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1.
Errors in the kinematic wave and diffusion wave approximations for time-independent (or steady-state) cases of channel flow were derived for three types of boundary conditions: zero flow at the upstream end, and critical flow depth and zero depth gradient at the downstream end. The diffusion wave approximation was found to be in excellent agreement with the dynamic wave approximation, with errors in the range 1–2% for values of KF (? 7.5), where K is the kinematic wave number and F0 is the Froude number. Even for small values of KF (e.g. KF20 = 0.75), the errors were typically less than 15%. The accuracy of the diffusion wave approximation was greatly influenced by the downstream boundary condition. The error of the kinematic wave approximation was found to be less than 13% in the region 0.1 ? x ? 0.95 for KF = 7.5 and was greater than 30% for smaller values of KF (? 0.75). This error increased with strong downstream boundary control.  相似文献   

2.
Pollutants affect not only the environment in which they originate since they are also transported by air currents to other locations. For this reason, air pollution is a global problem for all countries and the air and water quality need to be monitored carefully. More information on precipitation chemistry is required to determine the source of pollution as well as its effects on the ecosystems. In this study, precipitation chemistry has been analyzed for the first time by using simple bulk collectors located at four different sites in Northwest Turkey for a period of two years. About 650 sequential rainwater samples were collected and analyzed for pH, electrical conductivity, anions such as , , Cl?, and cations such as Na+, K+, Mg2+, Ca2+, and . The selected sites were under the effect of different environmental factors. Our results showed that the highest and concentrations were measured in the Northwest of the research area. Additionally, it has been found that Ca2+ ions are abundant within all rainwater samples.  相似文献   

3.
Three hundred and twenty‐two samples of desalinated household water were collected from 99 sampling locations that covered 95% of Kuwaiti's residential areas. Seventy‐one brands of bottled water were collected from Kuwaiti markets. The water quality parameters that were studied included pH, electrical conductivity (EC), total dissolved solids (TDS), F?, Cl?, Br?, , , , , , , , and the major macronutrients Na+, K+, Ca2+, and Mg2+. The analysis yielded a large range of results for most of these parameters, with differences in some cases exceeding 10‐fold. With a few exceptions, the results were found to comply with US‐EPA and WHO standards. Only the water in two brands of bottled water was acidic (pH < 6.5). The TDS was found to be higher than the US‐EPA regulated value in 4 and 3% of the household samples and bottled water brands, respectively. The fluoride levels were generally higher in bottled water than in household water. However, the household water that was produced by the Doha desalination plant and some of the European brands of bottled water were the best samples studied in terms of their quantity of Ca2+, Mg2+, and Na+ compared with the DRI values for those substances. EC and TDS were positively correlated with , , Na+, K+, Ca2+, and Mg2+ for household water but only with Ca2+ and Mg2+ for bottled water.  相似文献   

4.
Shallow and bedrock groundwater from granitic aquifers were investigated for the hydrogeochemistry of major and minor constituents in an agricultural area. Nitrate concentrations were observed up to 49 mg/l as NO3‐N, with 22% of samples exceeding the drinking water standard, which could pose a significant threat because most residents rely on groundwater as their drinking water source. Principal component analysis revealed three principal components (PCs): (1) nitrate contamination, contributed by major cations, Cl?, SO and NO , (2) reduction processes positively involving Fe, Mn and B, and negatively involving dissolved oxygen and NO and (3) natural mineralization, involving HCO and F?. Cluster analysis, performed on the PC scores, resulted in seven sample groups, which were successfully identified by total depth, elevation and land use. The nitrate‐contaminated groups had mixed land uses, with locally concentrated residential areas. Uncontaminated groundwater groups were found in the natural environment, including high‐altitude spring water and bedrock groundwater with a higher degree of natural mineralization. Shallow groundwater groups in paddy fields in lowlands were affected by reducing environments, of which one group was characterized by high Fe, Mn and B, and negligible nitrate. Groundwater with intermediate nitrate and lower Cl? and SO was found primarily in hilly terrains with orchards and vegetable gardens, indicating lower contaminant loadings than lowland areas. Higher concentrations of F? and nitrate were observed in the nitrate‐contaminated water, which seemed unlikely to be explained by groundwater mixing. The strong acidity generated from nitrification may infiltrate deeper into the aquifer, induce accelerated weathering of bedrock and result in the coexistence of F? and nitrate, which may be an evidence of intense nitrate loading, leading to soil acidification. Multivariate statistical analysis successfully delineated hydrochemical characteristics of groundwater attained by natural and anthropogenic processes in an agriculturally stressed area with complex topographic land use patterns. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

