Characterizing solute budgets of a tropical Andean páramo ecosystem

Viviana Arízaga-Idrovo; Juan Pesántez; Christian Birkel; Pablo Peña; Enma Mora; Patricio Crespo

doi:10.1016/j.scitotenv.2022.155560

Characterizing solute budgets of a tropical Andean páramo ecosystem

Sci Total Environ. 2022 Aug 20:835:155560. doi: 10.1016/j.scitotenv.2022.155560. Epub 2022 Apr 27.

Authors

Viviana Arízaga-Idrovo¹, Juan Pesántez², Christian Birkel³, Pablo Peña¹, Enma Mora¹, Patricio Crespo¹

Affiliations

¹ Departamento de Recursos Hídricos y Ciencias Ambientales, Facultad de Ingeniería & Facultad de Ciencias Químicas, Universidad de Cuenca, Cuenca, Ecuador.
² Departamento de Recursos Hídricos y Ciencias Ambientales, Facultad de Ingeniería & Facultad de Ciencias Químicas, Universidad de Cuenca, Cuenca, Ecuador. Electronic address: juanp.pesantezv@ucuenca.edu.ec.
³ Department of Geography and Water and Global Change Observatory, University of Costa Rica, San José, Costa Rica.

PMID: 35489488
DOI: 10.1016/j.scitotenv.2022.155560

Abstract

Monitoring solute fluxes in water quality studies is essential to reveal potential ecosystem disturbances, and is particularly important in Andean headwater catchments as they are the main sources of water for downstream populations. However, such studies have mainly focused on organic matter and nutrients, disregarding other solutes that can threaten water quality (e.g. arsenic, lead, calcium or magnesium). Additionally, routine low-resolution (weekly or monthly) sampling schemes may overlook important solute dynamics. Therefore, we collected water samples every four hours for the analysis of twenty-four solutes in a pristine tropical Andean páramo catchment. Solute fluxes were calculated using five different methods. The 4-hourly data set was filtered to test for an optimum sampling frequency without compromising export rates. Based on the available 4-hourly data, the results showed that the interpolation export method was best suited, due to a weak correlation with discharges. Of the twenty-four solutes analyzed, Dissolved Organic Carbon (DOC), Total Nitrogen bound (TNb), Si, Ca, Mg, K, and Na presented the highest input rates (with DOC = 4.167E+08 mEq km^-2 yr^-1 and Si = 1.729E+07 mEq km^-2 yr^-1) and export rates (with DOC = 2.686E+08 mEq km^-2 yr^-1 and Si = 2.953E+08 mEq km^-2 yr^-1). Moreover, DOC, TNb, NH₄-N, NO₂-N, NO₃-N, PO₄, Al, B, Cu, Fe, Zn, As, Cd, Cr, Pb, and V presented more input than export, while Ca, K, Mg, Na, Rb, Si, Sr, and Ba presented more export than input (geogenic sources). Filtered sampling frequencies demonstrated that a minimum of daily grab samples would be required to obtain reliable export rates with differences consistently below 10%, when compared to the 4-hourly solute export. These findings can be particularly useful for the implementation of long-term monitoring programs at low cost, and they provide high-quality information, for the first time, on biogeochemical budgets in a pristine páramo catchment.

Keywords: Sampling frequency; Solute fluxes; Solute loads; Tropics; Water quality; páramo.

MeSH terms

Carbon / analysis
Ecosystem*
Environmental Monitoring*
Nitrogen / analysis
Water Quality

Substances

Carbon
Nitrogen