235-5 Arsenic Dynamics in Waters and Sediments of the TDPS (Titicaca–Desaguadero–Poopó–Salar de Coipasa) System: Integrating Speciation, Natural Sources, and Anthropogenic Influences

Session: Advancing the Understanding and Management of Groundwater Pollution with Arsenic and Other Geogenic Contaminants Using Geospatial Tools, Machine Learning, and Data Science, Part I

Presenting Author:

Luis Fernando Caceres Choque

Authors:

Bhattacharya, Prosun¹, Quino, Israel Fernando², Ramos Ramos, Oswaldo Eduardo³, Ocola Salazar, Juan Jose⁴, Choque Aspiazu, Rigoberto Rogelio ⁵, Caceres Choque, Luis Fernando Fernando⁶

(1) KTH ROYAL INSTITUTE OF TECHNOLOGY, Department of Sustainable Development,, Stockholm, Sweden, (2) Laboratorio de Hidroquímica, Instituto de Investigaciones Químicas, Universidad Mayor de San Andrés, La Paz, Bolivia, (3) Laboratorio de Hidroquimica, Instituto de Investigaciones Químicas, Universidad Mayor de San Andrés, La Paz, Bolivia, (4) Autoridad Binacional del Lago Titicaca, ALT, La Paz, Bolivia, (5) Instituto de Investigaciones Químicas, Carrera de Ciencias Químicas, Universidad Mayor de San Andrés, La Paz, Bolivia, (6) Autoridad Binacional del Lago Titicaca, ALT, La Paz, Bolivia; Agencia Boliviana de Energía Nuclear, ABEN, La Paz, Bolivia,

Abstract:

This study investigates the distribution and speciation of As in surface water, groundwater, and sediments across the Titicaca–Desaguadero–Poopó–Salar de Coipasa (TDPS) system, which spans the Andean Altiplano between Bolivia and Peru. Previous studies in the southern Poopó sub-basin have established that As is primarily geogenic in origin, mobilized under oxidizing conditions, and predominantly present as arsenate [As(V)]. In this study, As speciation in water samples (surface and groundwater) was conducted using the Disposable Cartridges® manufactured by MetalSoft Centre to separate arsenate [As(V)] from arsenite [As(III)]. The measured  field parameters included pH, oxidation–reduction potential (ORP), temperature, electrical conductivity (EC), dissolved oxygen (DO), and total dissolved solids (TDS), while the laboratory analyses included major ions,such as Na, K, Li, Ca, Mg, HCO₃^-, CO₃^2-, Cl^-, SO₄^2- as well as the trace elements including total As, As(III), Cd, Fe, Mn, Pb, Zn, P, Cr, Cu, Ni, and B. Additionally, the sediment samples were digested in concentrated HNO₃ (EPA Method 3051A:2007), for the determination of B, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn, Sn, Al, and Bi. Surface water showed elevated As levels, with total As = 813 ± 1723 µg/L, As(V) = 734 ± 1687 µg/L and As(III) = 79 ± 165 µg/L. Groundwater samples exhibited lower concentrations with total As = 40 ± 67 mg/L, As(V) = 31 ± 61 µg/L and As(V) = 9 ± 20 µg/L, although several samples exceeded the WHO drinking water guideline of 10 µg/L). Furthermore, the As redox transformation patterns revealed a decreasing trend in the proportion of As(III) across the impact categories: natural waters (20.3 ± 10.3%) > urban impacted waters) %As(III) = 18.2 ± 10.3% > mining affected waters (15.0 ± 16.8%). In sediments, total As concentrations followed the trend: sediments in the mining-impacted sites (570.2 ± 950.1 mg/kg) > urban sediments (62.7 ± 99.1 mg/kg) > natural background sediments (15.8 ± 0.3 mg/kg). The majority chemical species is Arsenate [As(V)] was the dominant species in both surface [60.2 - 99.9%] and groundwater [63.7 - 99.9%], consistent with oxidizing, alkaline conditions and prior findings from the Poopó basin. The study confirms that As in the TDPS system is largely geogenic, influenced by regional geology and hydrology, while also modulated by anthropogenic pressures.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9464

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