CHARACTERIZING NATURAL VARIABILITY OF GROUNDWATER CHEMISTRY: IMPLICATIONS FOR DETECTION OF CO2 LEAKS FROM SUBSURFACE STORAGE SITES
In order to detect changes in aqueous chemistry driven by CO2 leaks, it is important to understand the natural variability of groundwater chemical parameters. Changes in ground water chemistry as a result of acidification only will be detectable if the variations resulting from CO2 leaks exceed natural variability of the groundwater chemistry. Comparing model results of CO2–driven changes in water chemistry to natural variability will allow us to determine the likelihood of early detection depending on the size and extent of CO2leaks from subsurface repositories.
To analyze natural variability, we analyzed the concentrations and ratios of major elements as well as trace metals from an existing dataset collected by the Ohio EPA to determine the natural variability of groundwater chemistry in wells from unconsolidated sediments, sandstone, and limestone wells. A key focus of our analysis was within-well variability across wells that have at least 15 years of data. Relationships between concentrations of major elements as well as trace metals were evaluated for significant correlations and should provide insight on the natural variability of major elements as well as trace metals. Reactive transport models will be used to quantify the size of CO2 fluxes needed to produce changes in groundwater chemistry that exceed natural variability.