Research Doctorate - Doctor of Philosophy (PhD) / Consolidation of clayey contaminant barriers, such as are employed as landfill liners, has been postulated as a cause of accelerated transit of contaminants and hence their earlier than expected appearance in secondary leachate. This proposition is theoretically investigated in this thesis using a novel large-deformation, one-dimensional continuum model of coupled mechanical consolidation and solute transport. The model is a generalization of existing coupled consolidation and solute transport models described in the literature. It takes into account both non-linearities in geometry as well as material constitutive relations. The latter relate the compressibility, hydraulic conductivity and effective diffusion coefficient to the deformation of the soil. In addition to providing details of the governing equations and constitutive relations, a detailed derivation of the three classical one-dimensional consolidation boundary conditions, i.e. undrained top and drained bottom, drained top and undrained bottom, drained top and bottom is also given. From the continuum model formulation, a numerical model was developed using proprietary finite element software – FEMLAB 2.3. The numerical model is verified by comparing results with those produced from other recently developed consolidation – transport models. In the course of conducting these comparisons, some results from a recent modelling investigation indicating that a twenty-fold reduction in the transit time of contaminants across a composite soil – geomembrane barrier may be possible were re-examined. This comparison reveals some apparent errors in the original analysis and indicates that the predicted large acceleration of contaminant transport induced by consolidation is probably unrealistic. The model is subsequently applied to a case study of a clay liner and geomembrane system. Results obtained are compared with those from various simplified models, including a “diffusion-only” (i.e. a rigid soil) model traditionally used in contaminant barrier design. For barriers incorporating low compressibility soils (such as well compacted clays), there is little difference between contaminant transit times predicted by the two models. However, for contaminant barriers incorporating more compressible soils, consolidation is shown to be capable of accelerating transport. These results indicate the potential importance of accounting for the effects of soil consolidation and they highlight some limitations of existing models when modelling solute transport through composite barriers utilizing soft soils. Based on these limited results, a way of taking into account soil consolidation using simplified models is suggested. In the penultimate chapter of this thesis, an extensive parametric sensitivity analysis of coupled consolidation and solute transport in composite contaminant barrier systems is presented. The analysis incorporates results of more than 3000 simulations for various combinations of barrier thickness, waste loading rate, initial void ratio, compression index, hydraulic conductivity and dispersion coefficient. Results are succinctly presented using dimensionless plots, which allow the comparison of results for a large number of parameter values, and hence, the clear identification of the most important factors affecting contaminant transport through a consolidating composite barrier system. The results demonstrate that there exists a pessimum rate of consolidation for which the contaminant transit time is minimised. In cases of extremely high barrier compressibility it is shown that an order of magnitude reduction in contaminant transit time may arise due to coupling between solute transport and consolidation. For barriers of low compressibility and porosity, such as well-engineered composite compacted clay landfill liners, it is found that the contaminant transit time is far less affected, though it may still be reduced by up to 30%. In general, the results suggest that the use of a coupled consolidation–contaminant transport model may be required for informed and conservative contamiant barrier design, especially if relatively compressible earthen components are utilised.

To address my first objective, I opportunistically collected road-killed bobcats (n=44) throughout Illinois during 2013-2014, and analyzed their liver tissue for the presence of PCBs, PBDEs, and various other alternative halogenated flame retardants. Concentrations of ∑PCBs ranged from 76.4 ng/g lw to 3782 ng/g lw (median 562.97 ng/g lw). Male bobcats had significantly higher concentrations of PCBs than females (p = 0.04). Concentrations of ∑PBDEs (including all detectable PBDE congeners) ranged from 8.3 to 1920 ng/g lipid weight (median: 50.3 ng/g lw). Among the alternative flame retardants screened, Dechloranes (including anti- and syn-Dechlorane Plus and Dechlorane-602, 603, and 604), tetrabromo-o-chlorotoluene (TBCT), and hexabromocyclododecane (HBCD) were also detected frequently, with median concentrations of 28.7, 5.2, and 11.8 ng/g lw, respectively. Dechlorane analogue compositions in bobcats were different from that reported in other studies, suggesting species- or analogue-dependent bioaccumulation, biomagnification, or metabolism of Dechlorane chemicals in different food webs. My findings, along with previously reported food web models, suggest Dechloranes may possess substantial bioaccumulation and biomagnification potencies in terrestrial mammalian food webs. Thus, attention should be given to these highly bioavailable flame retardants in future environmental biomonitoring and risk assessments in a post-PBDE era. To address my second objective I collected raccoons (n=32) from various sites across Illinois and Missouri during 2013-2015. Liver tissues were analyzed for the presence of PBDEs and Dechloranes. ∑PBDE concentrations ranged from 19.1 ng/g lw to 2124 ng/g lw (median = 98.0 ng/g lw) and did not differ between gender or age of raccoon. Although nonsignificant (p=0.06), adult raccoons appeared to have greater PBDE concentration loads compared to juveniles. These nonsignificant differences are likely due to large variation in contaminant concentrations, possibly reflecting differences in individual raccoon diet and behavior. This is the first study reporting bioaccumulation of halogenated flame retardants in a wild felid in North America, and also the first report of PBDE accumulation in North American raccoons. The wide detection of Dechloranes, HBCD and TBCT in bobcats suggests a broad exposure of these alternative flame retardants in terrestrial apex predators in terrestrial ecosystems. The comparatively high levels of PBDEs in raccoons also suggest that biota in terrestrial habitats are still widely exposed to and susceptible to the bioaccumulation of these flame retardants.

