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1.
The Ariake Sea, a typical semi-closed bay located in Kyushu Island, western Japan, has a maximum tidal range of 6 m in spring tide, and its vast tidal flats are composed of both sandy bottom areas and muddy bottom areas. In this study, two-dimensional depth-averaged finite difference numerical models have been developed for predicting the tidal flow velocity and suspended sediment concentration in the Ariake Sea. In the suspended sediment transportation model, a time-dependent sediment resuspension and deposition process was modeled as a response to the tidal flow by considering the presence of cohesive bottom sediment. The shifting-particles method, known as an operator-splitting technique, was used for time integration of the convective-dispersion equation. The model results were compared with in situ measurements of suspended sediment concentration and tidal flow velocity at several points in Isahaya Bay—located at the western part of the Ariake Sea—and also with the estimated suspended sediment concentration distribution via a Landsat Thematic Mapper image. The results indicated that the models were able to predict the measured values for suspended sediment concentration and tidal flow velocity, as well as the spatial distribution pattern of the suspended sediment concentration as estimated by the Landsat Thematic Mapper image. 相似文献
2.
A new coupled model (PCPF–SWMS) was developed for simulating fate and behavior of pollutant in paddy water and paddy soil.
The model coupled the PCPF-1, a lumped model simulating pesticide concentrations in paddy water and 1 cm-surface sediment
compartment, and the SWMS-2D, a finite element numerical model solving Richard's and advection-dispersion equations for solute
transport in soil compartment. The coupling involved improvements on interactions of the water flow and the concentration
the pollutant of at the soil interface between both compartments. The monitoring data collected from experimental plots in
Tsukuba, Japan in 1998 and 1999 were used to parameterise and calibrate hydraulic functioning, hydrodynamic and hydrodispersive
parameters of the paddy soil. The analysis on the hydraulic functioning of paddy soil revealed that the hard pan layer was
the key factor controlling percolation rate and tracer transport. Matric potential and tracer monitoring highlighted the evolution
of saturated hydraulic conductivity ( K
S) of hard pan layer during the crop season. K
S slightly decreased after puddling by clay clogging and strongly increased after mid term drainage by drying cracks. The model
was able to calculate residential time in every soil layers. Residential time of tracer in top saturated layers was evaluated
to be less than 40 days. It took 60 days to reach the unsaturated layers below hardpan layer. 相似文献
3.
The environmental behavior and fate of tributyltin (TBT) in the northern Ariake Sea, resulting from the use of TBT-containing
antifouling paints on hulls of ships, pleasure crafts and docking facilities, was assessed by numerical simulations. First,
a mathematical model was devised on the basis of a non-steady state equilibrium, one box multi-compartment model consisting
of the surface micro-layer, the water column, the mud-layer, and the bottom sediment compartments. The movement of TBT among
the four compartments was modeled by resuspension of bottom mud, deposition of suspended sediment, film penetration and water
advection in each compartment. Furthermore, a one-dimensional diffusion equation was introduced into the bottom sediment compartment
to calculate profile distribution of TBT. The reactivity of TBT considered within the compartments included biological degradation,
adsorption to particulate matter and diffusion. Next, the optimal amount of past TBT loads, reflecting the recent observations
of TBT concentration in the waters and sediments of the northern Ariake Sea, was searched by a simple genetic algorithm. The
relative sensitivity of various model parameters were also determined to identify the more important parameters for estimating
the environmental behavior and fate of TBT. Finally, the future status of TBT contamination of the northern Ariake Sea was
predicted assuming the discontinued use of TBT-containing antifouling paints. Despite its simple model structure relative
to hydraulics, it was concluded that this multi-compartment model adequately estimated the environmental behavior and fate
of TBT. 相似文献
4.
This paper describes an attempt to estimate the mass budget of irrigation ponds within a watershed and the possibilities to
control the effluent load of nutrients from the watershed located in the Kyotanabe area. The paddy field lots were irrigated
by the ponds and several mountain streams. In the study watershed, there were two ponds located on the upper and lower sides
of a paddy area. Water could be pumped up from the lower pond to the upper pond as necessary. At the ponds, the total amount
of nitrogen and phosphorus in the inflow loads including the sediment release was larger than those in the outflow loads.
