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Electricity generation at nuclear power plants produces a large amount of high-level radioactive waste (HLW) every year, which has long-term detrimental effects on humans and the environment. Other applications of nuclear technology (e.g., medicine, research, nuclear weapons, industry) also produce radioactive waste (e.g., low-level radioactive waste, LLW, Intermediate-level waste, ILW). The potential of deep geological repositories (DGRs) as an option for disposal of radioactive waste (HLW, ILW, LLW) has been examined in several countries, including Bulgaria, Canada, China, Finland, France, Germany, India, Japan, Russia, Spain, Sweden, Switzerland, Ukraine and the United Kingdom and are still under discussion. In Ontario, Canada, DGRs with a multi-barrier system comprised of a sedimentary rock formation (i.e., a natural barrier) and an engineered barrier system (EBS) are currently under consideration. An EBS consists of various components, such as waste containers, buffer, backfill, and tunnel sealing materials, intended to prevent the release of radionuclides. Several engineered barrier materials, including a mixture of bentonite and sand, are currently being considered for use in DGRs for nuclear waste in Ontario. Bentonite has some advantageous physical and chemical properties, such as low permeability, high plasticity, and high swelling potential, which provide it with a good sealing ability and thus make it an effective barrier. However, interaction between the compacted bentonite–sand mixture and underground water chemistry fluids (chemical factor) in the DGR could significantly alter the favourable properties of bentonite (e.g., swelling potential), thus influencing its performance when used in an EBS and eventually jeopardizing the overall safety of DGRs. In addition, other parameters, such as the clay content, initial dry density and moisture content of the compacted barrier (physical factors), as well as the presence of salts in groundwater may affect the physical and physiochemical properties of barrier materials. Moreover, during the lifetime of a DGR for used spent fuel, the bentonite–based barrier material will not only be exposed to a broad range of groundwaters with different chemical compositions, but also to high temperatures (heat generated by the nuclear wastes) (thermal factor). Thus, the interaction between the compacted bentonite–sand mixture, the surrounding groundwater and the heat from the nuclear waste material could jeopardize the favourable properties of the bentonite-based (bentonite-sand) barrier material. Properties of a bentonite-sand barrier is an important characteristic to study while designing and constructing an EBS for a DGR. Thus, to understand and assess the operations of DGRs in Ontario, comprehensive studies must be performed on engineering properties like swelling behaviour, permeability, and thermal conductivity. The goal of this research study is to experimentally investigate the physical, chemical and thermal factors that influencing the engineering properties of a barrier material made up of bentonite-sand composite used in DGRs for nuclear waste in Ontario. Compacted samples are subjected to one-dimensional free swell test to understand the swelling behaviour of the material. Hydraulic conductivity was investigated using a flexible wall permeability test. Thermal conductivity and diffusivity were tested using Decangon KD2 Pro with TR-1 and and KS-1 sensors. The specimens contain different bentonite–sand mixture ratios (20:80, 30:70, 50:50, and 70:30 dry mass), and they are tested under conditions with differing bentonite content, dry density, groundwater chemistry, and temperature. Additional tests were conducted to investigate the microstructure of the specimens. These tests include X-ray diffraction (XRD) analysis, mercury intrusion porosimetry (MIP), and thermogravimetric analyses (TG/DTG). The results reveal that the time and strain required to achieve maximum swelling of compacted bentonite–sand specimens increase with the increase of initial dry density. The simulated saline solutions of Guelph and Trenton groundwater are found to suppress the swelling of the bentonite–sand specimens. This in turn leads to the increase of hydraulic conductivity and decrease of thermal properties of the barrier material. However, the impact of the salinity is significantly reduced by increasing the dry densities and sand content of the compacted material. Moreover, the coupled effect of salinity and temperature decreases the swelling potential of the bentonite-sand mixture. Also, some transformation of Na-montmorillonite into Ca-Montmorillonite was observed. The results also indicate that some montmorillonites might have been transformed into illites, thereby further decreasing the swelling potential of the bentonite-based barrier.

