Top PDF Residence time of the Danshuei River estuary, Taiwan

Abstract The residence time of an estuary is defined in this study as the average time the initially existing water parcels reside in the system before they are flushed out. The residence time of the Danshuei River is calculated through a series of numerical experiments using a laterally integrated two-dimensional hydrodynamic eutrophication model (HEM-2D). The results show that the residence time is on the order of 1e2 days under the mean river flow to zero river flow condition, which is very short compared with most time scales of biogeochemical processes. A procedure is developed to quantify individual contribution to flushing by each of the three major physical transport mechanisms: tide, river discharge, and the density induced circulation. The results indicated that, in general conditions, tidal flushing exerts the greatest influence to the flushing of the Danshuei River estuary, while the density induced circulation hardly contributes any. Tidal transport contributes more than 50% of the flushing when river discharge is below its long- term mean. The suitability of applying the tidal prism method, the modified tidal prism methods, and the fraction of freshwater method in this estuary is also investigated. The relatively short residence time is likely to be one of the limiting factors that result in low phytoplankton biomass in spite of extremely high nutrient concentrations, and causes a significant fraction of pollutants to exert their effects in the coastal waters outside the estuary.

Because of the relatively large tidal range compared to the depth of the system, the residence time of the main stem estuary was found to be 2.2 days or less. [9] The estuarine portion of the river system runs through the capital City of Taipei, with a population of 6 million in its metropolitan area. Huge amounts of domestic wastewater, mostly untreated raw sewage, are discharged into the estu- ary daily. The water quality has been severely degraded for decades. Hypoxic/anoxic conditions commonly occur in the upper and middle reaches of the estuary during summer months. [10] Viable biological activities are observed only in the lowest reach of the estuary where the pollutant concen- trations are reduced as a result of dilution by seawater. [15] A three-year observational study of the system from 1998 to 2001 conducted by Taiwan’s Academia Sinica reported that the chlorophyll a concentration hardly exceeded 5 mg/m 3 . The primary production rate was on the order of 0.2 g C/m 3 /day. Zooplankton biomass was observed to range from 1 to 14 mg C/m 3 . If the amount of carbon fixed by the phytoplankton species is not transferred to the higher trophic level it is termed as nuisance species. Zooplankton play a pivotal role in the transfer of carbon from primary producer, such as phytoplankton, to higher consumers, such as fishes. However few studies have been conducted

For 3-D barotropic flow, the salt transport equation is uncoupled from the momentum equa- tions. A non-negative bottom friction coefficient is specified by the Manning–Chezy formula. If the advection terms are treated by an Eulerian–Lagrangian scheme with positive bottom friction, then the numerical scheme is unconditionally stable. For baroclinic flows, the density gradient terms are expressed explicitly in the momentum equations, and the solutions for the transport variables lagged by one time step are solved. In this case, the numerical scheme is subject to a weak stability condition due to the explicit treatment of the density gradient terms in the momentum equations. For stability, the integration time step must be chosen so that the propagation of internal wave must satisfy the Courant–Friedrich–Lewy (CFL) condition. In addition, the numerical scheme is also subject to a weak stability condition due to the explicit treat- ment of the horizontal diffusion in the momentum equations.

model run. Hourly measurements of water surface elevation at the Danshuei River mouth and daily average freshwater discharges upriver of the tidal limits were used for the boundary conditions. These conditions allow the investigation of the model response to the interaction of tidal forcing and varying river discharges. Fig. 5 shows computed surface elevation, together with field data at five locations. The comparison shows that the model can faithfully reproduce tidal propagation to within ±1.9 cm. An intensive survey was conducted by the Taiwan Water Resources Agency on May 5, 2000. Half-hourly measurements of water surface elevation and velocity were made continuously for 13 daylight hours. Fig. 6 shows the comparison of the time series data of the longitudinal velocity for May 5, 2000. Table 1 presents the mean absolute differences and root-mean- square differences between the computed and measured time series. Fig. 6 shows that there are discrepancies between model and field data when judging with point by point comparison. However, the model does prop- erly simulate the temporal variation of velocity in terms of current amplitude and phase. The calibrated and verified model has values of the Manning friction coefficient ranging from 0.026 to 0.035 for the Tahan River–

a Department of Applied Chemistry, National Chiao-Tung University, Hsin-Chu 30010, Taiwan b Department of Chemistry, University in Huntsville, Huntsville, Alabama, AL 35899, USA (Received: Sept. 28, 2013; Accepted: Dec. 23, 2013; Published Online: Apr. 14, 2014; DOI: 10.1002/jccs.201300491) Siegel’s analysis on membrane transport in the Laplace domain [J. Phys. Chem. 95 (1991) 2556] in terms of transmission matrix, T(s), has been extended to a more useful formulation. This is achieved by combin- ing uses of the matrix transport equations appropriate for void initial condition, or for saturated equilib- rium, or of Dirac delta functional type and the theorem det[T(s)] = 1. This formulation enables us to ex- pand T(s) in power series of the Laplace variable, s, with the expansion coefficients as the algebraic func- tions of the experimentally measurable transport parameters. Utility of the formulation is illustrated in the estimation of the experimentally inaccessible time moments for the first passage or residence times. It was also applied to the percutaneous drug delivery to obtain from the experimental data. The higher moments of the time lag or time lead using a graphic method.

