This thesis aimed to examine the possibilities and benefits of implementing agroforestry projects in Sierra Leone by comparing different agroforestry systems used in a Tanzanian project that consider carbon sequestration. Farmers involved in this type of projects get income from sold carbon credits as well as from other products that an agroforestry system could provide. Sierra Leone is one of the most vulnerable countries to climate change, with most of the population living in rural conditions. It was investigated what the potential economic and environmental impact different agroforestry systems considering carbon storage could have in Sierra Leone. The study was based on empirical material from a case community Makari. The conclusions were that Sierra Leone could benefit greatly from agroforestry projects, especially at community level where it could provide additional sources of food and income. From a greater perspective it could give environmental benefits as well as securing wood commodities like fuelwood for the future. Starting up a project would however be a high risk investment with a troublesome implementation process and complications on a daily basis.

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The aim of this study was to investigate the importance of winter season for the production of carbon dioxide (CO2) and methane (CH4) in humic and clear-water boreal aquatic systems. The study was conducted in 16 experimental ponds in northern Sweden during the winter of 2013. Half of the ponds had a higher concentration of dissolved organic carbon (DOC). CO2, CH4, DOC and dissolved inorganic carbon (DIC) were measured repeatedly under the ice from January to April. The results show that CO2 was accumulated continually during winter. No difference in winter accumulation were found between humic and clear ponds. CH4 was rarely accumulated in neither humic nor clear ponds, and was not an important part of the gas flux at spring ice melt. At ice melt, the flux from humic ponds accounted for 1.6 g C m-2 and 1.7 g C m-2 from clear ponds, which was equivalent for 15.6% respective 100% of the annual gas emissions. On a whole-year basis humic ponds acted as a source of 10.3 g C m-2, while clear ponds acted as a sink of 14.7 g C m-2. 76 mg m-2 d-1 DOC was consumed in humic and 59 mg m-2 d-1 DOC in clear ponds while the DIC accumulation was 125 mg m-2 d-1 in humic and 118 mg m-2 d-1 in clear ponds. This study stresses the importance of ice-covered boreal aquatic systems as a significant parts of the global carbon cycling.

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Widespread abandonment of agricultural land has occurred in northeastern North America over the past two centuries. Soil carbon often increases as sites naturally regenerate towards perennial grasslands or forests. Understanding the large-scale controls on the potential and rate of soil carbon sequestration is necessary in order to evaluate the significance of this sink to the global carbon cycle. Furthermore, we need to understand the key roles soil microorganisms play in regulating ecosystem processes through their control over soil carbon and nitrogen dynamics. Such studies are rare at the century long time scale of temperate forest succession. Additionally, research has taken place primarily on productive agricultural soils, while abandonment is more common on marginal agricultural soils. We characterized patterns of total and labile soil carbon and nitrogen and microbial dynamics in mature forest and adjacent agricultural field sites, and in replicated chronosequences of forest successional sites on marginal soils of southeastern Ontario, Canada. Total soil carbon was significantly depleted in the top 10 cm of current agricultural fields as compared to forest sites and increased at a rate of 10 g C m-2 yr-1 across our 100-year chronosequences. There was no difference in carbon loss or accumulation over time in three soil types differing in texture and parent material, suggesting that time since abandonment is more important than soil type in determining carbon accumulation within this climatic region. In contrast, free-light fraction carbon did not increase over time and thus most carbon accumulated in pools with slower turnover times. Soil microbial biomass carbon and nitrogen increased significantly following abandonment and our results strongly suggest that microbial growth during all phases of succession was limited by carbon supply. In contrast, net nitrogen mineralization and nitrification rates during mid-summer did not change consistently over the first 100 years following agricultural abandonment. Therefore, inorganic nitrogen supply rates into the plant available pool were similar across the entire successional sequence. Together, the results of these two studies demonstrate the potential for carbon sequestration in abandoned agricultural soils across this climatic region and highlight the importance of plant-soil interactions for understanding carbon cycling during ecosystem development. / Thesis (Master, Biology) -- Queen's University, 2007-12-14 10:04:57.395

Inputs of DOC in precipitation were low and increased with the passage of rainfall through different canopies. Throughfall, stemflow, leachates from A horizons and litterfall were identified as sources of DOC, while B and C horizons in upland areas provide a sink. Throughfall and stemflow displayed high temporal variability in DOC concentrations, while soil leachates and peat waters exhibited strong seasonal patterns. DOC concentrations in throughfall, stemflow and A horizons were highest in the predominantly coniferous site. In the fall, DOC concentrations from A horizons in the deciduous site were significantly higher than those from the coniferous site. / Factors influencing DOC in peat waters are: (1) peat thermal regime, (2) water chemistry, and (3) water table position. Large storms ($>$30 mm precipitation) appear to be the primary factor influencing exports of DOC in streamflow, particularly following dry antecedant soil moisture conditions. Slow rates of water movement through compact deep peats ($>$60 cm depth) and adsorption of DOC in B and C horizons of this catchment obstruct exports of DOC, which over the 5.5 month study period, were minimal in comparison to inputs.

