Volume Flux Of Water Research Articles

Nitrate sources and sinks in Elkhorn Slough, California: Results from long-term continuous in situ nitrate analyzers

Nitrate and water quality parameters (temperature, salinity, dissolved oxygen, turbidity, and depth) were measured continuously with in situ NO3 analyzers and water quality sondes at two sites in Elkhorn Slough in Central California. The Main Channel site near the mouth of Elkhorn Slough was sampled from February to September 2001. Azevedo Pond, a shallow tidal pond bordering agricultural fields further inland, was sampled from December 1999 to July 2001. Nitrate concentrations were recorded hourly while salinity, temperature, depth, oxygen, and turbidity were recorded every 30 min. Nitrate concentrations at the Main Channel site ranged from 5 to 65 mM. The propagation of an internal wave carrying water from ;100 m depth up the Monterey Submarine Canyon and into the lower section of Elkhorn Slough on every rising tide was a major source of nitrate, accounting for 80-90% of the nitrogen load during the dry summer period. Nitrate concentrations in Azevedo Pond ranged from 0-20 mM during the dry summer months. Nitrate in Azevedo Pond increased to over 450 mM during a heavy winter precipitation event, and interannual variability driven by differences in precipitation was observed. At both sites, tidal cycling was the dominant forcing, often changing nitrate concentrations by 5-fold or more within a few hours. Water volume flux estimates were combined with observed nitrate concentrations to obtain nitrate fluxes. Nitrate flux calculations indicated a loss of 4 mmol NO3 m 22 d21 for the entire Elkhorn Slough and 1 mmol NO3 m22 d21 at Azevedo Pond. These results suggested that the waters of Elkhorn Slough were not a major source of nitrate to Monterey Bay but actually a nitrate sink during the dry season. The limited winter data at the Main Channel site suggest that nitrate was exported from Elkhorn Slough during the wet season. Export of ammonium or dissolved organic nitrogen, which we did not monitor, may balance some or all of the NO3 flux.

Study of Liquid Pool Fire Suppression with Water Mists by Cone Calorimeter

An experimental study of the pool fire suppression with water mists was performed in this paper. Spatially resolved droplet size, velocity distributions, and volume flux of the fine water mist has been obtained by LDA/APV system. A method to correct for the presence of droplets is presented and used to determine the heat release rate using a cone calorimeter system, the effects of water mist application on the heat release rate for liquid pool fires were studied. It was found that the volume flux of the water spray mostly determined the liquid pool fire-behavior. For the current experimental conditions, the flame was enlarged when lower volume flux of water is used, and suppressed significantly when higher volumes of water are used. Two opposing mechanisms compete when water mists are applied, which is more complex than the halon agents, such as 1301. The combustion enhancement becomes insignificant when water mists with the proper characteristics such as adequate volume flux are applied to the diffusion flame in a confined space.

Experimental study on the interaction of fine water spray with liquid pool fires

An experimental study of the interaction of a fine water spray with liquid pool fires was performed. Spatially resolved droplet size, velocity distributions, and volume flux of the fine water spray have been obtained in two types of pressure-atomized fine spray, using LDA/APV technology. A method to correct for the presence of droplets is presented and used to determine the heat release rate using a cone calorimeter system, the effects of water spray application on the heat release rate for liquid pool fires were studied. It was found that the volume flux of the water spray is an important factor to determine the liquid pool fire behavior. For the current experimental conditions, the flame was enlarged when lower volume flux of water is used, and suppressed significantly when larger volumes of water are used. Two opposing mechanisms compete when water sprays are applied, which is more complex than the halon agents, such as 1301. The combustion enhancement becomes insignificant when water sprays with the proper characteristics such as adequate volume flux are applied to the diffusion flame in a confined space.

To What Extent Can Silviculture Enhance Sustainability of Forest Sites under the Immission Regime in Central Europe

Stand structure and tree species composition influence not only the volume flux of soil water but also the concentration of dissolved minerals in the soil solution. We found much higher element fluxes under spruce than under beech stands. This is mainly caused by different activities of nitrate in the soil solution and by different deposition rates of nitrogen and acids from the atmosphere which were ±60% lower in beech stands than in spruce stands. In old spruce stands, the acid output with the seepage water was more or less equal to the input, whereas in beech stands most of the acid deposition was buffered. The nitrogen balance in beech stands was characterized by a net uptake of about 60% to 75% of the input. In spruce stands only 40% of the nitrogen input was incorporated. In a clear-cut, a high mobilization rate of nitrate was found in the first 5 years, resulting in nitrate concentrations above the threshold for drinking water quality. The cutting of even a single tree in a spruce stand caused heavy mineralization and nitrification for at least 2 years, which indicates that the system is near nitrogen saturation.

