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91.
The effective density and the strength of flocs formed in the laboratory from mud from the Tamar Estuary reached a maximum
value at a salinity of 10–15‰ within the concentration range studied (0.1–1.0 g liter−1). For a constant salinity and concentration, the density decreases with increasing floc size. The strength of the flocs increases
with the floc diameter. However, the strength of the individual particle bonds within the floc decreases with size. Large
flocs were relatively more brittle than smaller ones. The results suggest that larger flocs may be disrupted by the formation
of unequal fragments. 相似文献
92.
Multivariate statistical techniques, cluster and factor analyses were applied on the Amman/Wadi Sir groundwater chemistry, Yarmouk River basin, north Jordan. The main objective was to investigate the main processes affecting the groundwater chemical quality and its evolution. The k‐means cluster analysis yields three groups with distinct ionic concentrations. Cluster 1 comprises the vast majority of the sampled wells, and the water that belongs to this cluster can be classified as freshwater. Cluster 2 comprises only 2% of the sampled wells; it has the highest ionic concentration. The water of this cluster can be classified as brackish water. Cluster 3 involves 23% of the sampled wells, and it has total ionic concentration intermediate to that of clusters 1 and 2. Factor analysis yields a three‐factor model, which explains 76.77% of the groundwater quality variation. Factor 1 ‘salinity factor’ involves EC, Na+, Cl‐, SO4‐2, K+ and Mg+2 and reflects groundwater salinization because of overpumping. Factor 2 ‘hardness factor’ includes Ca+2, HCO3‐ and the pH value and signifies soil–water/rock interaction. Factor 3 ‘nitrate factor’ involves only NO3‐ and points to groundwater contamination because of human activities, mainly untreated wastewater, and crops and animal cultivation in the unconfined portion of the aquifer. Factors 1 and 3 can be described as human‐induced factors, whereas factor 2 can be described as geogenic factor. Factors' scores were mapped to deduce the controlling processes on the groundwater chemistry. Stable isotope composition of 18O and 2H has revealed that the groundwater is a mixture of two water types. The radioactive isotopes tritium and 14 C were used to evaluate present day recharge to the aquifer and to estimate the groundwater age, respectively. Present day recharge to the groundwater is taking place in the unconfined portion of the aquifer as it is indicated by the measurable tritium content and low groundwater age. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
93.
Although evidence for Quaternary environmental changes in the Arabian Peninsula is now growing, research has mostly been conducted in the United Arab Emirates (UAE) and in the Sultanate of Oman. There have been virtually no recent studies in Saudi Arabia, especially in the central region such as around Al‐Quwaiayh. In this area there are a series of outwash plains developed along the eastern edge of the Arabian Shield that formed in the late Quaternary. Four sedimentary sections, which are representative of the deposits that have accumulated, have been studied and five luminescence ages obtained. These are the first luminescence ages acquired from Quaternary sediments in central Saudi Arabia. The preserved fluvial deposits in the study area have formed during humid events at ca. 54 ka, ca. 39 ka and ca. 0.8 ka. In more recent times aeolian sands have been encroaching on to the distal parts of the outwash plains. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
94.
Dean A. Shaw Garth Vanderkamp F. Malcolm Conly Al Pietroniro Lawrence Martz 《水文研究》2012,26(20):3147-3156
The fill–spill of surface depressions (wetlands) results in intermittent surface water connectivity between wetlands in the prairie wetland region of North America. Dynamic connectivity between wetlands results in dynamic contributing areas for runoff. However, the effect of fill–spill and the resultant variable or dynamic basin contributing area has largely been disregarded in the hydrological community. Long‐term field observations recorded at the St. Denis National Wildlife Area, Saskatchewan, allow fill–spill in the basin to be identified and quantified. Along with historical water‐level observations dating back to 1968, recent data collected for the basin include snow surveys, surface water survey and production of a light detection and ranging–derived digital elevation model. Data collection for the basin includes both wet and dry antecedent basin conditions during spring runoff events. A surface water survey at St. Denis in 2006 reveals a disconnected channel network during the spring freshet runoff event. Rather than 100% of the basin contributing runoff to the outlet, which most hydrological models assume, only approximately 39% of the basin contributes to the outlet. Anthropogenic features, such as culverts and roads, were found to influence the extent and spatial distribution of contributing areas in the basin. Historical pond depth records illustrate the effect of antecedent basin conditions on fill–spill and basin contributing area. A large pond at the outlet of the St. Denis basin, which only receives local runoff during dry years when upstream surface storage has not been satisfied, has pond runoff volumes that increase by a factor of 20 or more during wet years when upstream antecedent basin surface storage is satisfied and basin‐wide runoff contributes to the pond. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
95.
Bednarik Martin Holzer Rudolf Pivko Daniel Tornyai Rudolf Hornáčková Alžbeta 《Geotechnical and Geological Engineering》2022,40(6):3287-3305
Geotechnical and Geological Engineering - This research focuses on assessing the most important physical and mechanical properties of rocks that were quarried from the north-eastern part of the... 相似文献
96.
Al-Mallah Inass A. Al-Qurnawi Wasan S. Ghalib Hussein B. Al Hawash Adnan B. Abdulameer Mariam H. 《中国地球化学学报》2022,41(5):823-838
Acta Geochimica - The Dibdibba aquifer is considered to be the main source in the Al-Zubair area because agriculture depends on it to provide grazing water in the area. The groundwater well samples... 相似文献
97.