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M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Removal of wastewater pollutants is urgent as they are continuously defiling the limited freshwater resources, affecting the ecosystem, aquatic and terrestrial life. Carbon nanotubes-based adsorbent materials are effective for removal of wastewater pollutants owing to their large specific surface area. Surface modification of carbon nanotubes (CNTs) can mediate specific pollutant adsorption and increase CNTs colloidal stability and chemical reactivity. Heavy metal pollution of wastewater is one of the major threats, as this metals can be toxic to humans when present at certain concentrations in drinking water. This study report the synthesis of chlorine functionalized and nitrogen doped carbon nanotubes (ClNCNTs) loaded with iron oxide nanoparticles and their use as adsorbents for Pb2+ ions in aqueous solutions. Carbon nanomaterials that are functionalized with chlorine and doped with nitrogen were successfully synthesized. This was done through pyrolysis of a mixture of dichlorobenzene and acetonitrile (in a 1:1 volume ratio) over 10% Fe-Co/CaCO3 bi-metallic catalyst via chemical vapour deposition (CVD) method. Addition of chlorine and nitrogen to the CNTs was to enable defect and disorder creation on the surface of the nanotubes which is envisaged to create nucleation sites on the their surface for better adhesion of the iron oxide nanoparticles. Different loadings of magnetite (Fe3O4) nanoparticles on the surface of the ClNCNTs was achieved using a co-precipitation method. The synthesized materials were charaterized by Raman spectroscopy, Transmission electron microscopy (TEM), Powder X-ray diffraction (PXRD) spectroscopy, Thermal gravimetric analysis (TGA), Brunauer Emmett and Teller (BET) and X-ray photoelectron spectroscopy (XPS). Highly defected CNTs, some with hollow and others with bamboo-compartments due to nitrogen inclusion were obtained. The effect of metal salt concentration in wt.% (10, 20, 30 and 53 wt.%) was investigated. The increase in wt.% loading has resulted in an increase in surface area, and a decrease in thermal stability as a result of defected Fe3O4/ClNCNTs. In addition, agglomeration was observed at 30 and 53 wt.% loading, due to large amount of iron present. The identity of the Fe3O4 nanoparticles was confirmed by PXRD and XPS with two iron peaks deconvoluted at 725.6 eV and 721 eV respectively. The percentage loading of the Fe3O4 nanoparticles at the surface of the ClNCNTs was affirmed by TGA analysis, where the residual mass obtained from TGA were closely related to the mass percentages added. Different nitrogen environments namely, the quatenary, pyridinic, pyrollic and nitrogen oxides were also observed, whilst chlorine could not be deconvoluted because it was present in very limited amount probably it was masked by the iron oxide nanoparticle. Thus, a 20 wt.% Fe3O4/ClNCNTs was chosen as an optimum, due to uniform distribution of spherical nanopaticles observed along the radial length of ClNCNTs that had an average size of 10 ± 4.5 nm. The synthesized ClNCNTs and a nanocomposite made from a 20 wt.% Fe3O4/ClNCNTs were applied in the removal of Pb2+ ions from aqueous solution. The results obtained showed that a nanocomposite made from a 20 wt.% Fe3O4/ClNCNTs had a better adsorption capacity of 17.0 mg/g as compared with 14.8 mg/g for ClNCNTs.

