Introduction Of Seawater Research Articles

Arc Foundations and Subduction Initiation: Insights into the Magmatic Evolution of the Lower Crust/Upper Mantle of the Izu–Bonin Forearc during Subduction Initiation

Abstract Our understanding of the processes at work in the lower crust/upper mantle transition zone during subduction initiation and early arc development has suffered from a general lack of in situ samples. Here, we present the results of petrographic and geochemical analysis of 34 samples (9 harzburgites, 13 dunites, 2 orthopyroxenites, 3 olivine-gabbros, and 7 wehrlites) collected from the inner trench wall of the Bonin Ridge, Izu–Bonin forearc. The sample suite records three main melt–rock reaction events involving melts with forearc basalt (FAB)-like, boninitic, and transitional compositions. The wehrlitic and gabbroic rocks trend towards more transitional to FAB compositions and the rest towards more boninitic compositions. The crosscutting occurrence of all three events in a single sample (wehrlite D31–106) establishes a relative timing of the events like that reported for the volcanic edifice of the Bonin Ridge, which transitioned from forearc basalt volcanism at subduction initiation (c.a., 51–52 Ma) to boninitic volcanism (c.a., 50–51 Ma) as the subduction system matured. We therefore suggest that the lower crust/upper mantle transition of the Bonin Ridge preserves a record of the transition from FAB melts created by decompression melting at subduction initiation to arc-type flux melting and boninitic volcanism thereafter. Orthopyroxenites and two anomalously fresh harzburgites from the sample suite are suggested to represent the later boninitic melts and possibly the result of hybridization between such melts and residual peridotites, respectively. Diffuse melt–rock reaction between the later boninites and/or subduction-related fluids and the earlier-formed FAB-related crust is recorded by enrichments in fluid mobile elements and depletions in first row transition metals in clinopyroxenes from a metasomatic vein in wehrlite sample D31–106. The chemistry of the wehrlitic and gabbroic clinopyroxenes suggests that they crystallized from hydrous, highly depleted melts which lack a slab fluid signature. We thus suggest that highly depleted melt fractions might be created early on during subduction initiation by the introduction of seawater into the proto-mantle wedge. The overall FAB-like nature of the crustal wehrlites and gabbros would suggest that most of the lower arc crust was created by forearc extension during/following subduction initiation and that later, mature arc volcanism may have contributed little or no material to the lower crust/upper mantle record in the outer forearc.

Water cooling structure design and temperature field analysis of permanent magnet synchronous motor for underwater unmanned vehicle

Unmanned underwater vehicles (UUVs) have extremely harsh cooling conditions for permanent magnet synchronous motor (PMSM) due to global sealing and compact space, and an efficient heat dissipation system is essential for the safety and operational reliability of PMSM. Currently, with the introduction of seawater and the addition of heat exchanger, liquid reservoir are typically used for open-circuit heat dissipation, which not only adds weight, but seriously affects the flow characteristics of the UUV. In this paper, a novel dual channel water cooling structure is designed to achieve internal circulating heat dissipation without additional auxiliary devices. The temperature field of the PMSM with different water cooling structures is solved by Computational Fluid Dynamics (CFD) under rated operating conditions. The results show that the cooling efficiency of water cooling structures is more affected by low flow rates, accompanied by increasing the flow rate from 0.5 L/min to 24 L/min, the cooling performance is enhanced, but does not entirely obey a strict linear variation. Furthermore, at a flow rate of 6 L/min, the dual spiral water cooling structure performs the best heat dissipation, the maximum operating temperature of the PMSM is reduced by 51.72 K, the maximum temperature rise suppression rate reaches 53.02 %, and the minimum differential pressure of 10.18 kPa.

