Efficient exploitation and conservation of the oceans poses great technological challenges for scientists and engineers who must develop materials, structures and equipment for use in harsh environment of the oceans. For the applications of materials in marine environment, knowledge of the corrosion properties is essential for selection purposes. Presently, effort is being devoted to exploit deep-sea mineral resources. Deterioration of materials in the deep sea is due to the cumulative effect hydrostatic pressure, temperature, pH, dissolved oxygen, salinity and sea current. For the first time, in-situ corrosion measurements on the effect of deep sea environment on some metallic and composite materials were carried out at depths of 500,1200,3500, and 5100 m for 168,174 and 174 days of exposure in the Indian Ocean. Corrosion rate was obtained from weight loss measurements (mm/year) and surface morphology of as-exposed and cleaned specimens of the above materials was studied under scanning electron microscope and ED AX. Galvanic coupling of steel with zinc, magnesium and aluminium were also studied.. Tensile on metal and alloys and tensile, compressive, flexure and ILSS tests on carbon fibre reinforced composite specimen were performed on exposed specimens. XRD studies were conducted on the corrosion product of materials. In order to correlate the performance of materials in deep-sea environment, seawater current and temperature data were also collected at same period Results reveal that the corrosion behaviour of steels is controlled by dissolved oxygen prevailing and corrosion rate corresponds to dissolved oxygen available at these depth levels. This is due to the fact that oxygen acts as a cathodic deploarizer during corrosion reaction of steels in seawater. Corrosion rate of aluminium increases as the depth increases. This is due to the effect of hydrostatic pressure, which reduces the ionic radii of chlorine ions and facilitates easy penetration of these ions into surface layer. Titanium, titanium alloy (Ti-6A1-4V) and stainless steels did not show any deterioration at all depths studied. Morphology of as exposed and corroded coupons reveal different features. EDS analyses on exposed specimens are analyzed in light of seawater parameters. Carbon fibre reinforced composite did not show any change in properties like tensile, compression flexural and ILSS compared to control (unexposed) specimens. The deposition of calcium carbonate on galvanically coupled mild steel with zinc, aluminium and magnesium corresponds to availability of calcium in the deep ocean. EDS analyses on exposed coupons did not reveal calcium element below the calcium carbonate compensation depth (CCD) at 3800 m in Indian Ocean. Potentiodynamic polarization studies on some metals and alloys indicate that the behaviour of materials in deep-sea environment is a cumulative effect of all oceanographic parameters. Tensile test results on stainless steels SS-304 & SS-316L), titanium and titanium alloy (exposed) specimens did not show any significant change in their tensile properties and is again attributed to the passive film formed on its surface and nearly zero corrosion rate observed. Microbiological investigations on the exposed materials indicate that except carbon fibre reinforced composite all other metals and alloys harboured bacterial colonies. Results have been used to recommend structural materials suitable for the deep-sea applications.

Thesis--Woods Hole Oceanographic Institution. / "Technical report." Grant 04-7-158-44104 and 04-8-M01-149. Includes bibliographical references (p. 260-271).