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Sediments rich in sulfide were deposited in the Littorina sea in an environment that was shallow, anoxic,and reductive. The sediments were brought above sea level by isostatic uplift and can now be foundalong the coast of the Baltic sea. These sulfide rich sediments oxidize when they are exposed to air whenthe water table is lowered due to uplift, anthropogenic activities, or hydrological droughts. Oxidation ofsulfate soils will lower the pH and mobilize metals in the soil that will leach into adjacent rivers and willimpact the water chemistry and damage ecosystems. A few studies have noted that leaching increasesin sulfate soils after drought which has resulted in fish death. The impact of droughts on leaching from sulfate soils were investigated in nine rivers (Flarkbäcken,Hertsångerälven, Kvismare canal, Kyro river, Närpes River, Persöfjärden, Storbäcken, Tjuståsaån, andToby river) by looking at time series of sulfate concentrations and drought periods. The impact on riversafter a drought was studied by plotting the deviation from median specific discharge in summer andautumn against the deviation from median concentration of SO42-, a suite of metals and pH the followingseason with high discharge e.g. spring. The metals that were examined in the river were Aluminum (Al),Cadmium, (Cd), Cobalt (Co), Cupper (Cu), Iron (Fe), Manganese (Mn), Nickle (Ni), Zinc (Zn).TheKendall’s τ was then used to determine if the relationship between discharge and leached compoundconcentration was significant and which direction it had. In the sulfate timeseries the hydrological droughts generally coincided with low SO42- and werefollowed by SO42- peaks. The sulfate concentrations increased significantly after droughts, and theincrease in SO42- lasted for 1-3 years for most rivers. In two Finnish rivers the SO42- remained higher alonger time of 5 years in Kyro river and Närpes river after multiyear droughts. In Kvismare canal, Kyroriver, Närpes river and Tjuståsaån the SO42- concentration was higher in the mid-1900s which could bedue to changes in ditching activity, the acid sulfate soils transitioning to post active sulfate soils afterthe ditching activity stopped in the regions, or SO42- air deposition historically being greater. SO42-, Co, Ni, and Zn had negative significant correlations in a majority of the rivers, while pH, Fe,and total organic carbon had significant positive correlations a majority of rivers. A negative correlationindicates high concentrations of the leached compound after a drought while positive correlationsindicate low concentrations of the leached compound after a drought. Al, Cd, Cu, and Mn did not havea significant correlation in a majority of the rivers which could be due to their dependence on pH whichwill not always change in the rivers in spring due to acidic water leaching from acid sulfate soils sincethe acidic water will be diluted by meltwater. / Efter senaste istiden var vattnet i havet syrefritt och reducerande vid havsbotten, vilket ledde till attsulfidmineral avsattes. Dessa sulfidrika sediment har hamnat ovanför havsytan på grund avlandhöjningen och finns i kustnära områden runt östersjön. Sulfidsedimenten oxiderar om de kommer ikontakt med syre vilket kan ske på grund av landhöjning, mänskliga aktiviteter, eller torka som sänkergrundvattennivåerna. När sulfatjordarna oxiderar sänks pH i jorden och metaller frigörs vilka sedanlakas ur jorden och påverkar närliggande vattendrag och ekosystem. Lakning av metaller har i någrastudier setts öka efter extrem torka vilket i vissa fall har lett till fiskdöd. I nio vattendrag (Flarkbäcken, Hertsångerälven, Kvismare kanal, Kyro älv, Närpes å, Persöfjärden,Storbäcken Tjuståsaån och Toby å) undersöktes hur torka påverkar urlakning från sura sulfatjordar. Deämnen som undersöktes var Aluminium (Al), Kadmium (Cd), Kobolt (Co), koppar (Cu), Järn (Fe),Mangan (Mn), Nickel, (Ni), Totalt Organiskt Kol (TOC), och Zink (Zn). Sambandet mellanvattenföringens avvikelse från medianen under de sommar samt höst och avvikelsen avkoncentrationerna av urlakade ämnen från medianen följande årstid med högt flöde plottades för attundersöka hur sambandet såg ut. De statistiska testerna Kendalls τ användes för att utvärdera om enkorrelation existerade och i vilken riktning den gick. Sulfatkoncentrationerna var generellt sett väldigt låga under torrperioder men ökad snabbt efter atttorkan avtagit. Den förhöjda sulfatkoncentrationen varade generellt sett i 1-3 år för de flesta vattendrag.Det fanns däremot två undantagsfall då sulfatkoncentrationerna var förhöjda i Kyro älv och Närpes åunder 5 år efter en torrperiod som varat i flera år. I Kvismare kanal och Tjuståsaån varsulfatkoncentrationerna, högre under mitten av 1900-talet. De högre koncentrationerna av sulfat kanbero på att det var mer dikning, eller större mängd luftföroreningar under denna period. Sambanden för sulfat, Co, Ni och Zn visade att efter torra perioder var koncentrationerna högre i enmajoritet av vattendrag än normalt. pH, Fe och TOC visade på ett motsatt samband. Efter torrperiodersjönk därmed koncentrationen Fe och TOC i en majoritet av vattendragen. Al, Cd Cu, och Mn hadesignifikanta samband i mindre än 50 % av vattendragen vilket kan vara till följd av att de är beroendeav pH som själv inte hade en tydlig korrelation i alla vattendrag. pH sjunker i många fall inte särskiltmycket till följd av en torka då vattnet som lakas ut från sulfatjorden späds ut av smältvatten undervåren.