Use of Loose Part Media With Cardboard and Sand Materials in Islamic Children's Schools

The purpose of this study is to describe the use of loose parts media made from cardboard and sand in learning at the Islamic Children's School TKIT Permata Hati Kartasura Sukoharjo. The research subjects were teachers, informants such as school leaders, and students. Data collection techniques with interviews, observation, and documentation. While the data analysis with the stages of data reduction, data presentation, drawing conclusions, and verification, namely drawing conclusions and verifying the collected data. The results showed that loose parts media designed in ships and simple musical instruments have successfully stimulated the growth of 6 aspects of child development. Aspects of Moral Religion Values with the introduction of seawater that ships pass as a creation of God. Gross motoric physical aspects such as rowing. Physical aspects of fine motor skills include feeling the smooth and rough parts of the ship. A cognitive aspect with counting the number of doors, windows, and stairs on the boat. A language aspect with mentioning the vowel letters on the ship. Aspects of Social Emotional like patiently waiting for their turn in holding the boat. An aspect of art with hearing, imitating, and singing songs about ships. It is also strengthened by playing a musical instrument from a bottle filled with sand.

Evolution of microbial dynamics with the introduction of real seawater portions in a low-strength feeding anammox process

The salinity effect on anammox bacteria has been widely reported; however, rare studies describe the microbial dynamics of anammox-based process response to the introduction of real seawater at mainstream conditions. In this study, an anammox process at mainstream conditions without pre-enriching anammox bacteria was shifted to the feeds of a synthetic wastewater with a portion of seawater mixture. It achieved over 0.180 kg-N/(m3 day) of nitrogen removal rate with an additional seawater proportion of 20% in the influent. The bacterial biodiversity was significantly increased with the increase of seawater proportions. High relative abundance of anammox bacteria (34.24–39.92%) related to Ca. Brocadia was enriched and acclimated to the saline environment. However, the introduction of seawater caused the enrichment of nitrite-oxidizing Ca. Nitrospira, which was responsible for the deterioration of nitrogen removal efficiency. Possible adaptation metabolisms in anammox bacteria and other nitrogen transforming bacteria are discussed. These results highlight the importance of microbial diversity for anammox process under the saline environments of 20% and 40% seawater composition.

Linkage of sulfur isotopic enrichment to sulfur and arsenic release in the coastal aquifers of southwestern Taiwan

High arsenic concentration in groundwater is influenced by redox reactions in As-bearing iron (oxy)hydroxide minerals and elevated total organic carbon, resulting in arsenic contamination and enrichment in groundwater after introduction of seawater into an aquifer. In this study, hydrochemical and isotopic (S, O and C) techniques were used to relate arsenic contamination and seawater flooding/intrusion in groundwater aquifers in the Chianan Plain, southwestern Taiwan. Thirty-three samples (30 from groundwater and 3 from river water) were collected from April–June of 2014. Most of the groundwater samples collected from the Chianan Plain were dominated by As(III), indicating that reducing conditions prevailed within the aquifers. The δ18O-δD plots of most of the groundwater samples from the Chianan Plain are generally lined on the global meteoric water line (GMWL), but the δ18O and δD isotopic compositions of the river water samples show enriched signals. Salinity and sulfate concentrations of river water and shallow groundwater have been found to increase after seawater flooding/intrusion. The δ18O and δD isotopic compositions of the river water showed a gradual trend toward those of seawater. The trend in the isotopic compositions of the river and groundwater samples indicated a mixing of seawater and meteoric water. Up to the present, the groundwater levels in the coastal areas of the Chianan Plain have dropped to zero meters in elevation parallel to sea level due to excessive groundwater withdrawal, resulting in seawater intrusion into the aquifers in Budai, Yichu, and Beimen in the Plain. Moreover, high salinity (48.1‰) occurred only in the Beimen 2B shallow groundwater at a depth of 60 m is a result of seawater flooding infiltration from the nearby salinized Pachang River. The δ34S[SO4]/δ18O[SO4] isotopic ratios (2.63–2.82) of low-As (concentration < 50 μg/L) river water samples were similar to those of marine sulfate minerals dissolved in seawater, but were variable (0 − 2.93) among the high-As (concentration ≧ 50 μg/L) groundwater samples from the Chianan Plain. Sulfates in seawater were introduced into the coastal aquifers of the Chianan Plain under the Holocene marine transgression, wherein the mixing of paleo- and modern-sulfates due to seawater intrusion might have occurred or are occurring. The release of sulfur and arsenic (mostly arsenite) in the Chianan Plain groundwater under reducing environments indicating redox reactions in sulfates and iron (oxy)hydroxide minerals may change the isotopic (S and O in sulfate) compositions in groundwater, resulting in enrichment of δ34S[SO4] and δ18O[SO4]. Salinity can promote arsenic release in groundwater and thus enrich the δ34S[SO4] and δ18O[SO4] isotopic compositions, in which 6.0–22.8‰ δ34S[SO4] and 9.3–15.5‰ δ18O[SO4]occur in shallow fresh groundwater (depth < 60 m) but up to 27.7‰ δ34S[SO4] and 20.4‰ δ18O[SO4] occur in shallow saline groundwater, in comparison to 0‰ δ34S[SO4] and 5.4–6.5‰ δ18O[SO4] in deep fresh groundwater (depth between 60 and 318 m) and up to 38.5‰ δ34S[SO4] and 18.7‰ δ18O[SO4] in deep brackish groundwater. This study provides insights suggesting that the As-containing iron(II) minerals are oxidized to iron(III) minerals and then re-reduced to iron(II) which leads to As release.