The effects on water mass formation of surface mixed layer timedependence and entrainment fluxes

An air-sea buoyancy flux out of the ocean between the surface outcroppings of different isopycnals must be balanced by a convergence of advective and diffusive fluxes of buoyancy across those isopycnals (Walin, 1982; Tziperman, 1986; Garrett et al., 1995). For steady conditions, the diapycnal diffusive flux due to vertical mixing in the surface mixed layer is very small, so that the advective buoyancy flux dominates (Speer, 1993; Garrett et al., 1995). The associated advective buoyancy flux can then be used to estimate the volume flux of water out of the base of the surface mixed layer. The resulting thermodynamic algorithm provides a valuable estimate of water mass formation in the ocean. In contrast, for the time-dependent real ocean with horizontal and vertical gradients of the horizontal buoyancy gradient, diurnal and seasonal mixed layer deepening and entrainment in the presence of a buoyancy jump at the base of the mixed layer contributes to the annual volume flux out of the base of the deepest (wintertime) mixed layer. The mismatch between the predictions of the ideal algorithm and measured rates of water mass formation (Speer, 1997) may thus be partly due to mixed layer processes rather than diapycnal mixing in the thermocline.

Estimates of the transport through the East River, New York

The hydrodynamic characteristics of the East River, New York, which connects Long Island Sound to New York Harbor, have been investigated via a high‐resolution, topographically conformal and orthogonal curvilinear grid together with high‐quality acoustic Doppler current profiler measurements. The objective is to determine the volume flux of water through this important water body. The model was calibrated and validated through comparisons with measured salinities, water levels, current velocities, and data‐based estimates of volume flux. Detailed statistical analyses demonstrated that both the tidal and meteorological bands spanning inverse frequencies between 3 hours and 5 days were well simulated by the model. The climatological band (inverse frequencies greater than 5 days) did not exhibit uniformly good agreement because of the paucity of salinity and temperature measurements available for use as model forcing functions. Results from an 18‐month (1988 to 1989) simulation indicate that the net long‐term flux of water is directed out of Long Island Sound and toward New York Harbor. The total rate was found to be about 310 m3 s−1. At the eastern end of the East River near its confluence with Long Island Sound, the net flow was distinctly two‐layered with flows of about 260 m3 s−1 directed toward the sound in the surface layer and flows of approximately 570 m3 s−1 in the bottom layer directed toward New York Harbor. There appeared to be a 100 m3 s−1 monthly variation about the mean transport at the eastern end. However, on shorter timescales the transport reversed direction for days at a time.

Multiple states in doubly driven flow

It has been known since 1961 that if two components effect density, a convecting fluid may possess multiple stable states for the same boundary conditions. Until recently, analytical and numerical calculations have been conducted for application to climate models. Laboratory observations were absent. Experiments have now produced the anticipated multiple states and also give new insight into their physical nature. A new, wider range of applications to estuary and coastal water circulation is indicated. In the experiments a chamber of water was heated from below and exposed to a constant volume flux of salty water from above. This was connected to a large reservoir of fresh room temperature water through two horizontal tubes, one near the top and the other near the bottom. Parameters were such that the time constant for change of temperature was less than the time constant for change in salinity. The experiments confirmed the principal prediction of theory — that two states can exist for the same boundary conditions. The range of two stable states was mapped as a function of the temperature forcing for fixed salinity flux. For low thermal forcing, the salinity driven state was found. This had very slow exchange of warm and very salty water with the reservoir. Density due to salinity was greater than that from temperature. Above a critical forcing an additional state could exist. This possessed exchange with the reservoir in the opposite direction of warm and much lower salinity water above approximately 1.5 times the critical forcing, only the thermal state was found. A second example driven by stress and heat flux also exhibits multiple states. Two examples are analyzed.

