Mangal, Vaughn

Chromophoric dissolved organic matter (CDOM), a chemically diverse family of organic compounds defined by their ability to absorb ultraviolet and visible light, is a critical constituent of numerous environmental systems, including freshwater lakes. Industrial operations in the Athabasca Oil Sands Region (AOSR, Alberta, Canada) are major sources of acidic inorganic gases and organic contaminants to the atmosphere, the subsequent deposition of which posed the potential to alter the composition of natural CDOM within surrounding lake surface-waters. The objective of this thesis was to determine if OS sources measurably impacted CDOM quality within 50 regionally monitored acid sensitive lakes by means of a) altered acid-base chemical processes or b) industrial atmospheric CDOM inputs. Ultraviolet-visible light spectroscopy and excitation emission matrix (EEM) fluorescence spectroscopy were applied to characterize CDOM within regional lake surface-waters to identify the primary sources (e.g., natural, anthropogenic) and process (e.g., acid-base chemistry) influencing chromophoric organic matter quality. These spectroscopic techniques were further used to evaluate industrial CDOM within atmospheric aerosols and deposition to assist with the identification of industrial CDOM within lake waters. Spectroscopic analysis of regional lake surface-water found weak associations between CDOM and acid-base variables, suggesting that acid inputs from OS sources would have limited influence over surface-water chromophoric organic matter. A distinct fluorescent component (i.e., fluorophore) measured within the lake samples (C3) displayed decreasing emission intensity as a function of distance from OS sources and positive correlations with surface-water polycyclic aromatic compounds, implying industrial influence. Spectral similarity between C3 and industrial fluorophores observed from regional aerosol and atmospheric deposition samples further confirmed the lake fluorophore was linked to OS sources. This research suggests that EEM fluorescence spectroscopy could be used as a cost-effective technique to detect industrial pollution within lake surface-waters throughout the AOSR.

Author Keywords: atmospheric brown carbon, atmospheric deposition, atmospheric pollution, dissolved organic matter, fluorescence spectroscopy, lake chemistry

Aquatic contaminant mobility and biological availability is strongly governed by the complexation of organic and inorganic ligands. Dissolved organic matter (DOM) is a complex, heterogeneous mixture of organic acids, amino acids, lipids, carbohydrates and polyphenols that vary in composition and can complex to dissolved metals thereby altering their fate in aquatic systems. The research conducted in this doctoral dissertation addresses 1) how DOM composition differs between phytoplankton taxa and 2) how DOM composition affects metal speciation and its subsequent microbial bioavailability in laboratory and field conditions. To accomplish this, a series of analytical methods were developed and applied to quantify thiols, sulphur containing DOM moieties, and the molecular composition of DOM. The works presented in this thesis represents one of the first comprehensive and multipronged analyses of the impact of phytoplankton metabolite exudates on microbial metal bioavailability. This dissertation demonstrated the analytical versatility of high-resolution mass spectrometry as a tool for compound specific information, as well as having the capabilities to obtain speciation information of organometallic complexes. The work presented in this PhD strengthens the understanding compositional differences of both autochthonous and allochthonous DOM and their effects on metal biogeochemistry.

Author Keywords: Dissolved Organic Matter, Mercury, Metal Accumulation, Phytoplankton, Spring Melts, Thiol