5.
A study of the changes in the ionic loads of NO, NH, SO and H+ in a boreal forest snowpack at Lake Laflamme, Québec was carried out using hydrological and chemical data from field lysimeters. The results showed that depletion of the N-containing species occurs periodically in the snowpack during meltwater discharge. Rain-on-snow events led to in-pack losses of NO and NH at a rate of 130 μeq m?2 day?1 and 101·3 μeq m?2day?1 respectively. On dry days, however, dry deposition and deposition of organic debris from the canopy resulted in increases of 183·3 μeq m?2day?1 for NO and 4·5 μeq m?2day?1 for NH in the pack. In contrast, SO42? showed continual in-pack increases due to deposition of 5·0 μeq m?2day?1 for wet days and 92·6 μeq m?2day?1 for dry days. The depletion of NO and NH is due to microbiological uptake of these nutrients during periods when the free water content of the pack is high. Controlled melts in a laboratory snowmelt simulator containing snow and organic matter from the forest canopy at Lake Laflamme showed losses of NO and NH similar to those observed in the field. As the microbiological uptake proceeds at a rate comparable to that of ionic load increases in the pack by dry deposition, models of the chemical dynamics of snowmelt should take the former into account in any system where organic content of the snowpack is appreciable.  相似文献   

6.
This 2‐year study (2000, 2001) reports annual nutrient (phosphorus, nitrate) export from a first‐order agricultural watershed in southern Ontario based on an intensive monitoring programme. The importance of storm and melt events in annual export estimates is demonstrated and the temporal variability in nutrient loading during events is related to processes occurring within the catchment. The feasibility of predicting event‐related nutrient export from hydrometric data is explored. The importance of sampling frequency throughout events is also shown. Export of total phosphorus (TP), soluble reactive phosphorus (SRP) and nitrate ( ) for 2000 and 2001 averaged 0·35 kg ha?1 year?1, 0·09 kg ha?1 year?1, and 35 kg ha?1 year?1 (as N) respectively. Approximately 75% of annual TP export, 80% of annual SRP export and 70% of annual export occurred during 28 events per year. A small number of large‐magnitude events (>34 mm) accounted for 18–42% of annual TP export, 0–61% of annual SRP export and 13–33% of annual NO export. Our results show that temporal variability in nutrient export is largely governed by discharge in this basin, and export can be predicted from discharge. SRP and TP export can also be predicted from discharge, but only for events that are not large in magnitude. The sampling interval throughout events is important in obtaining precise estimates of nutrient export, as infrequent sampling intervals may over‐ or under‐estimate nutrient export by ± 45% per event for P. This study improves our understanding of and P export patterns and our ability to predict or model them by relating temporal variability in event nutrient export to discharge and processes occurring within the basin, and also by exploring the significance of sampling interval in the context of the importance of individual events, season and temporal variability during events. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