Understanding the geology and the hydrology of the subsurface is important to model the fluid flow and the behavior of the contaminant. It is essential to have an accurate knowledge of the movement of the contaminants in the porous media in order to track them and later extract them from the aquifer. A two-dimensional flow model is studied and then applied on a linear contaminant transport model in the same porous medium. Because of possible different sources of uncertainties, the deterministic model by itself cannot give exact estimations for the future contaminant state. Incorporating observations in the model can guide it to the true state. This is usually done using the Kalman filter (KF) when the system is linear and the extended Kalman filter (EKF) when the system is nonlinear. To overcome the high computational cost required by the KF, we use the singular evolutive Kalman filter (SEKF) and the singular evolutive extended Kalman filter (SEEKF) approximations of the KF operating with low-rank covariance matrices. The SEKF can be implemented on large dimensional contaminant problems while the usage of the KF is not possible. Experimental results show that with perfect and imperfect models, the low rank filters can provide as much accurate estimates as the full KF but at much less computational cost. Localization can help the filter analysis as long as there are enough neighborhood data to the point being analyzed. Estimating the permeabilities of the aquifer is successfully tackled using both the EKF and the SEEKF.

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One of the most promising technologies in groundwater contaminant remediation is the active use of natural microbial activity to reduce aromatic hydrocarbons and other contaminants to simpler, non-toxic compounds. Biological treatment technologies which clean an aquifer without removing aquifer material fall into the broad category of in situ bioremediation, and have the potential to provide cost-effective remediation plans. Mathematical models used to simulate in situ bioremediation must deal with spatial variation in contaminant and electron acceptor concentration, microbial population, and media properties. Research has shown that the use of sequential electron acceptors significantly impacts biodegradation results. Aquifer conditions may switch between primary and secondary electron accepting conditions, further complicating the modeling process. This research examines the two-dimensional, sequential electron acceptor computer model SEAM2D, developed by Widdowson (1992), and extends the SEAM2D model by developing the equations and coding for the newly recognized solid phase, iron(Ill)-based contaminant reduction. Both a sensitivity investigation and field simulations are provided. The sensitivity investigation identifies which input parameters most significantly impact model results (i.e. changes in contaminant mass and concentration). The modeling simulations provide an illustration of model capabilities and documents procedures used in applying SEAM2D to a USGS study site in Laurel Bay, South Carolina. The Laurel Bay site and subsequent model simulations are unique in that the natural, sequential electron acceptor process of oxygen-iron(Ill) reduction is specifically monitored and modeled. / Master of Science

