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1.
In the present study, chemical oxygen demand (COD) removal by packed‐columns of activated carbon (AC) derived from two different materials (coal activated carbon, CAC and wood activated carbon, WAC) is reported as part of an on‐site wastewater treatment system for handling small volumes of wastewater generated at wood‐floor industries for which there are no proper on‐site treatment options available in the market. The performance of the sorbents, the effect of bed depth (0.19 and 0.57 m) and volumetric load (0.10 and 0.24 m h?1) on the breakthrough curve of sorption systems were studied. The results indicated the feasibility of using both ACs to treat these wastewaters. At the bed depth (0.57 m), volumetric load (0.24 m h?1), and 30% breakthrough, CAC and WAC showed treatment capacity of 40.5 L kg?1 in 250 h and 23.8 L kg?1 in 63 h, respectively. This indicated that CAC requires longer retention times to reach a performance similar to WAC. The experimental data was fit into the bed depth‐service time model showing that under the same conditions, CAC had higher maximum sorption capacity (N0) than WAC. Moreover, thermal regeneration at 500°C temperature could be a cost‐effective procedure since the reuse of spent AC through such regeneration process for further treatment could still achieve 90% of the initial sorption capacity, reducing then costs for the use of new sorbents and also the need for waste disposal.  相似文献   

2.
H. Marttila  B. Kløve 《水文研究》2014,28(17):4756-4765
Lowland catchments in Finland are intensively managed, promoting erosion and sedimentation that negatively affects aquatic environments. This study quantified fine‐grained bed sediment in the main channel and upstream headwaters of the River Sanginjoki (399.93 km2) catchment, Northern Finland, using remobilization sediment sampling during the ice‐free period (May 2010–December 2011). Average bed sediment storage in river was 1332 g m?2. Storage and seasonal variations were greater in small headwater areas (total bed sediment storage mean 1527 g m?2, range 122–6700 g m?2 at individual sites; storage of organic sediment: mean 414 g m?2, range 27–3159 g m?2) than in the main channel (total bed sediment storage: mean 1137 g m?2, range 61–4945 g m?2); storage of organic sediment: mean 329 g m?2, range 13–1938 g m?2). Average reach‐specific bed sediment storage increased from downstream to upstream tributaries. In main channel reaches, mean specific storage was 8.73 t km?1, and mean specific storage of organic sediment 2.45 t km?1, whereas in tributaries, it was 126.94 and 34.05 t km?1, respectively. Total fine‐grained bed sediment storage averaged 563 t in the main channel and 6831 t in the catchment. The proportion of mean organic matter at individual sites was 15–47% and organic carbon 4–455 g C m?2, with both being highest in small headwater tributaries. Main channel bed sediment storage comprised 52% of mean annual suspended sediment flux and stored organic carbon comprised 7% of mean annual total organic carbon load. This indicates the importance of small headwater brooks for temporary within‐catchment storage of bed sediment and organic carbon and the significance of fine‐grained sediment stored in channels for the suspended sediment budget of boreal lowland rivers. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

3.
Sorptive removal of Ni(II) from electroplating rinse wastewaters by cation exchange resin Dueolite C 20 was investigated at the temperature of 30°C under dynamic conditions in a packed bed. The effects of sorbent bed length 0.1–0.2 m, fixed flow rate 6 dm3 min?1, and the initial rinse water concentration (C0) 53.1 mg L?1 on the sorption characteristics of Dueolite C 20 were investigated at an influent pH of 6.5. More than 94.5% of Ni(II) was removed in the column experiments. The column performance was improved with increasing bed height and decreasing the flow rate. The Thomas, Yoon–Nelson, Clark, and Wolborska models were applied to the experimental data to represent the breakthrough curves and determine the characteristic design parameters of the column. The sorption performance of the Ni(II) ions through columns could be well described by the Thomas, Yoon–Nelson, and Wolborska models at effluent‐to‐influent concentration ratios (C/C0) >0.03 and <0.99. Among the all models, the Clark model showed the least average percentage time deviation. The sorptive capacity of electroplating rinse water using Ni(II) was found to be 45.98 mg g?1.  相似文献   

