Water Sink Research Articles

Field measurements and monitoring of wastewater discharge in sea water

This paper reports a study of the field measurements and monitoring of wastewater discharge in sea water at Bari East (Italy). A wastewater sea outfall system is an integral and fundamental part of each wastewater treatment with ultimate sink in the sea water. The design of a water treatment plant and wastewater outfall must take into account the use of the environmental water, the values of physicochemical parameters to be respected in order to safeguard the use itself and the quality of the environmental water where wastewater is issued. In the present study measurements of sea current velocity components were carried out with a VM-ADP (Vessel-Mounted Acoustic Doppler Profiler). Salinity, wind directions and velocities were assessed with, for one survey, the total faecal coliforms and other biochemical parameters. It was emphasized that the measurements necessary for monitoring cannot be concentrated in the wastewater outfall pipe zone only, but should be extended to a neighbouring area of the outfall pipe, with an extension depending on the wastewater discharge, the polluting charge and the magnitude of the sea currents and the winds typical of the zone of interest. The analyses presented in this paper confirm that the sea zones close to the wastewater outfall pipe are particularly sensitive and vulnerable. Such results must be considered in the planning of a wastewater outfall pipe.

Echolocating Bats Use a Nearly Time-Optimal Strategy to Intercept Prey

Acquisition of food in many animal species depends on the pursuit and capture of moving prey. Among modern humans, the pursuit and interception of moving targets plays a central role in a variety of sports, such as tennis, football, Frisbee, and baseball. Studies of target pursuit in animals, ranging from dragonflies to fish and dogs to humans, have suggested that they all use a constant bearing (CB) strategy to pursue prey or other moving targets. CB is best known as the interception strategy employed by baseball outfielders to catch ballistic fly balls. CB is a time-optimal solution to catch targets moving along a straight line, or in a predictable fashion—such as a ballistic baseball, or a piece of food sinking in water. Many animals, however, have to capture prey that may make evasive and unpredictable maneuvers. Is CB an optimum solution to pursuing erratically moving targets? Do animals faced with such erratic prey also use CB? In this paper, we address these questions by studying prey capture in an insectivorous echolocating bat. Echolocating bats rely on sonar to pursue and capture flying insects. The bat's prey may emerge from foliage for a brief time, fly in erratic three-dimensional paths before returning to cover. Bats typically take less than one second to detect, localize and capture such insects. We used high speed stereo infra-red videography to study the three dimensional flight paths of the big brown bat, Eptesicus fuscus, as it chased erratically moving insects in a dark laboratory flight room. We quantified the bat's complex pursuit trajectories using a simple delay differential equation. Our analysis of the pursuit trajectories suggests that bats use a constant absolute target direction strategy during pursuit. We show mathematically that, unlike CB, this approach minimizes the time it takes for a pursuer to intercept an unpredictably moving target. Interestingly, the bat's behavior is similar to the interception strategy implemented in some guided missiles. We suggest that the time-optimal strategy adopted by the bat is in response to the evolutionary pressures of having to capture erratic and fast moving insects.

A rodent model of syncope: the effects of a CRH antagonist

Vasovagal syncope is accompanied by profound bradycardia, hypotension, and subsequent unconsciousness. Male Sprague Dawley rats exhibited these cardiovascular changes in response to swim stress; 50% of rats exposed to a cylindrical tank filled with 30 cm of 25°C water sank below the surface and failed to rise, requiring rescue. Sinking rats exhibited more severe bradycardia within 30 minutes of water immersion compared with non-sinkers (average minimum HR (bpm) ±SEM; 143±13 vs. 247±14). Cardiac vagal activity, as measured by PR interval, was also elevated to a greater extent in rats that sank; PR (msec ±SEM) increased from 51±1 to 76±1.5 in non-sinking and to 95±3.5 in sinking rats. Blood pressure changes also suggest sinking may be a manifestation of experimentally-induced syncope in rodents; mean arterial pressure dropped by 40 (±6) mmHg 10 seconds prior to sinking, whereas this effect failed to occur in non-sinkers. Antalarmin (32 mg/kg), a non-peptidic CRH-1 receptor antagonist, produced extreme bradycardia (135±11 bpm) and elevated vagal activity (PR: 106±4 msec) during water exposure, leading to sinking in all rats. The cardiovascular and behavioral consequences that led to sinking in untreated and antalarmin-treated rats were blocked by methylatropine confirming a vagally-mediated action at the sinoatrial node. We conclude that antalarmin facilitates these syncope-like cardiovascular events, and we suggest that differences in CRH dynamics may be related to disposition to syncope. Research supported by USPHS Grants DA14349 and GM07767