7.
Studies on the hydrogeological conditions of the Mesogea basin in east Attica reveal that the aquifers developed on the post‐alpine formations at the inner part of the coastal brackish zone exhibit positive hydraulic head. These Neogene and Quaternary deposits present high salt concentrations. Selected points were sampled (total 85: 51 wells and 34 boreholes) in order to obtain hydrogeological and hydrochemical data for a better understanding of the structure, operation and dynamics of the aquifer of the area. Statistical methods, R‐mode factor analysis and scatter‐plot diagrams were used for the hydrochemical analysis and presentation of the data. The groundwater resources are relatively weak and there is significant quality degradation due to the geological structure of the greater area, as well as the bad management of the aquifer and anthropogenic activities. Groundwater is characterized by high salt concentrations. Electrical conductivity values range between 260 and 6970 µS cm?1. High salt concentrations at the coastal aquifers are due to sea intrusion, whereas they are attributed to the dissolution of minerals of the geological environment in the inland area. The groundwaters of the study area can be classified into five water types: Ca–HCO3, Mg–HCO3, Na–HCO3, Na–Cl and Mg–Cl. They are saturated in dolomite and calcite, whereas they are unsaturated in anhydrite. High ion concentrations, e.g. ] (0‐221 mg l?1), ] (0·01‐1·88 mg l?1), ] (0·01‐6·75 mg l?1), as well as high heavy metals concentrations are attributed to anthropogenic impacts. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

8.
The knowledge of total inorganic carbon concentration (c) is important for characterizing natural waters. It is usually measured by the titration alkalinity (“m-value”) and pH which depend on temperature and ionic strength. This paper demonstrates that Ca (and Mg) can influence the calculation of from titration alkalinity, too. Errors result from neglecting this influence. In such cases the share of ion pair CaCO amounts to more than 50 % of . General relationships among the influencing factors are given by tables calculated with the help of a BASIC computer programme for calculation from titration alkalinity, pH and Ca concentration.  相似文献   

9.
We examined spatial and temporal variations in precipitation measured during summer season between 1976 and 2007 for 28 stations located in mountain areas across Japan using the amount of precipitation (Pr), the mean depth of precipitation events (η), and the inverse of the mean interval times (λ). We obtained positive correlations between the period mean Pr (Pr ) and the period mean η ( ) and between Pr and the period mean λ ( ) for the 28 stations. Pr was more strongly related to than to , indicating the spatial variations in Pr that are primarily related to the variations in . In addition, Pr was more strongly related to η than to λ for most stations on the basis of data for 1976–2007, indicating that the year‐to‐year variations in Pr are primarily related to η. We also examined temporal trends in Pr, η and λ for 1976–2007 and found no systematic trends for 23 of the 28 stations, suggesting long‐term trends that are not common in mountain areas of Japan. The relationships between Pr and and between Pr and η presented in this study enable us to generate a temporal precipitation distribution pattern based on only Pr and Pr data, respectively. Furthermore, probabilistic stochastic hydrological models require precipitation characteristics as input; thus, this study contributes to the determination of hydrological cycles and their possible future changes in Japanese mountain areas and therefore to water resource management. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

10.
Processes driving carbonate diagenesis in islands of the northern Bahamas are investigated using major ion, dissolved oxygen and dissolved organic carbon analyses of water samples from surface and ground waters, and measurements of soil gas P. Meteoric waters equilibrate with aragonite, but reactions are water controlled rather than mineral‐controlled and drive dissolution rather than concurrent precipitation of calcite. Surface runoff waters equilibrate with atmospheric P and rapidly recharge the vadose zone, limiting subaerial bedrock dissolution to only 6·6–15 mg l?1 Ca. P of soil gas measured in the summer wet season ((7·4 ± 3·7) × 10?3 atm) is elevated compared with that of the atmosphere, despite the thin skeletal organic nature of the soil and the discontinuous soil cover. Soil waters retained in surface pockets are equilibrated with respect to aragonite and have dissolved 51 ± 19 mg l?1 Ca. This is substantially less than the 93 ± 18 mg l?1 Ca in samples from pumping boreholes that sample meteoric waters from the freshwater lens. The high P of the freshwater lens ((16 ± 8·3) × 10?3 atm for pumping boreholes) suggests that significant additional CO2 may be derived by oxidation of soil‐ and surface‐derived organic carbon within the lens. The suboxic nature of the majority of the freshwater lens and the observed depletion in sulphate support this suggestion, and indicate that both aerobic and anaerobic oxidation may take place. Shallow lens samples from observation boreholes are calcite supersaturated and have a lower P than deeper lens waters, indicating that CO2 degasses from the water table, driving precipitation of calcite cements. We suggest that the geochemical evolution of waters in the vadose zone and upper part of the freshwater lens may be determined by the presence of a body of ground air with P controlled by production in the freshwater lens and soil and by degassing to the atmosphere. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

