Remediation of PAH-Contaminated Soils and Sediments: A ...

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soil (exudates) vary based on lifeform and species. For example, annual plants transfer 30-60% of new fixed photosynthetic carbon to the roots of which 40-90% is transferred directly into the rhizosphere (Olson et al., 2003). A similar range of photosynthetic carbon, 30-70%, is transferred to the soil in perennial plants, where 25-80% is transferred from the roots to soil (Olson et al., 2003). These contributions of carbon from plants to the soil stimulate microbial communities and thus the degradation of PAHs (Liste and Alexander, 2000; Binet et al., 2000; Chen et al., 2003; Robinson et al., 2003; Yu et al., 2006; Kamath et al., 2004). Though stimulation of microbial communities in the rhizosphere is the main process for PAH degradation, some studies have revealed that potential uptake and metabolism of PAHs is also possible (Harms, 1996). Uptake is controlled by molecular configuration and size as well as the capability for uptake by a specific plant species (Harms, 1996). Organic compounds with low water solubility (high log Kow) tend not to be transported within a plant, but organics with log Kow between 0.5 and 3.0 are likely to be transported within a plant (Burken and Schnoor, 1998; Olson et al., 2003). Additionally, plants typically transport LMW PAH compounds or HMW compounds that have been transformed outside the plant in the rhizosphere (Olson et al., 2003). Phytoremediation also helps reduce the offsite transfer of contaminants by controlling runoff, wind erosion and leaching, and is a non-disruptive selfsustaining process which requires relatively little management. However, phytoremediation is a very lengthy process (1-3 years) that is often limited by phytotoxic contaminant levels, and is usually used as a secondary treatment in soils contaminated with residual levels of PAH (Joner et al., 2002; Cunningham et al., 1995). The success of the process will depend on environmental factors such as adequate supply of oxygen, water, and nutrients, as well as edaphic factors like the soil texture, pH, EC, and the levels of pollutants (Cunningham et al., 1995). Some plant species that have been shown to have potential for remediation of petroleum hydrocarbons, including PAHs, and associated citations are listed in Table 9. Some examples of the influence of specific plant species on degradation of PAH compounds include: � Reilley et al. (1996) found the total accumulation of pyrene and anthracene in roots and shoots of different plants accounted for
� Yu et al. (2006) found no effects on plant growth or any sign of stress in corn (Zea mays L.), white clover (Trifolium repens), and perennial ryegrass (Lolium perenne L.) grown in greenhouse pots spiked with phenanthrene and pyrene at rates of 0-375 mg kg -1 . � Liste and Felgentreu (2006) reported up to a 50% decrease in root and shoot yield in summer vetch (Vicia sativa L.) , annual ryegrass (Lolium multiflorum Lam.) and white mustard (Sinapsis alba L.) growing on soil from an old coal gasification site (EPA Priority PAH content: 71.4 mg kg -1 ; total petroleum hydrocarbons: 1517 mg kg -1 ). Ryegrass was the most PAH-tolerant species in their study. The reduction in growth was thought to be due to toxicity of LMW constituents or to changes in physicochemical properties of the soil caused by petroleum hydrocarbon contamination. � Yi and Crowley (2007) reported that the uptake of PAH by 43 different plants was insignificant. Less than 0.01 mg kg -1 was detected in the roots and shoots of tested plants. � Increased degradation of HMW PAHs during phytoremediation has also been documented (Aprill and Sims, 1990; Binet et al., 2000; Paquin et al., 2002). Other researchers have found; however, that plants either inhibited or had little effect on biodegradation rates depending on the plant species and type of