The Role of Bimodal Magmatism in Seafloor Massive Sulfide (SMS) Ore-forming Systems at the Middle Okinawa Trough, Japan

Igneous rocks from three distinct morphological areas, Iheya North Knoll, Iheya Minor Ridge, and Izena Hole, in the actively rifting middle Okinawa Trough, Japan, were investigated to understand petrogenetic relations among seafloor massive sulfide (SMS) mineralization (including sources of metals), igneous processes, and tectonics. Mafic rocks in the Iheya Minor Ridge form mountain-chain-like morphology due to the eruption of low-viscosity magma through normal faults formed by the extensional regime. The normal faults also play a role as major pathways of seawater recharge and induced basalt-hosted hydrothermal circulation and mineralization. Felsic rocks in the Iheya North Knoll form lava dome-like morphology due to the periodic ascent of felsic magma. In contrast, the Izena Hole is a subsidence caldera formed by the voluminous eruption of felsic magma. In both cases, felsic magma is essentially formed by water-fluxed melting of basaltic materials formed by the previous mafic magmatism. This mechanism reasonably explains the similar isotopic signatures between mafic and felsic rocks by contemporaneous magmatism of bimodal composition, which has been suggested by previous studies. Introduction of seawater into the deep crust and water-fluxed melting in these areas inevitably involves high-temperature hydrothermal alteration and leaching of metal elements from mafic materials and produces Cu-rich, bimodal-mafic mineralization. Since the magmatism produces voluminous felsic rocks in the upper crust, Cu-poor but Zn- and Pb-rich, bimodal-felsic mineralization is an expected result of felsic magmatism.

Cl− as a Chemical Fingerprint of Solute Transport in the Aquitard-Aquifer System of the North Jiangsu Coastal Plain, China

Detailed vertical profiles of Cl− in porewaters through the aquitard-aquifer system were used to yield solute transport mechanism and build a conceptual model regarding evolution processes and transport time of natural tracer migration in North Jiangsu coastal plain, China. One-dimensional vertical simulated models of Cl− profiles illustrate that diffusion appeared to be the dominant solute transport mechanism in the aquitard-aquifer system. A downward groundwater flow did not improve the fitness between simulated and measured values. Several simulated models were constructed and suggested that the evolution of the Cl− profiles is mainly ascribed to the introduction of seawater and freshwater of transgression-regression to the first confined aquifer and the upper boundary. Groundwater in the first confined aquifer recharged by the Late Pleistocene glacial meltwater (25–15 ka BP) was supported in response to the low Cl− concentrations. The shallow groundwater in the first confined aquifer and porewater with high salt were attributable to the Holocene seawater intrusion. These timeframes were also consistent favorably with the results of previous studies into the palaeohydrology of the study area.

Direct Determination of Cadmium in Seawater by Standard Addition ICP-QMS/QMS with an ORC.