11.
Nano‐alumina modified by 9‐aminoacridine was used as a sorbent for separation and determination of dichromate ions from water. Statistical method, based on surface response design, has been used for the optimization of dichromate ions elution from 9‐aminoacridine nano‐alumina. The adsorbed dichromate ions were found to be eluted quantitatively with 0.8 mol L?1 KCl in 1.6 mol L?1 NaOH which optimized by response surface design. Under optimum conditions, the accuracy, precision (relative standard deviation, RSD%) and R‐square of the method were calculated as >98, <3, and >94%, respectively. Remarkable agreement between experimental and theoretical data was confirmed the predicted assumption. The method was applied to the simultaneous determination of dichromate in natural and industrial water samples. We also examined the retention of dichromate anions in the presence of Cl?, , and anions at pH 3.  相似文献   

12.
3D angle-domain common-image gathers for migration velocity analysis   总被引：2，自引：0，他引：2  
Angle‐domain common‐image gathers (ADCIGs) are an essential tool for migration velocity analysis (MVA). We present a method for computing ADCIGs in 3D from the results of wavefield‐continuation migration. The proposed methodology can be applied before or after the imaging step in a migration procedure. When computed before imaging, 3D ADCIGs are functions of the offset ray parameters (p, p) ; we derive the geometric relationship that links the offset ray parameters to the aperture angle γ and the reflection azimuth φ. When computed after imaging, 3D ADCIGs are directly produced as functions of γ and φ. The mapping of the offset ray parameters (p, p) into the angles (γ, φ) depends on both the local dips and the local interval velocity; therefore, the transformation of ADCIGs computed before imaging into ADCIGs that are functions of the actual angles is difficult in complex structure. By contrast, the computation of ADCIGs after imaging is efficient and accurate even in the presence of complex structure and a heterogeneous velocity function. On the other hand, the estimation of the offset ray parameters (p, p) is less sensitive to velocity errors than the estimation of the angles (γ, φ). When ADCIGs that are functions of the offset ray parameters (p, p) are adequate for the application of interest (e.g. ray‐based tomography), the computation of ADCIGs before imaging might be preferable. Errors in the migration velocity cause the image point in the angle domain to shift along the normal to the apparent geological dip. By assuming stationary rays (i.e. small velocity errors), we derive a quantitative relationship between this normal shift and the traveltime perturbation caused by velocity errors. This relationship can be directly used in an MVA procedure to invert depth errors measured from ADCIGs into migration velocity updates. In this paper, we use it to derive an approximate 3D residual moveout (RMO) function for measuring inconsistencies between the migrated images at different γ and φ. We tested the accuracy of our kinematic analysis on a 3D synthetic data set with steeply dipping reflectors and a vertically varying propagation velocity. The tests confirm the accuracy of our analysis and illustrate the limitations of the straight‐ray approximation underlying our derivation of the 3D RMO function.  相似文献   