To better understand abiotic dynamics in Southern reservoirs receiving heated effluents, water was analyzed before and after impoundment in 330 ha North Lake. Macronutrients, metals, and chlorinated hydrocarbons were measured. Concentrations of nutrients and metals in sediments were quantified in this 2 yr study. River water prior to impoundment contained 16 times more total phosphorus, and supported 23 times more Selenastrum capricornutum cells in an algal assay than reservoir water. The reservoir has essentially no drainage and since evaporation is high, the concentrations of many dissolved solids have increased since the reservoir was filled in 1958. North Lake is now phosphorus limited. Apparently altered chemical equilibria have caused precipitation or adsorption of phosphorus with calcium and iron.

Water quality was one of the biggest problems of environment in beginning of 90. of 20th century in the Czech republic. Since 90. the level of water quality was in czech rivers rapidly better. Mainly in big rivers have accomplished great changes. The small rivers haven't notice that rapid changes. The Czech republic, after entrance to the European Union have committed to comply with Directive 91/271/EEC reduce urban waste water and which should have big influence to water quality also in small rivers. During 90. industry technology, agriculture, cleaning technology of waste water etc. reached big development. Therefore the presumption is higher quality of water in the Czech republic since 90. Goal of the thesis is comparison of results from 1999-2000 with results from 2012- 2014 from Mladoticky brook catchment, which is lined up to small river catchments (79,77km2 ). From this comparison there is obvious trend, if conditions of the water quality are really better or not since 90. [33] Since 2012 to 2014 were taken 12 times samples from 11 profiles of water from Mladotice brook catchment and they were consequential chemically analyzed. The samples were evaluated according to ČSN 757221 and compared with results from 1999-2000. From comparison with data 1999-2000 and 2012-2014 was confirmed the...

The thesis, which contains nine chapters, reports extensive large scale atomistic molecular dynamics (MD) simulation studies of water structure and dynamics at the surface of an anionic micelle, hydration layer of two proteins, and in the grooves of a 38-base pairs long DNA. Understanding the structure and dynamics of water molecules at the surfaces of self-organized assemblies and complex biological macromolecules has become a subject of intense research in recent times. Chapter 1 contains a brief overview of the biomolecular hydration dynamics. Relevant experimental, computational, and theoretical studies of biomolecular hydration and the time scales associated with the water dynamics are discussed. In Chapters 2 and 3, the structure, environment, energetics, and dynamics of constrained water molecules in the aqueous anionic micelle of cesium perfluorooctanoate (CsPFO) have been studied using large scale atomistic molecular dynamics simulations. Based on the number of hydrogen bond (HB) that interfacial water molecule makes with the polar head group (PHG) oxygen of the micelle, we find the existence of three kinds of water at the interface. We introduce a nomenclature to identify the species as IBW2 (form two HBs with two different PHG), IBW1 (form one HB with PHG), and IFW (no HB with PHG). Despite of possessing two strong w-PHG bonds, the concentration of the IBW2 species is rather low due to entropic effect. The ion solvation dynamics study at the interface shows the presence of a slow component, with a relaxation time 1-2 order of magnitude slower than that in the corresponding bulk solvent in agreement with the experimental results. Both the translational and orientational dynamics of the water molecules near the micellar surface is found to be much slower than those in the bulk. The HB between the PHG of the micelle and the water molecule has almost 13 times longer life time than that in the bulk between two tagged water molecules. In Chapter 4, we present results of extensive atomistic MD simulation studies of the structure and dynamics of aqueous protein solution of the toxic domain of Enterotoxin (1ETN) and the chicken villin headpiece sub-domain containing 36 amino acid residues (HP-36). Reduced water structure and the faster water dynamics around the active site of these proteins have been observed which may have biological significance. Chapter 5 presents an extensive atomistic molecular dynamics simulations study of water dynamics in the hydration layer of a 38 base long hydrated DNA duplex. The