Progress 10/01/06 to 09/30/12
Outputs
OUTPUTS: Laboratory, greenhouse, and field experiments were conducted to determine the influence of plants and nutrient additions on the remediation of soil contaminated with organic compounds. Combinations of plant densities and increasing nitrogen addition rates were evalutated in greenhouse studies. Laboratory studies evaluated the rate of pyrene mineralization in three soils with differing physical, chemcial, and biological properties. Numbers of oil-degrading microorganisms were determined in crude oil-contaminated soil with various nitrogen addition rates and plants. Results were presented at national and international scientific meetings, conferences, and symposia including the Soil Science Society of America, Integrated Petroleum Environmental Consortium, and American Institute of Chemical Engineering. The findings from the studies were used to make recommendations for remediation of contaminated sites. Undergraduate and graduate students participated in the project and used the experience to gain employment in the private, government, and public sectors. Students have presented their findings in oral and poster presentations at local, state, national, and international conferences. Results from the project were incorporated in material presented in three university classes. PARTICIPANTS: Duane Wolf was the principle investigator for the study. Collaborators included Greg Thoma, Chemical Engineering Dept., Susan Zigler, Biological Sciences Dept., and Mary Savin, Crop, Soil, and Environmental Sciences Dept. Training for graudate students was provided to Paul White, Wes Kirkpatrick, Orina Alba, Alice Jernigan, Josh Swigart, and Nathan Walker. Undergraduate students working on the project were Satoshi Takaki and Doug Wolf. TARGET AUDIENCES: The information gained from the studies was used to help remediation consultants, regulatory agency personnel, and individuals in the oil and gas industry. The information would allow individuals to make economically and environmentally sound decisions for site clean-up. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Findings from the project demonstrated the benefits of selecting appropriate plant species to enhance remediation of soil contaminated with organic chemicals. Nitrogen additions were also shown to increase plant growth, increase the volume of rhizosphere soil, and increase the number of contaminant-degrading microorganisms. Increased contaminant degrader numbers and activity enhanced remediation of the contaminated soil. The results also indicated that there was a soil specific aspect and each soil and contaminant must be evaluated in laboratory and greenhouse studies to determine the potential for enhancing phytoremediation. Using plants and fertilizers in a phytoremediation program offers substantial economic benefit compared to landfilling or incineration for site clean-up.
Publications
- No publications reported this period
|
Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Drilling for natural gas has expanded dramatically in response to greater energy demands. The drilling process generates substantial quantities of hydraulic drilling fluids that contain high levels of salt and other components. Historically, the drilling fluid was land applied, but excessive application rates at some locations have resulted in challenges in establishing vegetation at the sites where drilling fluids were applied. A study was conducted to evaluate the use of a biosolids, poultry litter, and inorganic fertilizer amendments to facilitate vegetation establishment and growth in soil where excessive rates of drilling fluid had been applied. A greenhouse study was conducted to determine the growth of bermuda grass or sudan grass in a drilling fluid-contaminated soil with or without the addition of 5 Mg/ha biosolids or poultry litter or inorganic fertilizer at a rate recommended by soil testing procedures. The contaminated soil had a pH of 8.0, and electrical conductivity of 2.60 dS/cm, and extractable Na and Cl levels of 1775, and 2288 mg/kg, respectively. Initial results show that the bermuda grass sprigs and sudan grass seeds were able to grow in all soil treatments and the control. Plant growth and chemical concentrations in the soil and plants will be determined following the 10-wk growth period. PARTICIPANTS: Satoshi Takaki conducted the research project for his AFLS Honors Program thesis research. The project was funded in part by a research grant from the University of Arkansas Honors College. TARGET AUDIENCES: The information gained from the study can be used to help individuals in the oil and gas industry make environmentally sound decisions on the disposal or land application of drilling mud resulting from drilling operations. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The results from the study will be important in developing recommendations for vegetating sites where excessive application of drilling fluid has adversely impacted plant establishment and growth. Using biosolids or poultry litter as soil amendments offers the benefits of increasing plant growth and recycling nutrients contained in readily available waste products.