A method for direct and precise determination of Cd in seawater by ICP-QMS/QMS was developed, where a high matrix introducing unit permitted the direct introduction of seawater without clogging the cones while the matrix effect of seawater was canceled by standard addition. NH3 gas was selected as the reaction gas for removing the MoO interferences with the measurement of Cd isotopes, effectively improving the signal to background ratio. The lower limit of detection obtained at 114Cd was 0.0002 ng mL-1, which is enough for the determination of Cd in natural seawater. The validity of the present method was confirmed by the analysis of two certified reference materials, i.e. NASS-5 and NASS-6, whose observed values of Cd concentration agreed with the certified values. The analytical figures of merit of the present method were comparable to or better than those reported for direct analysis of seawater.

Origin of groundwater salinity (current seawater vs. saline deep water) in a coastal karst aquifer based on Sr and Cl isotopes. Case study of the La Clape massif (southern France)

In this study a typical coastal karst aquifer, developed in lower Cretaceous limestones, on the western Mediterranean seashore (La Clape massif, southern France) was investigated. A combination of geochemical and isotopic approaches was used to investigate the origin of salinity in the aquifer. Water samples were collected between 2009 and 2011. Three groundwater groups (A, B and C) were identified based on the hydrogeological setting and on the Cl− concentrations. Average and maximum Cl− concentrations in the recharge waters were calculated (ClRef. and ClRef.Max) to be 0.51 and 2.85mmol/L, respectively). Group A includes spring waters with Cl− concentrations that are within the same order of magnitude as the ClRef concentration. Group B includes groundwater with Cl− concentrations that range between the ClRef and ClRef.Max concentrations. Group C includes brackish groundwater with Cl− concentrations that are significantly greater than the ClRef.Max concentration. Overall, the chemistry of the La Clape groundwater evolves from dominantly Ca–HCO3 to NaCl type. On binary diagrams of the major ions vs. Cl, most of the La Clape waters plot along mixing lines. The mixing end-members include spring waters and a saline component (current seawater or fossil saline water). Based on the Br/Clmolar ratio, the hypothesis of halite dissolution from Triassic evaporites is rejected to explain the origin of salinity in the brackish groundwater.Groundwaters display 87Sr/86Sr ratios intermediate between those of the limestone aquifer matrix and current Mediterranean seawater. On a Sr mixing diagram, most of the La Clape waters plot on a mixing line. The end-members include the La Clape spring waters and saline waters, which are similar to the deep geothermal waters that were identified at the nearby Balaruc site. The 36Cl/Cl ratios of a few groundwater samples from group C are in agreement with the mixing hypothesis of local recharge water with deep saline water at secular equilibrium within a carbonate matrix. Finally, PHREEQC modelling was run based on calcite dissolution in an open system prior to mixing with the Balaruc type saline waters. Modelled data are consistent with the observed data that were obtained from the group C groundwater. Based on several tracers (i.e. concentrations and isotopic compositions of Cl and Sr), calculated ratios of deep saline water in the mixture are coherent and range from 3% to 16% and 0% to 3% for groundwater of groups C and B, respectively.With regard to the La Clape karst aquifer, the extension of a lithospheric fault in the study area may favour the rise of deep saline water. Such rises occur at the nearby geothermal Balaruc site along another lithospheric fault. At the regional scale, several coastal karst aquifers are located along the Gulf of Lion and occur in Mezosoic limestones of similar ages. The 87Sr/86Sr ratios of these aquifers tend toward values of 0.708557, which suggests a general mixing process of shallow karst waters with deep saline fossil waters. The occurrence of these fossil saline waters may be related to the introduction of seawater during and after the Flandrian transgression, when the highly karstified massifs invaded by seawater, formed islands and peninsulas along the Mediterranean coast.