4.
The adsorption of Ni(II) from aqueous solutions using base treated cogon grass or Imperata cylindrica (NHIC) was performed under batch and column modes. Batch experiments were conducted to determine the factors affecting adsorption such as pH, adsorbent dosage, initial nickel concentration, contact time and temperature. The fixed‐bed column experiment was performed to determine the practical applicability of NHIC and to obtain the breakthrough curve. Adsorption was fast as equilibrium was achieved within 60 min, and was best described by the pseudo second order model. According to the Langmuir model, a maximum adsorption capacity of 6.96 mg/g was observed at pH 5 and at a temperature of 313 K. Thermodynamic parameters such as ΔG0, ΔH0 and ΔS0 were calculated, and indicated that adsorption was a spontaneous and endothermic process. The mechanistic pathway of Ni(II) uptake was examined by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) spectroscopy. The Thomas and Yoon‐Nelson models were used to analyze the fixed‐bed column data.  相似文献   

5.
In this study, a new strain of microorganism Shewanella putrefaciens was used for biofiltration of a pyridine laden air stream in a corn‐cob packed biotrickling filter. In the biotrickling filter tested with S. putrefaciens, the maximum removal of pyridine is determined to be 100% at less than the average inlet concentration of 0.653 g m–3 and more than 93% at a higher average inlet concentration of 1.748 g m–3 (phase VIII) with an empty bed residence time (EBRT) of 106 s. However, when the biotrickling filter was operated at a low EBRT of 53 s and almost the same average inlet concentration of 1.752 g m–3 (phase VII), the removal level attained was not greater than 85%. The maximum elimination capacity (EC) of the biotrickling filter was 102.34 g m–3h–1 at an inlet pyridine load of 119.62 g m–3h–1 with an EBRT of 53 s in phase VII. The maximum deviation of the EC from the 100% conversion line varied from 0.257 to 10.166% when going from phase I to VIII. Kinetic analysis showed that the maximum removal rate, rmax, and saturation constant, Ks, values for pyridine were calculated as 0.24 g m–3h–1 and 6.44 g m–3, respectively, with a correlation coefficient, R2, of 0.9939 and a standard deviation of error of 23.94%. The information contained herein indicates that the corn‐cob packed biotrickling filter inoculated by S. putrefaciens should provide excellent performance in the removal of gaseous pyridine.  相似文献   

6.
This study investigated the effectiveness of a new packing material, namely mixed rice husk silica with dried activated sludge for removing H2S. Dried sewage sludge was collected from Putrajaya sewage treatment plant in Malaysia. Rice husk silica was prepared at temperature of 800°C, after acid leaching and mixed with dried sewage sludge to be utilized in a polyvinyl chloride filter. The system was operated under variable conditions of two parameters, different inlet gas concentration and different inlet flow rate. H2S was passed through the filter with one liter of the packing material. More than 99.96% removal efficiency (RE) with empty bed residence time (EBRT) of 90–45 s and 300 ppm inlet concentration was observed. However, the RE decreased to 96.87% with the EBRT of 30 s. The maximum elimination capacity (EC) of 52.32 g/m3/h was obtained with the RE of 96.87% and H2S mass loading rate of 54 g/m3/h, while at the RE of 99.96%, maximum EC was 26.99 g/m3/h with the H2S mass‐loading rate of 27 g/m3/h. A strong significant correlation between increasing of H2S mass loading rate and pressure drop was also detected (p < 0.01). Maximum pressure drop was 3.0 mm H2O after 53 days of operating time, the EBRT of 30 s, and 54 g/m3/h of H2S loading rate. These observations suggest that the mixture of rice husk silica with dried activated sludge is a suitable physico‐biological filter for H2S removal.  相似文献   

7.
Lowland permeable catchments in the UK are particularly prone to sedimentation problems, on account of the increased fine sediment loadings generated by recent land‐use change and their stable seasonal hydrological regimes, which are frequently depleted by groundwater abstraction. Fine‐grained sediment storage on the bed of the main channel systems of the Frome (437 km2) and Piddle (183 km2) catchments, Dorset, UK, has been examined at 29 sites using a sediment remobilization technique. Measurements encompassed the period February 2003–July 2004. At individual sites in the Frome, average values ranged between 410 and 2630 g m?2, with an overall mean of 918 g m?2. In the Piddle, the average values for individual sites varied between 260 and 4340 g m?2, with an overall mean of 1580 g m?2. Temporal variations in fine bed sediment storage at each site were appreciable, with the coefficients of variation ranging between 43 and 155% in the Frome and between 33 and 160% in the Piddle. Average reach‐scale specific bed sediment storage increased markedly downstream along each main stem from 2 to 29 t km?1 (Frome) and from 4 to 19 t km?1 (Piddle). Total fine sediment storage on the channel bed of the Frome varied between 479 t (5 t km?1) and 1694 t (17 t km?1), with a mean of 795 t (7 t km?1), compared with between 371 t (5 t km?1) and 1238 t (14 t km?1) with a mean of 730 t (9 t km?1) in the Piddle. During the study period, fine bed sediment storage was typically equivalent to 18% (Frome) and 57% (Piddle) of the mean annual suspended sediment flux at the study catchment outlets. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

