Groundwater remediation strategies have advanced toward more effective and economical remedial technologies. Monitored natural attenuation (MNA) has become accepted by federal regulatory agencies as a viable remediation strategy for contaminants under site-specific conditions. At chloroethene contaminated sites where MNA is used as a remediation strategy, microbially-mediated reductive dechlorination is typically the dominant pathway for natural attenuation. The efficacy of reductive dechlorination at sites with no anthropogenic carbon sources is often influenced by the availability of readily-biodegradable natural organic carbon along with favorable geochemical conditions for supporting microbial dehalogenation. Recent research studies have suggested that the pool of labile natural organic carbon, operationally defined as potentially bioavailable organic carbon (PBOC), may be a critical component related to sustaining reductive dechlorination at MNA sites. The objective of this study was to evaluate PBOC as a quantitative measure of the labile organic carbon fraction of aquifer sediments in relation to microbial reductive dechlorination of chlorinated solvents. In the first phase of this study, the variability of PBOC in aquifer sediments was examined among 15 chloroethene contaminated sites. Results showed that PBOC displayed considerable variability among the study sites, ranging over four orders of magnitude. Regression results demonstrated that a positive correlation existed between PBOC, solid phase total organic carbon (TOCs), and reductive dechlorination activity at the sites. Results supported that greater levels of PBOC and TOCs corresponded to higher reductive dechlorination activity at the sites. Composition results showed that 6-86% of PBOC consisted of proteins and amino acids. Results also suggested a positive relationship existed between PBOC, concentrations of potentially bioavailable organic compounds present in the aquifer system, expressed as hydrolyzable amino acids (HAA), and the natural attenuation capacity (NAC) at the sites. Higher PBOC levels were consistently observed at sites with greater NAC and levels of HAA. The results of this study suggested that the variability of PBOC in the aquifer sediments exhibited a reasonable correlation with TOCs, hydrolyzable amino acids, and chloroethene transformation among the selected sites. In the second phase of this study, the relationship between PBOC in aquifer sediments and site specific performance data was evaluated among 12 chloroethene contaminated sites. Results demonstrated that PBOC in aquifer sediments was directly correlated to independent field metrics associated with reductive dechlorination. Levels of PBOC demonstrated direct relationships with hydrogen (H2) and dissolved oxygen (DO) concentrations within the groundwater system at the selected study sites. Results also indicated that PBOC demonstrated positive relationships with reductive dechlorination activity and the natural attenuation capacity of the sites. The findings of this study suggested that the level of PBOC in aquifer sediments may be a key factor in sustaining conditions favorable for microbial reductive dechlorination. In the third phase of this study, the distribution of PBOC was investigated at a chloroethene contaminated site. PBOC was measured in surficial aquifer sediment samples collected at varying depths in the vicinity of a chloroethene plume. Results demonstrated that levels of PBOC were consistently higher in aquifer sediments with minimal chloroethene exposure relative to samples collected in the PCE-contaminated source zone. Regression results demonstrated that a statistically significant inverse correlation existed between PBOC levels and chloroethene concentrations for selected temporary wells in the contaminated source zone at the study site. Consistent with these findings, results also indicated a similar trend of increased PBOC in aquifer sediments outside the chloroethene plume relative to aquifer sediments inside the plume. Results from this study further suggested that differences in extracted carbon levels at the site for surficial aquifer sediment samples in the PCE-contaminated source zone could impact the extent of reductive dechlorination within the hydrographic unit. / Ph. D.

