Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System
Nitrate legacy is affecting groundwater sources across the tropics. This study describes isotopic and ionic spatial trends across a tropical, fractured, volcanic multi-aquifer system in central Costa Rica in relation to land use change over four decades. Springs and wells (from 800 to 2,400 m asl)...
| Autores Principales: | Sánchez-Gutiérrez, Rolando, Sanchez-Murillo, Ricardo, Esquivel-Hernández, Germain, Birkel, Christian, Boll, J., Rojas-Jiménez, L. D., Castro-Chacón, L. |
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| Formato: | Artículo |
| Idioma: | Inglés |
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John Wiley & Sons (Estados Unidos)
2024
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| Acceso en línea: |
http://hdl.handle.net/11056/27790 https://doi. org/10.1029/2023JG007554 |
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RepoUNACR277902024-04-30T20:06:32Z Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System Sánchez-Gutiérrez, Rolando Sanchez-Murillo, Ricardo Esquivel-Hernández, Germain Birkel, Christian Boll, J. Rojas-Jiménez, L. D. Castro-Chacón, L. NITRATE LEGACY TROPICAL VOLCANIC ACUÍFERO SISTEMA ISOTOPOS AGUAS SUBTERRÁNEAS COSTA RICA Nitrate legacy is affecting groundwater sources across the tropics. This study describes isotopic and ionic spatial trends across a tropical, fractured, volcanic multi-aquifer system in central Costa Rica in relation to land use change over four decades. Springs and wells (from 800 to 2,400 m asl) were sampled for NO3 − and Cl − concentrations, δ 18Owater, δ 15NNO3, and δ 18ONO3. A Bayesian isotope mixing model was used to estimate potential source contributions to the nitrate legacy in groundwater. Land use change was evaluated using satellite imagery from 1979 to 2019. The lower nitrate concentrations (<1 mg/L NO3 −N) were reported in headwater springs near protected forested areas, while greater concentrations (up to ∼63 mg/L) were reported in wells (mid- and low-elevation sites in the unconfined unit) and low-elevation springs. High-elevation springs were characterized by low Cl − and moderate NO3 −/Cl − ratios, indicating the potential influence of soil nitrogen (SN) inputs. Wells and low-elevation springs exhibited greater NO3 −/Cl − ratios and Cl − concentrations above 100 μmol/L. Bayesian calculations suggest a mixture of sewage (domestic septic tanks), SN (forested recharge areas), and chemical fertilizers (coffee plantations), as a direct result of abrupt land use change in the last 40 years. Our results confirm the incipient trend in increasing groundwater nitrogen and highlight the urgent need for a multi-municipal plan to transition from domestic septic tanks to regional sewage treatment and sustainable agricultural practices to prevent future groundwater quality degradation effectively. El legado de nitratos está afectando las fuentes de agua subterránea en los trópicos. Este estudio describe isotópico y tendencias espaciales iónicas a través de un sistema multiacuífero volcánico tropical, fracturado en el centro de Costa Rica en relación con el cambio de uso de la tierra durante cuatro décadas. Se tomaron muestras de manantiales y pozos (de 800 a 2.400 m snm) para concentraciones de NO3 − y Cl −, δ 18Oagua, δ 15NNO3 y δ 18ONO3. Se utilizó un modelo de mezcla de isótopos bayesianos para estimar las posibles contribuciones de las fuentes al legado de nitratos en las aguas subterráneas. Se evaluó cambio de uso de suelo utilizando imágenes satelitales de 1979 a 2019. Las concentraciones más bajas de nitrato (<1 mg/L NO3 −N) se informaron en manantiales de cabecera cerca de áreas forestales protegidas, mientras que se informaron concentraciones mayores (hasta ~63 mg/L) en pozos (sitios de elevación media y baja en la unidad no confinada) y manantiales de baja elevación. Manantiales de gran altura se caracterizaron por proporciones bajas de Cl − y moderadas de NO3 −/Cl −, lo que indica la posible influencia del nitrógeno del suelo. (SN) entradas. Los pozos y manantiales de baja elevación exhibieron mayores relaciones NO3 −/Cl − y concentraciones de Cl − superiores 100 µmol/L. Los cálculos bayesianos sugieren una mezcla de aguas residuales (fosas sépticas domésticas), SN (recarga forestal áreas), y fertilizantes químicos (plantaciones de café), como resultado directo del cambio abrupto de uso del suelo en los últimos 40 años. Nuestros resultados confirman la incipiente tendencia al aumento del nitrógeno en las aguas subterráneas y resaltan la urgente necesidad de Necesidad de un plan multimunicipal para la transición de tanques sépticos domésticos a tratamiento regional de aguas residuales y prácticas agrícolas sostenibles para prevenir eficazmente la futura degradación de la calidad del agua subterránea. Plain Language Summary. This study analyzed different nitrate sources in a complex tropical groundwater system and how they were affected by changes in land use over the last decades. In general, high-elevation areas near protected forests are represented by lower nitrate levels, while mid- and low-elevations areas exhibited greater nitrate and chloride