The host microbiome (mainly bacteria) is essential for host immune function, metabolism, and digestion. Alterations in these microbes, known as dysbiosis, generally results in adverse effects to the host, including diseases. Dysbiosis can be induced from exposures to various anthropogenic contaminants including constituents of municipal wastewater treatment effluents (MWWEs), namely, pharmaceuticals, antibiotics, and excess nutrients. Despite MWWEs being one of the largest dischargers to aquatic ecosystems, impacts of these contaminants on exposed organism microbiomes, especially in aquatic insects, is unclear. In addition, some aquatic contaminants may transfer to riparian habitats through predation on emergent insects that were exposed to contaminants as larvae, and subsequently alter microbiomes of terrestrial predators. Our study evaluated whether MWWEs altered microbiomes of freshwater larval and adult insects and their riparian spider predators using effluent-associated bacteria and stable nitrogen isotopes (δ15N) to confirm effluent exposure. We analyzed microbiome compositions through sequencing of the V3-V4 hypervariable region of the 16S rRNA gene and analyzed food web dynamics with stable carbon (δ13C) and nitrogen (δ15N) isotopes. We found that insects and spiders were enriched in δ15N at one site downstream of wastewater outfalls, indicating exposure to effluents and transfer of nutrients to terrestrial ecosystems. Microbiomes of most larval and adult insects were altered downstream of wastewater outfalls and had lower relative abundances of endosymbiont bacteria, shifts in bacterial diversities, increases in abundances of effluent-associated bacteria, and downregulation of some biosynthesis pathways than those collected at upstream sites. However, spider microbiomes had little evidence of dysbiosis, and were distinct from those of adult insects, despite a close association in their isotopic signatures. Overall, this study provides evidence of biological impacts from MWWEs to exposed insects and suggests that changes in microbial communities of invertebrates may be used as an effective indicator of effluent exposure as part of monitoring frameworks. / Thesis / Master of Science (MSc) / Municipal wastewater treatment facilities release contaminants into aquatic ecosystems that may affect the health of exposed organisms, including their microbiome, which contains bacteria essential for host digestion and immune function. Alterations in microbiomes of contaminant-exposed aquatic insects are poorly characterized and such effects may be transferred to terrestrial ecosystems through emergent insects. This study evaluated microbiomes and food web dynamics of freshwater insects and riparian spiders upstream and downstream of wastewater treatment facilities in the Bow River, AB. Results indicate that microbiomes of some downstream aquatic insects had lower relative abundances of endosymbiont bacteria, shifts in bacterial diversities, and increases in abundances of effluent-associated bacteria than those collected at upstream sites, but no such changes were observed in the spider predators. This study improves our understanding of how freshwater insect microbiomes are altered by municipal wastewater effluents and suggests that directly effluent-exposed organisms are more at risk of dysbiosis.

The objective of this research is to develop an integrated exposure model, which performs uncertainty analysis of exposure to the entire range of chemical contaminants in drinking water via inhalation, ingestion and dermal sorption. The study is focused on a residential environment. The various water devices considered are shower, bath, bathroom, kitchen faucet, washing machine and the dishwasher. All devices impact inhalation exposure, while showering, bathing and washing hands are considered in the analysis of dermal exposure. A set of transient mass balance equations are solved numerically to predict the concentration profiles of a chemical contaminant for three different compartments in a house (shower, bathroom and main house). Inhalation exposure is computed by combining this concentration profile with the occupancy and activity patterns of a specific individual. Mathematical models of dermal penetration, which account for steady and non-steady state analysis, are used to estimate exposure via dermal absorption. Mass transfer coefficients are used to compute the fraction of contaminant remaining in water at the time of ingestion before estimating ingestion exposure. Three chemical contaminant in water: chloroform, chromium and methyl parathion are considered for detailed analysis. These contaminants cover a wide range in chemical properties. The magnitude of overall exposure and comparison of the relative contribution of individual exposure pathways for each contaminant is evaluated. The major pathway of exposure for chloroform is inhalation, which accounts for 2/3rd of the total exposure. Dermal absorption and ingestion exposures contribute almost equally to the remaining 1/3rd of total exposure for chloroform. Ingestion accounts for about 60% of total exposure for methyl parathion and the remaining 40% of exposure is via dermal sorption. Nearly all of the total exposure (98%) for chromium is via the ingestion pathway. / Master of Science

The investigation of environmental impacts of 16 different contaminants originating from the E18 Highway (17 000 AADT) were carried out over the first six months of the highway‘s operational life. Investigative methods used include electrical resistivity surveying, water chemistry analyses, soil analyses, distribution modelling and transportation modelling. The investigation shows conclusively a year round infiltration due to melting of the snowpack from road salt, and a strong preferential anthropogenic pathway due to in-creased hydraulic conductivities of the road building materials relative to the natural soils. The resistivity surveys show values well below the expected values for the highway materials, indicating increased ionic content of the unsaturated zone. Time lapse resistivity modelling shows a clear downwards spreading of contamination from the roadway to subsurface distances greater than 5 m. Elevated concentrations of nearly every contaminant relative to baseline values were observed, with many concentrations of metals in the snow pack averaging values in excess of Swedish EPA groundwater limitations. Distribution modelling demonstrated a potential offset of peak values from the road surface due to ploughing and splash transport processes, but otherwise conformed to established distribution patterns. One dimensional transport modelling demonstrated the importance of adsorption and other retentive factors to the migration of contaminants to the water table, and provided an estimate for potential long term contaminant concentrations.

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