フラップ式水門の浮上・沈降挙動の解析

A flap-type gate for protecting against storm surge and tsunami is the mobile barrier hinged along a sea-bottom axis. Present paper describes the motion characteristics of the gate rising to the water surface or sinking to the bottom. Extensive experiments are performed with the scale model of the rising or sinking gate in a water tank. The effects of the air chamber volume in the gate and the side wall beside the gate on the motions are investigated.Further, a simple mathematical model is derived for the dynamics of rising motion of the gate. The rising motion predicted numerically using the mathematical model compares well with experiment motion, if the coefficients for the equation of the motion in the mathematical model can be suitably determined.

Dual Gas Lift in Wells With Downhole Water Sink Completions

Abstract Downhole Water Sink (DWS) technology controls water coning in dual-completed wells by concurrently producing water from the bottom completion below the oil-water contact, and oil from another completion at the top of the oil sand. It has been shown that DWS improves well productivity, increases oil recovery, and could produce oil-free water for direct injection or overboard dumping offshore. To date, DWS has been applied in natural flow wells or wells where a downhole pump can be easily installed. However, in many areas, such as the Louisiana Gulf Coast and Venezuela where water coning is commonplace, the only production method is gas lift. This paper presents a feasibility study and a design method for dual gas lifting in DWS wells. The design employs a two-tier nodal analysis for several combinations of two tubing strings- one for oil and a second one for water-installed in a production casing. First, nodal analysis is performed separately for the water and oil legs in order to define their operational range. Then, the two solutions are combined and coupled with the Inflow Performance Window (IPW) describing the operational domain (top inflow rate vs. bottom inflow rate) of the well. Using the new method, a simulation study was conducted using data from actual wells. The results indicate that the gas lift would limit the performance of DWS wells. Moreover, the design can be optimized for maximum production of oil with controlled water withdrawal from the bottom completion. Limitations such as maximum gas injection rate, or injection gas pressure, are discussed. Also, this paper presents an example of a theoretical performance of a DWS well with gas lift. Dual Gas Lift-State of the Art Gas lift is a flexible method. It is possible to use it in wells of 0.159 m3 (a few barrels) per day, or wells of 159 m3 (a thousand barrels) per day. There are several methods of producing hydrocarbons using gas lift, but continuous gas lift is most common. Presently, there are at least 1,500 wells in Venezuela producing by intermittent gas lift. Also, single well completions are the most used gas lift installations around the world. For any type of gas lift method, there is a maximum production rate, which is a function of depth, reservoir, completion, and surface conditions. This maximum production requires a specific optimized rate of gas injection. Any additional gas injection rate would result in an oil production rate smaller than the maximum rate. To optimize gas lift for a given well, which includes the selection of tubing strings, size limitations, and maximum available gas flow rate, it is necessary to find the best depth of injection point and the gas injection pressure. Although dual gas lift has been theoretically developed, it has not been practiced very much since single well completions are most commonly used around the world. In fact, only a few field cases of dual gas lift have been reported in the literature(1–8).

Wind-Induced Circulation in Semienclosed Homogeneous, Rotating Basins

Abstract The wind-induced circulation over laterally varying bathymetry was investigated in homogeneous systems using the three-dimensional Regional Ocean Model System (ROMS). The investigation focused on the influence of the earth’s rotation on the lateral distribution of the flow, with particular emphasis on the transverse circulation. Along-basin wind stress with no rotation caused a circulation dominated by an axially symmetric transverse structure consisting of downwind flow over the shoals and upwind flow in the channel along the whole domain. Transverse circulation was important only at the head of the system where the water sank and reversed direction to move toward the mouth. The wind-induced flow pattern under the effects of the earth’s rotation depended on the ratio of the maximum basin’s depth h to the Ekman depth d. The solution tended to that described in a nonrotating system as h/d remained equal to or below 1. For higher values of h/d, the longitudinal flow was axially asymmetric. Maximum downwind flow was located over the right shoal (in the Northern Hemisphere, looking downwind). The transverse component of velocity described three gyres. The main gyre was clockwise (looking downwind) and occupied the entire basin cross section, as expected from the earth’s rotation and the presence of channel walls. The other two gyres were small and localized and were linked to the lateral distribution of the along-channel velocity component, which in turn was dictated by bathymetry. These results compared favorably with a limited set of observations and are expected to motivate future measurements.

