京都大学 / 新制・課程博士 / 博士(地球環境学) / 甲第24955号 / 地環博第246号 / 新制||地環||49(附属図書館) / 京都大学大学院地球環境学舎環境マネジメント専攻 / (主査)教授 勝見 武, 准教授 高井 敦史, 教授 越後 信哉 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

The Bolivian Altiplano (BA) is a high plateau located in the western part of the country at an altitude of 3,600 to 3,900 meters above sea level and is bordered by the Eastern and Western Cordillera. Within the BA there is a large endorheic hydrologic system linking the Titicaca Lake in the north the Desaguadero River, lakes Uru-Uru and Poopó in the central part; and the Lacajahuira River and Coipasa and Uyuni salt pans in the south. Several mineralized areas, especially in the Eastern Cordillera, have been intensively exploited for centuries for the extraction of silver, gold, and tin from polymetallic sulfide ore deposits. Presently many urban centers are also contributing for an extensive contamination in localized areas; especially the Poopó Lake and some rivers are affected by high loads of wastewater and solid waste, in addition to the release of heavy metals and arsenic (As) due to acid mine drainage. The presence of As in the BA was known to be related to mining only, but recent studies revealed that As of geogenic origin also contributing to the elevated concentration of As in surface and groundwater. The Poopó Lake basin is characterized by a semiarid climate. Geologic formations predominantly are of volcanic origin and groundwater flow is sluggish in nature. These environmental settings have generated substantially elevated concen- trations of geogenic As and other trace elements in surface and groundwater. Both surface and groundwater used for drinking water have high concentrations of As that by far exceed the World Health Organization (WHO) guideline. The overall objective of the present study has been focused on the determination of the sources and principal mechanisms for mobilization of geogenic As into surface and groundwater of the Poopó Lake basin area. More specifically, this study has determined the spatial distribution and the extent of As contamination in surface and groundwater; chemical composition of surface and groundwater, rock and sediment; major geochemical mechanisms for As mobilization from solid phase to aqueous phases. This study also made an assessment of drinking water quality in rural areas within the Poopó Lake basin. Arsenic concentration exceeded the WHO guideline and national regulations for drinking water of 10 µg/L in 85% of the samples collected from the area around the Poopó Lake (n=27) and 90% of the samples from the southern part of the lake basin (n=42). Groundwater samples collected from drinking water wells had As concentrations up to 623 µg/L, while samples collected from piezometers had even higher up to 3,497 µg/L. Highest concentration in river water samples was observed 117 µg/L. Alkaline nature of water (median pH 8.3 for groundwater and 9.0 for surface water), predominance of Na-Cl-HCO3 water type and elevated Eh reflecting oxidized character has been revealed by As(V) as the major species in As speciation. Different rock types were analyzed for their As content and the highest concentration of 27 mg/kg was found in a coral limestone sample. In evaporate it was 13 mg and 11 mg As/kg was measured in calcareous sandstone. Elevated concentration of As was also observed in sediment cores collected from two drilling sites; 51 mg/kg in Condo K and 36 mg/kg in Quillacas. Physical and chemical weathering of volcanic rocks, limestone, carbonates and plagioclase minerals enhance the supply of Na+ and HCO3- into solution and as a consequence pH and alkalinity increase, which in turn, favor As desorption from solid mineral surfaces (especially Fe(III) oxyhydr- oxides) and therefore dissolved As in water is increased. / <p>QC 20150529</p>

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第22619号 / 地環博第198号 / 新制||地環||38(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 勝見 武, 教授 高岡 昌輝, 准教授 高井 敦史 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第22678号 / 地環博第199号 / 新制||地環||39(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 勝見 武, 教授 三村 衛, 准教授 高井 敦史 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

