<p> Aquifer storage and recovery (ASR) is a strategy in which water is injected into an aquifer when it is plentiful and pumped from the aquifer when water is scarce. An impediment to ASR in Florida is leaching of naturally-occurring arsenic from limestone of the Upper Floridan Aquifer System (UFAS) into stored water. The concentration of arsenic in surface water, which serves as the recharge water for many ASR systems, and native groundwater is usually much less than 3.0 &micro;/L. However, data from ASR wells in Florida show that arsenic in recovered water frequently exceeded the 10 &micro;g/L maximum contaminant level (MCL) established by the Environmental Protection Agency and were as high as 130.0 &micro;g/L. The cause of elevated arsenic concentrations is displacement of reduced native groundwater with oxygenated surface water that dissolves arsenic-bearing pyrite in limestone. Although arsenic can be removed from recovered water during final treatment, mobilization of arsenic in the aquifer at levels that exceed the MCL is problematic under federal regulations. </p><p> This dissertation investigated a number of aspects of the ASR/arsenic problem to provide additional insights into the mechanisms of arsenic mobilization and measures that could be taken to avoid or reduce the release of arsenic during ASR operations.</p><p> Chapter 2, involved development of a geochemical model to simulate an ASR system&rsquo;s injection of oxygenated surface water into reduced groundwater to determine whether aquifer redox conditions could be altered to the degree of pyrite instability. Increasing amounts of injection water were added to the storage-zone in a series of steps and resulting reaction paths were plotted on pyrite stability diagrams. Unmixed storage-zone water in wells plotted within the pyrite stability field indicating that redox conditions were sufficiently reducing to allow for pyrite stability. Thus arsenic is immobilized in pyrite and its concentration in groundwater should be low. During simulation, as the injection/storage-zone water ratio increased, redox conditions became less reducing and pyrite became unstable. The result would be release of arsenic from limestone into storage-zone water.</p><p> Chapter 3 examined the importance of maintaining a substantial volume of stored water around an ASR well to prevent recovery of reduced native groundwater to the vicinity of the well. Depleting the stored water and recovering reduced native groundwater would result in dissolution of arsenic-bearing hydrous ferric oxide (HFO) and release of arsenic into water recovered from the ASR well. Injection/recovery volumes for each cycle for each well were tracked to determine if a substantial volume of stored water was maintained for each cycle or if it was depleted so that reduced native groundwater was brought back to the well. Each well was assigned to either the &ldquo;storage zone maintained group&rdquo; where a zone of stored water was established in early cycles and largely maintained through the period of investigation, or the &ldquo;storage-zone depleted group&rdquo; where a zone of stored water was either established in later cycles and/or was depleted during the period of investigation. Graphical and statistical analyses verified that maximum arsenic concentrations for storage-zone maintained wells were nearly always lower in each cycle and declined below the MCL after fewer cycles than those of storage-zone depleted wells.</p><p> Chapter 4 was a mineralogical investigation of cores located at 20 m (ASR core 1), 152 m (ASR core 2), and 452 m (ASR core 3) from operating ASR wells to determine where mobilized arsenic in limestone is precipitated during ASR. If arsenic is precipitated distally, reduced concentrations of elements in pyrite, (iron, sulfur, arsenic, etc.) would be expected in ASR core 1 relative to more distant cores and there would be noticeable changes in appearance of pyrite crystals due to enhanced oxidation. The results showed that mean concentrations of the elements were lowest in ASR core 2, which did not support distal precipitation. However, scanning electron microscopy identified well-defined pyrite framboids only in core 3 while framboids in ASR cores 1 and 2 were less clear and distinct, indicating pyrite oxidation in cores closest to ASR wells.</p><p> Statistical comparison of concentrations of iron, sulfur, and arsenic between the three ASR cores and 19 control cores not subject to ASR, showed that mean concentrations in ASR cores 1 and 2 were statistically similar to concentrations in control cores. This indicated that concentrations in ASR cores 1 and 2 had not been significantly reduced by ASR. The concentrations of elements were higher in ASR core 3 than in ASR cores 1 and 2 and control cores and statistically dissimilar to all but one control core. This indicated natural heterogeneity in core 3 rather than diminution of elements in ASR cores 1 and 2 due to ASR. The statistical analysis supported local precipitation. Once arsenic is mobilized from dissolved pyrite, it is rapidly complexed with precipitated HFO near the well. As long as all of the stored water is not removed during recovery so that reduced native groundwater is brought back to the well, HFO remains stable and complexed with arsenic. The concentration of elements would not have been lowest in ASR core 1 for this reason and because calculations showed that the mass of arsenic removed during recovery events prior to coring was minor compared to the total in limestone surrounding the well. The implications of this are that while large quantities of arsenic are present near the ASR well, only a small percentage may be available for dissolution. Most arsenic occurs with pyrite in limestone, which may insulate it from exposure to oxidized injection water. Water recovered from ASR wells may continue to have low concentrations of arsenic indefinitely because as limestone is dissolved, more pyrite becomes exposed and available for dissolution. </p><p> The primary contribution of this dissertation to understanding and overcoming the arsenic problem in ASR systems is the empirical data developed to support or challenge important ASR/arsenic hypotheses. These data were used to 1) establish that background concentrations of arsenic in groundwater of the Suwannee Limestone were less than 1&micro;g/L, 2) demonstrate that redox conditions necessary for pyrite in limestone to become unstable and dissolve occur when oxygenated surface water is injected into the aquifer, 3) demonstrate that the concentration of pyrite in the Suwannee Limestone is spatially variable to a high degree, 4) support the hypothesis that following injection of oxygenated surface water, pyrite in limestone dissolves and releases arsenic into solution and HFO forms and complexes with the arsenic near the ASR well, 5) propose that only a small percentage of pyrite near an ASR well may be available for dissolution during each cycle because most occurs in the limestone matrix and is isolated from injection water, 6) propose that as a result of the previous conclusion, water recovered from ASR systems may continue to have low concentrations of arsenic indefinitely because as limestone that contains pyrite is dissolved with each cycle, additional pyrite is exposed and is available for dissolution, and 7) support the effectiveness of maintaining a zone of stored water in an ASR well as an effective means of minimizing arsenic in recovered water during ASR.</p>