13.
HCHO is ubiquitous and important chemical constitutes in the troposphere. The concentrations of the HCHO (aq) in the rainwater were measured in the Guiyang city, southeastern of China from May 2006 to April 2007 and 153 discrete samples were collected. Rainwater (N = 151) HCHO (aq) concentrations ranged from lower than method detection limit (MDL) to 40.2 µmol/L with a volume weighted mean value of 7.4 ± 8.8 µmol/L. The strong correlations between HCHO (aq) and HCOO? (r = 0.69, n = 137), HCHO (aq) and nss‐ (r = 0.74, n = 137), HCHO (aq) and (r = 0.67, n = 137), HCHO (aq) and (r = 0.74, n = 133) suggest the significant influence of the anthropogenic input for the HCHO (aq) levels. The concentration levels of rainwater HCHO (aq) was inversely proportional to the amount of rainfall, indicating the below‐cloud process is the most important mechanism for rainwater HCHO (aq) scavenging processes. More than 70% of the HCHO (aq) wet deposition took place during the early stage of the rainfall. According to the air mass back‐trajectory analysis, the rainwater with industrial back‐trajectories coming from the north had the highest levels of HCHO (aq) while the rainwater with the green‐covered or marine back‐trajectories from the southeast had the lowest concentrations, and this indicate the HCHO (aq) originated from urban or industrial regions served as an important source of the rainwater. The annual HCHO (aq) wet deposition flux was calculated as 6.96 mmol/m2 per year and the total deposition flux was estimated as 24.35 mmol/m2 per year, 71.4% of which was dominated by dry deposition.  相似文献   

14.
A study was performed in two submerged, pilot‐scale biofilm bioreactors operated under different conditions to determine the relationship between the operating parameters and H2S emission. H2S was always detected in the exhaust air at concentrations varying from 1 to 353 ppmv. The specific aeration rate was the most influencing parameter, with As < 30 kg COD (dissolved oxygen concentrations <4 mg L?1) increasing noticeably the H2S production. The periodical removal of the accumulated sludge reduced H2S emissions by ～14%.  相似文献   

15.
In the Pearl River Delta (PRD), river water quality deteriorates continually due to the population increase and ongoing industrialization and urbanization. In this study, a water quality management paradigm based on the seasonal variation is proposed. For better exploring the seasonal change of water quality, wavelet analysis was used to analyze the division of dry and wet seasons in the PRD during 1952–2009. Then water quality seasonal variation in 2008 and relevant impact factors were analyzed by multivariate statistic methods as a case to make some management measures. The results show that there are some differences of dry and wet seasons division among different years. Wet season mainly appear from April to September, which occupy the largest proportion among the 58 years (about 70%) and then followed by the wet season from May to October (about 13.8% of the total years). As to the water quality of 2008, significant differences exist between dry and wet seasons for 17 water quality parameters except TP, , Fe2+, and Zn2+. Levels of parameters pH, EC, CODMn, BOD5, , , and Cl? in dry season are much higher than those in wet season. In dry season the variations of river water quality are mainly influenced by domestic sewage, industrial effluents, and salt water intrusion. While in wet season, except the aforementioned pollution sources, drainages from cultivated land and livestock farm are also the main factors influencing water pollution. Thus, water quality management measures are proposed in dry and wet seasons, respectively. The results obtained from this study would further facilitate water quality protection and water resources management in the PRD.  相似文献   

16.
The paper presents the results of field measurements of critical conditions for bedload motion conducted in the Rio Cordon, a steep boulder‐bed stream in the Italian Alps, under conditions of high Reynolds numbers and low relative submergence poorly explored before. Two methods have been used to determine threshold of motion: the displacement of marked clasts and the flow competence approach, which uses the largest grain size diameter transported by each flood event. The high values of confirm the great relevance of non‐bedload effective shear stresses in step–pool streams given by the additional form drag associated with this morphology. Relative submergence effects on the dimensionless critical shear stress have been quantified by considering the relative submergence ratio Rh/D84, and the major effect of relative size on the mobility of each particle in steep, widely graded bed mixtures has been evaluated. Finally, the dimensionless critical unit discharge has also been adopted in the regression equations as the critical hydraulic parameter, because it may represent an easier parameter to use than the critical shear stress for steep, rough mountain rivers. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