In SS, the effect of load reduction in the ponds was high. It is assumed that organic load reduction was not expected in the
ponds. The study result indicates that it is possible to remove the nutrients in the ponds when a larger amount of water is
pumped up than when the ponds are only in irrigation use. Moreover, the removal capacities of the nutrients could probably
be increased in both ponds by controlling the amount of sediment releases.
Electronic Publication 相似文献
5.
A study was undertaken to estimate the sediment yield of the Karso watershed of Hazaribagh, Jharkhand State, India using modified
universal soil loss equation (MUSLE), remote sensing (RS) and geographic information system (GIS) techniques. The runoff factor
of MUSLE was computed using the measured values of runoff and peak rate of runoff at outlet of the watershed. The topographic
factor ( LS) was determined using GIS while crop management factor ( C) was determined from land use/land cover data, obtained from RS and field survey. The conservation practice factor ( P) was obtained from the literature. Sediment yield at the outlet of the study watershed was simulated for 345 rainfall events
spread over a period of 1996–2001 and validated with the measured values. Nash–Sutcliffe simulation model efficiency of 0.8
and high value of coefficient of determination (0.83) indicated that MUSLE model estimated sediment yield satisfactorily. 相似文献
6.
A year-long study on the water quality and hydrology was carried out to investigate the characteristics of the pollutant concentrations
and pollutant removal in a constructed irrigation pond. The pond is part of a circular irrigation system for paddy fields
within Lake Kasumigaura watershed, Japan. The average concentrations of the total nitrogen (TN), chemical oxygen demand (COD),
total phosphorus (TP), and suspended solids (SS) at the pond outlet were 7.4, 8.6, 0.2, and 18.8 mg L −1, respectively. The average removed loads for the same indices were 0.14, 2.47, 0.11, and 24.2 g m −2 day −1, respectively. The percentages of pollutant removals from the inflow loads for the same indices were 3, 26, 42, and 63%,
respectively. The pond discharged the TN loads of 128 kg due to sediments stirred by operation of a pump for April and May.
The average TN removal was 19% from June to August and was smaller than that reported in published literatures (40–50%). Major
reasons were considered to be that the turnover of water in the pond was rapid (86% per day) and that the TN concentration
of inflow water was relatively low (5.9 mg L −1). The percentages of pollutants that flowed into the pond to the outflow loads from the study site were 6.6, 4.8, 1.6, and
1.1% for TN, COD, TP, and SS loads, respectively. The pollutant removal will be increased if the design of the circular irrigation
system is reconsidered to utilize a pollutant removal function in the irrigation pond. 相似文献
7.
The Total Maximum Daily Load (TMDL) program is an integrated process of watershed assessment and management to address surface
water quality impairment. The management of organic contaminants and nutrients is a primary concern in conserving surface
water bodies. Watershed-scale pollutant loads simulation can assist stakeholders and watershed planners in making decisions
on immediate and long-term land use schemes to improve water quality. However, the behavior of contaminants in a watershed
needs to be characterized prior to such model applications. The objectives of this study were to characterize point and nonpoint
pollutants runoff at a watershed scale and to develop a Pollutant Load Calculation Model (PLCM), which facilitates the estimation
of pollutant delivery to a watershed outlet. The developed model was applied for the six sub-watersheds of the Saemangeum
estuarine watershed in Korea, where a large tidal reclamation project has been underway. Two years stream flow and water quality
data were used for the model calibration, while 1 year data were utilized for the model validation. The model calibration
resulted in the R
2 values of 0.58, 0.53, and 0.35 for BOD, TN, and TP, respectively. Overall performance for the validation period was similar
with that for the calibration period although the R
2 values were slightly decreased. The PLCM tends to substantially under or overestimate delivery pollutants loads during the
summer rainy seasons when most rainfall events occur. This is probably because once-a-month-measured water quality data, which
might not represent appropriately monthly water quality, particularly, for rainy seasons, were used for the loads calculation.
