Morales et al. (2025) Geochemical, hydrochemical and remote sensing study of an Andean calcareous wetland in Huanta, Peru

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2025
• Date: 2025-09-17
• Authors: Bruno Kadafi Cárdenas Morales, John K. Forrest, Walter V. Castro Aponte, H. E. Sanchez Cornejo, Braulio La Torre, Jorge H. Jhoncon, Patrick Byrne, T.T. Nguyen, C. H. W. Barnes, L. De Los Santos Valladares
• DOI: 10.1016/j.ejrh.2025.102767

Research Groups

• Escuela Profesional de Ingeniería y Gestión Ambiental, Universidad Nacional Autónoma de Huanta, Peru
• Cavendish Laboratory, Department of Physics, University of Cambridge, UK
• Laboratorio de Cerámicos y Nanomateriales, Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Peru
• Facultad de Agronomía, Universidad Nacional Agraria de la Molina, Peru
• Centro de Investigación en Agricultura Orgánica, Universidad Nacional de Educación Enrique Guzmán y Valle, Peru
• School of Biological and Environmental Sciences, Liverpool John Moores University, UK
• College of Natural Sciences, Can Tho University, Vietnam

Short Summary

This study provides the first integrated geochemical, hydrochemical, and remote sensing assessment of the Huaper Wetland, revealing early signs of water quality deterioration, declining surface moisture, and a weakening of its natural geochemical buffering capacity due to anthropogenic pressures and climatic variability.

Objective

• To elucidate how land-use stressors and climatic variability influence the buffering capacity and water quality of a calcareous wetland in the Central Andes.
• To test the hypothesis that anthropogenic salinization, oxygen depletion, and carbonate mineral shifts are progressively weakening the wetland’s natural buffering capacity and its ability to retain potentially toxic elements such as arsenic and lead.

Study Configuration

• Spatial Scale: Huaper Wetland, Huanta Province, Ayacucho Region, Central Peruvian Andes, at 2353 meters above sea level. The wetland covers approximately 8.4 hectares.
• Temporal Scale: Water samples were collected during four campaigns across two hydrological years (March and November 2023–2024). Seventeen sediment samples were collected in June 2023. Surface moisture dynamics were assessed using Sentinel-2 imagery from 2016–2023.

Methodology and Data

• Models used: Water Quality Index (WQI-PE) based on Peruvian Environmental Water Quality Standards (ECA-Water, Method 004–2017-MINAM, ANA Process N.º 084–2020-ANA), Normalized Difference Water Index (NDWI).
• Data sources:
  • In-situ measurements: pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), oxidation-reduction potential (ORP), and temperature using a portable multiparameter meter (Hanna HI98494).
  • Water samples: Filtered and acidified samples analyzed for potentially toxic elements (PTEs) using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Major cations and anions were also analyzed.
  • Sediment samples: Morphological and granulometric analysis (Dino-Lite optical microscope), elemental composition (Energy Dispersive X-ray Spectroscopy - EDX using JEOL JSM-6510LV SEM), and mineralogical composition (X-ray Diffraction - XRD using Bruker D8 Advance diffractometer).
  • Remote sensing: Sentinel-2A and Sentinel-2B satellite imagery (10 meter spatial resolution) for NDWI calculation.

Main Results

• The Water Quality Index (WQI-PE) declined from "Excellent" (94.92–100.00) in 2023 to "Good" (92.04) in 2024.
• Dissolved oxygen (DO) levels showed significant seasonal variation, dropping to a minimum of 1.43 mg/L in March 2024 and 1.93 mg/L in November 2024, falling below the 5.0 mg/L threshold for aquatic life.
• Electrical conductivity (EC) ranged from 866 µS/cm to 944 µS/cm, remaining below the Peruvian standard of 1000 µS/cm.
• Nitrate (NO₃⁻) levels reached 8.09 mg/L in November 2023, exceeding the Peruvian ECA-Agua threshold of 7 mg/L.
• Sodium (Na) concentrations (33.82 to 44.18 mg/L) exceeded the WHO drinking water guideline of 20 mg/L.
• Potentially toxic elements (As, Cd, Cr, Cu, Hg, Pb, Zn) generally remained below regulatory thresholds, though arsenic showed a decreasing trend from 0.0034 mg/L to 0.0014 mg/L.
• Sediment analysis confirmed calcite (up to 43.8 %) and magnesium calcite (32.8 %) as dominant minerals, with secondary silicates (quartz, diopside, muscovite, anorthite, clinoenstatite). Traces of nitratine (NaNO₃) were detected, suggesting agricultural influence.
• Normalized Difference Water Index (NDWI) analysis (2016–2023) revealed a persistent decrease in surface moisture, with a minimum mean NDWI of –0.4699 in 2017, indicating increasing dry-season moisture loss and surface fragmentation.
• Hydrochemical facies classification identified the water as calcium-magnesium-bicarbonate type, characteristic of carbonate-rich environments.

Contributions

• Provides the first integrated interdisciplinary assessment of a high-altitude calcareous wetland in Peru, combining hydrochemistry, sediment geochemistry (XRD-EDX), and remote sensing (NDWI).
• Establishes a crucial baseline dataset for the unmonitored Huaper Wetland, serving as a critical case study for detecting early degradation signals in fragile Andean systems.
• Offers new hydrological insights into how land-use stressors and climatic variability influence the buffering capacity and water quality of calcareous wetlands in the Central Andes.
• Highlights the urgency of implementing land-use regulation, salinity control, and cost-effective long-term monitoring to preserve the ecological integrity and buffering capacity of vulnerable Andean wetlands.

Funding

• Collaboration Agreement between the Universidad Nacional Autónoma de Huanta (Peru) and the University of Cambridge (UK), Contract Number G117323.
• Peruvian Council of Science and Technology CONCYTEC, grant No. PE501087367–2024-PROCIENCIA (for H. Sanchez).

Citation

@article{Morales2025Geochemical,
  author = {Morales, Bruno Kadafi Cárdenas and Forrest, John K. and Aponte, Walter V. Castro and Cornejo, H. E. Sanchez and Torre, Braulio La and Jhoncon, Jorge H. and Byrne, Patrick and Nguyen, T.T. and Barnes, C. H. W. and Valladares, L. De Los Santos},
  title = {Geochemical, hydrochemical and remote sensing study of an Andean calcareous wetland in Huanta, Peru},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.102767},
  url = {https://doi.org/10.1016/j.ejrh.2025.102767}
}