| dc.description.abstract | Soil contaminated by crude oil or drill cuttings poses a threat to ecosystem. The objective of this study was to test tolerance levels of grass species to drill cuttings and crude oil in seed germination and at the 5-leaf stage. Sixty five grass species were screened for their tolerance to crude oil and drill cuttings at the germination stage. Two species were grouped as tolerant, 18 species as moderately tolerant, 27 species as moderately sensitive, and 18 species as sensitive to drill cuttings. In the test with crude oil, 28 species were classified as tolerant, 29 species as moderately tolerant, 6 species as moderately sensitive, and 2 species as sensitive. Nine species were further tested at different contamination levels. Seed germination and seedling biomass of all species was reduced. Buffalograss (Buchloe dactyloides (Nutt.) Engelm.), showed the least reduction of germination and biomass when grown in contaminated soil. Thus, it is a potential species to be used in remediation of oil contaminated with hydrocarbons. Seventy two grass species also were screened at 5-leaf stage for their tolerance to crude oil and drill cuttings. Thirteen species, among which seven are cereal crops, showed visual injury index less than 20 in a 0 to 100 scale, when grown in soil contaminated with drill cuttings. Of the grass species screened, grassy weeds ranked in the top one-third of biomass reduction with only yellow foxtail (Setaria pumila (Poir.) Roem. & Schult.) and foxtail barley (Hordeum jubatum L.) as exceptions. Nine species were chosen to further test the growth and phytotoxicity at different levels of contamination. The responses of those species at mature stages were affected by growing conditions. Nevertheless, barley and yellow foxtail showed lower biomass reduction and phytotoxicity compared with the other species. Using Fourier transform infrared spectroscopy to test the soil samples, it was found that concentrations of hydrocarbons in soil were reduced differently by different species. Annual ryegrass (Lolium multiflorum Lam.) and barley (Hordeum vulgare L.) showed the highest reduction of hydrocarbons from drill cuttings, while yellow foxtail and annual ryegrass showed the highest reduction of hydrocarbons from crude oil contamination. | en_US |
