Grantee Research Project Results
Final Report: Diagnostic Monitoring of Biogeochemical Interactions of a Shallow Aquifer in Response to a CO2 Leak
EPA Grant Number: R834503Title: Diagnostic Monitoring of Biogeochemical Interactions of a Shallow Aquifer in Response to a CO2 Leak
Investigators: Goldberg, David S. , Matter, Juerg M. , O'Mullan, Gregory , Stute, Martin , Takahashi, Taro
Institution: Columbia University in the City of New York
EPA Project Officer: Aja, Hayley
Project Period: December 1, 2009 through November 30, 2012 (Extended to November 30, 2014)
Project Amount: $899,997
RFA: Integrated Design, Modeling, and Monitoring of Geologic Sequestration of Anthropogenic Carbon Dioxide to Safeguard Sources of Drinking Water (2009) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
The project investigates a shallow potable water aquifer system in sand/clay sequences of the Newark Basin group using laboratory and in situ experimental methods to study the effects of increased CO2 levels from potential leakage at sequestration sites. Previous studies have not fully considered the potential negative effects of CO2 leakage into shallow drinking water aquifers. A fundamental research question addressed in this study is: how does elevated CO2 concentrations caused by a hypothetical leakage of CO2 from deep injection reservoirs affect the chemical and microbiological conditions in a shallow aquifer? In situ injection and recovery experiments and groundwater logging tests were conducted to understand the processes resulting from CO2 enrichment of shallow aquifer water. Rock and water samples were extracted, and a series of geochemical and microbiological laboratory experiments were conducted, focusing on the mobility of health-hazard chemical elements and associated biogeochemical responses.
Summary/Accomplishments (Outputs/Outcomes):
Accomplishments/Outputs
- Established and characterized a field-test site for small-scale controlled aqueous CO2 injection.
- CO2-enhanced aquifer water was injected into a fractured sedimentary rock aquifer during two separate field experiments in 2011 and 2012.
- Elemental release rates, microbial cell concentrations, and 16S rRNA gene sequencing based successional patterns were determined before, during, and after field injection experiments.
- Laboratory incubation experiments were conducted to investigate elemental release rates in CO2-enhanced solutions consisting of various lithologies and sterilized, non-sterilized, and H2-treated aquifer water.
- Established diagnostic monitoring parameters that can be easily measured with available sensor systems to assess shallow groundwater quality in compliance with the EPA MCL (both trace elements and microbes) near potential CO2 sequestration sites
Findings/Outcomes
- Minor deterioration of groundwater quality was observed under a simulated CO2 leakage scenario but did not exceed the EPA MCL after the experiments.
- Mineral dissolution and trace element release were enhanced with increased acidity but returned to pre-injection levels towards the end of experiments.
- Elemental release rates in the field tests and in the laboratory experiments were dependent on pCO2 (pH) and were affected by redox condition and lithology.
- Microbial activity influenced elemental release rates (e.g., Fe), as determined in laboratory treatments containing non-sterilized aquifer water compared to autoclaved controls.
- Rapid microbial succession occurred within the injection region, with smaller alteration expected at greater distances from a CO2 source and with greater time after exposure.
- Demonstrated resilience of the in situ chemistry and microbial community in the later phases of these experiments, returning conditions toward their preinjection state and suggesting that CO2 leakage is unlikely to create permanent, large-scale alteration of the subsurface environment.
In situ experiments (geochemical)
The feasibility of carbon geosequestration in the Newark Basin has been studied previously and its sedimentary sequence provides potential reservoir targets that are abundant in iron oxide minerals and include sandstone, siltstone, and mudstone. The Palisade Sill, a diabase intrusion, is approximately 230 m thick at this location, capping sedimentary formations of late Triassic age, metamorphosed at the sill contact. These sequences are up to 3,350 meters thick in the center of the basin. At the site used in this study, a test well was drilled to a total depth of 457 m below the land surface through four major permeable zones.
Zakharova [2014] characterizes these zones and shows that, although fractures are abundant, hydraulic testing indicates that a majority of fractures do not contribute to hydraulic conductivity of the formation. Few transmissive zones in this region can be correlated laterally due to high anisotropy introduced by high-angle conductive fractures in the sediments and laterally variable sedimentary layering. The deepest zone in the test well (~396 m depth) had very low transmissivity of 0.0009 m2/day, a non-detectable ambient flow rate, and does not exhibit apparent fractures in recorded borehole images. Zakharova [2014] suggests that the zone at 362-366 meters depth below the surface is characterized by a combination of primary porosity (matrix) and fracturing, with a transmissivity of 0.023 m2/day. This localized zone in the sediment was selected for the study to provide low but sufficient transmissivity for our controlled injection experiments, minimizing the risk of losing injected solution and thus allowing a longer incubation with elevated concentration of CO2. If the transmissivities were greater, as in the upper two permeable zones at this site, a larger impact volume would be expected either in fracture-dominated rock or in porous sedimentary aquifers, or in both, under similar conditions.