The transition of a freshwater karst aquifer to an anoxic marine system

Jewfish Sink is located in the shallow seagrass flats of the Gulf of Mexico in west central Florida. Jewfish Sink was a submarine spring until the drought of 1961–1962 when it ceased flowing. Today, the sink is an anaerobic marine basin and provides the opportunity to study the implications of saltwater intrusion in coastal karstic areas. The biogeochemistry of Jewfish Sink was studied from summer 2001 through spring 2004. A distinct feature of the sink is the uniform cold temperature (16–17°C) of the deeper anoxic water that does not match groundwater found nearshore or onshore (22–24°C). There are four zones within the sink: oxic zone, transition zone, upper anoxic zone, and anoxic bottom water. The anoxic bottom water does not mix with water from above but may be linked to deep Gulf shelf water through ancient aquifer conduits. The other three zones vary seasonally in oxygen, salinity, and temperature because of limited mixing in the winter due to cooding and sinking of surface water. The walls of the anoxic zones have characteristic microbial mats that are found in other sulfidic karstic features in the area. Bacterial activity appears to be carbon, limited in the anoxic zones where sulfate reduction appears to be the major metabolic process. The reduction of sulfate to sulfide appears to be driven by irregular influexes of organic matter including macroalgae, horseshoe crabs, and stingrays that become entrapped within the sink. Bacterial activity in the oxic zones appears to be phosphate limited. Although the system is partially isolated from the overlying marine ecosystem, organic input from above drives the bacterial anaerobic ecosystem, resulting in a sulfide pump. In this model, sulfide percolates up through the karst and removes oxygen from the overlying sediment, which has likely caused changes in the shallow benthic ecosystem. Jewfish Sink appears to be part of an extensive anoxic subterranean estuary that extends under parts of at least three coastal counties in Florida and serve as a model for the effects of rising sea levels or aquifer mining.

Temporal and spatial variations in the geochemistry of major and minor particulate and selected dissolved elements of Thermaikos Gulf, Northwestern Aegean Sea

The objectives of this study were to examine both spatial and temporal changes of particulate major elements and minor metals, as well as dissolved Mn and Cd, in the waters of Thermaikos Gulf. Collections of water and suspended particulate matter (SPM), as depth profiles (5–8 depths), were undertaken at 10 principal stations, essentially on a N–S traverse of the western side of the Gulf. One of the principal aims of the study was to observe if there was any change in the patterning of the elements between the three occupations of the stations: (a) in September 2001, immediately before the commencement of trawling; (b) in October 2001, whilst fishing was active; and (c) in winter/early spring conditions (February 2002), when fishing was still active, but after a change of river/atmospheric conditions. Bottom (∼20 m) waters were dominated by sediment resuspension; this was identified by concentration changes in the aluminosilicate elements (e.g. Al, Ti, K, Fe) of the SPM. A two- to three-fold increase occurred between September and October, caused probably by trawling; this was sustained at the offshore stations, in February. During February, the western inshore stations showed little sediment resuspension, caused by extreme winter cooling and the sinking of water. Consequently, a N–S density discontinuity existed at all water depths, which prevented the thermohaline cyclonic circulation from penetrating into the western seaboard of the Gulf. The distribution of dissolved and particulate Mn in the lower waters was due to redox cycling of the element at the benthic boundary; this was more intense in the north, where the organic supply was higher. Biogenic element concentrations and Ca/Al, Si/Al ratios showed no evidence that trawling activity promoted higher biological production. Strong correlations of Co, Cr, Ni and V, with Al and K, showed that these elements were associated strongly with detrital aluminosilicates. However, the variable association of Cd, Pb and Zn, with K (and Al), especially in the upper waters, implied an anthropogenic source derived from the rivers and the city of Thessaloniki. Examination of the Kd's of Cd showed a two-order of magnitude decrease with depth, caused by resuspension and possible advection of relatively unpolluted sediments, into the western Gulf.