Publications
- Takaki, S. and D.C. Wolf. 2011. Plant growth in soil amended with drillin mud. Discovery 12:74-79.
|
Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Pyrene is a polyaromatic hydrocarbon that exhibits variable biodegradation rates in soils. The objective of the laboratory incubation study was to determine the mineralization rate of 14C-labeled pyrene in two soils. A Captina silt loam and a Roxana loam were unamended or amended with 200 mg pyrene/kg soil and the four replications of each treatment were maintained at a moisture potential of -33 kPa and 24C. The Captina and Roxana had initial pyrene degrader numbers of <2.70 and 3.78 log MPN/g, respectively. After 16 weeks, 2% of the 14C pyrene was recovered as 14CO2 from the Captina soil. During the 16-week incubation, a 5-week acclimation period was observed followed by rapid biodegradation of pyrene resulting in 40% mineralization of the labeled pyrene in the Roxana. For the Captina soil, with or without pyrene addition, the respiration rate was 69 and 68 mg C-CO2/100 g soil, respectively. For Roxana soil, with or without pyrene, the respiration rate was 21 and 13 mg C-CO2/100 g soil, respectively. PARTICIPANTS: Dr. Duane C. Wolf, Principle Investigator: Dr. Greg Thoma, Co-Investigator; Dr. C. N. Hestekin, Co-Investigator; A.C. Jerigan, Graduate Student TARGET AUDIENCES: Regulatory agencies and consulting companies involved in the clean-up of petroleum spills. PROJECT MODIFICATIONS: None
Impacts
Pyrene biodegradation rates for the two soils studied appeared to be determined by the number and activity of pyrene degrading microorganisms indigenous to the two soils. An initial screening of soils to evaluate the pyrene degrading microbial population could provide information on the potential of a given soil for pyrene bioremediation.
Publications
- Jernigan, A.C., G. Thoma, D.C. Wolf, and C.N. Hestekin. 2009. Monitoring Bioremediation Using Single-Strand Conformational Polymorphism and Capillary Electrophoresis. In Am. Institute Chem. Engineer. 2009. Annual Meeting, Nashville, TN. 15 July 2009.
|
Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Phytoremediation of crude oil-contaminated soil was evaluated through a 5-year study at a field site near El Dorado, Arkansas. The site was divided into twelve plots to study the effect of vegetation and fertilizer addition using three experimental treatments with four replicates. The treatments included non-vegetated non-fertilized control, fertilized ryegrass-fescue mixture, and fertilized bermudagrass-fescue mixture. The results showed that plant establishment and fertilizer addition increased microbial numbers and biomass which resulted in increased rhizodegradation of crude oil components. Total petroleum hydrocarbon (TPH) reduction in the vegetated plots was observed to be significantly higher than that of control plots and the vegetated and fertilized plots were not different. During the 57-mo study, there was a 72% reduction in TPH in bermudagrass-fescue + fertilizer and ryegrass-fescue + fertilizer treatments while the fraction removed through natural attenuation in the control plots was 58%. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Oil and gas producers. Remediation consultants. Regulatory agencies. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results from the field study show that using plants and fertilizer in a phytoremediation program can stimulate oil biodegradation and enhance clean-up of oil contaminated soil. Phytoremediation offers a substantial economic benefit compared to other clean-up strategies and results in environmental benefits beyond simply cleaning up the oil spill.
Publications
- Karim, K., G.J. Thoma, P.M. White, Jr., K.J. Davis, D.C. Wolf, and S.E. Ziegler. 2010. A five-year field study to evaluate phytoremediation of a crude oil-contaminated site. Int. J. Phytoremed. 12: (in press)
|
Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Phytoremediation can be a cost effective and environmentally acceptable method to cleanup crude oil-contaminated soils in situ. Our research objective was to determine effects of nitrogen (N) additions and plant growth on the number of total hydrocarbon (TH)-, alkane-, and polycyclic aromatic hydrocarbon (PAH)-degrading microorganisms in weathered crude oil-contaminated soil. A warm-season grass, sudangrass (Sorghum sudanense (Piper) Stapf), was grown for 7 wk in soil with a total petroleum hydrocarbon (TPH) level of 16.6 g TPH/kg soil. Nitrogen was added based upon TPH-C:added total N ratios (TPH-C:TN) ranging from 44:1 to 11:1. Unvegetated and unamended controls were also evaluated. The TH-, alkane-, and PAH-degrading microbial numbers/g dry soil were enumerated from rhizosphere and non-rhizosphere soil for vegetated pots and non-rhizosphere soil populations were enumerated from non-vegetated pots. Total petroleum-degrading microbial numbers were also calculated/pot. PARTICIPANTS: Dr. Duane Wolf, Principle Investigator; Dr. Greg Thoma, Co-PI; Mr. Nathan Walker, Graduate Student Researcher TARGET AUDIENCES: Regulatory agencies and consulting companies involved in the clean up of petroleum spills. PROJECT MODIFICATIONS: None
Impacts
The TH-, alkane-, and PAH-degrading microbial numbers/g dry soil in the sudangrass rhizosphere were 3.4, 2.6, and 4.8 times larger, respectively, than those in non-rhizosphere soil across all N rates. The presence of sudangrass resulted in significantly more TH-degrading microorganisms/pot when grown in soil with a TPH-C:TN ratio of 11:1 compared to the control. Increased plant root growth in a crude oil-contaminated soil and a concomitant increase in petroleum-degrading microbial numbers in the rhizosphere have the potential to enhance phytoremediation.