Yang et al. [2014] presented the results of two single-well push-pull injection tests in this freshwater aquifer and quantified the elemental release rates. In these tests, formation water was produced from the interval and continuous sensor measurements were made for background pH, specific conductance, dissolved oxygen, and oxidation reduction potential. The water was then acidified by saturating it with CO2 under 1 atmosphere pressure, and the acidified water was injected back into the aquifer layer for testing the chemical and microbial changes over an incubation period. Conservative tracers of bromide and SF6 were used to quantify the mixing processes and transport of injected CO2 and confirmed the dual-porosity, fractured system in the aquifer. Similar injections were conducted during the 2011 and 2012 field experiments and consisted of about 3 m3 of acidified groundwater into the sandstone/mudstone aquifer at the same depth. After 3-6 weeks of incubation time, the injected water was pumped out and the chemical and microbial properties were monitored in the pumped water samples.
Results were compared to pre-injection background conditions and to each other.
Relative to background conditions, the recovered aquifer water displayed a decrease of pH by 2-3 units, depletion of dissolved oxygen and a sharp drop of redox potential, and an increase of specific conductance. Major cation concentrations increased significantly to 3.0-5.2 times background levels for Ca, 1.8-3.5 times for Mg, and 1.8-2.1 times for Si, alkalinity increased dramatically to 7.9-11.9 times, while sulfate concentrations decreased by 20-30%. Trace elements showed two-fold or more concentration increases in Be, Cr, Co, Ni, Cu, Rb, Sr, Zr, Sb, Ba and U, up to 50-fold increase in Mn, Fe and Zn, and a decreased concentration of As and Mo. These geochemical parameters and elemental concentrations returned to the background levels towards the end of the extraction phase. Elevated levels of Pb and Cd, which were injected unintentionally due to the pumping procedure, were reduced to the background within about 200 hours. These changes in aquifer water geochemistry can be explained by a) the dissolution of silicate and carbonate minerals, and b) trace element releases, which appear to be dependent on pH and pCO2 and affected by the altered redox conditions in the aquifer.
Yang et al. [2014] attribute the mobilization of major cations and alkalinity to the enhanced dissolution of carbonate and silicate minerals under elevated pCO2 condition in the subsurface. The release rates of Ca, Mg, and Si are comparable with those from batch experiments in the laboratory (see below) and show strong dependence on pH and pCO2. Carbonate dissolution contributed to significant change of water geochemistry even though its content in the aquifer material is low (~1%). The decrease of pH and reducing conditions following aqueous CO2 injection enhanced mobilization of trace elements through reduction, dissolution, and desorption from aquifer minerals.
From these experiments, Yang et al. [2014] conclude that rapid and simultaneous changes of pH, specific conductance, major and trace metal release in aquifer water could be used as indicators of CO2 leakage from geologic sequestration sites. Under a hypothetical CO2 leakage scenario, the groundwater chemical parameters may change significantly, including enhanced acidity and increased specific conductance and total dissolved solid (TDS) due to mineral and trace element dissolution; all factors that can be easily monitored in real-time with commonly available sensor systems. Major elements including Ca, Mg, Si and alkalinity, and trace elements including Mn, Fe, Cr, Co, Ni, Cu, Zn, Rb, Sr, Ba, and U increased in concentration by up to 100-fold due to the increased acidity and altered redox conditions in the aquifer. Sulfate concentrations showed a slight decrease, probably due to associated microbial sulfate reduction. The concentration change in these elements may therefore be sensitive indicators of CO2 leakage at other geosequestration sites.
Fig 1. This plot shows the ratio of observed concentration of trace elements to the U.S. EPA
drinking water Maximum Contaminant Levels, which are highlighted by the red line at unity,
during 2011 and 2012 push–pull experiments in TW-3 well. Figure after Yang et al. [2014].
Compared to EPA's standards for Maximum Contaminant Levels (MCLs), no inorganic chemicals levels measured in this research exceeded the mandatory National Primary Drinking Water Regulation (NPDWR). However, elemental levels were above standard MCLs for non-mandatory National Secondary Drinking Water Regulations (NSDWR), in particular for pH, Fe, Mn, and Zn, and U, which showed significant differences from background levels under very low pCO2 conditions (Figure 1). These chemical parameters returned to background levels after the CO2 injection experiments. Rapid and simultaneous changes of pH, specific conductance, alkalinity, major and trace element release in aquifer water could thus be used as sensitive proxies of even small quantities of CO2 leakage or migration from deeper CO2 injection reservoirs. We conclude from this study that these parameters should be carefully and routinely monitored to assure compliance with EPA drinking water regulations.
In situ experiments (microbiological)
This study represents the first experimental effort using an in situ aqueous CO2 injection to examine the microbial response to CO2 migration or leakage from a geological sequestration reservoir, and addressed the following questions: (1) do observable microbiological responses to geochemical changes occur in a shallow drinking water aquifer following a potential CO2 leak? (2) can successional responses of the aquifer microbial communities be detected? and, (3) is it possible to identify microbial groups whose changing abundance may act as useful indicators of acidification due to CO2 migration or leakage?