Mixing Associated with Sills in a Canyon on the Midocean Ridge Flank*

Abstract To close the global overturning circulation, the production and sinking of dense water at high latitudes must be balanced elsewhere by buoyancy gain and upward vertical motion. Hydrographic and microstructure observations from the Brazil Basin in the South Atlantic Ocean indicate that most of the abyssal mixing there takes place on the topographically rough flank of the midocean ridge. In previous studies it has been suggested that the high level of abyssal mixing observed on the ridge flank is primarily caused by breaking internal waves forced by tidal currents. Here, the results from a detailed analysis of velocity, hydrographic, and microstructure data from a ridge-flank canyon are presented. Two-year-long current-meter records indicate that within the canyon there is a significant along-axial mean flow down the density gradient toward the ridge crest. Five hundred meters above the canyon floor the kinetic energy in the subinertial band exceeds that associated with the semidiurnal tides by approximately a factor of 2. The mean dissipation of kinetic energy inside the canyon exceeds that above the ridge-flank topography by approximately a factor of 5. The largest dissipation values were observed downstream of a narrow, 1000-m-high sill that extends across the full width of the canyon. Along the entire canyon, there is a strong association between the presence of sills and along-axial density gradients, while there is no similar association between the presence of depressions and density gradients. Together, these observations suggest that sill-related mixing contributes at least as much to the diapycnal buoyancy flux in the canyon as tidally forced internal-wave breaking, which is not expected to be associated preferentially with sills. While only ≈15% of the interfacial area between Antarctic Bottom Water and North Atlantic Deep Water in the Brazil Basin lie inside canyons, the available data suggest that approximately one-half of the diapycnal buoyancy fluxes take place there. In comparison, the region above the ridge-flank topography accounts for about one-third of the buoyancy fluxes. The apparent importance of sill-related processes for mixing in ridge-flank canyons is therefore of global significance, especially considering that such canyons occur on average every 50 km along 2/3 of the global midocean ridge system, and that sills partially block the canyon axes every few tens of kilometers.

Incremental Recovery Using Dual- Completed Wells in Gas Reservoirs With Bottom Water Drive: A Feasibility Study

Abstract Water drive reduces gas recovery through the mechanism of water coning, which results in liquid loading that kills the wells. Installation of a Downhole Gas Water Separator (DGWS) in the well may prevent liquid loading. This paper presents another solution to this problem: a dual-completed well with downhole water sink (DWS) drainage and injection installation. DWS wells are different from DGWS wells by the inclusion of a second bottom completion that controls water outside the well and prevents a commingled inflow of gas and water to the top completion. DWS wells have been successfully tested in oil reservoirs. This study analyzes the DWS concept for gas wells by comparing simulated performances of a conventional well and a DWS well. The simulation runs were made over a broad range of the initial reservoir pressure and permeability values for a gas reservoir with a large associated aquifer. Also included is a comparison between DGWS and DWS wells at selected conditions. The results demonstrate the considerable advantages of dual completion over conventional wells in low-pressure (subnormal), tight (1 md) reservoirs-a 2.6 fold recovery increase before the wells are killed by excessive water production. The advantage, however, reduces to 10% for a reservoir with normal pore pressure gradient and a permeability of 10 md, and almost disappears for a permeability of 100 md and abnormal reservoir pressure. When compared to DGWS wells, the final gas recovery of DWS wells is the same, but DWS produces the gas 35% sooner than DGWS. The study also identifies the best DWS completion design where top completion is used only for gas production, and bottom completion for inverse gas coning, gravity separation, and water injection. Introduction Water production reduces gas recovery by shortening the well's life. Water could invade the gas well and kill it when a lot of gas may remain in the reservoir. Various concepts and techniques have been used to solve the water-loading problems. Hutlas and Granberry(1) discussed the techniques used in Kansas, Northwestern Oklahoma, and the Texas Panhandle: pumping units, liquid diverters, gas lift, and a concentric dual-tubing string. They concluded that the pumping units are best suited for shallow gas fields with very low permeability, while a combination of liquid-diverter and gas-lift installation would perform best in deeper, higher-pressure fields. Libson and Henry(2) discussed the methods used to control liquid loading in the tight, low-gas rate reservoirs in the Intermediate Shelf area of Southwest Texas: pumping units, plunger lift, a small concentric dual-tubing string, soap injection, and flow controllers. They found the plunger lift and the small concentric dual-tubing string to be effective in wells with low water rates, while pumping units performed best when the liquid rate exceeded 10 BWPD. Stephenson, Rousen, and Rosenzweig(3) evaluated different methods for dewatering (unloading) gas wells in the Box Church Field-a high water-cut gas reservoir in Texas. The methods include rod pumps, soap sticks, swabbing, coiled tubing/nitrogen, venting, plunger lift, and gas lift.

