Nitrate Legacy in a Tropical and Complex Fractured Volcanic Aquifer System

• Published in: Journal of geophysical research. Biogeosciences 2023-08, Vol.128 (8), p.n/a
• Main Authors: Sánchez‐Gutiérrez, R., Sánchez‐Murillo, R., Esquivel‐Hernández, G., Birkel, C., Boll, J., Rojas‐Jiménez, L. D., Castro‐Chacón, L.
• Format: Article
• Language: English
• Subjects: Agricultural practices; Agrochemicals; Aquifer systems; Aquifers; Bayesian analysis; Bayesian theory; Chemical fertilizers; Coffee; Costa Rica; Elevation; Fertilizers; Forest protection; Fractures; Groundwater; Groundwater quality; Groundwater treatment; Headwaters; Isotopes; Land use; Mixtures; nitrate; Nitrates; Nitrogen; Plantations; Probability theory; Recharge; Recharge areas; Regional planning; Satellite imagery; Septic tanks; Sewage; Sewage tanks; Sewage treatment; Sewage treatment plants; Soils; stable isotopes; Sustainable agriculture; Sustainable practices; Tanks; Tropical environments; Urbanization; volcanic aquifers; Wastewater treatment; Water quality; water resources management; Water springs; Wells
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1029/2023JG007554

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, δ18Owater, δ15NNO3, and δ18ONO3. 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 (