Graduate Theses & Dissertations

effects of Dissolved Organic Matter (DOM) sources on Pb2+, Zn2+ and Cd2+ binding
Metal binding to dissolved organic matter (DOM) determines metal speciation and strongly influences potential toxicity. The understanding of this process, however, is challenged by DOM source variation, which is not always considered by most existing metal speciation models. Source determines the molecular structure of DOM, including metal binding functional groups. This study has experimentally showed that the allochthonous-dominant DOM (i.e. more aromatic and humic) consistently has higher level of Pb binding than the autochthonous-dominant DOM (i.e. more aliphatic and proteinaceous) by more than two orders of magnitude. This source-discrimination, however, is less noticeable for Zn and Cd, although variation still exceeds a factor of four for both metals. The results indicate that metal binding is source-dependent, but the dependency is metal-specific. Accordingly, metal speciation models, such as the Windermere Humic Aqueous Model (WHAM), needs to consider DOM source variations. The WHAM input of active fraction of DOM participating in metal binding (f) is sensitive to DOM source. The commonly-used f = 0.65 substantially overestimated the Pb and Zn binding to autochthonous-dominant DOM, indicating f needs to be adjusted specifically. The optimal f value (fopt) linearly correlates with optical indexes, showing a potential to estimate fopt using simple absorbance and/or fluorescence measurements. Other DOM properties not optically-characterized may be also important to determine fopt, such as thiol, which shows strong affinity to most toxic metals and whose concentrations are appreciably high in natural waters (< 0.1 to 400 nmol L-1). Other analytical techniques rather than Cathodic Stripping Voltammetry (CSV) are required to accurately quantify thiol concentration for DOM with concentration > 1 mg L-1. To better explain the DOM-source effects, the conditional affinity spectrum (CAS) was calculated using a Fully Optimized ContinUous Spectrum (FOCUS) method. This method not only provides satisfactory goodness-of-fit, but also unique CAS solution. The allochthonous-dominant DOM consistently shows higher Pb affinity than autochthonous-dominant DOM. This source-discrimination is not clearly observed for Zn and Cd. Neither the variability of affinity nor capacity can be fully explained by the variability of individual DOM properties, indicating multiple properties may involve simultaneously. Together, the results help improve WHAM prediction of metal speciation, and consequently, benefit geochemical modelling of metal speciation, such as Biotic Ligand Model for predicting metal toxicity. Author Keywords: Dissolved organic matter, Metal binding, Source, Windermere Humic Aqueous Model
Reconceptualizing Immigration in Canada
This thesis challenges the contemporary framework of immigration in Canada. Despite Canada’s effort to promote cultural diversity and multicultural citizenship, immigration policy in the last decade has moved towards a model of cultural assimilation. The recent Bill—Strengthening Canadian Citizenship Act—devalues non-European cultures and hinders the successful integration for new immigrants. The problem of contemporary immigration in Canada lies in the narrow and exclusive understanding of immigration. That is, the current immigration framework is rooted in Eurocentrism, which draws exclusively from the economic and cultural values of the West. The Eurocentric understanding of migration not only hinders the successful integration for new immigrants, but it also hinders economic growth and weakens the social cohesion of Canada. For this reason, this thesis offers an alternative framework for understanding immigration. I focus on Chinese migration in Canada and take an interdisciplinary and a conceptual approach in order to present an inclusive understanding of Chinese migration. In particular, I apply the idea of "connected histories" to the context of immigration, and I demonstrate that immigration is a complex and interconnected phenomenon which cannot be reduced to the narratives of economics and ‘Canadian values.’ Instead, immigration should be understood as a process of transnational interactions because it not only allows us to understand benefits that transnational interactions would bring to immigrants, their country of origin and Canada, but it also recognizes different values and the agency of immigrants. Author Keywords: Bill C-24, Chinese Canadians, Eurocentrism, Immigration, Multicultrualism, Transnational

Search Our Digital Collections

Query

Enabled Filters

Filter Results

Date

2009 - 2019
(decades)
Specify date range: Show
Format: 2019/10/22

Last Name (Other)