THE DYNAMICS OF ORIMULSION IN WATER WITH VARYING ENERGY, SALINITY AND TEMPERATURE

ABSTRACT Orimulsion is an oil-in-water emulsion of Venezuelan bitumen. Orimulsion was found to behave predictably in salt (33°/oo NaCl) and fresh water, driven by buoyancy to rise in salt water and sink in fresh water; but behaviour in brackish water (20°/oo NaCl) was difficult to predict. Temperature has also been indicated as having an influence on Orimulsion behaviour. The current study extended experimentation down to lower temperatures, and a variety of mixing energies. This study resulted in new information on the behaviour of Orimulsion spills in salt, fresh, and brackish water with salinity values of 20 and 33 degrees at temperatures of 5 and 15 degrees Celsius. Energy was varied by adjusting the applied rotational field and measurement with thermal probes. Depletion rates and characteristics were determined by adding Orimulsion to a 300-L tank of water, taking a time series of samples, and determining the concentration of bitumen and the particle size distribution. Changes in bitumen concentration and particle size distribution as a function of time were also measured. Using these data, simple equations were developed to describe and predict the concentration of bitumen in the water column as a function of time. Similarly nomograms showing the amount of oil on the bottom and on the water surface are presented.

Day and night wind drift and evaporation losses in sprinkler solid-sets and moving laterals

Wind drift and evaporation losses (WDEL) represent a relevant water sink in sprinkler irrigation, particularly in areas with strong winds and high evaporative demand. The objectives of this paper include: (1) characterize WDEL under day and night operation conditions for solid-set and moving lateral configurations; (2) propose adequate predictive equations; and (3) prospect the effect of sprinkler irrigation on the meteorological variables and on the estimates of reference evapotranspiration. A total of 89 catch can irrigation evaluations were performed in both irrigation systems and under day and night conditions. Different predictive equations of WDEL were proposed for combinations of the two irrigation systems and the two operation times. The equations were selected based on their capability to explain and predict WDEL. Most equations use wind speed alone as an independent variable, although some use relative humidity or combinations of both variables plus air temperature. In the semi-arid meteorological conditions of Zaragoza (Spain), the average WDEL for the solid-set were 15.4 and 8.5% during day and night irrigations, respectively. For the experimental moving lateral, losses amounted to 9.8% during the day and 5.0% during the night. The effect of sprinkler irrigation on the meteorological variables was moderate, with small increases in relative humidity (3.9%) and decreases in air temperature (0.5 °C) during the irrigation event and a few minutes afterwards. Consequently, reference evapotranspiration, estimated by the Penman-Monteith method, decreased during the irrigation event by 0.023 mm h −1 on the average. This decrease represents 2.1% of WDEL, suggesting that the WDEL do not significantly contribute to satisfy crop water requirements, and therefore constitute a consumptive water loss.

The role of vegetation patterns in structuring runoff and sediment fluxes in drylands

AbstractThe dynamics of vegetation‐driven spatial heterogeneity (VDSH) and its function in structuring runoff and sediment fluxes have received increased attention from both geomorphological and ecological perspectives, particularly in arid regions with sparse vegetation cover. This paper reviews the recent findings in this area obtained from field evidence and numerical simulation experiments, and outlines their implications for soil erosion assessment. VDSH is often observed at two scales, individual plant clumps and stands of clumps.At the patch scale, the local outcomes of vegetated patches on soil erodibility and hydraulic soil properties are well established. They involve greater water storage capacity as well as increased organic carbon and nutrient inputs. These effects operate together with an enhanced capacity for the interception of water and windborne resources, and an increased biological activity that accelerates breakdown of plant litter and nutrient turnover rates. This suite of relationships, which often involve positive feedback mechanisms, creates vegetated patches that are increasingly different from nearby bare ground areas. By this way a mosaic builds up with bare ground and vegetated patches coupled together, respectively, as sources and sinks of water, sediments and nutrients.At the stand scale within‐storm temporal variability of rainfall intensity controls reinfiltration of overland flow and its decay with slope length. At moderate rainfall intensity, this factor interacts with the spatial structure of VDSH and the mechanism of overland flow generation. Reinfiltration is greater in small‐grained VDSH and topsoil saturation excess overland flow. Available information shows that VDSH structures of sources and sinks of water and sediments evolve dynamically with hillslope fluxes and tune their spatial configurations to them.Rainfall simulation experiments in large plots show that coarsening VDSH leads to significantly greater erosion rates even under heavy rainfall intensity because of the flow concentration and its velocity increase. Copyright © 2005 John Wiley & Sons, Ltd.