Thus, more frequently monitored water quality data should be used for the delivery loads estimation at least for a rainy season
in order to improve the PLCM performance. Nevertheless, the developed model took the pollutant reduction process into account,
which is not allowed with the conventional unit loading method, and furthermore temporal variations of pollutant loads based
on stream flows were also incorporated into the pollutant loads estimation. The developed PLCM can be a useful tool to assess
pollutants delivery loads at a watershed scale and thus assist decision makers in developing watershed pollution management
schemes. 相似文献
8.
In Okinawa, red soil runoff emerged as a social problem long ago, and many control measures have been adopted. However, their
effect has been gauged as insufficient. So, models to predict red soil runoff are required. Within this context, we have been
developing the suspended sediment concentration (SSC) analysis model. In this study, the SSC analysis model, a lumped storage-type
runoff model that includes a sediment runoff process, has been applied to two watersheds with different circumstances of land
use. In the application of this model, we tried to do a multi-objective optimization and examined some policies concerning
the choice of parameter sets. As a result, we were able to conclude that the SSC analysis model produced a good agreement
between the calculated value and the observed value. In multi-objective optimization, the relation between the root mean square
error (RMSE) of discharge and SSC became the Pareto relation. Moreover, it was recognized that, in taking into consideration
the viewpoint of the RMSE of sediment load and the total sediment load error, the optimization of discharge should be regarded
as important in choosing the set of parameters in an actual application. 相似文献
9.
AbstractSoil moisture distributions in rainfed lowland rice environments are largely determined by the position in the toposequence. In this study, we developed an experimental sloping bed that can simulate the soil hydrological conditions in sloping rainfed lowland rice environments to examine if the expression of promoted root system development in relation to soil moisture availability along the soil profile may maximize water uptake and dry matter production under drought. The gradient of available water along both the surface soil layer and the vertical soil profile was successfully created by manipulating ground water levels in the experimental sloping bed indicating the practical effectiveness of this experimental system. Then, two contrasting genotypes, IRAT109 (upland rice adapted japonica) and KDML105 (lowland adapted indica) were grown for plasticity evaluation. Dry matter production was maintained even at a higher position in the toposequence in IRAT109, but decreased in KDML105. Such maintenance of dry matter production in IRAT109 was attributed to its greater ability to increase root length density in a deeper soil layer, where more soil moisture is available. In contrast, KDML105 maintained root length density in the upper soil layer, and could not utilize the soil moisture available in the deeper soil layer. These results imply that the genotype that expressed root plasticity with root system developing in the soil portion where more soil moisture was available showed greater dry matter production than the genotype that showed root plasticity in the soil layer where soil moisture was less available. 相似文献
10.
In watershed management, the determination of peak and total runoff due to rainfall and prediction of pollutant load are very important. Measurement of rainfall runoff and pollutant load is always the best approach but is not always possible at the desired time and location. In practice, diffuse pollution has a complex natural dependence on various land-use activities such as agriculture, livestock breeding, and forestry. Estimation of pollutant load is therefore essential for watershed management and water pollution control. In this study, a model of rainfall runoff and pollutant load, which uses a geographical information system (GIS) database, is a convenient and powerful tool for resolving the abovementioned complexities. This technology was applied in order to simulate the runoff discharge and the pollutant load of total nitrogen (TN) and total phosphorus (TP) in the Chikugo River basin of Kyushu Island, Japan. First, a hydrologic modeling system (HEC-HMS) and GIS software extension tool were used for simulations of elevation, drainage line definition, watershed delineation, drainage feature characterization, and geometric network generation. The spatial distributions of land cover, soil classes, rainfall, and evaporation were then analyzed in order to simulate the daily runoff discharge at the Chikugo Barrage from April 2005 to December 2007. An important point in this approach is that a new development for data input processing with HEC-HMS was introduced for optimizing parameters of the model. Next, the water quality indicators TN and TP were examined, and an efficient approach was investigated for estimating monthly pollutant loads directly from unit load and ground-observed hydrological data. Both nonpoint and point sources of pollutants were considered, including different land-cover categories, sewers, factories, and livestock farms. The observed and simulated results for the runoff discharges and pollutant loads were in good agreement and totally consistent, indicating that the proposed model is applicable to simulation of rainfall runoff and pollutant load in the Chikugo River basin. Further, this model will be able to provide managers with a useful tool for optimizing the water surface management of this river basin. 相似文献
11.
