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

The growing trend of data aggregation and analysis, along with emerging technologies like machine learning, has significantly improved our understanding of groundwater basins, enabling better assessments of water quality for direct consumption and treatment in groundwater supply management.

Wednesday, 22 October 2025
8:00 AM - 12:00 PM
HBGCC, 210AB

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

Paper number: 235-5
Program: Technical Sessions
Time: 9:05 AM – 9:20 AM

Authors

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-, CO32-, Cl-, SO42- 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 Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413805

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.