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

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PAH Transfer, Degradation and Sequestration Polycyclic aromatic hydrocarbon compounds are transferred, degraded and sequestered in soils and sediments. Transfer is the process by which PAHs are relocated without altering their structure, degradation is the process where PAH structures are altered from their original form, and sequestration occurs when PAHs are removed from bioavailable pools and stored for long periods of time. The following section will expand upon processes presented in Table 2 and the relative rates of transfers from pools presented in Figure 3. Table 2. Movement and fate of organic chemicals, such as PAHs, in the environment (adapted from Pierzynski et al., 2000). Process Consequence Factors Transfer (processes that relocate PAHs without altering their structure) Volatilization Loss of PAHs due to evaporation from soil, plant, or aquatic ecosystems Vapor pressure, wind speed, temperature Absorption Leaching Uptake of PAHs by plant roots or animal ingestion. Polycyclic aromatic hydrocarbons usually do no transfer into aboveground biomass from soil. Translocation of PAH either laterally or downward through soils Erosion Movement of PAH by water or wind action Degradation (processes that alter the PAH structure) Biological Chemical Degradation of PAHs by microorganisms, biodegradation and cometabolism Alteration of PAHs by chemical processes such as photochemical (i.e. UV light) and oxidation-reduction reactions Cell membrane transport, contact time, susceptibility, plant species Water content, macropores, soil texture, clay and organic matter content, rainfall intensity, irrigation Rainfall, wind speed, size of clay and organic matter particles with adsorbed PAH on them Environmental factors (pH, moisture, temperature, oxygen), nutrient status, organic matter content, PAH bioavailability, microbial community present, molecular weight of PAH (LMW or HMW) High and low pH, structure of PAH, intensity and duration of sunlight, exposure to sunlight, and same factors as for microbial degradation Sequestration (processes that relocate PAHs into long-term storage without altering structure) Adsorption Diffusion Removal of PAHs from bioavailable pools through interaction with soils and sediments Diffusion of PAH into soil micropores where it is unavailable for microbial degradation Clay and organic matter content, clay type, moisture Hydrophobic nature of micropores and PAH 18
Figure 3. Relative PAH concentrations with time under the following processes: transfer (lost fraction), degradation (available fraction) and sequestration (recalcitrant fraction) (Stokes et al., 2006). PAH Transfer Polycyclic aromatic hydrocarbons are readily transferred among water, air, terrestrial and biological systems. The following processes will be discussed as PAH transfers from soil or sediments to air, water or biological systems. Volatilization: This is an important transfer process of PAHs in both soil and water resources through diffusion and is expressed with Henry’s Law. Henry’s Law is based on that fact that when two phases are not in equilibrium, a concentration gradient forms and a net flux will occur from one phase to the other (Eweis et al., 1998). Henry’s Law: m = HRT = CG RT Where, m is Henry’s Law coefficient H is the dimensionless Henry’s Law coefficient R is the universal gas constant T is the temperature in Kelvins CG is the gas-phase contaminant concentration (g m -3 ) CL is the liquid-phase contaminant concentration (g m -3 ) CL 19
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: persist in the soil (Alexander, 199
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 and 52: The addition of inorganic nutrients
Page 53 and 54: � Yu et al. (2006) found no effec
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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Remediation of PAH-Contaminated Soils and Sediments: A ...

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