Physically-based global downscaling climate change projections for a full century

A global atmosphere/land model with an embedded subgrid orography scheme is used to simulate the period 1977-2100 using ocean surface conditions and radiative constituent concentrations for a climate change scenario. Climate variables simulated for multiple elevation classes are mapping according to a high-resolution elevation dataset in ten regions with complex terrain. Analysis of changes in the simulated climate leads to the following conclusions. Changes in precipitation vary widely, with precipitation increasing more with increasing altitude in some region, decreasing more with altitude in others, and changing little in still others. In some regions the sign of the precipitation change depends on surface elevation. Changes in surface air temperature are rather uniform, with at most a two-fold difference between the largest and smallest changes within a region; in most cases the warming increases with altitude. Changes in snow water are highly dependent on altitude. Absolute changes usually increase with altitude, while relative changes decrease. In places where snow accumulates, an artificial upper bound on snow water limits the sensitivity of snow water to climate change considerably. The simulated impact of climate change on regional mean snow water varies widely, with little impact in regions in which the upper bound on snow water is the dominant snow water sink, moderate impact in regions with a mixture of seasonal and permanent snow, and profound impacts on regions with little permanent snow.

Assessment of Down-Hole Water Sink Technology for Controlling Water Inflow at Petroleum Wells

Water inflow to petroleum wells hampers production of oil or gas leading to early shut downs of the wells without sufficient recovery of hydrocarbons in place. Downhole water sink (DWS) is a completion/production technique for producing water-free hydrocarbons with minimum amount of water from reservoirs with bottom water drive and strong tendency to water coning. DWS eliminates water invasion to hydrocarbon production by employing hydrodynamic mechanism of coning control in situ at the oil-water or gas-water contact. The mechanism is based upon a localized water drainage generated by another well completion (downhole water sink) installed in the aquifer beneath the oil/water or gas/water contact. The paper summarizes the development and state-of-the-art of DWS technology. Presented are results from theoretical studies, physical and numerical experiments, and field projects to date. It is demonstrated that DWS could increase recovery and control water production in vertical and horizontal oil wells—with natural flow, downhole pumps or gas lift, and in the gas wells producing from low-pressure tight gas reservoirs. To date, DWS has been used in reservoirs with bottom water. Moreover, in principle, the technology might also be used in the dipping reservoir structures with encroaching side-water.

Testing sediment biological effects with the freshwater amphipod Hyalella azteca: the gap between laboratory and nature

The freshwater amphipod, Hyalella azteca, is widely used in laboratory sediment toxicity and bioaccumulation tests. However, its responses in the laboratory are probably very different from those in the field. A review of the literature indicates that in its natural habitat this species complex is primarily epibenthic, derives little nutrition from the sediments, and responds primarily to contaminants in the overlying water column (including water and food), not sediment or porewater. In laboratory sediment toxicity tests H. azteca is deprived of natural food sources such as algal communities on or above the sediments, and is subjected to constant light without any cover except that afforded by burial into the sediments. Under these constraining laboratory conditions, H. azteca has been reported to respond to sediment or porewater contamination. In nature, contamination of overlying water from sediment is less likely than in the laboratory because of the large, generally non-static sink of natural surface water. H. azteca does not appear to be the most appropriate test species for direct assessments of the bioavailability and toxicity of sediment contaminants, though it is probably appropriate for testing the toxicity of surface waters. Toxic and non-toxic responses will be highly conservative, though the latter are probably the most persuasive given the exposure constraints. Thus H. azteca is probably a suitable surrogate species for determining sediments that are likely not toxic to field populations; however, it is not suitable for determining sediments that are likely toxic to field populations.