Mashael Al Saud 《Hydrogeology Journal》2010,18(6):1481-1495
Water shortage has become a problem in many arid regions where rainfall is low. Wadi Aurnah Basin, in Saudi Arabia (Arabian Peninsula), where the Holy Islamic cities are located, was selected for study, since it represents a water-scarce region. The potential for groundwater storage was investigated. This was achieved using remote sensing and geographic information system (GIS) techniques to cover the whole area (3,113 km2). Satellite images with high spatial resolution were processed to recognize terrain elements controlling the subsurface rock behavior. Landsat 7 ETM+, ASTER and SRTM satellite images were processed using ERDAS IMAGINE software. The influencing factors on groundwater storage were determined and digitally mapped as thematic layers. This included rainfall, lithology, rock fractures, slope, drainage and land cover/use. These factors were integrated in the GIS system (ArcView). A map was produced, indicating potential areas for groundwater storage. The map shows that 12–15% of Wadi Aurnah Basin has potential for groundwater storage, mainly in areas where intensive fracture systems exist. 相似文献
98.
ABSTRACTThe automated classification of ambient air pollutants is an important task in air pollution hazard assessment and life quality research. In the current study, machine learning (ML) algorithms are used to identify the inter-correlation between dominant air pollution index (API) for PM10 percentile values and other major air pollutants in order to detect the vital pollutants’ clusters in ambient monitoring data around the study area. Two air quality stations, CA0016 and CA0054, were selected for this research due to their strategic locations. Non-linear RPart and Tree model of Decision Tree (DT) algorithm within the R programming environment were adopted for classification analysis. The pollutants’ respective significance to PM10 occurrence was evaluated using Random forest (RF) of DT algorithms and K means polar cluster function identified and grouped similar features, and also detected vital clusters in ambient monitoring data around the industrial areas. Results show increase in the number of clusters did not significantly alter results. PM10 generally shows a reduction in trend, especially in SW direction and an overall minimal reduction in the pollutants’ concentration in all directions is observed (less than 1). Fluctuations were observed in the behaviors of CO and NOx during the day while NOx displayed relative stability. Results also show that a direct and positive linear relationship exists between the PM10 (target pollutant) and CO, SO2, which suggests that these pollutants originate from the same sources. A semi-linear relationship is observed between the PM10 and others (O3 and NOx) while humidity shows a negative linearity with PM10. We conclude that most of the major pollutants show a positive trend toward the industrial areas in both stations while tra?c emissions dominate this site (CA0016) for CO and NOx. Potential applications of nuggets of information derived from these results in reducing air pollution and ensuring sustainability within the city are also discussed. Results from this study are expected to provide valuable information to decision makers to implement viable strategies capable of mitigating air pollution effects. 相似文献
99.
In Romania, agriculture has developed concomitently with the increased industrialization, and today agriculture plays a main role as the third world producer of sun-flower and hemp, the eighth of maize, the ninth of vine, etc. As Romania is geographically situated in the same zone as the big granaries of the world in the northern hemisphere and as it has a favourable climate it records one crop on 4/5 of the arable land, two crops a year on 1/5 and experimentally, three successive crops in the south of Oltenia. Similarly, the relief favours the development of agriculture under optimum conditions of mechanization on 70% of the territory. Agriculture has existed in Romania for about 6 millenia. Following the socialist transformation and modernization of agriculture—production /ha was increased two or three times and the crops rotation changed by introducing, beside cereals, a larger acreage of industrial crops, forage, vegetables, etc. The agricultural scene has been changed by substantial works of land improvement, especially dams, irrigation systems and a better land utilization. Industry, which takes over the added raw material provided by agriculture, has turned out agricultural machines and tools, chemical fertilizers, etc., required by agriculture. Finally, the authors give an agro-geographical characterization of the main natural units—the plains, the hills and plateaus, the mountain region and the Danube Delta. 相似文献
100.
NARX neural network approach for the monthly prediction of groundwater levels in Sylhet Sadar,Bangladesh
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Abdullah Al Jami Meher Uddin Himel Khairul Hasan Shilpy Rani Basak Ayesha Ferdous Mita 《地下水科学与工程》2020,8(2):118-126
Groundwater is important for managing the water supply in agricultural countries like Bangladesh. Therefore, the ability to predict the changes of groundwater level is necessary for jointly planning the uses of groundwater resources. In this study, a new nonlinear autoregressive with exogenous inputs(NARX) network has been applied to simulate monthly groundwater levels in a well of Sylhet Sadar at a local scale. The Levenberg-Marquardt(LM) and Bayesian Regularization(BR) algorithms were used to train the NARX network, and the results were compared to determine the best architecture for predicting monthly groundwater levels over time. The comparison between LM and BR showed that NARX-BR has advantages over predicting monthly levels based on the Mean Squared Error(MSE), coefficient of determination(R~2), and Nash-Sutcliffe coefficient of efficiency(NSE). The results show that BR is the most accurate method for predicting groundwater levels with an error of ± 0.35 m. This method is applied to the management of irrigation water source, which provides important information for the prediction of local groundwater fluctuation at local level during a short period. 相似文献