Remediation of Acid Sulfate Soils

Characterization & Reclamation of Acid Sulfate Soils in Virginia

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.

acid sulfate soil

Photo: Gray reduced sulfidic materials are commonly encountered during active construction in the Fredericksburg/Stafford area of Virginia. These materials will usually acidify over time to pH < 3.5 unless large amounts of lime are added and incorporated.

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 setting s 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

Presentations, Research & Reports

How was the State Sulfide Hazard Risk Map Created?
Detailed field, laboratory, and literature studies were completed to develop a sulfide hazard rating ma for Virginia. Ratings were based on the acid producing potentials of the different materials, documentation of sulfide-bearing materials, and current reclamation capabilities. The ratings were then applied to the state geology map.

How can I create my own Sulfide Hazard Risk Map?
If you have GIS capability you can easily create your map using the files provided. To download the avl files: right click and select "save target as.." This will download the files to your computer. Do not select "open."

You will also need the DBF file, and due to the limitations of this website we can't create a link for you to download this file. Thus, please contact Zenah and she will send via email.

How are acid sulfate soils reclaimed?
Treatment of acid sulfate soils typically involves three main steps.

1) After notification of a possible acid sulfate site, a field investigation is completed which includes the collection of soil and drainage samples.

2) Laboratory analyses including pH, Potential Peroxide Acidity test, and other relevant characterization tests are completed.

3) A reclamation prescription is developed based on the laboratory results and the site specific conditions. The prescription includes a lime recommendation, emphasizing that the lime must be thoroughly incorporated into the top 6 inches of soil. Fertilization needs are also addressed, and incorporation of organic amendments or topsoil covers are typically recommended but not always essential for reclamation success. After incorporating these amendments, seeding should be completed only during established planting dates in the fall or spring.

Why is the Potential Peroxide Acidity test used to determine how much lime to apply?
A few different methods are commonly used to determine the acid-producing potential of sulfide bearing materials. In the CSES department at VT, the Potential Peroxide Acidity (PPA) method is commonly used. This method rapidly oxidized a sample of soil with hydrogen peroxide and then the amount of acidity produced is measured. The results are expressed as a calcium carbonate equivalence, ie. How much lime must be added to neutralize the acidity.

I think I have acid sulfate soils and I would like more information?
Please contact us with any questions, and we can provide guidance on reclamation of your site. You can call us (540) 231-7175 or email Dr. Lee Daniels at wdaniels@vt.edu.

Characterization and Reclamation of Acid Sulfate Soils in Virginia Poster - Click Here (PDF)

Rehabilitation of Drastically Disturbed Lands

W. Lee Daniels - Remediation of Acid Sulfate Soils

Reclamation -- Remediation -- Restoration -- Revegetation -- Revitalization