Matthew Johnson
Geological Research at the IGS

Sulfates in Indiana Substrates

Status Start Date End Date Locations
completed Oct 1, 2013 Dec 31, 2015 All Counties
Director: Tracy Branam
Other Researchers: Matthew Johnson, Nelson Shaffer Erika Elswick, IU Geol. Dept. Hourly assistants: Alex Effinger, Chris Hall, Robin Green, Anne Ayers, Oliver Wittman
Funding: Indiana Department of Transportation (INDOT)
Issue: Indiana Department of Transportation desires less expensive and time-consuming method for determining sulfate content in soils than currently being used. Sulfate content important to know for road construction due to formation of expanding minerals such as ettringite, which form in the presence of soluble sulfate and materials used for road construction.
Objective: Project designed to assist by developing screening method, comparison of accuracy between different soluble sulfate analytical methods, and providing GIS maps showing areas of concern for elevated sulfates, as well as gaps in statewide distribution for existing soil and groundwater data sets.
Approach: Screening method to be developed on suite of soil samples provided by INDOT, testing conductivity on crushed vs crushed/sieved samples, heated vs stirred samples, and compared to sulfate concentrations to determine threshold conductivity value to require sulfate analyses. Turbidometric method compared to ion chromatographic method for sulfate determination conducted to evaluate feasibility of using less expensive, quicker turbidometric method. GIS maps constructed from soil data and groundwater data to illustrate distribution of potential sulfate hotspot areas, and to show areas of state where data is lacking.
Products: A new, improved method of analyzing for soluble sulfate that will include a rapid, inexpensive screening step, eliminating costly analyses of all soil samples; a less expensive, equally accurate analytical method for determining sulfate concentration; GIS maps of the state showing potential areas of concentrated sulfate in soils and grouindwater plus areas where data is lacking to provide areas where future work should be focused.
Benefits: Cost saving to state agency through less expensive screening methods, more efficient turnaround time for data, and visual aids showing areas of elevated sulfate concentrations in soils and groundwater and areas where more data is needed.

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