The baseline of uncertainty in aerosol radiative forcing is large and depends on aerosol characteristics (e.g. size and composition), which can vary significantly on a regional scale. Sources (natural and anthropogenic) can be directly linked to the aerosol characteristics of a region, making monitoring campaigns to determine aerosol composition in different regions very important. Limited data currently exists for atmospheric aerosol black carbon (BC) and organic carbon (OC) in South Africa. In this study, BC and OC concentrations were explored in terms of spatial and temporal patterns, mass fractions of BC and OC of the overall aerosol mass, as well as possible sources. Primary pollutants, of which BC is an example, are emitted directly from the source. Certain primary pollutants can react with other pollutants to form secondary pollutants. OC can either be a primary or secondary pollutant, e.g. formed by gas-to-particle conversion of volatile organic compounds (VOCs) in the atmosphere (nucleation and condensation of gaseous precursors). Greenhouse gases (GHG) and BC absorb terrestrial long wave radiation causing an increase of atmospheric temperature. In contrast, OC generally reflects incoming radiation, cooling the atmosphere. GHGs have a long residence time in the atmosphere (10 to 100 years), while the residence time of aerosols is usually only a week or more. The climatic effects of aerosols are therefore particularly important from a regional perspective. Aerosols are also important from an air quality perspective, especially since ultrafine particles (diameter smaller than 100nm) are small enough to go through the membranes of the respiratory tract and into the blood stream. They can then be transported to the brain. Up to 2005, DEBITS (Deposition of Biogeochemical Import Trace Species) activities in South Africa did not include aerosol measurements. In order to initiate aerosol monitoring, campaigns were launched during the 2005 to 2007 period. Additionally, OC and BC measurements for the PM10 and PM2.5 (particulate matter smaller than or equal to 10 and 2.5 μm, respectively) fractions were started in 2009. PM10 and PM2.5 samples were collected at five sampling sites in South Africa operated within the DEBITS network, i.e. Louis Trichardt, Skukuza, Vaal Triangle, Amersfoort and Botsalano, with MiniVol samplers. The selected sites are mostly located in rural areas, but with the surrounding atmosphere influenced by industries, transportation, biomass burning, etc. Winters are characterised by an increase in biomass burning (fires) and combustion for domestic use (cooking and space heating). Samples were analysed with a Thermal/Optical Carbon analyser (Desert Research Institute). OC and BC results showed that the total carbonaceous content decreased during the summer due to less biomass burning (fires). BC was the highest at the industrially influenced sites, while OC was highest at regional background sites. OC was higher than BC concentrations at all sites in both size fractions. Most OC and BC occurred in the PM2.5 fraction. OC/BC ratios reflected the setting of the different DEBITS sites, with sites in or close to anthropogenic source regions having the lowest OC/BC ratios, while background sites had the highest OC/BC ratios. The OC mass fraction percentage of the total aerosol weight varied up to 24% and the BC up to 12%. The highest OC mass fraction was found at Skukuza, which was attributed to both natural (lies within the savannah biome) and anthropogenic (dominant path of air mass movement from the anthropogenic industrial hub of South Africa) reasons. The highest mass fraction of BC was found in the Vaal Triangle, since it is situated within a well-known anthropogenic source region. Household combustion for space heating and cooking also seemed to make a significant contribution to BC at this site in the cold winter months. A relatively well-defined seasonal pattern was observed, with higher OC and BC concentrations measured from May to October, which coincides with the dry season in the interior of South Africa. Positive correlations between OC and BC concentrations with the distance back trajectories passed fires were observed, indicating that fires contribute significantly to both atmospheric OC and BC during the burning season. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

The baseline of uncertainty in aerosol radiative forcing is large and depends on aerosol characteristics (e.g. size and composition), which can vary significantly on a regional scale. Sources (natural and anthropogenic) can be directly linked to the aerosol characteristics of a region, making monitoring campaigns to determine aerosol composition in different regions very important. Limited data currently exists for atmospheric aerosol black carbon (BC) and organic carbon (OC) in South Africa. In this study, BC and OC concentrations were explored in terms of spatial and temporal patterns, mass fractions of BC and OC of the overall aerosol mass, as well as possible sources. Primary pollutants, of which BC is an example, are emitted directly from the source. Certain primary pollutants can react with other pollutants to form secondary pollutants. OC can either be a primary or secondary pollutant, e.g. formed by gas-to-particle conversion of volatile organic compounds (VOCs) in the atmosphere (nucleation and condensation of gaseous precursors). Greenhouse gases (GHG) and BC absorb terrestrial long wave