Influence of geological faults on dissolved arsenic concentrations in an overexploited aquifer with shallow geothermal heat

González, Viridiana Piña; Miranda-Avilés, Raúl; Anguiano, Jesús Horacio Hernández; Knappett, Peter S.K.; Martinez, Jorge Luis Morales; Alquiza, María de Jesús Puy; Naves, Acacia; Bian, Jianmin; Liu, Jianli; González, Lucía Magali Ramírez; Céspedes, Juan Manuel Navarro; Li, Yanmei

doi:10.1016/j.apgeochem.2022.105395

Cited by 5 publications

(3 citation statements)

References 39 publications

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“…In future decades, since wells must be deepened to continue to produce water at a high enough rate to satisfy demand, a greater proportion of groundwater from Aquifer 2 will be pumped. In this region with shallow geothermal heat, this presents specific health risks [ 12 , 79 ]. Currently, the steady-state As concentration in water from Well 2 within the CARL aquifer is approximately 18 µg/L ( Table S1 ), which was below the Mexican guideline of 25 µg/L [ 80 ] but above the WHO limit (10 µg/L).…”

Section: Discussionmentioning

confidence: 99%

Water Quality Assessment Bias Associated with Long-Screened Wells Screened across Aquifers with High Nitrate and Arsenic Concentrations

Huang

Knappett

et al. 2022

IJERPH

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Semi-arid regions with little surface water commonly experience rapid water table decline rates. To hedge against the falling water table, production wells in central Mexico are commonly installed to depths of several hundred meters below the present water table and constructed as open boreholes or perforated casings across their entire length. Such wells represent highly conductive pathways leading to non-negligible flow across chemically distinct layers of an aquifer—a phenomenon known as ambient flow. The objectives of this study were to estimate the rate of ambient flow in seven production wells utilizing an end-member mixing model that is constrained by the observed transient chemical composition of produced water. The end-member chemical composition of the upper and lower layers of an urban aquifer that overlies geothermal heat is estimated to anticipate the future quality of this sole source of water for a rapidly growing urban area. The comprehensive water chemistry produced by seven continuously perforated municipal production wells, spanning three geologically unique zones across the city of San Miguel de Allende in Guanajuato State, was monitored during one day of pumping. The concentration of conservative constituents gradually converged on steady-state values. The model indicates that, relative to the lower aquifer, the upper aquifer generally has higher specific conductance (SC), chloride (Cl), nitrate (NO3), calcium (Ca), barium (Ba) and magnesium (Mg). The lower aquifer generally has a higher temperature, sodium (Na), boron (B), arsenic (As) and radon (Rn). Ambient flow ranged from 33.1 L/min to 225.7 L/min across the seven wells, but this rate for a given well varied depending on which tracer was used. This new 3D understanding of the chemical stratification of the aquifer suggests that as water tables continue to fall, concentrations of geothermally associated contaminants of concern will increase in the near future, potentially jeopardizing the safety of municipal drinking water.

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Section: Discussionmentioning

confidence: 99%

Water Quality Assessment Bias Associated with Long-Screened Wells Screened across Aquifers with High Nitrate and Arsenic Concentrations

Huang

Knappett

et al. 2022

IJERPH

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“…Groundwater becomes the primary, and occasionally the only, source of supplies for the population, agriculture, and industry in arid and semi-arid regions in central and Northern Mexico, mainly where precipitation is less than 500 mm/year. Considering that water that is pumped at greater depths is mineralized mostly because of the residence time and interaction with geological materials, it is essential to characterize groundwater to detect hydrogeochemical processes, changes in its chemical composition, and the mixing of different groundwater sources via local or regional flows [9,10]. Arsenic and fluoride have been reported in some areas of Bajío Guanajuatense [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…Some works have characterized low-temperature thermal systems in central Mexico or water-rock interaction processes using hydrogeochemistry [15][16][17] and using a multivariate statistical analysis of geochemical data to determine the processes that control the geochemical evolution of groundwater [18,19]. On the other hand, the authors of [9] investigated the impact of geological faults on thermalism and the levels of fluoride and arsenic in the groundwater of the Laguna Seca aquifer in Guanajuato State.…”

Section: Introductionmentioning

confidence: 99%

Hydrogeochemical Characterization of Groundwater at the Boundaries of Three Aquifers in Central México

Ibarra-Olivares,

Miranda-Avilés,

Ramos-Leal

et al. 2023

Water

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This study investigates the natural hydrogeochemical mechanisms that govern groundwater chemistry at the margins of the Silao-Romita, Valle de León, and La Muralla aquifers in Mexico’s “Bajío Guanajuatense”. The wells of the La Muralla aquifer have temperatures ranging from 25 to 45 °C, while in the valleys, the temperatures range from 25 to 29 °C. In the Sierra de Guanajuato recharge zone, the thermal spring registers 95 °C. High Na concentrations (125 to 178 mg/L) are measured due to thermalism. One sample includes 316 mg/L of SO4, which is related to a potential gypsum zone. Three hydrogeochemical facies are identified (Ca-Mg HCO3, Na-Ca-HCO3, and Na-HCO3). The hydrogeochemical characterization and processes imply hydraulic linkage via regional thermal flows enhanced by faults and the mixing of local flow waters with intermediate flows. The isotopic results indicate that part of the groundwater volume has been exposed to local evaporation processes due to the presence of surface water bodies and irrigation returns. The highest isotopic enrichment is observed near or in the recharge regions. In contrast, the most depleted zones are in the valleys, where there is a more significant interaction with the rock and a longer residence time, implying a mixture of local water flows with deeper or intermediate flows, which, when combined with water geochemistry, indicates a connection between the aquifers studied. The Kruskal–Wallis variance tests, used to compare the differences between aquifers, show that the Valle de León aquifer has more significant differences with respect to the Silao-Romita and La Muralla aquifers. This study’s findings are essential for one of central Mexico’s most populous and economically active areas.

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Assessments of Pollution Status and Human Health Risk of Potentially Toxic Elements in Primary Crops and Agricultural Soils in Guanajuato, Mexico

Liao,

Li,

Miranda-Avilés

et al. 2023

Water Air Soil Pollut

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Influence of geological faults on dissolved arsenic concentrations in an overexploited aquifer with shallow geothermal heat

Cited by 5 publications

References 39 publications

Water Quality Assessment Bias Associated with Long-Screened Wells Screened across Aquifers with High Nitrate and Arsenic Concentrations

Water Quality Assessment Bias Associated with Long-Screened Wells Screened across Aquifers with High Nitrate and Arsenic Concentrations

Hydrogeochemical Characterization of Groundwater at the Boundaries of Three Aquifers in Central México

Assessments of Pollution Status and Human Health Risk of Potentially Toxic Elements in Primary Crops and Agricultural Soils in Guanajuato, Mexico

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