17.
Pharmaceutical compounds, widely produced and used all around the world, are partly responsible for the widespread water pollution in the environment. Carbamazepine (CBZ) is an antiepileptic drug that persists in the environment for many years. In the present study, we used the TiO2/UV, nanoparticulate zero‐valent iron (NZVI), and NZVI/H2O2 treatment processes to compare efficiency of CBZ removal from water. Influence of NZVI loading, H2O2 concentration, TiO2 loading, UV lamp power, and the matrix (distilled water and groundwater) on CBZ removal efficiency was evaluated using full factorial design. Results indicated that the NZVI/H2O2 process oxidized CBZ within 5 min. On the other hand, the NZVI process alone did not reduce CBZ concentration after 120 min of process time. The NZVI/H2O2 process was equally effective in CBZ removal from both distilled water and groundwater whereas the TiO2/UV process was less effective due to the presence of ions in groundwater. CBZ removal efficiency of the TiO2/UV process declined 30% when the matrix was changed from distilled water to groundwater. Negative divalent ions, i.e., and , were the main cause of reduction of CBZ removal efficiency from groundwater. It is likely that these two ions adsorb onto, and consequently prevent the superoxide anion and hydroxyl radical OH? from being generated on, the surface of the TiO2.  相似文献   

18.
J. Lewin  M. G. Macklin 《水文研究》2010,24(20):2900-2911
Floodplains may be transformed when environmental changes or human activity causes alluvial systems to cross channel pattern thresholds. Thresholds between pattern states based on occurrence fields are only available for some pattern distinctions, and these may not encompass the alluvial contexts and range of dynamic factors involved. Pattern changes now known from the UK Holocene are reviewed as a basis for appreciating the potential for future transformations in a changing environment. These involved episodic boulder and gravel spreads in upland environments, and braiding meandering, anastomosing → meandering and active inactive transformations in more lowland contexts. Concern for possible impacts of climatic change need to be grounded in an appreciation of the nature and scale of these past changes. Some potential future changes may be relatively predictable in location (braiding meandering); others are more difficult given both present knowledge and the varying, modified and inheritance‐rich ‘contexts of vulnerability’ that floodplains now represent. Implications for management are discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

19.
A novel method has been put forward to retrofit the wet ammonia desulfurization process to realize the combined removal of sulfur dioxide and nitric oxide by introducing soluble cobalt(II) salt into aqueous ammonia solution. The active constituent of scrubbing NO from the flue gases is the produced by ammonia coordinating with Co2+. The regeneration of can be realized under the catalysis of activated carbon so as to sustain a high NO removal efficiency for a long time. In this paper, the adsorption–reduction behavior of on activated carbon has been researched using scanning electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. A conclusion can be drawn from the results that cobalt ions in the aqueous solution are adsorbed by activated carbon and most of them are reduced to Co2+ ions, and some of the Co2+ ions are further reduced into metallic cobalt. The results also demonstrate that the functional groups on the surface of carbon take part in this redox reaction. The C? H groups on the carbon surface are oxidized into C? OH, and then some of the hydroxyl groups are further oxidized into carbonyl or carboxyl groups.  相似文献   

20.
In this study, bench‐scale experiments were conducted to examine the UV/H2O2 oxidation of 17α‐ethynyestradiol (EE2) in water in a batch operation mode. The EE2 degradation exhibited pseudo‐first‐order kinetics, and the removal was ascribed to the production of hydroxyl radicals (?OH) by the UV/H2O2 system. Typically, the EE2 oxidation rate increased with increasing UV intensity and H2O2 dose, and with deceasing initial EE2 levels and solution pH. At EE20 = 650 µg/L, UV intensity = 154 µW/cm2, H2O2 = 5 mg/L, and neutral pH, the UV/H2O2 treatment was able to remove 90% of the EE2 content within 30 min. Four anions commonly present in water were found to inhibit EE2 degradation to varying degrees: > > Cl? > . Our results demonstrate that the described UV/H2O2 process is an effective method to control EE2 pollution in water.  相似文献   

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