Publications
- Kirkpartick, W.D., P.M. White, D.C. Wolf, G.J. Thoma, and C.M. Reynolds. 2008. Petroleum-degrading microbial numbers in rhizosphere and non-rhizosphere crude oil-contaminated soil. Int. J. Phytoremed. 10:210-221.
- Jernigan, A.C., G. Thoma, D.C. Wolf, and C.N. Hestekin. 2008. Characterizing the Abundance and Activity of Soil Microbes by Capillary Electrophoresis Using Single-Strand Conformational Polymorphism. In Am. Institute Chem. Engineer. 2008 Annual Meeting Philadelphia, PA, 16-21 November 2008.
|
Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Phytoremediation is a method in which plants, soil microorganisms, amendments, and agronomic techniques interact to enhance contaminant degradation. We hypothesized that bermudagrass (Cynodon dactylon L) and an appropriate amount of N fertilizer would improve remediation of pyrene-contaminated Captina silt loam soil. The soil was contaminated with 0 or 1000 mg pyrene/kg of soil and amended with urea at pyrene-C:urea-N (C:N) ratios of 4.5:1, 9:1, 18:1, or unamended (36:1). Either 0, 1, 2, or 3 bermudagrass sprigs were planted per pot and -33 kPa moisture potential was maintained. Pyrene concentrations, inorganic-N levels, shoot and root parameters, and pyrene degrader microbial numbers were measured following a 100-d greenhouse study.
PARTICIPANTS: Dr. Duane Wolf, Principle Investigator Dr. Greg Thoma, Co-PI Ms. Oriana Alba Thompson, Graduate Student Researcher
TARGET AUDIENCES: Regulatory agencies and consulting companies involved in the clean up of petroleum spills.
PROJECT MODIFICATIONS: None
Impacts
At a C:N ratio of 4.5:1, the presence of plants increased pyrene biodegradation from 31% for the no plant treatment to a mean of 62% for the 1, 2, and 3 plant treatments. With no plants and C:N ratios of 4.5:1, 9:1, 18:1, and 36:1, the mean pyrene biodegradation was 31, 52, 77, and 88%, respectively, indicating that increased inorganic-N concentration in the soil reduced pyrene degradation in the treatments without plants. Additionally, none of the 1, 2, or 3 plant treatments at any of the C:N ratios were different with a mean pyrene degradation value of 69% after 100 d. Pyrene resulted in reduced shoot and root biomass, root length, and root surface area, but increased root diameter. The pyrene degrading microbial numbers were approximately 10,000-fold higher in the pyrene-contaminated soil compared to the control. At the highest N rate, bermudagrass increased pyrene degradation compared to the no plant treatment, however, in the unvegetated treatment pyrene
degradation was reduced with added N.
Publications
- Thompson, O.A., D.C. Wolf, J.D. Mattice, and G.J. Thoma. 2008. Influence nitrogen addition and plant root parameters on phytoremediation of pyrene-contaminated soil. Water, Air, and Soil Pollution 189:37-47
- Kirkpartick, W.D., P.M. White, D.C. Wolf, G.J. Thoma, and C.M. Reynolds. 2008. Petroleum-degrading microbial numbers in rhizosphere and non-rhizosphere crude oil-contaminated soil. Int. J. Phytoremed. 10: (in press)
- Thoma, G., N. Alahari, K. Sublette, E. Jennings, D. Wolf, K. Duncan, T. Todd, M. Callaham. 2007. Earthworms ad ecoengineers in the restoration of oil and brine-impacted soils following remediation. 2007 Arkansas Water Resources Center Annual Water Conference. Fayetteville, AR. 24-25 April 2007.
- Karim, Khursheed, G.J. Thoma, K.J. Davis, and D.C. Wolf. 2007. Evaluation of phytoremediation using total petroleum hydrocarbon working group (TPHCWG) approach: A field study at El Dorado, Arkansas. 14th Annual Int. Petroleum Environ. Conf. Houston, TX. 6-9 November 2007.
|
|