contamination (Watkins et al., 1994; Gunther et al., 1996). � Liste and Felgentreu (2006) suggested that a slowing of PAH degradation during phytoremediation could be due to increased nitrogen demand, which decreased the amount of nitrogen available to degrading microorganisms. Incorporating a nitrogen-fixing component into a species mix during phytoremediation could prevent this. When selecting phytoremediation species, there are several factors to consider; climate, water availability, salinity, and the presence of other phytotoxins (Hutchinson et al., 2003). Climate includes the length of growing season, rainfall and temperature patterns. Water availability is influenced by soil texture, bulk density, hydraulic conductivity and is related to climate. Dense clay soils have less water movement or lower infiltration, while sandy soils have greater infiltration and hydraulic conductivities. Sandy soils also drain quickly and have lower water storage. Salt resistant species selection for soils or sediments with high salinity is extremely important for establishment and health of plants. Other toxins are also a concern, as some contaminants can be too toxic in soils to support plants. Obviously, if the contaminant levels are too high, phytoremediation will not be successful (Hutchinson et al., 2003). 53
Page 1 and 2: Remediation of PAH-Contaminated Soi
Page 3 and 4: Abstract Polycyclic aromatic hydroc
Page 5 and 6: soil is the primary environmental r
Page 7 and 8: Solubility Solubility of PAH compou
Page 9 and 10: Figure 1. Structures of US EPA’s
Page 11 and 12: � If you were to add 2 benzene ri
Page 13 and 14: and their mutagenic and carcinogeni
Page 15 and 16: PAH in humans The carcinogenicity o
Page 17 and 18: persist in the soil (Alexander, 199
Page 19 and 20: Figure 3. Relative PAH concentratio
Page 21 and 22: the gas phase was attributed to tem
Page 23 and 24: increasing rainfall intensity or wi
Page 25 and 26: in contaminated soils than uncontam
Page 27 and 28: Ideal biodegradation of PAHs, where
Page 29 and 30: Figure 5. Aerobic degradation of PA
Page 31 and 32: Cometabolism is explained by three
Page 33 and 34: donate electrons. The redox potenti
Page 35 and 36: 1. Fenton’s reagent - formation o
Page 37 and 38: Figure 7. Schematic of integrated e
Page 39 and 40: Figure 8. Possible mechanism for di
Page 41 and 42: Freundlich adsorption equation: x/m
Page 43 and 44: Diffusion: Weber et al. (1992), Web
Page 45 and 46: Biological Techniques for Enhancing
Page 47 and 48: oot extract resulted in continuous
Page 49 and 50: Composting Composting is a form of
Page 51: The addition of inorganic nutrients
Page 55 and 56: Carrot Daucus carota Wild and Jones
Page 57 and 58: Surfactants Mass transfer of PAH co
Page 59 and 60: � Straube et al. (2003) showed th
Page 61 and 62: encountered with biodegradation, an
Page 63 and 64: volatilization of some compounds, s
Page 65 and 66: Regulatory Framework Dredged materi
Page 67 and 68: transition phase between slurried s
Page 69 and 70: In addition to equation manipulatio
Page 71 and 72: Coastal Zone Management Act (CZMA)
Page 73 and 74: EPA Region V NA http://www.epa.gov/
Page 75 and 76: Indiana Department of Environmental
Page 77 and 78: New York State Department of Enviro
Page 79 and 80: Analytical Methods The following is
Page 81 and 82: Sample Cleanup After extraction, cl
Page 83 and 84: Table 13. Detection limits for cert
Page 85 and 86: Citations Accardi-Dey, A., and P.M.
Page 87 and 88: Cerniglia, C.E., and D.T. Gibson. 1
Page 89 and 90: EPA. 2008. Integrated Risk Informat
Page 91 and 92: Harmsen, J. 2007. Measuring bioavai
Page 93 and 94: Kelsey, J.W., B.D. Kottler, and M.
Page 95 and 96: Mackay, D., and D. Callcott. 1998.
Page 97 and 98: O’Mahony, M., A. Dobson, J. Barne
Page 99 and 100: Saison, C., C. Perrin-Ganier, M. Sc
Page 101 and 102: Vessigaud, S., C Perrin-Ganier, L.

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