published_or_final_version / Biological Sciences / Master / Master of Philosophy

Desalination is considered to be a major source of usable water in the Middle East, especially the Gulf countries which lack fresh water resources. A key and sometimes the only solution to produce high quality water in these countries is through the use of seawater reverse osmosis (SWRO) desalination technology. Membrane fouling is an economic and operational defect that impacts the performance of SWRO desalination technology. To limit this fouling phenomenon, it is important to implement the appropriate type of intake and pre-treatment system design. In this study, two types of systems were investigated, a vertical well system and a surface-water intake at a 9m depth. The purpose of this investigation is to study the impact of the different intake systems and pre-treatment stages in minimizing the concentrations of algae, bacteria, natural organic matter (NOM) and transparent exopolymer particles (TEP), in the feed water prior to pre-treatment, through the pre-treatment stages, and in the product water and concentrate. Water samples were collected from the surface seawater, the intakes (wells for site A, 9 m depth open ocean intake at site B), after the media filter, after the cartridge filter, and from the permeate and reject streams. The measured parameters included physical parameters, algae, bacteria, total organic carbon (TOC), fractions of dissolved NOM, particulate and colloidal TEP. The results of this study prove that the natural filtration and biological treatment of the seawater which occur in the aquifer matrix are very effective in improving the raw water quality to a significant degree. The results demonstrated that algae and biopolymers were 100% removed, the bacterial concentrations were significantly removed and roughly 50% or greater of TOC concentrations was eliminated by the aquifer matrix at site A. The aquifer feeding the vertical wells reduced TEP concentrations, but to differing degree. There is a slight decrease in the concentrations of, algae, bacteria, TOC, NOM, and TEP in the feed water at 9 m depth compared to the surface seawater at site B. The pre-treatment was of significant effectiveness and the improvements in reducing the membrane fouling potential were quite high and strong at this site. Investigation of the permeate stream showed some breakthrough of bacteria which is of concern because it may indicate a problem within the membrane system (e.g., broken seal and perforation). The aquifer feeding the wells in the subsurface system plays a main role in the improvement of water quality, so the pre-treatment seems less effective in site A plant. This proves that the subsurface intake is better than open ocean intake in terms of providing better raw water quality and ultimately reducing membrane biofouling.

Downhole sampling of unboiled liquid at 1350 and 1500 m depth in the seawater-dominated Reykjanes high-temperature geothermal system in Iceland shows that metal concentrations measured at surface are minimum values due to mineral precipitation in the wells; by analogy of similar tectonic setting, host rocks and fluid composition, the metal concentrations measured in many black smoker vents at the seafloor are also minima. Fluids in the Reykjanes geothermal system react with mid-ocean ridge basalt at temperatures as high as 346°C and contain Fe 9-140 ppm, Cu 14-17 ppm, Zn 5-27 ppm, Pb 120-290 ppb, 1-6 ppb Au, and 28-107 ppb Ag. Fluids discharged at surface from the same wells have orders of magnitude lower metal concentrations due to precipitation caused by boiling and vapor loss during depressurization. Upstream of the orifice plate at high pressure (40 bar, 252°C) the precipitates consist mainly of sphalerite and chalcopyrite with a trace of galena and bornite. At the orifice plate of old wells, the pressure decreased sharply to 11 bar (188°C), resulting in abundant deposition of amorphous silica together with minor sphalerite and traces of chalcopyrite. In new wells the pressure at the orifice plate decreases to 22 bar (220°C); this pressure decrease and concomitant boiling causes deposition of fine-grained bornite-digenite solid solution together with sphalerite and galena on the fluid flow control valve. In high-pressure wells (average wellhead pressure 45-35 bar) most metals (mainly as sphalerite) are deposited downstream of the orifice plate, with up to 950 ppm Au and 2.5 wt.% Ag. Bulk concentrations in the scales vary between 15-60 wt.% upstream and downstream of the orifice plate and diminish from there. Iron increases up well from 8 to ~20 wt.% and decreases downstream of the orifice plate from 6 to 2 wt.% at the separation station; Cu downhole is ~3 wt.% but increases to 25 wt.% on the fluid flow control valve and then decreases; Pb downhole 100s ppm but at the wellhead is ~3 wt.%, increasing to 15 wt.% at the fluid flow control valve, then decreasing sharply from there.