Detrital gold is widely dispersed in the Southern Uplands and attributed to minor Au-bearing vein mineralisation hosted by Ordovician and Silurian turbidites. Field, mineralogical and geochemical studies in the Glendinning area indicate the pervasive and laterally extensive nature of hydrothermal alteration and element zonation associated with As-Sb-Au mineralization. Geochemical anomalies are characterised by elevated chalcophile (As, Sb, S, Cu. Pb, Ti, Hg) and depleted siderophile (Fe, Mg, Zn) and alkali group (Na) elements. Broad areas of sodium depletion are indicative of primary hydrothermal activity and together with anomalous arsenic values locate 8 zones of As-Sb- Au-Hg mineralization within 10km of the Glendinning mine and some 60 locations elsewhere in the Southern Uplands of Scotland and the Longford Down, Ireland. Electron microprobe studies demonstrate that an initial phase of arsenopyrite mineralisation forms the principal locus of submicroscopic and lattice-hosted gold concentration in the Glendinning, Knipe, Cairngarroch Bay and Clontibret As-Sb-Au deposits. Gold deposition was initiated during wallrock alteration and hydraulic brecciation, possibly as a result of fluid chilling, while later stibnite vein deposition was accompanied and overprinted by minor chalcopyrite, sphalerite, galena and a variety of sulphosalts. Hydrothermal alteration and As-Au mineralisation in the Southern Uplands postdates arc-related volcanism, turbidite deposition and early deformation. The model envisaged invokes the discharge of highly reducing, sulphur-rich hydrothermal fluids, related to the emplacement of structurally constrained, late Silurian calc-alkaline minor intrusives at the close of the Caledonian orogeny. Different levels of crustal emplacement and subsequent exhumation are considered to explain the various styles of As-Sb-Au mineralization exposed in the Southern Uplands. The complex tectonic hlstory of the Southern Uplands and Longford Down is mirrored by significant variations in the chemical composition of strike parallel greywacke tracts admixed with sediments derived from ophiolites, calc-alkaline volcanic arcs, stable cratons and carbonate shelves. Non-parametric K-means cluster analysis applied to 840 petrographlcally defined samples, determined the chemical variation within each petrofacies and provides a satisfactory method of classifying individual members. Geochemical traverses through the Southern Uplands and Longford Down reveal lateral continuity over a strike length of 350km.