The efficiency to improve the water quality of industrial and municipal wastewater in a constructed wetland/filter basin treatment system was investigated. The wetland system was constructed in a closed phosphate mine used for clay settling and sand tailings in Polk County, Florida. During 18-months of monitoring the chemical/microbiological composition of treated wetland water remained relatively constant, despite significant seasonal variations in temperature, rainfall and humidity. The following changes in water quality between input and output were observed: substantial decrease of water temperature (up to 10°C), reduction of As, SO4, F, Cl, NO3, NO2, Br, Na, K, Ca, and Mg, change in pH from 9 to 6.5-7, increase of H2S (up to 1060 micrograms/L), and a change from positive to negative ORP. There were no exceedances of the primary drinking water standards, volatile organic compounds, synthetic organic compounds, and radionuclides, but a number of exceedances for the secondary drinking water standards (Al, F, Fe, Mn, color, odor, total dissolved solids, and foaming agents). The concentration of fecal and total coliform bacteria in the wetland water was high, but subsequently reduced during filtration in the filter basin from 30 - 730 and 1000 - 7000 count/100 mL to < 2 and < 100 count/ 100 mL, respectively. To resolve the complex hydrogeological conditions a combined isotope/chemical mass-balance approach was applied. The results were the following: (1) the composition of water in the wetland varied throughout the period of the study; (2) a change in isotopic composition along the wetland flow path; (3) the wetland contained mainly wastewater (88 - 100 %) during normal pumping operations; however, hurricanes and inconsistent pumping added low conductivity water directly and triggered enhanced groundwater inflow into the wetland of up to 78 %; (4) the composition of water in monitor wells was mostly groundwater dominated; however periodically seepage from a water body to the north was detected; and (5) seepage from adjacent water bodies into the wetland was not identified during operation, which would indicate a potential water loss from the wetland. To test if the wetland system could be a prospective pre-treatment option for water used in aquifer storage and recovery (ASR) scenarios, a set of bench-scale leaching experiments was carried out using rocks from the Avon Park Formation, the Suwannee Limestone and the Ocala Limestone. Since As in the Floridan Aquifer was mainly present as an impurity in the mineral pyrite the elevated iron and sulfide concentrations in the wetland water were thought to prevent pyrite dissolution. The experiments which covered a range of redox conditions showed that the amount of As released from the aquifer matrix was not perfectly correlated with the bulk rock As concentration, nor the redox state of the water. The following important results were obtained: (1) the highest concentration of As was leached from the Avon Park Formation and the lowest - from the Suwannee Limestone, although the Ocala Limestone had the lowest bulk rock As; (2) minor to no As was released using native Floridan groundwater; (3) Tampa tap water, which chemically and physically resembled the ASR injection water, caused the As leaching of up to 27 micrograms/L, which was higher than the As drinking water standard; (4) the wetland and filter basin waters caused the highest release of As (up to 68 micrograms/L), which was unexpected because those water types were less oxygenated than Tampa tap water and thus should be less aggressive; (5) the in-situ filtration of the wetland water through a 0.2 micrometer membrane resulted in a reduction of As from 30 microgram/L to 16 microgram/L; and (5) the UV treatment significantly reduced both fecal and total coliform bacteria, but facilitated the increase of DO in initial waters, a change from negative to positive ORP, and the increase of As concentration in leachates. The experiments confirmed that perturbations of native aquifer conditions caused the release of As from the Floridan aquifer matrix, although the reaction may not be as simple as the dissolution of pyrite by oxygen, but additionally governed by a complex set of factors including the ORP of the system, SO4²?/S², Fe³?/Fe²?, dissolved organic carbon and microbial activity. In addition, the trend of As leaching could be governed by a set of factors, such as the porosity and permeability of the aquifer matrix influencing the rate and degree of free water saturation, amount of pyrite to be exposed to the preferential water flow paths, limited surface reactivity of pyrite with favored reactions on fractured mineral surfaces, the concentration and the selective leaching of As from individual pyrite crystals. To characterize and verify the geochemical processes in the column experiments, the Geochemist's Workbench reactive transport models (React and X1t) were developed. Results from the models correlated well to those from the column experiments and confirmed the following: (1) the water-rock reaction between the aquifer matrix and native groundwater was favorable for pyrite stability preventing the release of As into solution; (2) the injection of oxidizing surface water into reducing native groundwater caused a change in redox potential of the system thus promoting the dissolution of pyrite, and (3) 1D reactive transport model of water-rock reaction between the aquifer matrix and surface water indicated a diverse behavior of As along the column, such as the oxidative dissolution of pyrite, mobilization and simultaneous sorption of As onto neo-formed HFO, followed by the reductive dissolution of HFO and secondary release of adsorbed As, and the potential non-oxidative dissolution of pyrite contributing the additional source of As to the solution.