In the era of intense pressures on water resources, the loss of groundwater by increased seawater intrusion (SWI), driven by climate, sea level and landscape changes, may be critical for many people living in commonly populous coastal regions. Analytical solutions have been derived here for interface flow in coastal aquifers, which allow for simple quantification of SWI under extended conditions from previously available such solutions and are suitable for first-order regional vulnerability assessment and mapping of the implications of climate- and landscape-driven change scenarios and related comparisons across various coastal world regions. Specifically, the derived solutions can account for the hydraulically significant aquifer bed slope in quantifying the toe location of a fresh-seawater sharp interface in the present assessments of vulnerability and safe exploitation of regional coastal groundwater.  Results show high nonlinearity of SWI responses to hydro-climatic and groundwater pumping changes on the landside and sea level rise on the marine side, implying thresholds, or tipping points, which, if crossed, may lead abruptly to major SWI of the aquifer. Critical limits of coastal groundwater change and exploitation have been identified and quantified in direct relation to prevailing local-regional conditions and stresses, defining a safe operating space for the human use of coastal groundwater. Generally, to control SWI, coastal aquifer management should focus on adequate fresh groundwater discharge to the sea, rather than on maintaining a certain hydraulic head at some aquifer location. First-order vulnerability assessments for regional Mediterranean aquifers of the Nile Delta Aquifer, the Israel Coastal Aquifer  and the Cyprus Akrotiri Aquifer show that in particular the first is seriously threatened by advancing seawater. Safe operating spaces determined for the latter two show that the current pumping schemes are not sustainable under declining recharge. / <p>The thesis was founded by two research programmes: NEO private-academic sector partnership and Ekoklim, a strategic governmental funding through Stockholm University</p><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p><p> </p>

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1984. / Includes bibliographical references. / Microfiche. / x, 216 leaves, bound ill. 29 cm

Recent regulation mandates that ships conduct mid ocean ballast water exchange (BWE) prior to discharging foreign ballast in territorial waters of Australia, the U.S. and elsewhere. The enforcement of ballast water exchange legislation is undermined, however, by a lack of sensitive and reliable methods for verifying compliance. One way to assess compliance is to compare the concentrations of chemical tracers in ballast tanks with their known distributions in the open ocean. In this work, dissolved organic matter and trace elements are investigated as potential tracers of mid-ocean ballast water exchange on commercial voyages in the North Pacific and Atlantic Oceans. The optical properties of chromophoric dissolved organic matter (CDOM) are frequently used as tracers of water masses in bays and estuaries. Characterization of the underlying fluorescence spectra in seawater dissolved organic matter was performed using parallel factor analysis, allowing the identification of at least nine independently varying fluorescent components present in varying concentrations in the ocean and in ballast water. Two of the humic components were terrestrial in origin and their signals could be traced in the open ocean (Pacific and Atlantic) at levels of approximately 1.5% of riverine concentrations. One humic terrestrial component was sufficient for predicting the coastal vs. oceanic source of most ballast water samples, suggesting that single and dual channel fluorometers could be optimized for verifying ballast water exchange. Barium, manganese and phosphorus were also investigated as potential tracers. Measurements of Ba and P obtained via engine-cooling pipes on commercial vessels were consistent with previous oceanographic measurements. While Ba behaved conservatively in ballast water, concentrations of phosphorus fluctuated and Mn was removed in ballast tanks over time. Ba and P demonstrated considerable promise as ballast water tracers, exhibiting predictable concentrations in exchanged ballast tanks, given a priori knowledge of the ocean (Atlantic versus Pacific) in which BWE was performed.

