Assessing the impact of CO2 and brine leakage on shallow groundwater quality: Results from a natural analog study in New Mexico, USA
Abstract
A vital aspect to public and regulatory acceptance of carbon sequestration is assurance that drinking water in overlying aquifers will be protected. Direct observations of CO2 flowing through shallow drinking water aquifers are invaluable for informing credible risk assessments. To this end, we have sampled shallow wells in a natural analog site in New Mexico, USA, where CO2 from natural sources is upwelling from depth, and have conducted laboratory experiments on aquifer sediments. Collectively, this work has generated insights into the processes controlling major ion and trace element geochemistry in a CO2-rich system. One finding has been that impacts related to upwelling saline water far exceed those related to in-situ CO2-induced trace metal mobilization. We have also developed 3-D reactive-transport simulations to represent the key aspects of this particular type of drinking water aquifer. In this paper we will summarize field and laboratory findings, and compare reactive-transport simulations with field data. We will then show how field-tested simulations can be used to predict the temporal evolution of shallow groundwater in hypothetical CO2 leakage scenarios. These simulations highlight the importance of transient, non-equilibrium effects. These effects should be carefully considered in risk assessments and monitoring network design. We conclude by presenting sensitivity analysis results showing the most important uncertain model parameters; these results can be used to guide future laboratory and field studies.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H32B..07K
- Keywords:
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- 1806 HYDROLOGY / Chemistry of fresh water;
- 1832 HYDROLOGY / Groundwater transport