Chung-Min Liao a a Department of Agricultural Engineering, National Taiwan University, Taipei, Taiwan R.O.C. To cite this Article Liao, Chung-Min'Use of residence time distribution for evaluation of gaseous pollutant volatilization from stored swine manure', Journal of Environmental Science and Health, Part B, 32: 1, 127 — 145

"Institute of Chemistry, Academia Sinica, Taipei, Taiwan Abstract The metal string complexes with di!erent metal ions and various lengths have been successfully synthesized and structurally characterized. The crystal and molecular structure of nonanickel complex [Ni9(l9-(peptea)4Cl2] which is the longest metal string at this moment will be reported. Crystal data for [Ni9(l9-(peptea)4Cl2](C2H4Cl2)10: Space group, monoclinic C 2/c, a"27.0453(6), b"42.6678(5), c"37.4268(6) A s , b"109.539(1)3, <"40702(1) As3, Z"12, RF"12% for the observed re#ections (I'2p(I)). The band structure calculation of in"nite one-dimensional metal chains of Ni II and CrII based on the structure of nonanickel complex will be presented. Finally, the metal string complexes [M IInL4X2] will be chemisorbed on the Ag or Au surface and the potential application of these complexes as a molecular metal wire will be demonstrated. ( 2000 Elsevier Science B.V. All rights reserved.

Irradiation of the signal at one doublet resulted in the change of the other doublet to a singlet, confirming that the protons of the amine group are nonequiva[r]

In this study, it is the flushing time of the entire tidal portion of the Tanshui River system we were in- vestigating, not just the portion of the river conforming to the [r]

Available online 22 April 2007 Abstract A three-dimensional, time-dependent, baroclinic, hydrodynamic and salinity model, UnTRIM, was performed and applied to the Danshuei River estuarine system and adjacent coastal sea in northern Taiwan. The model forcing functions consist of tidal elevations along the open boundaries and freshwater inflows from the main stream and major tributaries in the Danshuei River estuarine system. The bottom friction coefficient was adjusted to achieve model calibration and ver- ification in model simulations of barotropic and baroclinic flows. The turbulent diffusivities were ascertained through com- parison of simulated salinity time series with observations. The model simulation results are in qualitative agreement with the available field data.

A BSTRACT : The net, long-term transport of materials in estuaries is governed primarily by the residual (or tidally averaged) circulation in the system. Knowledge of the residual circulation is essential for predicting the transport of algal patches, debris, and pollutants of concern in an estuary. A real-time, two-dimensional, laterally averaged hydrodynamic model is used to analyze residual current and salinity distributions in the Tanshui River estuary. The model results were filtered to arrive at the subtidal, or residual quantities. The characteristic two- layered estuarine circulation prevails for most of the time at Kuan-Du station near the river mouth. Though the circulation strengthens with increasing river discharge at low flow, its strength decreases at moderate river discharge and the two-layered circulation ceases at moderately high flow. This implies a weak trapping capacity in the estuary. At the upriver stations where salinity is lower, strength of circulation generally decreases with increasing river discharge. The response of residual velocity to the spring-neap cycle indicates stronger residual circulation during neap tide than spring tide.

Department of Fisheries and Oceans, Beddford Institute of Oceanography Post Office Box 1006, Dartmonth, Nova Scotia B2Y 4A2, Canada Abstract.—In Taiwan, there has been a shortage of local Japanese eel Anguilla japon- ica elvers for culture, so culturists have imported American eel Anguilla rostrata (Le Sueur) elvers from North America to meet their needs. From 1999 to 2001, six exotic adult American eels were found in the estuary of the Kaoping River of Taiwan that had escaped from aquaculture ponds as young eels and stayed in the river until silvering.

The third batch was heated constantly to maintain a temperature of 50±1 °C for three days, and stirred when the temperature is lower than the designated temperature, while other conditio[r]

Abstract Five species of larval engraulids, Engraulis japonica Schlegel, Encrasicholina punctifer Fowler, E. heteroloba (Ruppell), Stolephorus insularis Hardenberg, and Thryssa dussumieri (Valenciennes), were found in coastal waters off the Tanshui River Estuary, northern Taiwan during the period from May 1992 through November 1993. Their sizes ranged between 8 and 46 mm SL. Comparing the meristics, morphometrics, and pigmentations of the 5 species, we found pigment patterns on the ventral side of the larvae that can be used as a key character to discriminate these species.

