What are acid sulfate soils?
Acid sulfate soils form when sulfide-bearing materials are excavated from below the Earth’s surface and are exposed to the atmosphere. The sulfides (primarily pyrite) oxidize to produce sulfuric acid, iron oxides/hydroxides, and sulfate precipitates. The resulting soil is typically highly acidic (pH less than 3.0), and is often associates with acidic, metal-laden surface runoff.
If you think you have acid sulfate soils and would like more information, please contact us with any questions, and we can provide guidance on reclamation of your site. You can call us at (540) 231-7175 or email Dr. Lee Daniels at firstname.lastname@example.org.
What problems are associated with acid sulfate soils?
In construction sites such as road corridors, industrial parks, airports, and housing developments, the exposure of sulfidic materials can present a number of technical, environmental, and social problems:
- Acids degrade metal and concrete building materials.
- Weathering of fill material and precipitation of sulfates compromise structural stability.
- Highly acidic soils cannot support roadside vegetation resulting in increased erosion and acid runoff.
- Highly acidic and metal-laden runoff impairs surface water quality and aquatic life.
- Visible pollution and adverse conditions for aquatic life limit recreational use of impacted surface waters.
Which geologic formations in Virginia are associated with acid sulfate soils?
Acid sulfate soils occur at several sites in different geologic and geomorphic settings across the state, including:
- Coastal Plain: Tertiary marine sediments and the Tabb formation
- Piedmont: Phyllite and slate of the Quantico Formation
- Blue Ridge: Alum phyllite
- Valley and Ridge: Devonian black shale including the Marcellus, Millboro, and Chattanooga shale and Needmore Formation
- Appalachian Plateau: Coal seams and shale including the Wise, Kanawha, Norton, New River, Lee and Pocahontas Formations
By following this link (not operational yet, check back), you will download a Google Earthtm map file (.kmz) for the Commonwealth of Virginia that portrays the relative risk of encountering acid sulfate soil conditions. Once opened, the map will allow you to zoom into your location of interest and once you click on it, information on the potential risk of encountering these materials in near-surface excavations will appear in a pop-up note.
This map is based on the Digital Representation of the 1993 Geologic Map of Virginia (VDMR, 2003), and is best interpreted with an understanding of the local geology and landforms for a given area.
Please keep in mind the following:
1) This map is based on small-scale (state-wide) geologic mapping and therefore provides only a rough guideline for site-specific planning.
2) This map is based on surficial geology, so:
a) Significant geologic changes may occur with depth – i.e. an area mapped as no- or low-risk may have problematic sulfide-bearing formations occurring within excavation depth beneath the surficial geologic formation, and;
b) a “high-risk” geologic unit which has undergone significant geologic weathering may no longer be acid forming through the depth of weathering.
Presentations: Recognition and Remediation of Acid Sulfate Soil Conditions in the Fredericksburg Area. 24 Jan 2020
- Overview of Acid Sulfate Conditions, Weathering Processes & Effects W. Lee Daniels, Virginia Tech
- Acid Base Accounting and Other Predictive Tools Zenah Orndorff, Virginia Tech
- Field Recognition and Prediction of Acid Forming Materials W. Lee Daniels, Virginia Tech
- Distribution of Acid Forming Materials in Virginia & the Fredericksburg Region Zenah Orndorff, Virginia Tech
- Remediation Methods for Acid Forming Materials W. Lee Daniels, Virginia Tech
Acid Sulfate Soils: Recognition, Remediation and Impact Prevention, MAPSS/VAPSS Technical Session, Fredericksburg, VA. Nov. 3-4, 2011
- Introduction W. Lee Daniels, Virginia Tech.
- Sulfidization – Where sulfides in our soils and sediments come from Marty Rabenhorst, University of Maryland.
- Sulfuricization – what happens when sulfidic materials are abruptly exposed to oxidizing conditionsDel Fanning, University of Maryland.
- Occurrence of acid sulfate soils in Virginia Zenah Orndorff, Virginia Tech.
- Effects of acid sulfate soils on building materials W. Lee Daniels, Virginia Tech.
- Acid sulfate soil problems in the mid-Atlantic and world Del Fanning, University of Maryland.
- Prediction, remediation and revegetation of acid sulfate soils W. Lee Daniels, Virginia Tech.
- Stafford Airport remediation project Zenah Orndorff, Virginia Tech, and Ed Wallis, Stafford Airport Manager.
- Homeowner perspectives on acid sulfate soils Susan Chaney, Falmouth.
- FIELD TRIP GUIDEBOOKDel Fanning, University of Maryland
Acid Sulfate Information
- Acid Sulfate Soils in Virginia: A Primer
- Characterization and Remediation of Acid Forming Dredge Materials
- 8th International Acid Sulfate Soils Conference Field Trip, July 22-23, 2016
- Potential Peroxide Acidity Test
- Reclamation of Acid Sulfate Soils
- Acid Sulfate Research and Reports:
- Overview of Acid Sulfate Problems
- Sulfidic Materials in Virginia Highway Corridors (presentation)
- Virginia Tech’s Recommendations for Screening for Acid Sulfate Soil Conditions
- Remediation of Acid Sulfate Conditions at Stafford Airport
- Orndorff, Zenah (2001). Sulfidic Materials in Virginia Highway Corridors. Ph.D. Dissertation
- 2002 Contract Report to VDOT on Acid Sulfate Soil Conditions
- 2007 Acid Materials Testing Policy by City of Fredericksburg
- Characterization and Reclamation of Acid Sulfate Soils in Virginia – Poster
- Fredericksburg Acid Sulfate Soils Study Report (2019/2020)