A method for the fractionation of wheat, rye, and barley flours without using aqueous solvents was developed. The separation of protein and starch was based on differences in their densities. Therefore, ball-milled flour was suspended in a mixture of inert solvents (toluene/tetrachoroethene) with a density of 1.47 g/cm 3 and centrifuged. Owing to its higher density, the starch fraction was obtained as sediment whereas the protein fraction (PF) formed a layer on the surface of the solvent because of its lower density. The PF was enriched in a solvent mixture with a density of 1.355 g/cm 3 yielding a middle fraction (sediment) and the enriched PF (upper layer). The latter was then defatted with toluene (0.87 g/cm) providing a lipid fraction in addition. The influence of ball milling under air or in the sedimentation solvent on the yield and the purity of the fractions was studied. Three varieties of wheat, and one rye and barley variety were fractionated by the optimised method and the obtained fractions were characterised by chemical methods e.g. gel permeation chromatography, SDS electrophoresis, and a combined extraction/HPLC method. 相似文献
12.
The equation of Reynolds averaged Navier-Stokes with the term of additional stress resulted from fibers and the equation of
probability distribution function for mean fiber orientation are derived and solved numerically to explore the characteristics
of fiber suspension flow in a channel. The mathematical model and numerical code are validated by comparing the computational
results with the corresponding experimental ones. The effect of Reynolds number, fiber concentration and fiber aspect-ratio
on the velocity profile, turbulent intensity, and turbulent dissipation rate is analyzed. The results show that the effect
of fibers on turbulent channel flow is equivalent to an additional viscosity, but at this range of fiber concentration, the
effect of the presence of fibers was small. The turbulent velocity profiles of fiber suspension become gradually sharper in
the central region of channel by increasing the fiber concentration and/or decreasing the Reynolds number. The velocity gradient
near the wall decreases gradually as the fiber aspect-ratio increased. The turbulent kinetic energy will increase with increasing
Reynolds number, fiber concentration, and fiber aspect-ratio. The turbulent dissipation rate will increase with increasing
fiber concentration or decreasing fiber aspect-ratio. Finally, the equation of velocity profile for turbulent fiber suspension
channel flow, involving the effect of Reynolds number, fiber concentration, and aspect-ratio, is derived. 相似文献
13.
The study compares the prediction performances of evapotranspiration by the FAO56 Penman–Monteith method and the pan evaporation
method using the artificial neural network. A backpropagation neural network was adopted to determine the relationship between
meteorological factors and evapotranspiration or evaporation. The evapotranspiration in the ChiaNan irrigated area of Tainan
was considered. Weather data compiled by Irrigation Experiment Station of ChiaNan Irrigation Association were the input layer
variables, including (1) the highest temperature, (2) the lowest temperature, (3) the average temperature, (4) the relative
humidity, (5) the wind speed, (6) hours of sunlight, (7) amount of solar radiation, (8) the dew point, (9) morning ground
temperature and (10) afternoon ground temperature. The importance of the ten weather factors was ranked by the general influence
(GI) factor. Results show that the correlation coefficient between the evapotranspiration in 2004 calculated by FAO56 Penman–Monteith
method and the one predicted by the neural network model with a hidden layer of ten nodes is 0.993. The actual evapotranspiration
is 911.6 cm, and value prediction by the neural network is 896.4 cm, between which two values the error is 1.67%. The results
reveal that the backpropagation neural network based on the FAO56 Penman–Monteith method can accurately predict evapotranspiration.