Carbon accreditation of forest development projects is essential for sequestering atmospheric CO2 under the provisions of the Kyoto Protocol. The carbon sequestration potential of surface coal-mined lands is not well known. The purpose of this work was to determine how to measure carbon sequestration and estimate the additional amount that could be sequestered using different reforestation methods compared to the common practice of establishing grasslands. I developed a thermal oxidation technique for differentiating sequestered soil carbon from inorganic and fossilized carbon found at high levels in mine soils along with a geospatial and statistical protocol for carbon monitoring and accounting. I used existing tree, litter, and soil carbon data for 14 mined and 8 adjacent, non-mined forests in the Midwestern and Eastern coal regions to determine, and model sequestered carbon across the spectrum of site index and stand age in pine, mixed, and hardwood forest stands. Finally, I developed the framework of a decision support system consisting of the first iteration of a dynamic model to predict carbon sequestration for a 60-year period for three forest types (white pine, hybrid poplar, and native hardwoods) at three levels of management intensity: low (weed control), medium (weed control and tillage) and high (weed control, tillage, and fertilization). On average, the highest amount of ecosystem carbon on mined land was sequestered by pine stands (148 Mg ha-1), followed by hardwood (130 Mg ha-1) and mixed stands (118 Mg ha-1). Non-mined hardwood stands contained 210 Mg C ha-1, which was about 62% higher than the average of all mined stands. After 60 years, the net carbon in ecosystem components, wood products, and landfills ranged from 20 to 235 Mg ha-1 among all scenarios. The highest net amount of carbon was estimated under mixed hardwood vegetation established by the highest intensity treatment. Under this scenario, a surface-mined land of average site quality would sequester net carbon stock at 235 Mg C ha-1, at a rate of 3.9 Mg C ha-1 yr-1, which was 100% greater than a grassland scenario. Reforestation is a logical choice for mined land reclamation if carbon sequestration is a management objective. / Ph. D.

MESHWR / Department of Hydrology and Water Resources / Siloam, a village in the Northern province of South Africa has groundwater reportedly characterised by concentration of fluoride greater than 1.5 mg/L permissible limit. Regional investigation has been done to determine the possible fluoride sources in the northern province of South Africa, but no localised investigation has been documented. The World Health Organization and South Africa National Standard permissible limit is 1.5 mg/L for a duration of time. Therefore, this study focuses on investigating the sources of fluoride in the groundwater of Siloam village in response to reported high incidences (80%) of dental fluorosis in Siloam village. This study also elaborates more on the hydrochemical and geochemical processes favouring the release of fluoride into the groundwater of Siloam village. Two (2) surface rocks, one (1) surface clay deposit, twelve (12) borehole cuttings and four (4) groundwater samples were used for this study. Temperature, total dissolved solids (TDS), conductivity (EC) and pH of the groundwater were determined using a combined multimeter because these parameters are proxy indicators of geogenic influence on groundwater fluoride concentration. Total fluoride in the groundwater samples and the leachates obtained during a leaching experiment were determined using Ion Chromatograph (IC) and Fluoride Ion Selective Electrode (FISE). X-ray fluorescence spectrometry is the most preferred method for rock analysis by earth scientists because it is faster and does not require ambiguous training on the part of the analyst, therefore, it is mostly the standard methods used in whole rock chemistry. Elemental composition and mineralogy were determined using X-ray Fluorescence (XRF) and X-ray diffraction (XRD), respectively. Clay, greywacke, argillaceous sedmients and basalt were analysed. Results obtained indicated that the groundwater fluoride concentration ranges from 3.92 to 4.95 mg/L, which are far above the WHO permissible limit and South African standard. Insitu temperature reading obtained ranges from 25 to 48°C thus classifying the groundwater to be hot and tepid. The groundwater pH ranges from 8.1 to 9.1 which indicates an alkaline water condition. The groundwater conductivity ranges from 330 to 730 μS/cm while the Total dissolved solids ranges from 130.12 to 423.07 mg/L. Groundwater proxy indicators showed geologic sources to be responsible for the high fluoride concentration in the groundwater of Siloam village. Hydrochemical investigation revealead that the mineralisation of groundwater in Siloam village is as a result of rock water interaction and the process of groundwater enrichment is through base ion exchange and reverse ion exchange. The dominant water type in the village was identified to be Na-Cl water type and the abundance of sodium (Na) is due to the heavy weathering of plagioclase of the parent rocks. Total fluoride content of the rocks and soils of the village ranges from 10 to 2000 mg/L. The leachable fluoride, however, ranged in concentration from 0.27 to 14.88 mg/L under induced temperature v and 0.05 to 10.40 mg/L without temperature. Mineralogical investigation revealed the abundance of smectite clay, which is known for its enrichment and leaching of fluoride into groundwater sources, thus, the research question and assumption about the possible source of fluoride and the assumption that fluoride increases downwards towards the aquifer were answered. Leaching experiments identified the main contributors of fluoride to groundwater in Siloam village as smectite clays and the muscovite present in the sandstone, greywacke and basalt. Time based leaching experiment, geochemical modelling and dating of different hydrogeological unit was recommended / NRF