computed rotational time correlation function (TCF) of the minor groove water dipoles is found to be markedly non-exponential with a slow component at long time. The constrained water molecule is also found to exhibit anisotropic diffusion in both the major and minor grooves. At short-to-intermediate times, translational motion of water molecules in minor groove is sub-diffusive. Chapter 6 presents the study of water entropy in both the grooves DNA. The average values of the entropy of water at 300K in both the grooves of DNA are found to be significantly lower than that in bulk water. We propose that the configurational entropy of water in the grooves can be used as a measure of the mobility (or micro viscosity) of water molecules in a given domain. In Chapter 7, we study the specific DNA base-water hydrogen bond lifetime (HBLT) dynamics at the major and the minor grooves of a hydrated duplex. The base-water HBLT correlation functions are in general multi-exponential and the average lifetime depends significantly on the specificity of the DNA sequence. The average HBLT is longer in the minor groove than that in the major groove by almost a factor of 2. Chapter 8 presents the solvation dynamics of constituent bases of aqueous DNA duplex. The solvation TCFs of the four individual bases display highly non-exponential decay with time. An interesting negative cross-correlation between water and counterions is observed which makes an important contribution to relaxation at intermediate to longer times. In the concluding note, Chapter 9 presents a brief summary of the outcome of the thesis and suggests several relevant problems that may prove w orthwhile to be addressed in future

River export has a strong influence on the productivity of coastal waters. During storm events, rivers deliver disproportionate amounts of nutrients and organic matter to estuaries. Anthropogenic changes to the land use/cover (LULC) and water use also have a strong influence on the export of nutrients and organic matter to estuaries. This study specifically addressed the following questions: 1) How does river water chemistry vary across LULC patterns in the Mission and Aransas river watersheds? 2) How do fluxes of water, nutrients, and organic matter in the rivers vary between base flow and storm flow? 3) How do variations in nutrient/organic matter concentrations and stable isotope ratios of particulate organic matter (POM) in Copano Bay relate to river inputs? Water was collected from the Mission and Aransas rivers and Copano Bay from July, 2007 through November, 2008 and analyzed for concentrations of nitrate, ammonium, soluble reactive phosphorus (SRP), dissolved organic nitrogen, dissolved organic carbon, particulate organic nitrogen, particulate organic carbon (POC), and the stable C and N isotope ratios of the POM. The first half of the study period captured relatively wet conditions and the second half was relatively dry compared to long term climatology. Riverine export was calculated using the USGS LOADEST model. The percentage of annual constituent export during storms in 2007 was much greater than in 2008. Concentration-discharge relationships for inorganic nutrients varied between rivers, but concentrations were much higher in the Aransas River due to waste water contributions. Organic matter concentrations increased with flow in both rivers, but POM concentrations in the Aransas River were two fold higher due to large percentages of cultivated crop land. Values of [delta]¹³C-POC show a shift from autochthonous to allochthonous organic matter during storm events. Following storm events in Copano Bay, increases and quick draw down of nitrate and ammonium concentrations coupled with increases and slow draw down of SRP illustrate nitrogen limitation. Organic matter concentrations remained elevated for ~9 months following storm events. The [delta]¹³C-POC data show that increased concentrations were specifically related to increased autochthonous production. Linkages between LULC and nutrient loading to coastal waters are widely recognized, but patterns of nutrient delivery (i.e. timing, duration, and magnitude of watershed export) are often not considered. This study demonstrates the importance of sampling during storm events and defining system-specific discharge-concentration relationships for accurate watershed export estimation. This study also shows that storm inputs can support increased production for extended periods after events. Consideration of nutrient delivery patterns in addition to more traditional studies of LULC effects would support more effective management of coastal ecosystems in the future. / text