8.
The increased accumulation of toxic pharmaceuticals and personal care products in the environment is a concern of worldwide relevance. Efficient technologies are needed to mitigate the level of such chemicals in natural waters. The suitability of multi‐walled carbon nanotubes (MWCNTs) to remove aqueous triclosan (a widely used anti‐microbial agent) was investigated in the present study. Tested operational parameters included the pH (3.0–11.0) value and the ionic strength (10?3, 10?2, and 10?1 M). Kinetic and thermodynamic studies were conducted at different initial concentrations (4, 8, and 10 mg/L) and temperatures (288, 298, and 308 K). Results showed higher triclosan adsorption at pH 3.0 (157.7 mg/g) than at pH 11.0 (103.9 mg/g). With an increase of ionic strength from 10?3 to 10?2 M, the adsorption capacity increased from 136.1 to 153.1 mg/g and from 80.8 to 105.8 mg/g at pH 3.0 and 10.0, respectively, while further increase of ionic strength to 10?1 M slightly reduced the triclosan adsorption to 149.9 and 94.7 mg/g due to the aggregation of MWCNTs. The Polanyi–Manes model (PMM) provided a best fitting of adsorption isotherms to the experimental data, and the kinetic process was well described by the pseudo second‐order kinetic model. The calculated thermodynamic parameters (ΔH0 = ?88.08 kJ/mol, ΔS0 = ?173.38 J/mol K) suggested that the adsorption of triclosan is spontaneous and exothermic in nature. The findings of the present work have significant implications for the removal of triclosan from aqueous solution with MWCNTs.  相似文献   

9.
A stable extractor of metal ions was synthesized through azo linking of o‐hydroxybenzamide (HBAM) with Amberlite XAD‐4 (AXAD‐4) and was characterized by elemental analyses, IR spectral, and thermal studies. Its water regain value and hydrogen ion capacity were found to be 12.93 and 7.68 mmol g?1, respectively. The optimum pH range (with the half‐loading time [min], t1/2) for Cu(II), Cr(III), Ni(II), Co(II), Zn(II), and Pb(II) ions were 2.0–4.0 (5.5), 2.0–4.0 (7.0), 2.0–4.0 (8.0), 4.0–6.0 (9.0), 4.0–6.0 (12.0), and 2.0–4.0 (15.0), respectively. Comparison of breakthrough and overall capacities of the metals ascertains the high degree of column utilization (>70%). The overall sorption capacities for Cu(II), Cr(III), Ni(II), Co(II), Zn(II), and Pb(II) ions were found to be 0.29, 0.22, 0.20, 0.16, 0.13, and 0.11 mmol g?1 with the corresponding preconcentration factor of 400, 380, 380, 360, 320, and 320, respectively. The limit of preconcentration was in the range of 5.0–6.3 ng mL?1. The detection limit for Cu(II), Cr(III), Ni(II), Co(II), Zn(II), and Pb(II) were found to be 0.39, 0.49, 0.42, 0.59, 0.71, and 1.10 ng mL?1, respectively. The AXAD‐4‐HBAM has been successfully applied for the analysis of natural water, multivitamin formulation, infant milk substitute, hydrogenated oil, urine, and fish.  相似文献   

10.
In order to investigate the rate of dissolution of gypsiferous rocks under natural conditions in streams of the Ebro river basin, 55 dissolution trials were carried out with spheres of alabastrine gypsum placed in flowing water. Experimental conditions involved flow velocities between 0·3 and 1·2 m s?1, electrical conductivities between 0·3 and 1·9 dS m?1, and the saturation indices of gypsum between ?2·1 and ?0·33. Mean values of dissolution rate obtained vary from 104 to 226 gm?2 h?1. This loss of mass corresponded to a volume of gypsum of between 393 and 853mmm?2 year?1. The factors most affecting the dissolution of gypsum are in descending order of importance: flow velocity > electrical conductivity > gypsum saturation.  相似文献   

