing the importance of considering riparian area heterogeneity in predicting solute export in streams. This research contributes to understanding how stream corridor substrate and geomorphic context controls the biogeochemical and hydrologic processes influencing the quality of water exported from agricultural landscapes.
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End-Point Predictors of Water Quality in Tropical Rivers
End-point evaluation of stream health is essential for the quantification of water quality. To this end, many Multi-Metric Indices (MMIs) have been developed to quantify water quality. The most extensive work has occurred in North America and Europe, while other areas of the world are in development. In this study, we compared the use of relevant physical, chemical and biological parameters in MMIs to various other stream health indicators to assess water quality throughout a three-river corridor along the north central Pacific slope of Costa Rica. Analysis of the data suggested MMIs were the best indicators of water quality and, more specifically, insect MMIs were the most predicative. MMIs were also best at pinpointing anthropomorphic impact throughout the corridor. Further, less complex insect MMIs such as compilations of family diversity using Ephemeroptera, Plecoptera and Trichoptera (EPT) orders were equally as predictive as the more complex models. With a need to better understand and use citizen monitors to predict water quality in these tropical environments, less complex insect MMIs show promise as a solution.
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- Award ID(s):
- 2153558
- PAR ID:
- 10638980
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Pollutants
- Volume:
- 3
- Issue:
- 4
- ISSN:
- 2673-4672
- Page Range / eLocation ID:
- 461 to 476
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/pollutants3040032