radiation causing an increase of atmospheric temperature. In contrast, OC generally reflects incoming radiation, cooling the atmosphere. GHGs have a long residence time in the atmosphere (10 to 100 years), while the residence time of aerosols is usually only a week or more. The climatic effects of aerosols are therefore particularly important from a regional perspective. Aerosols are also important from an air quality perspective, especially since ultrafine particles (diameter smaller than 100nm) are small enough to go through the membranes of the respiratory tract and into the blood stream. They can then be transported to the brain. Up to 2005, DEBITS (Deposition of Biogeochemical Import Trace Species) activities in South Africa did not include aerosol measurements. In order to initiate aerosol monitoring, campaigns were launched during the 2005 to 2007 period. Additionally, OC and BC measurements for the PM10 and PM2.5 (particulate matter smaller than or equal to 10 and 2.5 μm, respectively) fractions were started in 2009. PM10 and PM2.5 samples were collected at five sampling sites in South Africa operated within the DEBITS network, i.e. Louis Trichardt, Skukuza, Vaal Triangle, Amersfoort and Botsalano, with MiniVol samplers. The selected sites are mostly located in rural areas, but with the surrounding atmosphere influenced by industries, transportation, biomass burning, etc. Winters are characterised by an increase in biomass burning (fires) and combustion for domestic use (cooking and space heating). Samples were analysed with a Thermal/Optical Carbon analyser (Desert Research Institute). OC and BC results showed that the total carbonaceous content decreased during the summer due to less biomass burning (fires). BC was the highest at the industrially influenced sites, while OC was highest at regional background sites. OC was higher than BC concentrations at all sites in both size fractions. Most OC and BC occurred in the PM2.5 fraction. OC/BC ratios reflected the setting of the different DEBITS sites, with sites in or close to anthropogenic source regions having the lowest OC/BC ratios, while background sites had the highest OC/BC ratios. The OC mass fraction percentage of the total aerosol weight varied up to 24% and the BC up to 12%. The highest OC mass fraction was found at Skukuza, which was attributed to both natural (lies within the savannah biome) and anthropogenic (dominant path of air mass movement from the anthropogenic industrial hub of South Africa) reasons. The highest mass fraction of BC was found in the Vaal Triangle, since it is situated within a well-known anthropogenic source region. Household combustion for space heating and cooking also seemed to make a significant contribution to BC at this site in the cold winter months. A relatively well-defined seasonal pattern was observed, with higher OC and BC concentrations measured from May to October, which coincides with the dry season in the interior of South Africa. Positive correlations between OC and BC concentrations with the distance back trajectories passed fires were observed, indicating that fires contribute significantly to both atmospheric OC and BC during the burning season. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Northern peatlands represent a significant carbon reservoir, containing approximately a third of the terrestrial carbon pool. The stability of these carbon stores is poorly understood, and processes of accumulation and degradation appear to be finely balanced. Over the last decade, it has become increasingly clear that losses of dissolved organic carbon (DOC) from peatlands can be of considerable size and this flux appears to have increased substantially over the last 20 years. Despite its significance, the chemical composition of peatland-derived DOC remains poorly understood. This study aimed to characterise dissolved organic matter (DOM) at the molecular level using a novel combination of techniques. The study site (Cors Fochno, Wales, UK) is an ombrotrophic bog on which a number of studies into carbon cycling and hydrology have been carried out, providing a useful context for this project. The size and compositions of the DOC pool was monitored over 18 months, from three banks of piezometers, sampling from depths of 15 cm to 6 m. DOM which is representative of bog runoff was also monitored. DOC concentrations varied considerably between locations, spanning an order of magnitude (11.4 to 114 mgC l-1). Several relationships between DOC concentration and environmental and physical factors were established: DOC levels near the surface of the peatland varied with temperature, those in the runoff were most affected by recent rainfall events and the apparent DOC concentration at depth was related to the hydraulic conductivity of peat at that depth. The annual flux of DOC from the site was estimated at 113 tonnes, or 17.4 gC m-2. Only a small portion of the DOC pool could be characterised by analysis of dissolved combined amino acids (DCAA) and dissolved carbohydrates (as neutral sugars). Non-protein amino acids were most abundant in runoff samples, suggesting microbial reworking of DOM on entering drainage systems. DCAA yields decreased with depth, and the DCAA pool in deeper peat layers was characterised by more hydrophobic compounds. Interpretation of semi-quantitative results from TMAH thermochemolysis GC-MS analysis suggested oxidative degradation of organic matter near the surface of the