11.
This paper describes delta development processes with particular reference to Cimanuk Delta in Indonesia. Cimanuk river delta, the most rapidly growing river delta in Indonesia, is located on the northern coast of Java Island. The delta is subject to ocean waves of less than 1 m height due to its position in the semi‐enclosed Java Sea in the Indonesian archipelago. The study has been carried out using a hydrodynamic model that accounts for sediment movement through the rivers and estuaries. As an advanced approach to management of river deltas, a numerical model, namely MIKE‐21, is used as a tool in the management of Cimanuk river delta. From calibration and verification of hydrodynamic model, it was found that the best value of bed roughness was 0·1 m. For the sediment‐transport model, the calibration parameters were adjusted to obtain the most satisfactory results of suspended sediment concentration and volume of deposition. By comparing the computed and observed data in the calibration, the best values of critical bed shear stress for deposition, critical bed shear stress for erosion and erosion coefficient were 0·05 N m?2, 0·15 N m?2, and 0·00001 kg m?2 s?1, respectively. The calibrated model was then used to analyse sensitivity of model parameters and to simulate delta development during the periods 1945–1963 and 1981–1997. It was found that the sensitive model parameters were bed shear stresses for deposition and erosion, while the important model inputs were river suspended sediment concentration, sediment characteristics and hydrodynamic. The model result showed reasonable agreement with the observed data. As evidenced by field data, the mathematical model proves that the Cimanuk river delta is a river‐dominated delta because of its protrusion pattern and very high sediment loads from the Cimanuk river. It was concluded that 86% of sediment load from the Cimanuk river was deposited in the Cimanuk delta. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

12.
We used hydrochemistry and environmental isotope data (δ18O, δD, tritium, and 14C) to investigate the characteristics of river water, groundwater, and groundwater recharge in China's Heihe River basin. The river water and groundwater could be characterized as Ca2+? Mg2+? HCO3?? SO42? and Na+? Mg2+? SO42?? Cl? types, respectively. Hydrogeochemical modelling using PHREEQC software revealed that the main hydrogeochemical processes are dissolution (except for gypsum and anhydrite) along groundwater flow paths from the upper to middle Heihe reaches. Towards the lower reaches, dolomite and calcite tend to precipitate. The isotopic data for most of the river water and groundwater lie on the global meteoric water line (GMWL) or between the GMWL and the meteoric water line in northwestern China, indicating weak evaporation. No direct relationship existed between recharge and discharge of groundwater in the middle and lower reaches based on the isotope ratios, d‐excess, and 14C values. On the basis of tritium in precipitation and by adopting an exponential piston‐flow model, we evaluated the mean residence time of shallow groundwater with high tritium activities, which was around 50 years (a). Furthermore, based on the several popular models, it is calculated that the deep groundwaters in piedmont alluvial fan zone of the middle reaches and in southern part of the lower reaches are modern water, whereas the deep groundwaters in the edge of the middle reaches and around Juyan Lake in the lower reaches of Heihe river basin are old water. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

13.
Synoptic water sampling at a fixed site monitoring station provides only limited ‘snap‐shots’ of the complex water quality dynamics within a surface water system. However, water quality often changes rapidly in both spatial and temporal dimensions, especially in highly polluted urban rivers. In this study, we designed and applied a continuous longitudinal sampling technique to monitor the fine‐scale spatial changes of water quality conditions, assess water pollutant sources, and determine the assimilative capacity for biochemical oxygen demand (BOD) in an urban segment of the hypoxic Wen‐Rui Tang River in eastern China. The continuous longitudinal sampling was capable of collecting dissolved oxygen (DO) data every 5 s yielding a ~11 m sampling interval with a precision of ±0.1 mg L?1. The Streeter and Phelps BOD‐DO model was used to calculate: (1) the oxygen consumption coefficient (K1) required for calibration of water quality models, (2) BOD assimilative capacity, and (3) BOD source and load identification. In the 2014 m river segment sampled, the oxygen consumption coefficient (K1) was 0.428 d?1 (20°C), the total BOD discharge was 916 kg d?1, and the BOD assimilative capacity was 382 kg d?1 when the minimum DO level was set to 2 mg L?1. In addition, the longitudinal analysis identified eight major drainage outlets (BOD point sources), which were verified by field observations. This new approach provides a simple, cost‐effective method of evaluating BOD‐DO dynamics over large spatial areas with rapidly changing water quality conditions, such as urban environments. It represents a major breakthrough in the development and application of water quality sampling techniques to obtain spatially distributed DO and BOD in real time. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

