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Understanding the behavior of contaminants in the environment is essential for an adequate assessment of a chemicals' fate, subsequent exposure to organisms, and potential for toxic effects. However, contaminant behavior can be complex, involving multiple interactions such as sorption to, and desorption from, particles present in the water column and sediment phase, competition for binding sites, and sequestration deep within particle pores, altering the chemical and biological availability of the contaminants. Therefore, one way to understand a contaminants? behavior in the environment is to assess its bioavailability, or fraction of contaminant available for uptake by organisms. This is generally accomplished by measuring the concentration of a contaminant present in organism tissue, and comparing it to concentrations in different environmental compartments (water, sediment). In this study, numerous toxicokinetic parameters, bioconcentration factors and biota-sediment accumulation factors for 46 polycyclic aromatic hydrocarbons in freshwater mussels were measured. Elimination rates ranged from 0.04 (perylene) to 0.26/day (2,6-dimethylnapthalene), half-lives ranged from 2.6 to 16.5 days, and times to reach 95% of steady-state ranged from 11.3 to 71.3 days. The ranges and individual values compare well to available published literature values. Bioconcentration factors ranged from 1.54 (naphthalene) to 5.20 (coronene), depending on individual analyte and study conditions, but generally increased with increasing PAH hydrophobicity. Bioconcentration factors exhibited sensitivity to concentrations of dissolved and particulate organic carbon present in the water column, and to partition coefficients used to account for these parameters. Additionally, biota-sediment accumulation factors demonstrated that pyrogenic PAH (associated with incomplete-combustion) have much lower bioavailability than petrogenic PAH (associated with petroleum), with average values ranging from 0.
This dissertation focuses on the fate and the movement of polycyclic aromatic hydrocarbons (PAHs) from contaminated soil. The main objectives of this study are to understand the relationship between PAH association with contaminated soil and its availability, and to provide fundamental understandings of mass transfer phenomena of PAHs between the soil or sediment and its surroundings in the aspect of in-situ stabilization of the contaminant by adding sorbent. As a case study, a PAH-contaminated industrial site soil was studied. Various carbonaceous materials including coal, coke, pitch, and tar decanter sludge were identified and most of the PAHs were found to be associated with the polymeric matrix of tar sludge or hard pitch as discrete particles, or as coatings on soil mineral particles, or as complex aggregates. The PAH availability from these particles was very low due to the hindered diffusive release with very small apparent diffusivities. Significant concentrations of PAHs were observed in the interior of solid tar aggregates. The release of PAHs from the interior of such particles would require diffusion over a substantial distance. These findings explain the results from three years of phytoremediation of the site soil, for which no significant changes in the total PAH concentrations were observed in the test plot samples. Sorption isotherms and kinetics were studied for phenantherene and pyrene with organic model sorbents: polyoxymethylene (POM), coke, and activated carbon (AC). These findings were combined with the direct observation of the diffusion of phenanthrene and pyrene using microprobe laser-desorption laser-ionization mass spectroscopy (muL2MS). POM showed reasonable agreement between the independent muL2MS-measurements and the predicted intraparticle concentration profiles from kinetic batch experiments and a polymer diffusion model. For coke and AC, the muL 2MS-measurements showed faster radial diffusion into the particle interior than predicted from diffusion models. A numerical model based on the intraparticle diffusion was employed to simulate long-term effects of sorbent amendment on changes in aqueous concentration and mass transfer between different soil domains. The model could reproduce the laboratory scale experiments qualitatively. The model was applied to different contamination scenarios and provided sound predictions of the likely long-term changes in the system.
This study aims to improve knowledge of how suspended particulate matter (SPM) affects hydrophobic contaminant transport in the lower Columbia River and its estuary, using polycyclic aromatic hydrocarbons (PAHs) as model compounds. It is hypothesized that PAHs are transported to the estuarine turbidity maximum (ETM), a prime feeding zone in the Columbia estuary, where organisms encounter and consume contaminants adhered to particles as part of their diet. During a CMOP (Center for Coastal Margin Observation and Protection) cruise aboard the RV Barnes in August 2007, water samples were collected from sites throughout this study region. In addition, bi-monthly water samples were collected over a one-year period in coordination with the USGS NASQAN program. The PAH content and composition was analyzed in all samples and interpreted in perspective with the SPM concentration and particulate organic carbon content of the SPM. Results show that the dominant source of PAH to the study region is a characteristic suite of compounds derived from high temperature combustion. Perylene, a compound of yet to be determined natural origin, represents a PAH of comparable quantitative significance. These compounds are transported via riverborne SPM to the estuary and hydrodynamically trapped in the ETM with the trapping process operating somewhat differently between the two sources. The concentration of individual combustion PAHs measured in SPM from the Columbia River and its estuary exceed the thresholds of concern stipulated by environmental protection policies. Surprisingly, measured PAH levels are similar to those measured in other, far more industrialized river and estuarine systems around the world.