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Title: Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO[subscript 2] sequestration natural analog site in Chimayo, New Mexico

Abstract

Migration of carbon dioxide (CO{sub 2}) from deep storage formations into shallow drinking water aquifers is a possible system failure related to geologic CO{sub 2} sequestration. A CO{sub 2} leak may cause mineral precipitation/dissolution reactions, changes in aqueous speciation, and alteration of pH and redox conditions leading to potential increases of trace metal concentrations above EPA National Primary Drinking Water Standards. In this study, the Chimayo site (NM) was examined for site-specific impacts of shallow groundwater interacting with CO{sub 2} from deep storage formations. Major ion and trace element chemistry for the site have been previously studied. This work focuses on arsenic (As), which is regulated by the EPA under the Safe Drinking Water Act and for which some wells in the Chimayo area have concentrations higher than the maximum contaminant level (MCL). Statistical analysis of the existing Chimayo groundwater data indicates that As is strongly correlated with trace metals U and Pb indicating that their source may be from the same deep subsurface water. Batch experiments and materials characterization, such as: X-ray diffraction (XRD), scanning electron microscopy (SEM), and synchrotron micro X-ray fluorescence ({mu}-XRF), were used to identify As association with Fe-rich phases, such as clays or oxides, inmore » the Chimayo sediments as the major factor controlling As fate in the subsurface. Batch laboratory experiments with Chimayo sediments and groundwater show that pH decreases as CO{sub 2} is introduced into the system and buffered by calcite. The introduction of CO{sub 2} causes an immediate increase in As solution concentration, which then decreases over time. A geochemical model was developed to simulate these batch experiments and successfully predicted the pH drop once CO{sub 2} was introduced into the experiment. In the model, sorption of As to illite, kaolinite and smectite through surface complexation proved to be the key reactions in simulating the drop in As concentration as a function of time in the batch experiments. Based on modeling, kaolinite precipitation is anticipated to occur during the experiment, which allows for additional sorption sites to form with time resulting in the slow decrease in As concentration. This mechanism can be viewed as trace metal 'scavenging' due to sorption caused secondary mineral precipitation. Since deep geologic transport of these trace metals to the shallow subsurface by brine or CO{sub 2} intrusion is critical to assessing environmental impacts, the effective retardation of trace metal transport is an important parameter to estimate and it is dependent on multiple coupled reactions. At the field scale, As mobility is retarded due to the influence of sorption reactions, which can affect environmental performance assessment studies of a sequestration site.« less

Authors:
; ; ; ; ; ; ; ;  [1];  [2];  [2];  [2]
  1. (EPA)
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - BASIC ENERGY SCIENCES
OSTI Identifier:
1047302
Resource Type:
Journal Article
Journal Name:
Int. J. Greenh. Gas Con.
Additional Journal Information:
Journal Volume: 10; Journal Issue: 09, 2012; Journal ID: ISSN 1750-5836
Country of Publication:
United States
Language:
ENGLISH
Subject:
54 ENVIRONMENTAL SCIENCES; AQUIFERS; ARSENIC; BRINES; CALCITE; CARBON DIOXIDE; CARBON SEQUESTRATION; CHEMISTRY; CLAYS; DATA; DRINKING WATER; ELEMENTS; ENVIRONMENTAL IMPACTS; FAILURES; FLUORESCENCE; GROUND WATER; ILLITE; IONS; KAOLINITE; LEAKS; LEVELS; MATERIALS; METALS; MIGRATION; MINERALS; MOBILITY; OXIDES; PERFORMANCE; POTENTIALS; PRECIPITATION; SCANNING ELECTRON MICROSCOPY; SCAVENGING; SEDIMENTS; SIMULATION; SMECTITE; SOLUTIONS; SORPTION; STORAGE; SURFACES; SYNCHROTRON RADIATION; TRACE AMOUNTS; TRANSPORT; US EPA; WATER; WELLS; X-RAY DIFFRACTION

