It has been common in forestry and agriculture to drain waterlogged areas through ditching in order to cultivate them. The ditches that drain water are usually connected to some watercourse, such as a river. When the water flow of the river decreases and becomes more still, particles will settle and fall to the bottom of the water body and form sediment. If there is an increasing amount of nutrients and metals transported with the water, it could affect the water quality negatively, since an increased amount of nutrients could result in eutrophication and many metals are toxic in high amounts. In the Sangis River there is an increased amount of sediment deposited at the mouth of the river and inside the estuary, which has resulted in the river and the estuary becoming shallower. The origin of the deposited sediments is believed to partly be from ditching. The residents of the village of Sangis have said that it is difficult to cross the estuary by boat because of the deposited sediments, therefore, their wish is for a channel dredged in the Sangis River and its estuary that they can use. The main aim of this master's thesis was to analyse the geochemical status of the surface water and the sediment in the estuary of the Sangis River and to give recommendations for future actions preventing sedimentation of the river channel. The analyse of the geochemical status of the sediment was achieved by sampling six sediment- cores in the estuary and analysing for different parameters. The analyse of the geochemical status of the surface water was achieved by comparing the water quality regarding metal concentrations in the estuary with other nearby rivers and classifying the concentration of phosphorous in the estuary, to determinate if there was an ongoing eutrophication. The following analyses were conducted for the sediment-cores: Element distribution were analysed with P-XRF, pH and electrical conductivity were measured and loss on ignition was also calculated trough combustion of the sub-samples. The results showed for the P-XRF that the dominating main elements were iron, sulfur, calcium and potassium. Iron and sulfur were correlated to each other in all profiles and had a peak between 20-35 cm in the sediment. This indicated that there could be formation of iron sulfides at that depth. Therefore, sub-sample 4.D was analysed with SEM-EDS instrument and framboidal pyrite (FeS2) was detected in the sample. The results from the pH and conductivity showed that the pH-value varies greatly both with depth and between the sediment cores. However, for the conductivity it could be seen how it peaked at around 20-35 cm in all profiles, with the highest EC-value in profile 4. It could be concluded that the surface water in the estuary contains elevated concentrations of copper and that there is an ongoing eutrophication as well. Due to the eutrophication, it has most likely resulted in an increased amount of aquatic plants during the summer. The increased amount of organic material has probably resulted in oxygen-free bottoms, since all the oxygen has been consumed when the organic material has been decomposed. The formation of framboidal pyrite shows that the redox ladder has reached the two last steps, since framboidal pyrite (FeS2) consists of reduced sulfur and dissolved iron and is formed during anoxic conditions. Reduced sulfur forms when sulfate is reduced in order to oxidize organic matter and dissolved iron forms when iron-oxide hydroxides are reduced in order to oxidize organic matter. If dredging is carried out in the Sangis river and its estuary, oxidation of framboidal pyrite will occur, this could result in formation of acid and leachate of metals that were previously bound to framboidal pyrite. The consequences if it leaches into the river and the estuary is that it creates an acidic environment with elevated metal concentrations, where marine life would find it hard to live. The extent and impact of leached acidity and metals needs to be studied further.

This study looks at relationships along the hydrologic gradient between and within six pools; including the vegetation community, soil characteristics and hydrology. Pool conditions were monitored weekly throughout the 2011 and 2012 growing seasons. Each pool was equipped with permanent platinum-tipped redox probes to quantify the severity and duration of soil reduction. We described and analyzed 12 soil profiles in each pool, distributed in summit/upland, basin, and rim/transition positions as defined by the high water line. The pools were systematically surveyed for understory vegetation during the 2012 growing season. Vegetation patterns varied between study areas. No clear pattern of unique vegetation was evident from an ordination of the gradient communities. Time series redox potential data showed a visual relationship to water table fluxuation, but also a dampening effect from soil organic matter content in the basin positions.

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Plants absorb light for photosynthesis, but not all is used. Excess light energy may lead to photoinhibition of photosynthesis and irreversible photooxidative damage. Plants have evolved mechanisms for energy dissipation under high light stress. One such response may involve production of ELIP. It is of interest to know what signal(s) may be involved in ELIP expression. My hypothesis is that redox status of the chloroplast photosynthetic electron transport Chain (PETC) and/or chlororespiration may induce ELIP expression. Using the Arabidopsis thaliana immutans (im) chlororespiratory mutant, this hypothesis was tested. Etiolated seedlings of this variegated mutant were subjected to various light intensities over 0-24 hr period and ELIP mRNA levels were analyzed. These were compared with the wild type plants treated in the same manner. It was found that mature thylakoids may not be required for ELIP expression, and that both photoreceptor-dependent and independent components may be involved in ELIP expression.

Recently, work in ethanol production is exploring the fermentation of syngas (primarily CO, CO2, and H2) following gasification of cellulosic biomass. The syngas fermentation by clostridium microbes utilizes the Wood-Ljungdahl metabolic pathway. Along this pathway, the intermediate Acetyl-CoA typically diverges to produce ethanol, acetic acid, and/or cell mass. To develop strategies for process optimization, a thermodynamic analysis was conducted that provided a detailed understanding of the favorability of the reactions along the metabolic pathway. Thermodynamic analysis provided identification of potentially limiting steps. Once these limiting reactions were identified, further thermodynamic analysis provided additional insights into the ways in which reaction conditions could be adjusted to improve product yield as well as minimize the effect of such bottlenecks. In this way, strategies to enhance product formation were effectively formed. A thermodynamic analysis regarding electron utilization suggested that it would be unlikely that H2 is utilized in favor of CO for electron production when both species are present. Therefore, CO conversion efficiency to products will be sacrificed during syngas fermentation since some of the CO will make electrons at the expense of product and cell mass formation. Furthermore, the analysis showed the thermodynamic difference of ethanol production, acetate production, and acetate to ethanol conversion, at varying reaction conditions, such as at different pH and redox potential levels. These differences were then incorporated into a strategy to optimize production of desired product, improve bioreactor design, and decrease the amount of by-product formed. Based on the thermodynamics analysis, experiments with varying experimental conditions were performed. The results showed that sulfide concentration in the media changed. In order to assess the effects of experimental conditions on syngas fermentation and decrease the experimental variability, experiments with controlled sulfide, redox potential, and pH were designed and the results indicated that these factors play key roles on cell growth, product formation and product distribution. Furthermore, experimental conditions had different effects on fermentation during different phases. For example, cell growth is much better at pH=5.8 than pH=4.5. However, the ethanol production rate at pH=4.5 is better than pH=5.8. A strategy involving controlling the pH and redox potential at different phases was effectively applied to improve ethanol production. This work provided significant insights on how varying experimental conditions can affect the syngas fermentation process.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24177号 / 理博第4868号 / 新制||理||1697(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 北川 宏, 教授 有賀 哲也, 教授 吉村 一良 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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