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Thirty-eight oligotrophic lakes located around the Reservoir Gouin in central Quebec (48°N, 75°W) were sampled over three years to test the hypothesis that forest clearcutting and fires should be reflected in both higher nutrient export rates and ultimately in greater areal hypolimnetic oxygen deficit rates (AHOD). Significant differences in estimated total phosphorus export rates across treatments were found. However, no effect of clearcutting or forest fire on hypolimnetic oxygen consumption rates could be demonstrated as the result of a much greater and confounding variation in the effect of lake morphometry and the absence of information on the role of catchment-derived organic matter on the AHOD. Consequently, only lake morphometry (hypolimnetic volume to hypolimnetic surface area ratio) served as a predictor of the AHOD. Covariation of mean hypolimnetic water temperature with morphometric variables underlines the influence of lake morphometry on heat dynamics and hypolimnetic respiration rates in these lakes. / This research made considerable use of specialized data manipulation techniques involving a relational database management system, owing to the size of the dataset used (114 lake-years of data). The specific approach used in this thesis is presented in an appendix.

Trace elements added to the soil by human activities could contaminate it and occasionally cause a threat to environmental and human health. The toxicity and mobility of a trace element are affected by the element's solubility, which in turn is influenced by the soil properties. When mobile, trace elements can be leached out of the soil. If leaching occurs at a faster rate than atmospheric deposition, element concentrations in the soil will decrease by natural attenuation. / We analyzed soil properties in 40 soils and their soil solutions to obtain a set of equations with the most significant predictors of As, Cd, Co, Cu, Mo, Ni, Pb and Zn in solution. The total element concentration and the pH were the best predicting variables of the amount of element in solution for all trace elements analyzed, while organic carbon and Al or Mn oxides also influenced the solubility of some trace elements. Using the equations predicting elemental solubility, we wrote a model for natural attenuation in the computer program Stella that considers atmospheric deposition as the input for trace elements and leaching as the output. Simulations were carried out for the 40 soils during 1,000 years with steady deposition inputs. / At current atmospheric deposition rates and the neutral to alkaline pH of these soils, attenuation occurred in most soils for Mo. For As, Cd, Co, Cu and Ni it occurred only in soils with abundant total element concentrations or an acidic pH. Minor retention occurred with Pb and Zn. Only Cd and Cu were of concern in leaching waters. The developed model can serve as a decision making tool in the selection of natural attenuation as a remediation strategy.

Perfluorinated carboxylates (PFCAs), sulfonates (PFSs) and perfluoroalkylsulfonamides (PFOSAs) have been detected in whole blood and serum of non-occupationally exposed humans, yet sources of exposure have not been fully elucidated. The objectives of this study were to estimate dietary exposure to perfluorooctane sulfonate (PFOS), PFCAs (C7--C 11) and fluorotelomer unsaturated carboxylates (FTUCAs) for the general Canadian and Inuit populations prior to the phase-out of perfluorooctyl-sulfonyl production by 3M and voluntary reductions in PFOA emissions under the PFOA stewardship program. PFCs were measured in 65 archived composite food samples prepared for the 1998 Canadian Total Diet Study (TDS) and 68 archived traditional foods from Nunavut using a newly developed methanol extraction combined with a solid phase extraction clean up. Dietary exposure was estimated using food intake data available from studies carried out between 1997 and 1998 in southern Canada and Nunavut. / PFCs were detected in eight composite food samples from the Canadian TDS and in 61 traditional food samples. Elevated concentrations of PFCs were found in caribou liver (6.2+/-5.5 ng/g), ringed seal liver (7.7, 10.2 ng/g), polar bear meat (7.0 ng/g), beluga meat (7.0, 5.8 ng/g), luncheon meats (5.02 ng/g), cookies (2.7 ng/g), processed cheese (2.1 ng/g) and peppers (1.8 ng/g). Low levels of total PFCs (<1.5 ng/g) were measured in 41 traditional foods including: meat (caribou, ptarmigan, snow goose, bearded seal, walrus, black duck), berries, and fish (lake trout, arctic char). PFCs were not detected in beverages, unprocessed meats, breads, cereals and fruits from the TDS composite samples analyzed. / The ranges of estimated daily exposure to PFCs were between 2 and 59 ng-person-1 and 210 to 610 ng-person-1 for average Canadians and Inuit in Nunavut respectively. There were no statistically significant differences in mean PFC exposure levels for different age and gender groups in the general Canadian population. Inuit men in the 41 to 60 year old age group had statistically significantly higher estimated daily exposure to PFCs (p<0.05) than younger men and women from the same age group. This higher exposure was associated with the consumption of beluga muktuk, caribou liver and bearded seal intestine. / Traditional foods contributed a higher percentage to PFC exposure than market foods in all age and gender groups for the Inuit population. In general, caribou meat, arctic char meat and cookies contributed most to dietary exposure for Inuit, with caribou flesh contributing 43 to 75 percent to daily PFC dietary exposure. Dietary exposure for the general Canadian population was associated with the consumption of cakes and cookies, processed cheese, and regular cheese. / Levels of dietary exposure to PFCs estimated in these studies do not pose any significant health risk to either population based on current toxicological information.