Seawater desalination performance of MFI type membranes made by secondary growth

Seawater desalination is now commonly performed using membrane technology but new materials research is however needed to address issues such as membrane fouling. Ceramic materials such as zeolites are capable of providing the required desalination properties while being potentially tolerant to waters which readily foul polymer membranes and/or can withstand more cost effective cleaning methods. In this paper, we developed Silicalite and ZSM-5 zeolite membranes and tested desalination using the thermally based pervaporation, and more common reverse osmosis (RO) operation modes. Zeolite membranes were synthesised by the template-free secondary growth technique with varying Si/Al ratios. X-ray diffraction spectra of all membranes showed randomly oriented MFI structure. For intact membrane films, gas permeation was not measurable at room temperature until membrane was first heated to at least 125 °C under dry helium implying minimal defects and zeolite pore plugging by water. In pervaporation with 3.8 wt% seawater feed, zeolites containing alumina actively rejected ions, displaying equivalent rejections exceeding 99%. Flux typically decreased after introduction of seawater, but the membrane with Si/Al ratio of 100 uniquely showed a 30% increase in flux which could only be explained by an ion exchange/interaction mechanism which opened the zeolite structure to permeation. Optimal temperature for pervaporation was found to be 80 °C, where high rejections persisted, and flux increased to 0.72 kg m −2 h −1. In RO, the Silicalite membrane achieved highest rejections, but had not reached steady state after 25 h of operation. Negative rejections were initially observed, but eventually crossed into positive values over time. Despite the complexity of water and multiple ion diffusion through molecular dimensioned zeolites with complex charged surfaces, MFI zeolite membranes with tailored Si/Al ratios are ideal candidates for desalination.

Gypsum saturation degrees and precipitation potentials from Dead Sea - seawater mixtures

Environmental context. Since the 1960s the Dead Sea water level has dropped by nearly 30 m and over the last decade the rate of decline accelerated to over 1 m per year. Conveying seawater to the Dead Sea to stabilise or even raise its water level is currently being considered but may result in ‘whitening’ of the surface water through the formation of minute gypsum crystals that will remain suspended in the water column for a prolonged period of time. This paper is a first step in attaining the relevant physical and chemical parameters required to assess the potential for such whitening of the Dead Sea. Abstract. Introduction of seawater to the Dead Sea (DS) to stabilise its level raises paramount environmental questions. A major concern is that massive nucleation and growth of minute gypsum crystals will occur as a result of mixing between the SO42–-rich Red Sea (RS) water and Ca2+-rich DS brine. If the gypsum will not settle quickly to the bottom it may influence the general appearance of the DS by ‘whitening’ the surface water. Experimental observations and theoretical calculations of degrees of saturation with respect to gypsum (DSG) and gypsum precipitation potentials (PPT) were found to agree well, over the large range but overall high ionic strength of DS–RS mixtures. The dependency of both DSG and PPT on temperature was examined as well. Based on our thermodynamic insights, slow discharge of seawater to the DS will result in a relatively saline upper water column which will lead to enhanced gypsum precipitation.

Non-controlled biogenic emissions to the atmosphere from Lazareto landfill, Tenerife, Canary Islands

Goal, Scope and Backgound Historically, landfills have been the simplest form of eliminating urban solid waste with the minimum cost. They have been the most usual method for discarding solid waste. However, landfills are considered authentic biochemical reactors that introduce large amounts of contaminants into the environment in the form of gas and leachates. The dynamics of generation and the movement of gas in landfills depend on the input and output parameters, as well as on the structure of the landfill and the kind of waste. The input parameters include water introduced through natural or artificial processes, the characteristics of the urban solid waste, and the input of atmospheric air. The main output parameters for these biochemical reactors include the gases and the leachates that are potentially pollutants for the environment. Control systems are designed and installed to minimize the impact on the environment. However, these systems are not perfect and a significant amount of landfill gas could be released to the atmosphere through the surface in a diffuse form, also known as Non-controlled emission. In this paper, the results of the Non-controlled biogenic gas emissions from the Lazareto landfill in Tenerife, Canary Islands, are presented. The purpose of this study was to evaluate the concentration of CH4 and CO2 in the soil gas of the landfill cover, the CH4 and CO2 efflux from the surface of the landfill and, finally, to compare these parameters with other similar landfills. In this way, a better understanding of the process that controls biogenic gas emissions in landfills is expected.