Water samples were collected from six aquifers and three rainstations in the UK. Boron and major cations were determined using inductively coupled plasma - atomic emission spectrometry, while anions were determined using ion chromatography. Prior to boron isotope ratio determination, the boron was separated from the matrix and preconcentrated using ion exchange chromatography. The Inductively coupled plasma mass spectrometer was optimised for preCise and accurate boron isotope ratio determination with repect to nebuliser noise, sample carry over, senSitivity, mass bias and data acquisition. Under optimum conditions a precision of 0.2 %RSD ( 1511] of 20 / 00 ) at a boron concentration of 200 pg.rl was achieved. Major element chemistry identifies that the chalk aquifers of the Isle of Wight and Buckinghamshire, and the Lincolnshire Limestone as Ca HC03-type waters. The Lower Greensand unconfined groundwaters also have Ca HC03- chemistry, whilst the confined zone is characterised by NaCl waters. The Ashdown Sands groundwaters are NaHC03- type waters whilst the continental sands of the Otter Valley are (Ca + Mg) HC03- waters. Generally, boron concentrations in the confined zones of the aquifers are higher than the unconfined. For example, the Lower Greensand unconfined groundwater have a boron concentration ranging from 14 to 49 pg.rl , whilst the confined have a range from 59 to 145 )JgII. The boron isotopic signature (811J3) for the range of waters sampled ranges from -14 to + 48 0/00 , For precipitation samples the ratio is very variable, and the smallest range is seen for the stream samples. The main controls on boron geochemistry in the groundwaters are precipitation, water-rock interaction, mixing with connate waters and isotopiC equilibration. Precipitation is the dominant control on the limestone aquifers, which contrasts with the Lower Greensand and Ashdown Sands where waterrock interaction and mixing with connate waters are most significant. The boron geochemistry of the Otter Sandstone is probably controlled by precipitation and water-rock interaction.

No description available.

The Halmahera arc is a north-south linear intraoceanic arc cutting across the islands of Halmahera and Bacan in NE Indonesia. The arc is the result of the eastward subduction of the Molucca Sea Plate, accommodating the westward movement of the Pacific and Philippine Sea Plates (PSP) against the Eurasian margin. To the south of the Halmahera arc is a major left-lateral strike-slip fault system: the Sorong Fault Zone (SFZ), which separates the northward movement of Australia from the westward movement of the PSP. This plate boundary has been stable throughout the Neogene to the present day, and has been responsible for the transfer of continental fragments from the Australian margin into the southern Molucca Sea region. K/Ar dating has revealed the migration of volcanism along the length of the Halmahera arc from south to north. The oldest volcanics (ca. 11 Ma) are from Obi, the southernmost island in the region, where volcanism is now extinct. Moving north into Bacan, ages range from 7 Ma to the Quaternary, whereas in central Halmahera they range from 6-2 Ma. The present-day arc currently lies to the west of central Halmahera and stretches up the north-west arm of the island. On the basis of spatial, temporal and geochemical variations a possible seven Neogene volcanic centres can be distinguished along the length of the arc. Major element, trace element and Sr-Nd-Pb-O isotopic analyses reveal a wide diversity in geochemical characteristics between the centres. This is due to heterogeneity within the arc mantle wedge, the type of arc crust through which the volcanics were erupted and variations in contribution to the mantle wedge from a subducted component. Volcanic rocks from Obi, central Halmahera and north Bacan display geochemical characteristics typical of intraoceanic arc lavas. The lack of a continental component within these centres enables a greater understanding of the variety of processes and source components affecting arc magmatism in this region. Similarities in certain incompatible trace element characteristics between volcanic rocks of the Mariana and Halmahera arc suggest both arcs are products of a variably depleted mantle beneath the Philippine Sea Plate (PSP). Pb isotopic data from the Halmahera arc, combined with data from back-arc basaltic rocks from the PSP, suggests an I-MORB-type mantle wedge exists beneath this plate and hence that it was once part of the Indo- Australian plate. Volcanic rocks from west and south Bacan lie outside the isotopic ranges displayed by lavas from Obi, north Bacan and Halmahera, reaching extreme Sr-Nd-Pb isotopic ratios consistent with the assimilation of a continental component. Isotopic analyses of Permo-Triassic granitic material, found exposed in the Sula- Banggai islands, New Guinea margin, and Queensland, NE Australia, indicate that this is the most likely contaminant of volcanic rocks in the south Bacan region. In contrast, volcanic rocks from west Bacan are contaminated with a component similar in isotopic composition to highly metamorphosed rocks found exposed in the Sibela Mountains, south Bacan. The geochemical signature and age of the Halmahera arc lavas has implications for the arrival and movement of continental crust in the region. Combined with stratigraphic and tectonic knowledge of the region this study has been used to construct a possible model for the development of the Halmahera arc. The contaminated signature of the Bacan Neogene volcanic rocks supports the hypothesis of overthrusting of ophiolitic and continental material, derived from the PSP and Australian plates respectively, due to collision between the Australian continent and a PSP arc during the Early Miocene. This initiated the development of the Sorong Fault Zone, which was responsible for the recent movement of these 'terranes' into the southern Molucca Sea region.