14.
The Agua Negra drainage system (30 12′S, 69 50′ W), in the Argentine Andes holds several ice‐ and rock‐glaciers, which are distributed from 4200 up to 6300 m a.s.l. The geochemical study of meltwaters reveals that ice‐glaciers deliver a HCO3?? Ca2+ solution and rock‐glaciers a SO42?? HCO3?? Ca2+ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulphide oxidation (i.e. abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source of NaCl. The fine‐grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g. Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved rare earth elements (REE) tends to increase with discharge. Through PHREEQC inverse modelling, it is shown that gypsum dissolution (i.e. sulphide oxidation) is the most important geochemical mechanism delivering solutes to the Agua Negra drainage system, particularly in rock‐glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non‐glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e. gypsum and calcite). Meltwater chemistry in glacierized arid areas appears strongly influenced by sublimation/evaporation, in contrast with its humid counterparts. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

15.
A field tracer test was carried out in a light nonaqueous phase liquid (LNAPL) source zone using a well pattern consisting of one injection well surrounded by four extraction wells (5‐spot well pattern). Multilevel sampling was carried out in two observation wells located inside the test cell characterized by heterogeneous lithology. Tracer breakthrough curves showed relatively uniform flow within soil layers. A numerical flow and solute transport model was calibrated on hydraulic heads and tracer breakthrough curves. The model was used to estimate an average accessible porosity of 0.115 for the swept zone and an average longitudinal dispersivity of 0.55 m. The model was further used to optimize the relative effects of viscous forces versus capillary forces under realistic imposed hydraulic gradients and to establish optimal surfactant solution properties. Maximum capillary number (NCa) values between injection and extraction wells were obtained for an injection flow rate of 16 L/min, a total extraction flow rate of 20 L/min, and a surfactant solution with a viscosity of 0.005 Pa?s. The unconfined nature of the aquifer limited further flow rate or viscosity increases that would have led to unrealistic hydraulic gradients. An NCa range of 3.8 × 10?4 to 7.6 × 10?3 was obtained depending on the magnitude of the simulated LNAPL‐water interfacial tension reduction. Finally, surfactant and chase water slug sizing was optimized with a radial form of the simplified Ogata‐Banks analytical solution (Ogata and Banks 1961) so that injected concentrations could be maintained in the entire 5‐spot cell.  相似文献   

16.
Dust deposition in the sea at an iron ore unloading terminal in the Firth of Clyde, Scotland, was measured by means of sediment collectors placed 10 m above the sea bed on the outer face of the unloading jetty. A ‘background’ sedimentation of up to 64 g m?2 day?1 of non-ferrous material was obtained with no ships in port. During unloading dust quantities up to 18 021 g m?2 day?1 were obtained, but the quantities depended on the type of ore unloaded, and much smaller quantities of sediment were obtained with ores less prone to fine particle formation. Any ecological effects would involve sea bed benthos, although rates of transportation of the sedimented dust are probably rapid in the immediate vicinity of the ore terminal.  相似文献   

17.
Flow diversion terraces (FDT) are commonly used beneficial management practice (BMP) for soil conservation on sloped terrain susceptible to water erosion. A simple GIS‐based soil erosion model was designed to assess the effectiveness of the FDT system under different climatic, topographic, and soil conditions at a sub‐basin level. The model was used to estimate the soil conservation support practice factor (P‐factor), which inherently considered two major outcomes with its implementation, namely (1) reduced slope length, and (2) sediment deposition in terraced channels. A benchmark site, the agriculture‐dominated watershed in northwestern New Brunswick (NB), was selected to test the performance of the model and estimated P‐factors. The estimated P‐factors ranged from 0·38–1·0 for soil conservation planning objectives and ranged from 0·001 to 0·45 in sediment yield calculations for water‐quality assessment. The model estimated that the average annual sediment yield was 773 kg ha?1 yr ?1 compared with a measured value of 641 kg ha?1 yr?1. The P‐factors estimated in this study were comparable with predicted values obtained with the revised universal soil loss equation (RUSLE2). The P‐factors from this study have the potential to be directly used as input in hydrological models, such as the soil and water assessment tool (SWAT), or in soil conservation planning where only conventional digital elevation models (DEMs) are available. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

