Transformation of Fulvic Substances in the Rhizosphere during Phytoremediation of Used Motor Oil

Abstract

Changes in the chemical composition of fulvic acids in used oil-contaminated soils treated with different plant species and fertilization (fertilized, F; and nonfertilized, NF) were analyzed by Fourier-Transformed Infrared Spectroscopy (FTIR). Soil contaminated with 1.5% (w/w) used motor oil was seeded with sunflower (Helianthus annuus)/Indian mustard (Brassica juncea); soybean (Glycine max)/green bean (Phaseolus vulgaris); mixed grasses/maize (Zea mays); mixed clover (red clover, Trifolium pratense/ladino clover, T. repens); wheat (Triticum aestivum)/oats (Avena sativa); and control (no vegetation). FTIR of soil fulvic acids under plants at 150 days showed changes in functional groups compared with nonvegetated soil fulvic acids. Results indicate the incorporation of oily compounds and decomposition of others. Soybean/bean (NF), clover mix (NF), and wheat/oats (NF) showed new bands at 1800 cm⁻¹ related to the presence of carbonyl groups, associated with microbially induced beta-oxidation of oily hydrocarbons. A new band at 2300–2270 cm⁻¹ in sunflower/mustard (F and NF), soybean/beans (F and NF) and wheat/oats (NF) indicated the presence of N-based degradation products. Fertilizer treatment resulted in new bands at 1400–700 cm⁻¹ in soybean/bean and grass/maize. In contrast, clover mix fulvic acid experienced disappearance of aromatic bands at 885 cm⁻¹ and in wheat/oats at 2276 cm⁻¹ (aliphatic-N).

Keywords:

• Hydrocarbons
• Fourier-transformed infrared spectroscopy
• Fulvic acid
• Phytoremediation
• Rhizosphere
• Used motor oil

Acknowledgments

Financial support from The Eppley Foundation for Research, the Indiana Academy of Science, and the Ball State University Office of Academic Research and Sponsored Programs is gratefully acknowledged. The authors are grateful to Patti Lang, Ball State University Chemistry Department, for interpretations of analytical data.