Measurement of hydraulic conductivity in isolated arterioles of rat brain cortex

We have developed a new method for quantification of arteriolar hydraulic conductivity (Lp) from isolated rat brain vessels. The volume flux of water per unit surface area across the arteriole wall (Jv/S) was assessed from measurements of silicon oil drop movement within an occluded vessel at two to three pressures (between 20 and 70 mmHg); the Lp was derived from the slope of the relationship between Jv/S and applied pressure. Lp was measured in isolated cerebral arterioles 1) at room temperature (22 degrees C) without spontaneous vessel tone (control Lp; n = 11), 2) at room temperature with 10(-4) M adenosine (n = 5), and 3) at 37 degrees C with vessels dilated submaximally with 10(-4) M adenosine (n = 6). Lp at 22 degrees C without adenosine was 13.2 +/- 4.2 x 10(-9) (+/- SE) cm.s-1.cmH2O-1 for all vessels studied. Lp values ranged from 1.2 to 44.1 x 10(-9) cm.s-1.cmH2O-1 with a median value that was 5.9 x 10(-9) cm.s-1.cmH2O-1. Lp increased significantly (on average, 2.6-fold) with adenosine at 37 degrees C but not with adenosine at 22 degrees C. Control Lp bore no relationship to either the development of spontaneous tone or the diameter response to pH change, two recognized indicators of vessel viability.

EFFECTS OF WATER DEFICIT ON CIRCADIAN PATTERNS OF ROOT WATER FLUX IN HONEY LOCUST

The volume flux of water (Jv) through roots of 2-month-old honey locust seedlings (Gleditsia triacanthos var. inermis) was estimated by using applied hydrostatic pressure. Shoots were severed 8 cm above the root collar, and root systems were mounted in the lid of a pressure chamber with the cut stump protruding through a gasket. The chamber, filled with Hoagland solution, was pressurized to 0.34 MPa, and exudate was delivered from each root system to an electronic balance via an automated system. Jv was expressed on a fibrous-root dry weight basis and plotted over time for water-stressed seedlings and well-watered controls. A highly defined endogenous circadian rhythm in Jv was observed, regardless of treatment, with maximal and minimal fluxes occurring at mid-day and midnight, respectively; the rhythm continued for up to 90 h. Seedlings subjected to water stress exhibited an approximately 4-fold reduction in Jv at comparable points in the cycle. The severity of stress influenced both the amplitude and trajectory of the rhythm. Daily peaks of Jv decreased gradually over a 3-day period in both moderately-stressed and well-watered plants. In contrast, peak Jv from roots of severely-stressed plants increased by approximately 28% per day over the same time course. The electrical conductivity of the efflux also exhibited a highly defined rhythm which was phase-shifted from that of the Jv rhythm by approximately 12 h.

A study of the climatic system in the Barents Sea

The climatic conditions in the Barents Sea are mainly determined by the influx of Atlantic Water. A homogeneous wind-driven numerical current model was used to calculate the fluctuations in the volume flux of Atlantic Water to the Barents Sea which are caused by local wind forcing. The study period is from 1970 to 86. When compared with observed variations in temperature, ice coverage, and air pressure, the results show remarkably good agreement between all three parameters. The climate system of the Barents Sea is discussed with emphasis on the interrelations and feedback mechanisms between air, sea, and ice.

A study of the climatic system in the Barents Sea

The climatic conditions in the Barents Sea are mainly determined by the influx of Atlantic Water. A homogeneous wind-driven numerical current model was used to calculate the fluctuations in the volume flux of Atlantic Water to the Barents Sea which are caused by local wind forcing. The study period is from 1970 to 86. When compared with observed variations in temperature, ice coverage, and air pressure, the results show remarkably good agreement between all three parameters. The climate system of the Barents Sea is discussed with emphasis on the interrelations and feedback mechanisms between air, sea, and ice.