Per- and polyfluoroalkylated substances (PFASs) are a large group of organic chemicals that have gained an increased attention during recent years. Many of the compounds have shown to be persistent, toxic and bioaccumulating and they are found in water, soils, sediments, biota, animals and humans across the globe. The effects of PFASs to humans and animals are still being debated. It is suspected that the compounds can be carcinogenic, disrupt different hormone systems and have other severe effects. The main transport pathways of PFASs to soil are applied PFAS based firefighting foam, soil improvers and waste from industries producing PFASs or PFAS based products. Once the PFASs find their way to the soil the risk for leaching to drinking water supplies and aquatic ecosystems becomes some of the issues of great concern. In order to be able to evaluate the potential leakage of PFASs from different contaminated soils it is important to know how the PFASs interact with the soil matrix and what parameters that affects these interactions. The objective of this study was to investigate the influence of organic carbon (OC), Ca2+ ions and active carbon (AC) on the n of PFCAs and PFSAs to soil. The PFCAs examined were PFHxA, PFOA, PFNA, PFDA, PFUnDA, PFOcDA, PFHxDA and PFOcDA and the PFSAs examined were PFBS, PFHxS, PFOS and PFDS. Batch experiments were performed on soils with varying concentrations of TOC, Ca2+ and AC. The samples were spiked with PFAS native standard solution containing the 12 target PFASs. All studied parameters showed a positive influence on the sorption of PFASs to soil. The AC was found to have the highest influence on the sorption. The OC was however found to be the most important soil parameter influencing the sorption of PFASs to soil. In order to investigate the influence of aging on the sorption of PFASs, batch experiments were also conducted on soils from four different PFAS contaminated sites. The results showed that the aging positively influenced the strength of the interactions between PFASs and soil. The organic carbon normalized distribution coefficients (Koc) showed a positive correlation with the carbon chain length of the PFAS molecules and also with the substitution of a carboxylic group with a sulfonic group. The log Koc values calculated in this study decreased in the following order PFDS (log Koc3.8 0.3) > PFOS > (log Koc2.8 0.3) > PFUnDA (log Koc 3.2 0.2) > PFDA (log Koc2.7 0.1) > PFNA (log Koc2.0 0.1) > PFHxS (log Koc1.9 0.1) > PFOA (log Koc1.8 0.3) > PFHxA (log Koc1.6 0.3) > PFBS (log Koc 1.5 0.2). The log Koc values found in this study were within the range of previously reported log Kocvalues.

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In the face of ever increasing atmospheric CO₂ a better understanding of soil properties and processes and the effect of management practices, such as the application of nitrogen fertilizer is of importance and could potentially improve our ability to sustainably manage forestry systems. With that in mind this study was conducted in order to investigate the effects of tree species and fertilization on soil carbon and the soil microbial community. To this end, soil from fertilized and unfertilized plots at Berwick forest, under stands of Pinus radiata and Sequoia sempervirens at Hanmer and under six different tree species at Holt forest was sampled. Two glasshouse pot trials were established using soil collected from the Hanmer and Berwick forest sites and seedlings of Pinus radiata, Sequoia sempervirens, and Eucalyptus nitens were grown. Soil properties were determined from both the field sites and pot trials including soil organic matter, carbon, nitrogen, and microbial biomass by chloroform fumigation extraction. Biolog ecoplates were used to determine the relative differences in diversity based on substrate utilization patterns of the soil microbial communities in soil sampled from the glasshouse pot trials. Soil microbial biomass carbon, nitrogen and the ratio of microbial biomass carbon:nitrogen differed significantly between Pinus radiata and the other tree species sampled at Holt forest. Significant effects of fertilization and tree species on soil carbon and microbial biomass were observed in both pot trials. Soil carbon differed significantly between Eucalyptus nitens and both Pinus radiata and Sequoia sempervirens in the first pot trial and relative to both, E. nitens contributed significantly more carbon. No significant effect of either fertilization or tree species on the catabolic diversity of the soil microbial community in both glasshouse pot trials was observed. The results demonstrated the effects that fertilization and tree species can have. Particularly notable was the short-time period in which tree species effects became apparent coupled with the absence of any aboveground inputs to the soil.

Due to its unique characteristics, carbon fiber is one of the leading materials for light weight, high strength and stiffness applications in composite materials. The development of carbon fibers approaching theoretical strengths and stiffness is a continuing process which has led to improved mechanical and physical properties over the recent years. Improvements in carbon fiber properties are directly dependent on the quality of the precursor fiber. Research and development of PAN precursor fiber requires extensive experimentation to determine how processing conditions affect the structure and properties of the precursor fibers. Therefore, it is the goal of this thesis to analyze the results of varying coagulation rates on fiber shape, density and porosity, to determine the effect of cross-sectional shape, density, and fiber diameter on the tensile strength of the fiber, and to investigate the most effective method for the reduction of fiber diameter. Results indicate a low temperature, high solvent concentration coagulating bath leads to a rounder cross section with lower void content. Reduction in fiber diameter was found to increase tensile strength while increased molecular orientation experienced during high draw down ratios led to an increase in fiber modulus.