Estuarine ecosystems are under enormous stress due to rapid coastal developments and climate change. Proper management of these important ecosystems requires a good understanding of their key processes. In this thesis, riparian groundwater-surface water interaction is explored for an aquifer-estuary system primarily by a series of numerical experiments. The work focuses on riparian-scale groundwater flow and salinization. The overall aim of the study was to extend our understanding of aquifer-estuary exchange, which is currently centered on the lower marine estuarine reach, to middle estuaries (i.e., the estuary reach that has variable salinity). The numerical experiments were guided by previous studies and observations made from an exploratory field investigation conducted in and next to Sandy Creek, a macro-tidal estuary incised in the alluvial aquifer of the Pioneer Valley, North-eastern Australia (Longitude 49.11°, Latitude -21.27°). The following observations were made from the field investigation: Sandy Creek estuary experiences a variable salinity regime in its mid reaches that consists of periods of 1) freshwater flushing due to up catchment-derived flooding, 2) persistent freshwater conditions for at least 2 months following the flooding, 3) tidal salinity fluctuations and 4) constant near-seawater salinity; laterally extensive and disconnected aquitards were found to occur at the field site; Sandy Creek had an essentially ‘vertical’ bank slope. Numerical simulations were conducted using the finite element modeling code FEFLOW for saturated unsaturated, variable-density groundwater flow and solute transport, to examine the influence of the following factors on aquifer-estuary exchange: a tidally varying estuarine salinity and hydraulic head, a seasonal freshwater flush (i.e., estuary with freshwater and an elevated stage due to an up catchment sourced flood), near estuary aquitard layers, lateral asymmetry (about the estuary centerline) in hydraulic conductivity and regional hydraulic gradients. The simulations neglected seepage face development after numerical experiments showed that for a vertical bank estuary interacting with a sandy loam aquifer, seepage face effects on groundwater flow and associated salinity distribution were minimal. The following observations were drawn from the range of numerical experiments considered. Tidal salinity fluctuations in the estuary (varying between 0 and 1 - i.e., using a relative salinity scale where a salinity of 1 is seawater) produced flow paths and residence times that were distinctly different to the constant seawater salinity case. While the constant average 0.5 salinity case and the corresponding tidally-varying salinity case (i.e., salinity varying between 0 and 1) produced somewhat comparable results in terms of RUC and RLC (RUC represents groundwater discharge to the estuary that originated from recharge to the estuary bank and RLC groundwater discharge to the estuary that originated from recharge through the estuary bed), whereas flow paths and the total salt mass in the aquifer differed. Freshwater flushing simulations indicated that the near-estuary aquifer responds rapidly to a 2-day ‘wet season’ flushing event with a short-lived freshwater lens created through freshening of the hyporheic zone. Annual cycling of the seasonal flushing led to significant disruption of the estuary water circulation in the aquifer thereby impacting on residence times, transport pathways, and RUC and RLC, and acting to potentially remobilize groundwater and contaminants previously trapped in continuous and semi-continuous re-circulation cells. Although groundwater flow paths determined using tide-averaged velocity vectors were representative of flow paths from transient tidally driven flow vector field, residence times calculated from the two flow fields were markedly different. The influence of riparian scale aquitards and lateral asymmetry (about the estuary centreline) in hydraulic gradients and hydraulic conductivity on groundwater flow and associated salinity distribution was also found to be sensitive to estuarine salinity conditions. The results indicate that observations made about aquifer-estuary interaction in the lower estuary may not be directly applicable to the middle estuary. According to the simulations, tidal salinity variations in the estuary are important factors that affect hyporheic-riparian salt transport processes and that the use of a time averaged estuarine salinity as an approximation to variable salinity conditions is unsuitable for the accurate prediction of the near-estuary dynamics in middle estuaries. This study was based on a two dimensional representation of the riparian scale interaction and it is clear that future research needs to focus on the three-dimensionality of the aquifer-estuary system, incorporating spatially and temporally varying flow and transport characteristics. That is, many estuaries are tortuous and the aquifer geology spatially complex such that assumptions required for the two-dimensional section will most likely restrict application to the field. The tidal dynamics in the middle estuary is also expected to generate three dimensional aspects to the aquifer-estuary interaction. Thus further investigation that explicitly models the hydrodynamics and salt transport in the estuary and estuarine morphology is required to refine the insight provided by the simple conceptual model adopted in this study.