Electronic waste or `e-waste' is a rapidly growing form of solid waste worldwide. The heavy metals present in various electronic components demand attention because such metals may leach and pose significant health and environmental hazards (U.S. EPA, 2007). Knowledge of the potential of heavy metal leaching from e-waste represents an important contribution for developing U.S. standards for classifying e-waste as hazardous waste. Hazardous elements which leach from a variety of electronics wastes were assessed in laboratory batch studies. Electronic components evaluated included PC cathode ray tubes, PC motherboards, PC mice, television remote controls, and cellular phones. Each component was disassembled and digested using the Toxicity Characteristic Leaching Procedure (TCLP), EPA Method 1312, Method EA NEN 7371 (Dutch Environmental Agency), and Method DEV-S4 (Germany). The extracts were analyzed for lead, cadmium, chromium, silver, and cobalt. The TCLP consistently leached the greatest amounts of all metals; TCLP-soluble lead was extracted well beyond federal limits for several electronic devices. / Department of Natural Resources and Environmental Management

Evaluation of heavy metal accumulation in soils and plants is of environmental importance due to their health effects on humans and other biota. Phytoremediation is an emerging technology that can stabilize or remove heavy metals in soil utilizing metal tolerant plant species (metallophytes). The objectives of this study were to: (1) assess a Superfund site, and a lead-acid battery dump for concentrations of soil lead (Pb) and cadmium (Cd); (2) assess the various chemical fractions of Pb and Cd at both sites; (3) identify native herbaceous vegetation surviving in the contaminated soils; and (4) evaluate plant uptake of Pb and Cd. Soil Pb and Cd concentrations at the Superfund site averaged 55,480 and 8.5 mg/kg, respectively. Soil Pb at the Superfund site occurred primarily in the carbonate, sulfide/residual, and organic chemical fractions (41.6, 28.6, and 26.7, respectively). Soil Pb and Cd concentrations at the dump site averaged 29,400 and 3.9 mg/kg, respectively. Soil Pb occurred mostly in the organic and carbonate fractions as 48.5 and 42.5% respectively. Plant uptake of Pb at both sites ranged from non-detectable (Agrostemma githago, Plantago rugeli, Alliaria officinalis shoots), to 1800 mg/kg (Agrostemma githago root). Cd uptake was maximal in Taraxacum officinale at 15.4 mg/kg (Superfund site). In the majority of plants studied, root Pb and Cd content was higher than for shoots (>_65%). Tissue and soil fractions yielded r2 of 0.61 and 0.57 for the soluble and carbonate-Pb fractions, respectively. The plants with the greatest tissue concentrations of Pb and Cd were predominantly herbaceous species, some of which produce sufficient biomass to be practical for phytoremediation technologies. / Department of Natural Resources and Environmental Management

Freshwater ecosystems will likely become sinks for future silver loadings as a result of increased nanosilver (n-Ag) use in industrial and commercial applications. A series of bioassays was performed to assess how n-Ag toxicity may be influenced by abiotic factors associated with natural freshwater ecosystems. Additionally, these bioassays provide insight into how environmentally relevant concentrations of n-Ag may sublethaly affect the freshwater benthic gastropod, Physa acuta, that plays pivotal roles in maintaining the structure and function of freshwater ecosystems. In sediment with no benthic organic carbon (BOC), gastropod vital rates decreased in treatments containing any n-Ag, gastropods in sediment with relatively low BOC appeared to trade off growth for reproduction at high n-Ag treatments, while gastropod vital rates in high BOC sediment remained unaffected at all nanosilver treatments. Sediment type may abate nanosilver toxicity as a result of organic carbon content. Effects of n-Ag on gastropod vital rates were not dependant on pH, suggesting aqueous pH does not directly influence n-Ag toxicity. Nanosilver (0.2 μg/L) stressed gastropods, altering their growth and reproduction tradeoff dynamics. Nanosilver concentrations modeled to exist in natural freshwaters, disrupted gastropod ability to detect and respond to a natural predator, while greater n-Ag concentrations stimulated gastropods to exhibit contaminant avoidance behavior and thereby attempted to flee their habitat. This study provides direction in understanding how adverse n-Ag effects may be influenced by abiotic parameters, while assessing sublethal effects of n-Ag on freshwater gastropods that are likely to occur in natural freshwater ecosystems, given current estimates of environmental n-Ag concentrations. / Department of Biology