However, the correlation coefficient between the actual evaporation in 2004 and the value prediction by the neural network
with a hidden layer of ten nodes and an output layer with the pan evaporation as its target output is 0.708. The pan evaporation
is 1,673.1 cm, while the value predicted by the backpropagation neural network is 1,451.7 cm, between which values the error
is 13.23%. The backpropagation neural networks with pan evaporation as target outputs predict the evaporation with large errors.
Moreover, the use of four agricultural weather factors (determined by the GI) including wind speed, average temperature, dew
point and maximum temperature as input variables, and a hidden layer of three nodes in the backpropagation neural network
model can successfully predict evapotranspiration based on the FAO56 Penman–Monteith method ( R = 0.98, error = 1.35%). 相似文献
15.
Bed shear stress and turbulence quantities are important parameters to understand sediment erosion, transport, and hydraulic processes in most hydraulic studies. An experimental investigation was conducted to understand the effect of injection on the bed shear stress and turbulence characteristics of flows during low sediment transport rate in a closed conduit, which is similar in construction to the erosion function apparatus. In particular, the effect of injection on the bed shear stress, mean velocity profiles, turbulence intensities, Reynolds shear stress, and higher-order moments of the closed conduit flows in the seepage zone as well as at the upstream edge of the seepage zone was examined. The instantaneous velocities were measured using two-dimensional particle image velocimetry (PIV) to evaluate the turbulence structure in both the seepage zone and at the upstream edge of the seepage zone. The bed shear stress estimated by the Reynolds shear stress approach was found to be more appropriate than that estimated by the usual logarithmic law approach. However, a spatial fluctuation in the bed shear stress was noticed as the injection intensity was increased. Injection was found to decrease the velocity near the bed and to increase the velocity near the center of the conduit in comparison to the no-seepage condition in both zones. The injection resulted in more of a decrease in bed stability in the seepage zone in comparison to the upstream edge of the seepage zone as the injection intensities were increased. The introduction of injection increased the magnitudes of the various turbulence parameters in comparison to the no-seepage condition in the seepage zone. The effect of injection was not only visible in the near-bed region, but in both zones as the water depth (measured from top of the sediment surface) increased. 相似文献
16.
The effects of vegetable type, vegetable dimensions, and solar drier load on dehydration rate; and texture, color, water activity, and carotene content of solar-dried carrots, sweet potatoes, and collard greens were studied. Mean dehydration rates (moisture loss,%/hr) for solar dried loads of 430 g/m 2 and 715 g/m 2 were 3.3 ± 0.30% and 3.8 ± 0.20% for carrots and sweet potatoes, respectively. Loads of 360 g/m 2 and 465 g/m 2 of collard greens had dehydration rates of 6.3 ± 0.10% moisture loss per hr. The results showed that vegetable type accounted for significant differences ( p < 0.01) in dehydration rate, and beta-carotene content. Vegetable dimensions affected ( p < 0.05) water activity. Solar drier load affected water activity ( p < 0.01), and hue angle ( p < 0.05). Beta-carotene contents (dry basis) of dehydrated carrot, sweet potato, and collard treatments were 10.9–17.4%, 7.6–9.8%, and 11.9–21.5%, respectively. Among the carrot treatments, the 5-mm thick slices packed at a load of 715 g/m 2 contained the highest beta-carotene (17.4%, dry basis) and vitamin A activity (362 IU/g, dry basis), and good physical properties. For collard greens, the 2-cm and 3-cm wide strips packed at 360 g/m 2 loads had the best combinations of high beta-carotene (21.5% and 17.2%, dry basis, respectively), vitamin A activity (357.2 and 293.1 IU/g, dry basis, respectively), and optimal color, texture, and water activity. Beta-carotene losses due to solar dehydration were 48.9–67.5%, 4.0–5.8%, and 1.9–19.8% (dry basis) in carrots, sweet potato and collard greens, respectively. 相似文献
17.