peatland and photochemical degradation where DOM entered drainage networks, and this was supported by novel interpretation of results from ultrahigh resolution mass spectrometry analysis. The deepest porewaters were dominated by nalkanes, with notable contributions from fatty acids, suggesting a plant wax source for this DOM. The highest DOC concentrations were found at intermediate depth from a site midway between the centre of the bog and the southern boundary where hydraulic conductivities were low, and DOM from these piezometers were characterised by high contributions from a suite of phenolic compounds (with mainly para-hydroxyphenyl structures). These compounds have been linked to Sphagnum species, and are known to be functionally important to the development and maintenance of the unusual chemical environment in peatlands which slows decay rates, reduces microbial activity, and allows the sequestration of the large carbon reservoir. The findings of this study highlight the dynamic nature of peatland derived DOM, both in the size of the carbon pool and its composition which change dramatically with both season and depth.

The effects of predicted future climate change was investigated with special emphasis on the association of organic contaminants with dissolved organic carbon (DOC) in the Baltic Sea. An automated method was developed for the measurements of DOC - water distribution constants at realistic DOC concentrations in brackish water. The method proved to be valid for 30 organic contaminants with different structural elements in the 5 – 100 mg car bon/L DOC concentration range. There were limitations of this method. Firstly, its applicability is limited towards contaminants with lower affinity to DOC. Secondly, at higher (>100 mg carbon/L) DOC concentrations the sorption of contaminants was underest imated. Afterwards, water samples were collected from 15 points within the Baltic Sea in a north - south gradient t o examine the spatial differences in DOC characteristics and sorption properties . The DOC samples were analyzed using proton nuclear magnetic resonance and ultraviolet spectroscopy. Results from both techniques indicated that the aromatic nature of the DOC pool increased towards the northern Baltic Sea. This was expected as the freshwater inflow has high significance in controlling the hydrograp hic conditions in the Bothnian Bay. Sorption of organic contaminants was subsequently measured in the same samples. The results showed decreased sorption from north to south for hydrophobic contaminants such as chlorinated benzenes but for contaminants lik e tributyl - phosphate no spatial tendencies were observed. The data generated was used to determine molecular descriptors of DOC using linear free energy relationships. The results indicated a higher significance of hy drogen bond donor/acceptor functional g roups of the DOC in the south. Changes in contaminant distribution were simulated in model pelagic ecosystems at possible endpoints predicted by future climate change scenarios. Separate and combined effects of temperature a nd DOC were studied in mesocosms. The results indicated interesting tendencies. Increased temperature resulted in increased losses in the amounts of organic contaminants. Increased DOC levels promoted sedimentation and sorption of contaminants to particulate matter and biota. Hi gher amounts of contaminants were retained. The combined effects of the two factors led to and overall decrease in dissolved amounts. Higher losses or increased sedimentation and sorption to particles were also observed depending on contaminant properties. / EcoChange

Paleosols contain information about the rates of soil organic carbon turnover when the soil was actively forming. However, this temporal information is often difficult to interpret without tight stratigraphic control on the age of the paleosol. Here we apply ramped pyrolysis/oxidation (Ramped PyrOx) C-14 analyses to evaluate age spectra of transgressive early Holocene paleosols from the Mississippi Delta in southeastern Louisiana, USA. We find C-14 age spectra from soil organic matter (SOM) in both paleosols and overlying basal peats that represent variability in age that is close to, or only slightly greater than, analytical uncertainty of C-14 measurements, despite different sources of carbon with likely disparate ages. Such age spectra have not previously been observed in the sedimentary record. Here they indicate vigorous soil carbon turnover prior to burial, which homogenized C-14 ages within SOM across the entire thermochemical spectrum. The weighted bulk C-14 ages from Ramped PyrOx of paleosols and overlying peats are identical within analytical and process-associated uncertainty, and corroborate C-14 ages from charcoal fragments and plant macrofossils from the overlying peat. The youngest ages from Ramped PyrOx age spectra may also potentially be applied as chronometers for stratigraphic burial ages. Our results suggest rapid turnover (<<300 years) of carbon in these soils relative to input of allochthonous carbon, indicating that the C-14 age of different soil components is decoupled from thermochemical stability and instead reflects vigorous turnover processes. The concurrence of paleosol and peat C-14 ages also suggests that pedogenic processes were linked with the development of coastal marshes, and that the priming effect potentially masked the signal of allochthonous carbon inputs during sea level rise.