Offshore export versus in situ fractionated mineralization: a 1-D model of the fate of the primary production of the Rías Baixas (Galicia, NW Spain)

A linked hydrodynamic mineralization model is described and used to evaluate offshelf fluxes and fractionated mineralization of particulate phytogenic materials in the coastal upwelling system of the Rías Baixas (NW Spain), under three different typical situations of the upwelling season. The simulations made indicate that the intensity of upwelling controls: (a) net community production (NCP); (b) particulate organic matter (POM) accumulation; (c) in situ mineralization; and (d) matter export in the ‘Rías Baixas.’ Under strong upwelling conditions, there is an important horizontal offshelf flux, having only a small mineralization effect on NCP; if weak upwelling conditions are simulated, POM export is dramatically reduced and in situ mineralization is significantly enhanced; finally, under average upwelling conditions, the offshelf export of POM is about one third of the POM accumulation inside the domain, evidencing its importance in the productivity enhancement of near-shore areas. According to our sensitivity tests, the net vertical velocity (water velocity plus sinking velocity) has a critical role in the C/N/P stoichiometry of POM.

Attenuation of water coning using dual completion technology

Water coning causes a reduction of oil production and an increase of production costs. Dual completion (downhole water sink) is one of the methods adopted to attenuate water coning. This work describes numerical results associated with this completion technique. The water cone shape and water breakthrough time are investigated to define the mechanism and performance of this technical procedure. The numerical results show that dual completion deforms the shape of the cone. For instance, the top of the water–oil interface is shifted away from the well yielding (under high water production rates) oil breakthrough into water perforations. The water breakthrough is proportional to dimensionless density difference and horizontal permeability and inversely proportional to oil production rate, mobility, and anisotropy ratios. High oil production rates yield elevation of water coning height that intercepts oil flow. Paradoxically, high production rate at water sink is not recommended, the improvement of water breakthrough begins when dimensionless density difference is greater than 0.05. The dual completion technique delays water breakthrough time (BT*). In general, the BT* is delayed by two times that of single completion and critical oil rate is augmented compared to single completion.

Causes and consequences of extreme Permo-Triassic warming to globally equable climate and relation to the Permo-Triassic extinction and recovery

Permian waning of the low-latitude Alleghenian/Variscan/Hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high-CO 2 atmosphere and global warming. The correspondingly reduced delivery of nutrients to the biosphere caused further increases in CO 2 and warming. Melting of polar ice curtailed sinking of O 2- and nutrient-rich cold brines while pole-to-equator thermal gradients weakened. Wind shear and associated wind-driven upwelling lessened, further diminishing productivity and carbon burial. As the Earth warmed, dry climates expanded to mid-latitudes, causing latitudinal expansion of the Ferrel circulation cell at the expense of the polar cell. Increased coastal evaporation generated O 2- and nutrient-deficient warm saline bottom water (WSBW) and delivered it to a weakly circulating deep ocean. Warm, deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling WSBW. With the loss of polar sinking, the ocean was rapidly filled with WSBW that became increasingly anoxic and finally euxinic by the end of the Permian. Rapid incursion of WSBW could have produced ∼20 m of thermal expansion of the oceans, generating the well-documented marine transgression that flooded embayments in dry, hot Pangaean mid-latitudes. The flooding further increased WSBW production and anoxia, and brought that anoxic water onto the shelves. Release of CO 2 from the Siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse. Increasingly frequent and powerful cyclonic storms mined upwelling high-latitude heat and released it to the atmosphere. That heat, trapped by overlying clouds of its own making, suggests complete breakdown of the dry polar cell. Resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest Permian coal forests that could not migrate any farther poleward because of light limitations. Loss of water stored by the forests led to aquifer drainage, adding another ∼5 m to the transgression. Non-peat-forming vegetation survived at the newly moist poles. Climate feedback from the coal-forest extinction further intensified warmth, contributing to delayed biotic recovery that generally did not begin until mid-Triassic, but appears to have resumed first at high latitudes late in the Early Triassic. Current quantitative models fail to generate high-latitude warmth and so do not produce the chain of events we outline in this paper. Future quantitative modeling addressing factors such as polar cloudiness, increased poleward heat transport by deep water and its upwelling by cyclonic storms, and sustainable mid-latitude sinking of warm brines to promote anoxia, warming, and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data.

Saltier Water Sink Deep

Saltier Water Sink Deep