O’Mullan et al. [2015] used large-scale 16S ribosomal RNA gene sequencing from aquifer water samples collected during the 2011 and 2012 in situ experiments to investigate the patterns of microbial succession before, during, and after injection of CO2-saturated water into the test aquifer. In both experiments, a decrease in pH following injection of CO2-saturated water was accompanied by mobilization of trace elements (e.g. Fe and Mn) and increased bacterial cell abundance in the recovered water samples. 16S rRNA gene sequence libraries from samples collected before and after the injection were compared. Linking the variability in geochemistry to changes in aquifer microbiology, significant changes in microbial composition were found after the injections, compared to background conditions, including a decrease in Proteobacteria, and an increased presence of Firmicutes, Verrucomicrobia and microbial taxa associated with iron and sulfate reduction. The concurrence of increased microbial cell concentrations and rapid microbial community succession indicate significant changes in aquifer microbial communities immediately following CO2 injection. Samples collected in the late phase of the experiments and 1 year postinjection were similar in cell number to the original background conditions and community compositions, although not identical, and began to revert back toward the initial pre-injection conditions. This suggests that the subsurface environment in Newark Basin is resilient and that low levels of CO2 leakage or migration from a potential deeper reservoir are unlikely to create a permanent, large-scale alteration of the subsurface microbial community.
O’Mullan et al. [2015] indicate that the microbial community displays large and significant shifts as geochemical conditions, such as pH, changed in the early phase of the experiments (Figure 2). Both cell abundance and composition of the microbial communities responded, providing potential biogeochemical interactions with metabolically relevant factors such as ORP, Fe, and sulfate, especially within the injection volume near the borehole. Background microbial cell concentrations were low in both injection experiments with a mean of 4.0 x 104 cells mL-1, and decreased slightly during preparatory CO2 bubbling and injection, but spiked significantly after injection (to 2.0 x 105 in 2011 and 3.5 x 105 cells mL-1 in 2012). The observed increase of nearly an order of magnitude in cell count following the injection disturbance indicate either microbial growth and/or the mobilization of microbes from surface-attachment or suspension in the aquifer water. Cell concentrations and pattern of microbial abundance estimated by microscopy and DNA concentration were in close agreement for both injections, displaying similar dynamics that confirm an initial peak in microbial abundance in the early phases of recovery and that approached background concentrations in later phases of the experiment.
, and were affected by redox conditions and lithology; minor deterioration of groundwater quality was detectable under this simulated CO<sub>2</sub> leakage scenario but reverted to pre-injection background levels. Microbial cell concentrations and successional patterns determined before, during, and after field injection experiments were affected in the injection region. The microbial community and aquifer chemistry displayed resilience on longer time scales and under environmental conditions after injection. Similar conditions near geosequestration sites are unlikely to create permanent, large-scale alterations of the sub-surface microbial community. Such microbial and chemical studies may be useful to improve the criteria for water quality monitoring and risk assessment associated with potential EPA Class VI injection wells.</div>
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The comparison of these geochemical and microbial parameters in other sedimentary environments will require careful monitoring of the <em>in situ</em> composition of aquifer water, both before and after future CO<sub>2</sub> injections. The specific aquifer conditions of potential sequestration sites should be studied using the laboratory and in situ techniques and the measured parameters considered in this research project. Future research should also be undertaken to consider the potential for both oxidative and reductive microbial mechanisms to influence the chemistry and metal mobilization in aquifer waters at CO<sub>2</sub> sequestration sites. </div>
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<strong>Journal Articles
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4 Displayed | Download in RIS Format
| Other project views: | All 18 publications | 4 publications in selected types | All 4 journal articles |
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O'Mullan G, Dueker ME, Clauson K, Yang Q, Umemoto K, Zakharova N, Matter J, Stute M, Takahashi T, Goldberg D. Microbial stimulation and succession following a test well injection simulating CO2 leakage into a shallow Newark basin aquifer. PLoS One 2015;10(1):e0117812. |
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Yang Q, Matter J, Stute M, Takahashi T, O’Mullan G, Umemoto K, Clauson K, Dueker ME, Zakharova N, Goddard J, Goldberg D. Groundwater hydrogeochemistry in injection experiments simulating CO2 leakage from a geological storage reservoir. International Journal of Greenhouse Gas Control 2014;26:193-203. |
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Yang Q, Matter J, Takahashi T, Stute M, O’Mullan G, Clauson K, Umemoto K, Goldberg D. Groundwater geochemistry in bench experiments simulating CO2 leakage from geological storage in the Newark Basin. International Journal of Greenhouse Gas Control 2015;42:98-108. |
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Zakharova N, Goldberg D, Olsen P, Kent D, Morgan S, Yang Q, Stute M, Matter J. New insights into lithology and hydrogeology of the northern Newark Rift Basin. GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 2016;17 IS-6:2070-2094. |
R834503 (Final) |
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Supplemental Keywords:
Sequestration, pollution prevention, metals, microbiology, groundwaterRelevant Websites:
Project information, bibliography, abstracts and presentations, well specifications, well log data, geochemical data, and a web-based data search engine are available via the world wide web: http://springfield.ldeo.columbia.edu:8090/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.