From Snowball to Phaneorozic Earth

The so-called Late Proterozoic snowball Earth disappeared at the beginning of Phanerozoic time: the surface of the Phanerozoic Earth was enveloped by an ocean and oxygen-rich atmosphere, and the planet had a warm climate. We propose that this dramatic change resulted from the return flow of seawater into the mantle beginning at 750 Ma, as a consequence of the cooling of the Earth and start of the main glacial epoch. Phase relations for minerals in the system MORB + H2O and peridotite + H2O suggest that old, cold subducting oceanic slabs would transport surface water through ultrahigh-P hydrous silicates to the mantle transition zone at depths of 410-660 km. This zone could store abundant H2O, inasmuch as hydrous β and γ phases of the olivine composition may contain up to 2 to 3 wt% water. Geotherms computed for rocks of ancient subduction zones from regional metamorphic belts around the world record such a warm-to-cold transition in and below the lithosphere at 750 Ma. The runaway cooling of the Earth's interior along consuming plate boundaries started at 750 Ma by propagation of a hydration front into the mantle from 70 km depth to 410-660 km through a narrow channel above the Wadati-Benioff plane, or directly by the descent of hydrated slab peridotites. Resultant hydration of the mantle wedge and adjacent regions caused a rapid sea-level drop during the interval of 750-600 Ma, and large landmasses appeared. This change was due to the increase of water content from 0.5 for amphibole peridotite to 6.5 wt% for antigorite peridotite in the wedge mantle, and to the popcorn effect to push up continental margins. The total seawater lost since then is estimated to have lowered sea level about 600 m. Introduction of seawater into the mantle drastically lowered the melting temperature and viscosity of mantle materials, both of which reactivated the plate and plume tectonic processes. Surface volcanism released mantle CO2, causing the greenhouse effect to melt global glaciers of the snowball Earth since about 750 Ma. The emergence of huge continental landmasses diversified surface environments; erosion and deposition of sediments became significant as in the present-day Earth. Extensive formation of sedimentary basins and accretionary complexes along consuming plate boundaries drastically increased free oxygen in the atmosphere by the burial of organic matter in those sediments, which was critical to the evolution of large multicellular organisms.

生態系の変動を考慮した順応的管理―物質収支からみて―

Nitrogen budgets and fauna of benthic organisms were examined at the pond of Osaka Nanko Bird Sanctuary, an artificial tidal flat of Hannan Second District and the natural tidal flat of Wakagawa estuary. These salt marsh and tidal flats, each locates at urban areas, are thought to be a typical ecosystem maintained by artificial environmental manipulation. The introduction of seawater to the salt marsh by sluice pipes and the conveyance of river water from inner tidal flat by pumps are effective methods to preserve the benthic ecosystems at Nanko Bird Sanctuary and Wakagawa Tidal Flat, respectively.

The impact of sea water flushing on biological nitrification-denitrification activated sludge sewage treatment process

The process performance of the two largest activated sludge processes in Hong Kong, the Sha Tin and the Tai Po Sewage Treatment Works (STW), deteriorated in the initial period after the introduction of seawater flushing in 1995 and 1996, respectively. High effluent ammonia nitrogen (NH4-N) and total suspended solids (TSS) in excess of the discharge standards resulted from incomplete nitrification and changes in floc characteristics. A desktop study on the inhibitory effects of salinity, particularly on nitrification, was subsequently conducted using the Tai Po STW operating data. To assist the upgrade of the Sha Tin STW a five-month extensive bench-scale investigation on a simple but flexible modified Ludzack-Ettinger configuration with bio-selector was conducted to quantify the inhibitory effects due to the saline concentration. The Sha Tin STW upgrade consists of restoration of its original design capacity (conventional process) of 205,000 m3/day from its currently much reduced capacity as a Bardenpho process. Only the volume of the existing biological process and clarifier is to be utilized. The saline concentration ranges from 3,500 up to 6,500 mg Cl-/L, both daily and seasonally. High and greatly fluctuating saline concentrations have been known to inhibit nitrification. Design consideration should also be given to the peak daily and seasonal TKN loading of up to three times the average. Although the nitrifiers maximum specific growth rate was significantly reduced to a low 0.25 day(-1), the inhibition was considered to be tolerable with effluent NH4-N and NO3-N consistently at < 1 and < 6 mg/L. The bio-selector was demonstrated to be efficient in control of sludge foaming and bulking with SVI consistently < or = 125 mL/g. Results from the IAWO Model No. 1 and the hydraulic model of the secondary clarifiers allowed overall process capacity maximization. With an anoxic mass fraction of 25-30%, operating sludge age of 9-14 days and SVI < or = 125 mL/g, both the design requirements and the effluent discharge standards could be met. Without these investigations, an unnecessarily large reaction basin and secondary clarifier volume, and hence capital investment, would have resulted.