Lakes play an important role in the global carbon (C) cycle as they process carbon from terrestrial (allochthonous) and within lake (autochthonous) sources and may store C over long periods of time. Some arctic lakes contain high concentrations of dissolved organic carbon (DOC) that does not absorb light and thus remains colourless. The origin of this DOC remains unknown, but the sediment of these lakes have been suggested to accumulate primarily autochthonous (algal) C. I developed an experimental chamber for hydrogen (H) isotope pre-treatments and applied a novel H isotope tracing approach to determine the origin of the DOC and sediment C of a lake on SW Greenland known to contain colourless DOC. I hypothesized that autochthonous C was the prime source of DOC and sediment C, in line with previous theories. Analyses of algae and soil samples from the catchment revealed that local allochthonous and autochthonous C sources had a δ2H composition of -139 ‰ and -209 ‰, respectively. In contrast to my hypothesis, the analysed DOC had a mean δ2H isotopic composition of -147 ‰ indicating a dominance (ca 80-90 %) of allochthonous C. Similarly, the sediment had a mean δ2H isotopic composition of -155 ‰, suggesting that about 84 % of the C accumulating in the sediment was derived from terrestrial sources. The terrestrial origin was supported by field observations of high DOC seepage water (up to 70 mg L-1) with uncharacteristically low light absorption values entering the lake during high precipitation events. My results indicate that terrestrial processes are fundamental C sources for arctic lakes, even in regions with very low precipitation.

Rivers are arteries that connect land and sea, and provide a conduit and reactor for allochthonous and autochthonous organic carbon sources (OC) delivered to the coastal ocean. In comparison to marine waters, inland waters quantitatively represent only a fraction of the marine system; however, their importance to global C cycling maybe disproportional to its actual size. Inland systems are subject to multiple sources of OC (autochthonous and allochthonous) that vary individually in space and time with respect to their concentration and potential bacterial bioavailability. This study investigates the impact of high and ambient inorganic nutrient concentrations on the bacterial bioavailability of potential exogenous and internal organic C sources to bacterial decomposition in the Chickahominy River using a long term incubation approach. In addition the elemental composition of each organic C substrate is investigated as a predictor of OC source bioavailability. The results of sole source incubations showed that autochthonous SAV sources were the most labile whereas soil derived OC was the least bioavailable, irrespective of nutrients. However, leaf litter sources showed relatively high bioavailability. The C:N ratios of SAV, Peltandra virginica, Botryococcus braunii, leaf litter, and soil (19.6, 12.4, 15, 29.7, 8.4 respectively) oppose historically accepted theory that autochthonous OC sources with low C:N ratios are a more bioavailable substrate for bacteria than allochthonous OC substrates with higher C:N ratios. The results of this study should provide a better of understanding of the interaction between inorganic nutrients and OC decomposition from allochthonous and autochthonous sources as well and potentially allow model prediction of OC lability based on its elemental signature.