concentrations. Our results suggest that groundwater nitrate reflects a legacy mixture of sewage (domestic septic tanks), soil nitrogen (forested recharge areas), and chemical fertilizers (coffee plantations), as a direct result of abrupt land use change in the last 40 years. The identified nitrate groundwater legacy in the Central Valley of Costa Rica, evidenced by unprecedented decadal nitrate isotope data, could serve as a valid example of the potential impact of abrupt urbanization growth across the wet tropics. Resumen en lenguaje sencillo. Este estudio analizó diferentes fuentes de nitrato en una compleja zona tropical. sistema de aguas subterráneas y cómo se vieron afectados por los cambios en el uso de la tierra durante las últimas décadas. En general, Las áreas de alta elevación cerca de bosques protegidos están representadas por niveles más bajos de nitrato, mientras que las elevaciones medias y bajas las áreas exhibieron mayores concentraciones de nitrato y cloruro. Nuestros resultados sugieren que el nitrato del agua subterránea refleja una mezcla heredada de aguas residuales (fosas sépticas domésticas), nitrógeno del suelo (áreas de recarga boscosas) y productos químicos. fertilizantes (plantaciones de café), como resultado directo del cambio abrupto de uso del suelo en los últimos 40 años. El identificado El legado de nitrato en las aguas subterráneas en el Valle Central de Costa Rica, evidenciado por una década de nitrato sin precedentes. datos isotópicos, podrían servir como un ejemplo válido del impacto potencial del crecimiento abrupto de la urbanización en todo el mundo. trópicos húmedos. Universidad Nacional, Costa Rica John Wiley & Sons, Estados Unidos Escuela de Química 2024-04-30T20:06:28Z 2024-04-30T20:06:28Z 2023 http://purl.org/coar/resource_type/c_6501 2169-8961 http://hdl.handle.net/11056/27790 https://doi. org/10.1029/2023JG007554 eng Acceso embargado http://creativecommons.org/licenses/by-nc-nd/4.0/ application/pdf John Wiley & Sons (Estados Unidos) Journal of Geophysical Research: Biogeosciences Vol.128 No.8 1-16 2023 |
| institution |
Universidad Nacional de Costa Rica |
| collection |
Repositorio UNA-Costa Rica |
| language |
Inglés |
| topic |
NITRATE LEGACY TROPICAL VOLCANIC ACUÍFERO SISTEMA ISOTOPOS AGUAS SUBTERRÁNEAS COSTA RICA |
| spellingShingle |
NITRATE LEGACY TROPICAL VOLCANIC ACUÍFERO SISTEMA ISOTOPOS AGUAS SUBTERRÁNEAS COSTA RICA Sánchez-Gutiérrez, Rolando Sanchez-Murillo, Ricardo Esquivel-Hernández, Germain Birkel, Christian Boll, J. Rojas-Jiménez, L. D. Castro-Chacón, L. Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System |
| description |
Nitrate legacy is affecting groundwater sources across the tropics. This study describes isotopic
and ionic spatial trends across a tropical, fractured, volcanic multi-aquifer system in central Costa Rica in
relation to land use change over four decades. Springs and wells (from 800 to 2,400 m asl) were sampled for
NO3 − and Cl − concentrations, δ 18Owater, δ 15NNO3, and δ 18ONO3. A Bayesian isotope mixing model was used to
estimate potential source contributions to the nitrate legacy in groundwater. Land use change was evaluated
using satellite imagery from 1979 to 2019. The lower nitrate concentrations (<1 mg/L NO3 −N) were reported in
headwater springs near protected forested areas, while greater concentrations (up to ∼63 mg/L) were reported
in wells (mid- and low-elevation sites in the unconfined unit) and low-elevation springs. High-elevation springs
were characterized by low Cl − and moderate NO3 −/Cl − ratios, indicating the potential influence of soil nitrogen
(SN) inputs. Wells and low-elevation springs exhibited greater NO3 −/Cl − ratios and Cl − concentrations above
100 μmol/L. Bayesian calculations suggest a mixture of sewage (domestic septic tanks), SN (forested recharge
areas), and chemical fertilizers (coffee plantations), as a direct result of abrupt land use change in the last
40 years. Our results confirm the incipient trend in increasing groundwater nitrogen and highlight the urgent
need for a multi-municipal plan to transition from domestic septic tanks to regional sewage treatment and
sustainable agricultural practices to prevent future groundwater quality degradation effectively. |
| format |
Artículo |
| author |
Sánchez-Gutiérrez, Rolando Sanchez-Murillo, Ricardo Esquivel-Hernández, Germain Birkel, Christian Boll, J. Rojas-Jiménez, L. D. Castro-Chacón, L. |
| author_sort |
Sánchez-Gutiérrez, Rolando |
| title |
Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System |
| title_short |
Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System |
| title_full |
Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System |
| title_fullStr |
Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System |
| title_full_unstemmed |
Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System |
| title_sort |
nitrate legacy in a tropical and complex fractured volcanic aquifer system |
| publisher |
John Wiley & Sons (Estados Unidos) |
| publishDate |
2024 |
| url |
http://hdl.handle.net/11056/27790 https://doi. org/10.1029/2023JG007554 |
| _version_ |
1797994955450351616 |
| score |
12.245687 |