CONDITIONING AND DEWATERING OF PULP AND PAPER SLUDGE

ABSTRACT The dewaterability of pulp and paper sludges is usualy poor. In this study, biological sludge samples from two pulp and paper mills were conditioned with three cationic polyelectrolytes that have similar molecular weights and different charge densities. Cationic polyelectrolyte of high charge density could efficiently enhance sludge dewaterability and markedly reduce the residual moisture content in the dewatered cake. On the other hand, the introduction of seawater to pulp and paper sludge would increase the demand of the cationic polyelectrolyte.

Reciprocating Wear of WC-17 Co Coatings in aqueous Environments

Surface Engineering is briefly reveiwed and the deposition of hard coatings by a High Velocity Oxygen Fuel process is described. Features of the deposit microstructure are discussed in terms of production parameters and their effect on both strength and wear behaviour. An experimental programme to create controlled reciprocating wear of the coatings in the presence of air, aqueous and aqueous abrasive media is described. The resulting wear is assessed quantitatively in terms of volume los and change in surface roughness. Introduction of seawater to the wearing interface reduces wear by a factor of four and the introduction of alumina slurries results in wear rates, and scar roughness values intermediate between those in seawater and air. The reduced wear rates in aqueous media are attributed to the cushioning effects of the liquid and the relatively benign effects of the abrasive to the replacement of early adhesive wear (in air) by abrasive wear. The fine (0.1 μm) abrasive to the replacement of early adhesive wear (in air) by abrasive wear. The fine (0.1 μm) abrasive is more damaging than the coarse (7μm) one which is thought to be due to the easy embedding of the 0.1 μm alumina in the soft phase, which has a typical microstructural mean free path of about 0.5 μm

Concomitant evolution of tectonic environment and magma geochemistry, Ambrym volcano (Vanuatu, New Hebrides arc)

Abstract Ambrym volcano lies in the central part of the New Hebrides island arc near the latitude where the D’Entrecasteaux Zone is colliding with the arc. It is a 35 km × 50 km, mainly basaltic stratovolcano constructed in four distinct parts: (i) well-preserved remnants of an old edifice in the north; (ii) a N100°-aligned, oval-shaped basal Hawaiian-type shield volcano; (iii) a pyroclastic cone, cut by a concentric 12 km wide caldera; and (iv) post-caldera basaltic suites, both intra- and extra-caldera. Considering K 2 O, La and Zr variations, three major trends characterize the geochemistry of Ambrym; one medium-K (MK) to high-K (HK) tholeiitic to calc-alkaline basaltic trend, and two more evolved trends, respectively MK and HK, from basaltic to dacitic and rhyodacitic compositions. These magmatic suites correspond to several volcanic phases: (1) older MK basalts forming the Tuvio-Vetlam-Dalahum edifice; (2) MK to HK basalts forming the basal shield volcano; (3) MK andesites and rhyodacites forming the first pyroclastic sequence of the Ambrym Pyroclastic Series (APS), which probably initiated the formation of the caldera; (4) MK to HK basalts and andesites forming Surtseyan then Strombolian pyroclastic sequences 2, 3 and 4 of the APS; and (5) post-caldera MK to HK basalts forming the recent olivine porphyritic- and plagioclase-porphyritic suites, locally associated with more evolved HK andesitic volcanic rocks in the eastern part of the caldera. (La/Yb) n and (La/K) n ratios (2–5.9 and 1.3–2.2, respectively) and Zr contents indicate that the parental magmas originated from incremental batch melting or fractional melting (21–25%) during uplift of a single spinel lherzolite source (from at least 60 to 45 km depth) in response to modifications in the tectonic environment due to ongoing collision with the D’Entrecasteaux Zone. However, K and La contents require prior enrichments by possible mantle metasomatism associated with subduction. Fractionation of olivine, plagioclase, clinopyroxene and Fe-Ti oxides explain most of the major and trace element variations in the resulting liquids and interaction between magmas rising from two distinct chambers combined with massive introduction of seawater into the edifice appear to be the major causes of the giant eruption leading to caldera formation. More recent activity of the volcano is principally related to shallow incremental batch melting or fractional melting and to fractionation in magma chambers associated with N100° rifting.