No description available.

No description available.

The project was conducted on four coals seams, the Shallow and Yard (Lower Coal Measures) from Lea Hall Colliery at Rugeley, and the Park and-Eight Feet seams from Littleton Colliery, near Cannock. Ultimate, proximate analyses and moisture contents showed them to be of high volatile bituminous 'B' coal-rank, and typical of high Cl coals. The Cl investigation showed a relationship with organic matter where ash is a dilutant, reaching c. 1% (by weight) in the coals, almost an order higher than in the associated mudrocks. It is related to the internal surface area and is thus highest in the vitrinite dominated 'bright rocks' and lowest in the 'dull coals'. Two types of Cl were identified, originating from saline ground waters, the former representing present ground water solutions trapped in the larger pores and readily water-soluble, and the latter held in organic combination within smaller or closed pores produced by Hercynian rank imposition. Varying levels of this Cl can be released by ion exchange with carbonates in leaching experiments. The mudrock and coal ash mineralogy was conducted on low temperature ashed material which suffered the side-effect of gypsum formation during oxidation. The mudrock mineralogy is dominated by detrital minerals, quartz and clays predominating. Diagenetic minerals rarely account for 7% of the normative minerals except in localised pyrite and siderite nodules., Climate played an important role in the detrital mineralogy, the lower seam floor measures being dominated by a tropically leached suite of kaolinite and quartz. Continental movement led to increased aridity characterised by illite and chlorite which dominate the higher seams. The intraseam dirt bands are composed of very fine clays, rapidly deposited over wide areas by minor base-level changes or river (ii) bank bursts. The roof measures show least evidence of leaching and are often highest in diagenetic siderite. Ba, Sr, Rb (illite) and Zr (zircon) are predominantly detrital trace elements whilst oxyhydroxide material was-the transporting media. for the diagenetically located elements, Ni, Pb (pyrite), Co and Mn (siderite). Cu is primarily associated with organic matter. The detrital coal mineralogy reflects the fine mudrock material and is usually highest associated with the dirt bands. Diagenetic minerals dominate the ash, reaching 95% (by weight), the major component being late diagenetic cleat. A paragenetic sequence of mineralisation follows a widespread trend from sulphides, silicates to carbonates reflecting changing ground water composition. The cleat fractures represent microjointing produced with stress release during uplift. Its frequence decreases with bed thickness, and the brittle nature of vitrinite causes it to have the earliest formed and most abundant cleat. The strength of multimaceral lithotypes such as durain is much greater and therefore fracture least, later änd with a greater dilation.

No description available.

No description available.