Contaminated aquatic sediments pose health risks to fish, wildlife, and humans and can limit recreational and economic uses of surface waters. Technical and cost effective in situ approaches for sediment management and remediation have been identified as a research need. Subaqueous in situ capping is a promising remedial approach; however, little is known regarding its impact on underlying sedimentary processes and the feasibility of bioaugmented caps at sites subject to contaminated groundwater seepage. This work specifically addresses (1) the impact of capping on biogeochemical processes at the sediment-water interface, (2) the ability and degree to which indigenous sediment microorganisms colonize an overlying cap, (3) the effect of advective flow direction on redox conditions within a cap, (4) natural contaminant bioattenuation processes within capped sediment, and (5) limitations toward a functional bioreactive in situ cap. Laboratory-scale experiments with capped sediment columns demonstrated that emplacement of a sand-based in situ cap induced an upward, vertical shift of terminal electron accepting processes into the overlying cap while simultaneously conserving redox stratification. Upflow conditions simulating a groundwater seep compressed anaerobic processes towards the cap-water interface. Microorganisms indigenous to the underlying sediment colonized cap material and spatial population differences generally reflected redox stratification. Downflow of oxic surface water through the cap, simulating tidally-induced recharge, created fully oxic conditions within the cap, demonstrating that flow direction strongly contributes to redox conditions. Experiments simulating capped sediment subject to contaminated groundwater seepage revealed a reduction of natural bioattenuation processes with time, stemming from the elimination of labile organic matter deposition to the sediment and a subsequent lack of electron donor. Thus, parent contaminants within groundwater seeps will be subject to minimal biotransformations within the sediment before entering a reducing cap. A bioreactive cap, inoculated with microorganisms capable of reductive dehalogenation, was established to reductively dechlorinate tetrachloroethene present in the groundwater; however electron donor amendments to sediment effluent were required to achieve complete dechlorination of tetrachloroethene to non-toxic ethene. Results from this work improve understanding of biogeochemical and bioattenuation processes within capped aquatic sediments and should aid in the development of active capping technologies.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22485号 / 農博第2389号 / 新制||農||1075(附属図書館) / 学位論文||R2||N5265(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 吉田 天士, 教授 澤山 茂樹, 教授 菅原 達也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Bottled drinking water is a common form of water consumption that has grown in popularity and dependency. With countless types and brands available, there are factors to consider regarding the variations in mineral content and microbiological quality, and environmental consequences associated with importing natural bottled waters. Saudi Arabia is the largest desalinated water producer, and although there are scarce natural water resources, consuming locally produced water can alleviate environmental pressures, so long as local bottled water is of good quality and provides the basic function of drinking water. The objective of this study is to scrutinize the variations in bottled waters available in the Saudi market and compare local and imported waters regarding water quality and compliance with health regulations. Surveying local bottled waters revealed that over 60% were imported, adding to the environmental significance. Results from inductively coupled plasma-atomic emission spectroscopy, ion chromatography, and pH meters indicate most bottled waters were compliant with health standards. Flow Cytometry (FCM) was used to determine microbial cell densities. Purified waters, on average, contained significantly lower concentrations than other water types, while mineral waters contained the most cells per milliliter. Microbiological stability was examined through incubating samples at 30°C to promote microbial growth, and results were analyzed using an online FCM system. Purified waters had the least amount of growth and to a lesser degree than mineral and sparkling, which varied in microbial growth responses. DNA extractions and microbial community analyses were performed on select mineral waters before and after incubation. Results showed microbial genera found were similar between samples from the same country and some were unique. All samples exhibited some change in microbial community composition after incubation, signifying that certain communities thrived more than others. Proteobacteria was the most common abundant phylum among samples. Although analysis was restricted to the genera level, there were no health concern associated with types of bacteria discovered. In conclusion, local purified waters had greater microbiological quality and stability than imported waters, and mineral compositions were within the healthy range. Reducing reliance on foreign natural waters may help alleviate environmental consequences and improve local economy