Golf Course Irrigation with Reclaimed Wastewater

Irrigation with treated municipal wastewater has been conducted at the Mas Nou Golf Course since September 1989, in the framework of a jointly sponsored demonstration project. The results obtained during the first 18 months have provided useful criteria for ensuring a satisfactory public health protection and adequate aesthetics of the golf course facilities. The established disinfection strategy together with the natural microbial inactivation taking place at the two landscape impoundments can provide an irrigation water with consistently less than 10 cfu/100 mL of faecal conforms and faecal streptococci. Sudden episodes of algae removal from suspension have been experienced in the first impoundment. However, no aesthetic deterioration or mosquito development has occurred in either of the two impoundments. Preliminary studies of the microbial content of aerosols have shown that by an adequate disinfection of the secondary effluent and the operation of the water jets only during low wind periods it is possible to prevent microbial dispersion by aerosols. The operation and maintenance cost of irrigation with reclaimed municipal wastewater is close to 56 ptas/m3, including pumping costs. An effort to improve the quality of water supply, by preventing the introduction of seawater or brackish water into the sewerage network, as well as improving efficiency and reliability of wastewater treatment processes and operation and management of irrigation systems will greatly contribute to expand the water resources available at many coastal resort towns in the Mediterranean.

Meren Field-The Geology and Reservoir Characteristics of a Nigerian Offshore Field

Summary The Meren field is located offshore Nigeria. The field contains 1.3 billion bbl original oil in place (OOIP) and may be classed as a major oil accumulation. The more landward-lying fault blocks within the field contain an increasingly greater preponderance of oil reserves to gas reserves. All field pays display evidence of the depositional process occurring contemporaneously with fault movement. Sand sections have a tendency to become magnified in the downthrown portion of a fault block. The reservoirs are composed of sandstone with minor accumulations of authigenic kaolinite. The amount of kaolinite within a particular sand is a major factor in determining the porosity and permeability. The high porosities and permeabilities and the ability of the reservoir rock to remain unaltered by the introduction of seawater should minimize many of the operational problems ordinarily coincident with the installation of a water-injection project in the Meren field. This study indicates the possibility of using a combination of well-log interpretation with laboratory analyses of sidewall cores to help determine the areal variation of porosity and permeability within a particular reservoir. Introduction The Meren field is jointly owned by Nigerian Natl. Petroleum Co. (NNPC) (60%) and Gulf Oil Co. (40%); however, the field is operated be Gulf Oil Co. (Nigeria) Ltd. (GOCON). Fig. 1 shows the location of the field, offshore Bendel State and approximately 25 miles northwest of the GOCON/NNPC Escravos River Tank Farm and Export Terminal. The water depth in the field varies from 48 to 60 ft. Fifty-seven wells have been drilled in the Meren field, three of which are dry holes. The field was discovered in 1965. Production began in Sept. 1968. As of July 1, 1980. the Meren field has produced 347,194,961 STB oil, 321,545,190 Mcf gas, and 10,123,132 bbl water. Cumulative recovery is 26% OOIP. Performance analysis has shown that the majority of the reservoirs producing from the Meren field are being affected by minimal water influx. The reservoirs appear to be producing by a depletion-drive/gas-cap expansion mechanism. In 1978 GOCON and NNPC authorized a full-fledged feasibility study to determine the true worth of enhancing oil recovery from the Meren field. The first portion of the study ascertained reservoir configurations and their reservoir rock and fluid characteristics. The following segments were contained in this preliminary field definition study. Geological Study The Meren field was subjected to a complete geological study. All geological data were analyzed, and proper corrections were made to the original interpretations. Core Analysis The Meren 57 well was drilled and cored in late 1978 to confirm the results of the coring of the Meren 5 well in 1968. JPT P. 2095^