18.
Surface water–groundwater interaction in the hyporheic zone may enhance biogeochemical cycling in streams, and it has been hypothesized that streams exchanging more water with the hyporheic zone should have more rapid nitrate utilization. We used simultaneous conservative solute and nitrate addition tracer tests to measure transient storage (which includes hyporheic exchange and in‐stream storage) and the rate of nitrate uptake along three reaches within the Red Canyon Creek watershed, Wyoming. We calibrated a one‐dimensional transport model, incorporating transient storage (OTIS‐P), to the conservative solute breakthrough curves and used the results to determine the degree of transient storage in each reach. The nitrate uptake length was quantified from the exponential decrease in nitrate concentration with distance during the tracer tests. Nitrate uptake along the most downstream reach of Red Canyon Creek was rapid (turnover time K?1c = 32 min), compared with nitrate uptake reported in other studies (K?1c = 12 to 551 min), but other sites within the watershed showed little nitrate retention or loss. The uptake length Sw‐NO?3 for the most downstream reach was 500 m and the mass transfer coefficient Vf‐NO?3 was 6·3 m min?1. Results from 15 other nitrate‐addition tracer tests were used to create a regression model relating transient storage and measures of stream flow to nitrate uptake length. The model, which includes specific discharge and transient storage area, explains almost half the variability in nitrate uptake length (adjusted R2 = 0·44) and is most effective for comparing sites with very different stream characteristics. Although large differences in specific discharge and storage zone area explain inter‐site differences in nitrate uptake, other unmeasured variables, such as available organic carbon and microbial community composition, are likely important for predicting differences in nitrate uptake between sites with similar specific discharge rates and storage zone areas, such as when making intra‐site comparisons. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

19.
The aim of this study is to investigate the concentrations of U, Th, V, Mo, and Zr in natural waters taken from Turkey. Among these water species, Lake Van is the largest soda lake and the fourth largest closed basin on Earth. The water samples were collected from 51 locations between 2008 and 2009. The inductively coupled plasma‐MS was used for determinations. The obtained U and Zr concentrations are in the range of 37–110 µg L?1 and 17–78 µg L?1 in Lake Van and 0.53–0.81 µg L?1 and 0.15–0.19 µg L?1 in Lake Hazar, respectively. The concentration of uranium in other studied waters varies from the lowest 0.09 µg L?1 in Tigris (Dicle) river to the highest 4.0 µg L?1 in Mediterranean Sea water. Mean Mo and V concentrations in the studied water samples were found to be in ranges of 0.1–17 and 2.7–113 µg L?1, respectively. The obtained highest U concentration in Lake Van correlates with the highest Mo and Zr levels compared to the Lake Hazar and river waters. These results imply that there is a young occurrence of uranium minerals around Lake Van. It is concluded that there is about 50.000 ton of uranium in Lake Van water.  相似文献   

20.
In several empirical and modelling studies on river hydraulics, dispersion was negatively correlated to surface roughness. In this study, it was aimed to investigate the influence of surface roughness on longitudinal dispersion under controlled conditions. In artificial flow channels with a length of 104 m, tracer experiments with variations in channel bed material were performed. By use of measured tracer breakthrough curves, average flow velocity, mean longitudinal dispersion, and mean longitudinal dispersivity were calculated. Longitudinal dispersion coefficients ranged from 0·018 m2 s?1 in channels with smooth bed surface up to 0·209 m2 s?1 in channels with coarse gravel as bed material. Longitudinal dispersion was linearly related to mean flow velocity. Accordingly, longitudinal dispersivities ranged between 0·152 ± 0·017 m in channels with smooth bed surface and 0·584 ± 0·015 m in identical channels with a coarse gravel substrate. Grain size and surface roughness of the channel bed were found to correlate positively to longitudinal dispersion. This finding contradicts several existing relations between surface roughness and dispersion. Future studies should include further variation in surface roughness to derive a better‐founded empirical equation forecasting longitudinal dispersion from surface roughness. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

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