Avalanche paths are unique ecosystems that represent a significant portion of the landscape in the northern Rocky Mountains. Frequent avalanche disturbance results in vegetative cover that is unlike the adjacent coniferous forest. These high relief environments have the potential to remove carbon from the atmosphere at rates differing from those of the surrounding forest, and to regulate matter and/or energy fluxes to downslope ecosystems. This thesis attempts to estimate organic carbon on south-facing avalanche paths in the southern portion of Glacier National Park, Montana. I am specifically interested in total organic carbon density, compartmental carbon density, and change in organic carbon over time as a function of shrub and tree diameter. Using an integrated sampling method, estimates of total organic carbon on avalanche paths appear to be different than those of the adjacent forest and similar to those of other shrub formation types in the area. However, the potentially moveable litter compartment is consistently larger. Organic carbon from shrub and trees growing on paths appears to be increasing at a continuous rate leading up to disturbance, while a typical individual's rate of increase appears to be slowing. The organic material temporarily stored on avalanche paths could serve as an important outside carbon source for near and distant aquatic ecosystems.

Black carbon, a proxy for woodsmoke was measured indoors and outdoors for an occupied residence in Cambria, CA during the winter months of 2009. The purpose was to investigate the infiltration parameters: air exchange rate, deposition rate, and penetration factor. The second part of this study investigated the light absorption properties of organic carbon from residential wood combustion, the dominant fraction of woodsmoke. To assess woodsmoke variation, a study conducted parallel to the one presented in this thesis (Ward, 2009), a grid array of personal emission monitors (PEMS) and aethalometers were placed in a small area, approximately one square kilometer, within a community in Cambria, California between the months of November 2008 and March 2009. In this study, PEMS were used to collect particles on filters, which were analyzed for tracers for woodsmoke, including levoglucosan, elemental carbon, and organic carbon. Aethalometers measured black carbon, an indicator of carbon combustion. Additional PEMS and aethalometers were placed inside one residential home to better understand infiltration of woodsmoke. To model the infiltration of woodsmoke, the Lawrence Berkeley National Laboratory Air Infiltration Model was used. The home of interest was chosen such that indoor sources of particulate matter (PM) were minimal. This insures that all PM measured indoors was from outdoor sources, namely household chimneys. While indoor sources such as indoor fires and resuspension of particles were of concern, homes were chosen to minimize these sources. To investigate the infiltration parameters, four different solution techniques were used. Two of the solution techniques used SOLVER, a Microsoft Excel program, to minimize the sum of squared differences between calculated indoor concentrations and measured indoor concentrations, with all three parameters (air exchange rate, penetration, and deposition) as independent variables. The other two solution techniques used the Air Exchange Rate (AER) model from Lawrence Berkeley National Laboratory (LBNL) (Sherman & Grimsrud, 1980) and then used SOLVER to calculate deposition rate and penetration factor. Solution techniques 1 and 3, which used SOLVER to find all three parameters, had average penetration factors of 0.94 and 0.97 respectively, while solution techniques 2 and 4, which used the LBNL AER model had average penetration factors of 0.85 and 0.78 respectively. The deposition rates for solution techniques 1,2,3, and 4 were 0.10, 0.07, 0.08, and 0.04 hr-1 respectively. The air exchange rates varied throughout the study and ranged from 0.1 to 0.7 hr-1. The average indoor/outdoor ratio was also found to be 0.75. The aerosols derived from the study samples were found to have light absorption properties that were heavily spectrally dependent, which is consistent with expectations for wood combustion aerosols. Conversely, traffic derived aerosols are not found to be heavily spectrally dependent and follow the power law relationship of λ-1 whereas our samples followed λ-1.7 across all wavelengths and λ-2.25 for wavelengths less than 600 nm. The reason for the difference in spectral dependence is the presence of light absorbing organic carbon in wood smoke that is not found in diesel aerosols. The optical absorbances were also calculated for our samples and average values were found to be 3 and 1 m2/g for 370 and 450 nm wavelengths respectively.