Estuarine ecosystems are under enormous stress due to rapid coastal developments and climate change. Proper management of these important ecosystems requires a good understanding of their key processes. In this thesis, riparian groundwater-surface water interaction is explored for an aquifer-estuary system primarily by a series of numerical experiments. The work focuses on riparian-scale groundwater flow and salinization. The overall aim of the study was to extend our understanding of aquifer-estuary exchange, which is currently centered on the lower marine estuarine reach, to middle estuaries (i.e., the estuary reach that has variable salinity). The numerical experiments were guided by previous studies and observations made from an exploratory field investigation conducted in and next to Sandy Creek, a macro-tidal estuary incised in the alluvial aquifer of the Pioneer Valley, North-eastern Australia (Longitude 49.11°, Latitude -21.27°). The following observations were made from the field investigation: Sandy Creek estuary experiences a variable salinity regime in its mid reaches that consists of periods of 1) freshwater flushing due to up catchment-derived flooding, 2) persistent freshwater conditions for at least 2 months following the flooding, 3) tidal salinity fluctuations and 4) constant near-seawater salinity; laterally extensive and disconnected aquitards were found to occur at the field site; Sandy Creek had an essentially ‘vertical’ bank slope. Numerical simulations were conducted using the finite element modeling code FEFLOW for saturated unsaturated, variable-density groundwater flow and solute transport, to examine the influence of the following factors on aquifer-estuary exchange: a tidally varying estuarine salinity and hydraulic head, a seasonal freshwater flush (i.e., estuary with freshwater and an elevated stage due to an up catchment sourced flood), near estuary aquitard layers, lateral asymmetry (about the estuary centerline) in hydraulic conductivity and regional hydraulic gradients. The simulations neglected seepage face development after numerical experiments showed that for a vertical bank estuary interacting with a sandy loam aquifer, seepage face effects on groundwater flow and associated salinity distribution were minimal. The following observations were drawn from the range of numerical experiments considered. Tidal salinity fluctuations in the estuary (varying between 0 and 1 - i.e., using a relative salinity scale where a salinity of 1 is seawater) produced flow paths and residence times that were distinctly different to the constant seawater salinity case. While the constant average 0.5 salinity case and the corresponding tidally-varying salinity case (i.e., salinity varying between 0 and 1) produced somewhat comparable results in terms of RUC and RLC (RUC represents groundwater discharge to the estuary that originated from recharge to the estuary bank and RLC groundwater discharge to the estuary that originated from recharge through the estuary bed), whereas flow paths and the total salt mass in the aquifer differed. Freshwater flushing simulations indicated that the near-estuary aquifer responds rapidly to a 2-day ‘wet season’ flushing event with a short-lived freshwater lens created through freshening of the hyporheic zone. Annual cycling of the seasonal flushing led to significant disruption of the estuary water circulation in the aquifer thereby impacting on residence times, transport pathways, and RUC and RLC, and acting to potentially remobilize groundwater and contaminants previously trapped in continuous and semi-continuous re-circulation cells. Although groundwater flow paths determined using tide-averaged velocity vectors were representative of flow paths from transient tidally driven flow vector field, residence times calculated from the two flow fields were markedly different. The influence of riparian scale aquitards and lateral asymmetry (about the estuary centreline) in hydraulic gradients and hydraulic conductivity on groundwater flow and associated salinity distribution was also found to be sensitive to estuarine salinity conditions. The results indicate that observations made about aquifer-estuary interaction in the lower estuary may not be directly applicable to the middle estuary. According to the simulations, tidal salinity variations in the estuary are important factors that affect hyporheic-riparian salt transport processes and that the use of a time averaged estuarine salinity as an approximation to variable salinity conditions is unsuitable for the accurate prediction of the near-estuary dynamics in middle estuaries. This study was based on a two dimensional representation of the riparian scale interaction and it is clear that future research needs to focus on the three-dimensionality of the aquifer-estuary system, incorporating spatially and temporally varying flow and transport characteristics. That is, many estuaries are tortuous and the aquifer geology spatially complex such that assumptions required for the two-dimensional section will most likely restrict application to the field. The tidal dynamics in the middle estuary is also expected to generate three dimensional aspects to the aquifer-estuary interaction. Thus further investigation that explicitly models the hydrodynamics and salt transport in the estuary and estuarine morphology is required to refine the insight provided by the simple conceptual model adopted in this study.