Citation Formats

Viswanathan, Hari, Dai, Zhenxue, Lopano, Christina, Keating, Elizabeth, Hakala, J. Alexandra, Scheckel, Kirk G., Zheng, Liange, Gutherie, George D., Pawar, Rajesh, LBNL), LANL), and NETL). Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO[subscript 2] sequestration natural analog site in Chimayo, New Mexico. United States: N. p., 2012. Web. doi:10.1016/j.ijggc.2012.06.007.
Viswanathan, Hari, Dai, Zhenxue, Lopano, Christina, Keating, Elizabeth, Hakala, J. Alexandra, Scheckel, Kirk G., Zheng, Liange, Gutherie, George D., Pawar, Rajesh, LBNL), LANL), & NETL). Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO[subscript 2] sequestration natural analog site in Chimayo, New Mexico. United States. doi:10.1016/j.ijggc.2012.06.007.
Viswanathan, Hari, Dai, Zhenxue, Lopano, Christina, Keating, Elizabeth, Hakala, J. Alexandra, Scheckel, Kirk G., Zheng, Liange, Gutherie, George D., Pawar, Rajesh, LBNL), LANL), and NETL). Wed . "Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO[subscript 2] sequestration natural analog site in Chimayo, New Mexico". United States. doi:10.1016/j.ijggc.2012.06.007.
@article{osti_1047302,
title = {Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO[subscript 2] sequestration natural analog site in Chimayo, New Mexico},
author = {Viswanathan, Hari and Dai, Zhenxue and Lopano, Christina and Keating, Elizabeth and Hakala, J. Alexandra and Scheckel, Kirk G. and Zheng, Liange and Gutherie, George D. and Pawar, Rajesh and LBNL) and LANL) and NETL)},
abstractNote = {Migration of carbon dioxide (CO{sub 2}) from deep storage formations into shallow drinking water aquifers is a possible system failure related to geologic CO{sub 2} sequestration. A CO{sub 2} leak may cause mineral precipitation/dissolution reactions, changes in aqueous speciation, and alteration of pH and redox conditions leading to potential increases of trace metal concentrations above EPA National Primary Drinking Water Standards. In this study, the Chimayo site (NM) was examined for site-specific impacts of shallow groundwater interacting with CO{sub 2} from deep storage formations. Major ion and trace element chemistry for the site have been previously studied. This work focuses on arsenic (As), which is regulated by the EPA under the Safe Drinking Water Act and for which some wells in the Chimayo area have concentrations higher than the maximum contaminant level (MCL). Statistical analysis of the existing Chimayo groundwater data indicates that As is strongly correlated with trace metals U and Pb indicating that their source may be from the same deep subsurface water. Batch experiments and materials characterization, such as: X-ray diffraction (XRD), scanning electron microscopy (SEM), and synchrotron micro X-ray fluorescence ({mu}-XRF), were used to identify As association with Fe-rich phases, such as clays or oxides, in the Chimayo sediments as the major factor controlling As fate in the subsurface. Batch laboratory experiments with Chimayo sediments and groundwater show that pH decreases as CO{sub 2} is introduced into the system and buffered by calcite. The introduction of CO{sub 2} causes an immediate increase in As solution concentration, which then decreases over time. A geochemical model was developed to simulate these batch experiments and successfully predicted the pH drop once CO{sub 2} was introduced into the experiment. In the model, sorption of As to illite, kaolinite and smectite through surface complexation proved to be the key reactions in simulating the drop in As concentration as a function of time in the batch experiments. Based on modeling, kaolinite precipitation is anticipated to occur during the experiment, which allows for additional sorption sites to form with time resulting in the slow decrease in As concentration. This mechanism can be viewed as trace metal 'scavenging' due to sorption caused secondary mineral precipitation. Since deep geologic transport of these trace metals to the shallow subsurface by brine or CO{sub 2} intrusion is critical to assessing environmental impacts, the effective retardation of trace metal transport is an important parameter to estimate and it is dependent on multiple coupled reactions. At the field scale, As mobility is retarded due to the influence of sorption reactions, which can affect environmental performance assessment studies of a sequestration site.},
doi = {10.1016/j.ijggc.2012.06.007},
journal = {Int. J. Greenh. Gas Con.},
issn = {1750-5836},
number = 09, 2012,
volume = 10,
place = {United States},
year = {2012},
month = {10}
}