Humate-Induced Remediation of Petroleum Contaminated Surface Soils

EPA Grant Number: R827015-01-0
Title: Humate-Induced Remediation of Petroleum Contaminated Surface Soils
Investigators: Mark A. Nanny, R. Paul Philp, Vladimir E. Andrusevich
Institutions: University of Oklahoma
EPA Project Officer: Bala Krishnan
Project Period: June 1, 2000 to June 30, 2001
Project Amount: $102,228
Research Category: Bioremediation of oil spills

Description:

Objective(s) of the Research Project:

To determine: 1) if humate-induced remediation is a viable and feasible remediation technique, and 2) if it is, determine the primary remediation mechanism, i.e., stimulation of biodegradation, adsorption, or a combination of both. These objectives will be accomplished by: 1) identifying the humate, or humates, with the greatest sorption capacity, and 2) identifying and characterizing the predominant mechanism(s) of the humate-induced remediation process(es) using microcosms containing either pristine or contaminated surface soil collected from a petroleum drilling field near Oklahoma City, OK.

Progress Summary/Accomplishments:

Total organic carbon (TOC) of eight humate products, obtained from sites around the world, were found to vary greatly, indicating the diversity of these materials in their organic and ash composition.

Humate TOC (w%)
HRL Organic Humate (Australia) (#2) 66.9
Earthgreen Menefee Humate (New Mexico) (#5) 53.2
U-Mate International (#7) 39.5
Organic Approach (Siberia) (#8) 36.3
Live Earth Product Humate 26.3
Organic Approach Humate (Russia) 7.9
HRL K-Humate (Australia) 6.7
Nuest Humate 4.2

Elemental analysis of the two humates (#2 and #5) with the greatest TOC showed that these humates are more reduced and have a greater aromatic content (i.e., have low atomic hydrogen/carbon and oxygen/carbon ratios) than typical soil or aquatic humic acids; the humates are more similar to coal humic acids. Because of the TOC and elemental analysis results, humate #2 was chosen for use in the microcosm studies.

Fresh petroleum samples, as well as pristine and petroleum-contaminated soil samples were collected, with the assistance of Arrow Petroleum and Gas (Norman, OK), from one of their oil drilling sites east of Norman, Oklahoma. SARA analysis of the fresh petroleum showed it contained very little to none asphaltenes. Two hundred and eighty eight 500 mL microcosms were set-up and started, representing various combinations of pristine soil, contaminated soil, these soils with fresh petroleum, and with or without humate #2, as well as all of these combinations with sodium azide to act as sterile controls. Replicate microcosm samples were collected on Days 2, 10, and 38, subject to Soxhlet extraction with CH2Cl2:methanol (50:50 v/v), and the extracts analyzed for biodegradation with gas chromatography by measuring n-C17/pristine and n-C18/phytane ratios. No indication of biodegradation was observed in any of the microcosms. The contaminated soil did indicate slight evidence of weathering and/or biodegradation.

Preliminary Rock Evaluation Analysis experiments with all of the humates demonstrated that humates contain variable amounts of moisture. Moisture content was found to be a function of humate particle size, time exposed to the atmosphere, and storage conditions (i.e., closed container vs. desiccator). All further experiments characterizing humates by Rock Evaluation Analysis will compare humates "as is" and humates that have been freeze-dried and stored in a desiccator.

Publications/Presentations:

None to date.

Future Activities:

Supplemental Keywords: Adsorption, biodegradation