Role of unsaturated soil above a heavily contaminated aquifer in the natural attenuation of arsenic

Nadia Martinez-Villegas; Andrea Del Pilar Gómez; Armando Zamora-Morales; Jejanny Lucero Hernández Martínez; Diana Meza-Figueroa; Bhaskar Sengupta

doi:10.1051/e3sconf/20199809017

Role of unsaturated soil above a heavily contaminated aquifer in the natural attenuation of arsenic

Nadia Martinez-Villegas^*, Andrea Del Pilar Gómez, Armando Zamora-Morales, Jejanny Lucero Hernández Martínez, Diana Meza-Figueroa, Bhaskar Sengupta

^*Corresponding author for this work

Research output: Contribution to journal › Conference article › peer-review

3 Scopus citations

Abstract

Large attenuation of arsenic is observed in a shallow aquifer in central Mexico, where the concentration decreases from 91.5 to 11.3 mg/L, over 1.3 km horizontal distance. To investigate possible mechanisms of attenuation of this pollutant, we dug a pit between the surface and the saturated zone. We then described the soil profile and determined arsenic and iron concentrations in soil samples as a function of depth. Next, we determined particle size distribution, bulk density, particle density, soil moisture and porosity of the soil material. We also analyzed arsenic concentration in the groundwater. The 2.2 m deep profile intersected 4 soil horizons (A, AB, B1 and B2). We found arsenic accumulation in the B2 horizon, directly overlying the saturated zone. These accumulations coincide with the thickness of the capillary fringe, revealing that arsenic is drawn up in the soil profile by capillary rise of arsenic-contaminated groundwater. Furthermore, arsenic accumulation showed a direct relationship with iron, likely due to arsenic adsorption on iron oxides. Results from this study contribute to understanding a capillary-driven natural attenuation mechanism that removes contaminants from groundwater by sinking them in the capillary fringe.

Original language	English
Article number	09017
Journal	E3S Web of Conferences
Volume	98
DOIs	https://doi.org/10.1051/e3sconf/20199809017
State	Published - 7 Jun 2019
Event	16th International Symposium on Water-Rock Interaction, WRI 2019 and 13th International Symposium on Applied Isotope Geochemistry, 1st IAGC International Conference - Tomsk, Russian Federation Duration: 21 Jul 2019 → 26 Jul 2019

Bibliographical note

Funding Information:
This study was funded by grant NA140182 Newton Advanced Fellowship from the Royal Society. NMV is thankful to CONACyT for Grant No. 7073. APG and JLHM are thankful to CONACYT for 588409 and 166112 graduate and postdoctoral fellowships, respectively. We thank land owners who kindly permitted access to their properties and Felipe Barraza who helped to prepare Figure 1.

Publisher Copyright:
© The Authors, published by EDP Sciences, 2019.

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abstract = "Large attenuation of arsenic is observed in a shallow aquifer in central Mexico, where the concentration decreases from 91.5 to 11.3 mg/L, over 1.3 km horizontal distance. To investigate possible mechanisms of attenuation of this pollutant, we dug a pit between the surface and the saturated zone. We then described the soil profile and determined arsenic and iron concentrations in soil samples as a function of depth. Next, we determined particle size distribution, bulk density, particle density, soil moisture and porosity of the soil material. We also analyzed arsenic concentration in the groundwater. The 2.2 m deep profile intersected 4 soil horizons (A, AB, B1 and B2). We found arsenic accumulation in the B2 horizon, directly overlying the saturated zone. These accumulations coincide with the thickness of the capillary fringe, revealing that arsenic is drawn up in the soil profile by capillary rise of arsenic-contaminated groundwater. Furthermore, arsenic accumulation showed a direct relationship with iron, likely due to arsenic adsorption on iron oxides. Results from this study contribute to understanding a capillary-driven natural attenuation mechanism that removes contaminants from groundwater by sinking them in the capillary fringe.",

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AU - Martinez-Villegas, Nadia

AU - Gómez, Andrea Del Pilar

AU - Zamora-Morales, Armando

AU - Hernández Martínez, Jejanny Lucero

AU - Meza-Figueroa, Diana

AU - Sengupta, Bhaskar

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N2 - Large attenuation of arsenic is observed in a shallow aquifer in central Mexico, where the concentration decreases from 91.5 to 11.3 mg/L, over 1.3 km horizontal distance. To investigate possible mechanisms of attenuation of this pollutant, we dug a pit between the surface and the saturated zone. We then described the soil profile and determined arsenic and iron concentrations in soil samples as a function of depth. Next, we determined particle size distribution, bulk density, particle density, soil moisture and porosity of the soil material. We also analyzed arsenic concentration in the groundwater. The 2.2 m deep profile intersected 4 soil horizons (A, AB, B1 and B2). We found arsenic accumulation in the B2 horizon, directly overlying the saturated zone. These accumulations coincide with the thickness of the capillary fringe, revealing that arsenic is drawn up in the soil profile by capillary rise of arsenic-contaminated groundwater. Furthermore, arsenic accumulation showed a direct relationship with iron, likely due to arsenic adsorption on iron oxides. Results from this study contribute to understanding a capillary-driven natural attenuation mechanism that removes contaminants from groundwater by sinking them in the capillary fringe.

AB - Large attenuation of arsenic is observed in a shallow aquifer in central Mexico, where the concentration decreases from 91.5 to 11.3 mg/L, over 1.3 km horizontal distance. To investigate possible mechanisms of attenuation of this pollutant, we dug a pit between the surface and the saturated zone. We then described the soil profile and determined arsenic and iron concentrations in soil samples as a function of depth. Next, we determined particle size distribution, bulk density, particle density, soil moisture and porosity of the soil material. We also analyzed arsenic concentration in the groundwater. The 2.2 m deep profile intersected 4 soil horizons (A, AB, B1 and B2). We found arsenic accumulation in the B2 horizon, directly overlying the saturated zone. These accumulations coincide with the thickness of the capillary fringe, revealing that arsenic is drawn up in the soil profile by capillary rise of arsenic-contaminated groundwater. Furthermore, arsenic accumulation showed a direct relationship with iron, likely due to arsenic adsorption on iron oxides. Results from this study contribute to understanding a capillary-driven natural attenuation mechanism that removes contaminants from groundwater by sinking them in the capillary fringe.

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JO - E3S Web of Conferences

JF - E3S Web of Conferences

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T2 - 16th International Symposium on Water-Rock Interaction, WRI 2019 and 13th International Symposium on Applied Isotope Geochemistry, 1st IAGC International Conference

Y2 - 21 July 2019 through 26 July 2019

ER -

Role of unsaturated soil above a heavily contaminated aquifer in the natural attenuation of arsenic

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