A preliminary study on species composition and seasonal abundance of fish eggs and larvae from the coastal waters adjacent to the Tanshui River estuary, Taiwan, J. Sha[r]

Press Release 23 April 2002 C ROSS -B OUNDARY S TUDY ON P OLLUTED P EARL R IVER E STUARY A 3-year study by the Hong Kong University of Science and Technology (HKUST) and its Chinese Mainland partners on pollution in the Pearl River Estuary has been completed, laying a solid foundation for continuing cross-border environmental investigation.

© 2000 American Institute of Physics. 关S0021-9606共00兲50810-1兴 INTRODUCTION Diffusion is a ubiquitous process in the physical world. It is of great theoretical importance with a multiplicity of applications in such diverse fields as chemical reaction, 1,2 electrochemistry, 3 colloidal science, 4 solid state physics, 5 semiconductor-device fabrication and operation, 6 physical ceramics, 7 biophysics, 8 drug delivery, 9 and environmental science. 10 One way to characterize a diffusion system in which a particle initially located at x ⫽x 0 within a finite do- main is by means of the probability density of the time re- quired for the particle escaping from this domain for the first time, i.e., the distribution of the first-passage time. 11,12 Com- plete information of the probability distribution can be ob- tained only for some particular cases. Thus, one is usually forced to resort to the time moments. Of the most important among them is the first moment, i.e., the mean first passage time. The latter is often related to the reciprocal of a 共first- order 兲 rate constant if a chemical reaction is modeled by diffusion over a potential. 12 In order to have more informa- tion about the distribution, higher moments are required. For example, without the second moment the dispersion of the distribution cannot be estimated. 13

Abstract The ability of a simple linear response model is evaluated to explain the mixing e0ciencies in an incomplete mixing ventilated airspace. Data interpretation and mean residence time calculation for a speci2ed output concentration pro2le can also be evaluated. The residence time distribution (RTD) functions take the form of the two-parameter gamma distribution and account for di!erent mixing types such as complete mixing, piston 4ow (no mixing), incomplete mixing, and various combinations of the above types. In these combinations, the di!erent mixing types simulated by di!erent RTDs conceptually represent air4ow regions in series. The mixing e0ciency was introduced to characterize the extent or degree of mixing in a ventilation system in that mixing e0ciency equals zero for piston 4ow (no mixing), unity for complete mixing, and a value in between these two extremes for incomplete mixing. An environmental chamber experiment was conducted to generate several output pro2les to evaluate the applicability of the model. Carbon dioxide was employed as the tracer gas. Our results show that an overall root-mean-squared error value of 8:64 ± 5:25 ppm is low, indicating that the combination mixing patterns are generally found to be minimally biased and give better 2tting than other simpler mixing patterns. Despite their neglect of molecular di!usion and possible temporal=spatial nonlinearities, these linear response models appear reasonably robust, making them at least as useful to building microenvironment designers in reconsidering the possibilities and consequences of various forms of incomplete mixing related to indoor air quality problems. ? 2002 Elsevier Science Ltd. All rights reserved.

For the second issue, the maximal generated thermal lesions in this heating scenario are limited to 3.2 × 3.2 × 3.2 cm 3 for blood perfusion rates 1 and 5 kg m −3 s −1 and 2.4 × 2.4 × 2.4 cm 3 for 10 kg m −3 s −1 . In the case of a PTV larger than 3.2 × 3.2 × 3.2 cm 3 , it cannot be completely covered by a single lesion with physical geometrical limitations. In this case, the entire PTV could be partitioned into several sub-regions and be treated sequentially. Cooling time is therefore necessary to be introduced between each sub-region’s heating to prevent the near-field heating problem. Although the total treatment time could be extended, the number of cooling periods has been largely reduced due to lesion volume enlargement in one single exposure. As a result, the treatment can be performed in a reasonable amount of time.

Index Terms—Cell residence time, excess life, handover, mobility management. I. I NTRODUCTION A MOBILE telecommunications network is populated with several base stations (BSs). Mobile users receive mobile telecommunications services by using mobile stations (MSs) connecting to the BSs. When an MS moves from the radio coverage (called cell) of a BS to the radio coverage of another BS, the MS is disconnected from the old BS and reconnected to the new BS. This process is called handover. Fig. 1 illustrates the relationship between movement of an MS and a call session to that MS. The MS moves to cell 1 at time t 0 , and then moves to cell i at time t i for i > 1. A call for the MS arrives at time t 1 . If the call is not blocked or dropped, it completes at time t 5 . At time t 1 , if cell 1 does not have enough radio resources to accommodate this call (which can be a plain voice call or