A nitrogen balance study was carried out by setting up a test paddy in order to estimate the nitrogen pollution load potential
(NPLP) from farmland in the Tedori River Alluvial Fan Areas and the load from the entire area under consideration was estimated
using the cropping record and fertilizer application rate (FAR). The total NPLP was estimated to be 261 tons/year and the
load from the paddy 79 tons/year for 5,704 ha, which would translate to an intensity of 14 kg/ha, while the load from the
vegetable field was estimated to be 118 tons/year for 215 ha, which would equate to an intensity of 549 kg/ha. The pollution
loads for the vegetables were significantly greater than those for the rice. The load for the barley was 57 tons/year for
261 ha (216 kg/ha) and that for the orchards was 23 tons/year for 64 ha (359 kg/ha). The estimation of soybean load was a
negative 15 tons/year for 717 ha (−21 kg/ha), which meant that the nitrogen in the yield was greater than the FAR. The results
also confirmed the yield absorption ratio in relation to the FAR. The load from the paddy for the entire area was also estimated
using the percolation rate and the water quality load underneath the farmland was estimated to be 89 tons/year. 相似文献
18.
This paper studies buckling behavior of non-uniform fiber columns under axially distributed compressive load and presents
a new approach for determining buckling load. For free-built-in fibers, a Fredholm equation is derived from solving the governing
equation with end constraints. Critical load and critical length can be evaluated by seeking the lowest eigenvalue of the
resulting equation. For the cases of the cross-sectional moment of inertia and axially distributed load as power functions
with respect to the axial distance from the free end, a necessary condition for buckling is derived, and a polynomial characteristic
equation is then obtained and solved. The effect of the weight and axial profile of tapered fibers on the critical length
is discussed. 相似文献
19.
The objective of this study was to evaluate the effect of proanthocyanidins (PAs) on iron uptake from soybean seed ferritin
(SSF) crude by rats with iron deficiency anemia (IDA) for the first time. Six groups of Sprague–Dawley (SD) rats ( n = 10) were used, which contain (1) SSF crude group; (2) SSF crude + PAs group; (3) PAs group; (4) FeSO 4 group; (5) iron deficiency control group; and (6) control group. The bioavailability of iron was examined by measuring hemoglobin
(Hb) concentration value, red blood cell (RBC) numbers, and serum iron stores. After 8 weeks, Hb concentration was almost
recovered to the normal level upon feeding SSF crude or FeSO 4 to rats. In contrast, Hb concentration was recovered to less extent when SSF crude plus PAs was used instead of SSF crude
alone ( P < 0.05). A similar profile was observed with these three sample groups when serum iron and RBC were used as parameters. All
rats in PAs group died at the 8th week. Taken together, all these results demonstrated that PAs inhibited iron uptake of rats
from SSF, and are toxic for rats with IDA. 相似文献
20.
Crop consumptive water requirement (Crop-ET) is a key variable for developing management plans to optimize the efficiency
of water use for crop production particularly in semiarid zone. In Burkina Faso, the unfavorable climatic conditions characterized
by the low and unevenly distribution of rainfall have pushed water resources management to the forefront of the crop production
issue. Crop-ET is extremely required in rainwater effective management for mitigating the impact of water deficit on the crops.
Basically, Crop-ET determination involves reference evapotranspiration (ETo) and crop coefficient (Kc) which required complete
climatic data and specific site crop information, respectively. ETo estimation with the recommended FAO56 Penman–Monteith
(PM) equation is limited in Burkina Faso due to the numerous meteorological data required which are not always available in
many production sites. In such circumstances, research to compute directly Crop-ET as an alternative to the two-step approach
of calculating ETo and determining site specific Kc, seems desirable. Therefore, this study aims to evaluate the performance
of a mixture principal component analysis neural network (PCANN) model for computing rice Crop-ET directly from temperatures
data in Fada N’Gourma region located in Eastern Burkina Faso, Africa. From the statistical results, rice Crop-ET can be successfully
computed by using PCANN methodology, when only temperatures data are available in this African semiarid environment. Thus,
in poor data situation, Crop-ET direct computation can be rapidly addressed through PCANN model for agricultural water management
in African semiarid regions. 相似文献
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