Hydraulic conductance and anatomy of roots of Vicia faba plants infected by Uromyces viciae-fabae

Infection of faba bean ( Vicia faba L.) by rust [ Uromyces viciae-fabae (Pers.) Shroet.] inhibited increases in the length of tap and primary lateral roots both in soil columns and in solution culture. In whole root systems exicsed from plants grown in solution culture, rust infection reduced volume flux of water slightly but increased hydraulic conductance (Lp) per unit area of root or of endodermal surface; these changes occurred over a range of imposed hydrostatic pressures and temperatures. Rust-induced increases in Lp occurred in tissue produced after infection, but not in tissue produced before infection, the sub-terminal segment. Examination of lateral roots from the upper 18 cm of the soil profile showed infection reduced root diameter and increased specific root length (cm root mg −1 dry weight). In tissues formed after inoculation, infection had no effect on the diameter of the cortex or the number of cortical cells along a radius. However, the diameter of the endodermal cylinder was reduced in both tap and lateral roots. Since radial resistance to water flow is the major component of total root resistance in faba bean, it is proposed that these changes were responsible for the increased Lp caused by infection.

Generalized calculus and its applications

This paper gives a simple development of generalized differentiation and integration with examples and applications. The concept of symmetric derivatives is discussed with examples and applications to complex potential functions. A comparison is made between ordinary and symmetric derivatives. Some important examples of continuous non‐differentiable functions are stated. The calculus of generalized functions and its physical significance are also presented. With a short historical development, the fractional calculus is discussed with examples and simple applications. The different approaches to derivatives and integrals of fractional orders are elaborated with illustrations. The use of the Laplace transforms for determining the fractional derivatives and integrals is discussed with simple examples. Some simple and important applications of fractional calculus to Abel's problem of isochrones, volume flux of water through a river dam, the heat conduction problem and the Rayleigh problem of unsteady boundary flows are investigated in detail.

Water transport in a cluster of closely packed erythrocytes at subzero temperatures

A one-dimensional model has been developed to describe the kinetics of water transport in a cluster of closely packed cells. For the case of human red blood cells, the intracellular medium has been treated as an ideal, hydrated, nondilute multicomponent electrolyte solution. Results show that the volume flux of water out of the interior cells of the cluster lags behind that of the exterior cells. At any given temperature (or time), the amount of water retained within a cluster of closely packed cells of a given type exceeds (on an overall percentage basis) the amount of water retained within a single isolated cell of the same type. For a given cooling rate the probability of intracellular ice nucleation at any given temperature will therefore be greater for cells in the interior of a cluster, and the survival signature for a cell cluster should peak at a cooling rate which is less than the corresponding optimal value for a single, isolated cell. These results are consistent with experimental observations.

The residual flow in a tidal stream

Consideration is given to the problem of the boundary conditions that must be specified when calculating the residual flow in a tidal stream. A particular example is discussed that relates to the tidal flow adjacent to a straight coastline. It is shown that the long-shore mean volume flux of water must be prescribed in order to determine the corresponding residual flow. A theory is given that relates to flows in water of non-uniform depth, and by considering a particular case, it is shown that this may have a profound effect upon the structure of the residual current system.

ANALYSIS OF THE FLOW INDUCED BY AIR-BUBBLE SYSTEMS

The pattern of vertical velocities induced by an orifice discharging air into water can be represented by Gaussian distribution curves with a linear spread in the vertical except for the regions near the orifice and close to the free surface. An analytical treatment considering the momentum-flux increase due to the buoyancy of the air together with experimental information about the spread of the velocity profiles and the mean rising speed of the air bubble stream, which has been obtained from velocity and density measurements over a wide range of conditions, leads to a complete description of the flow field. The ratio of the water volume flux to the air discharge rate, which has been proposed as an efficiency criterion, is now at hand as a function of depth and air supply for both single orifices and rows. The experimental evidence supports the analysis well and suggests that extrapolation to larger water depths and air supplies should be permissible, which would allow approximate predictions of the volume flux for any air-bubble system.

A Study of Currents in the Strait of Dover

As part of an investigation into the difference of absolute sea-level across the English Channel, a detailed series of measurements of currents at all depths was recently made in the Strait of Dover. The main object of the measurements was to relate the residual non-tidal flow of water to the voltage on a cross-channel cable generated by electromagnetic effects. Over 6000 readings of current strength and direction were made during ideally calm conditions. This paper describes the results of analysis of these measurements, which covers vertical current profiles and tidal components, besides the non-tidal flow. Distinction is made between mean current measured at a fixed depth or at the surface, and the mean volume flux of water which involves tidal variation of depth. A method of tidal analysis based on Fourier sums, which is convenient for use with an electronic computer, is outlined in the Appendix.