Pumping optimization of coastal aquifers based on evolutionary algorithms and surrogate modular neural network models   总被引：4，自引：0，他引：4  

George Kourakos  Aristotelis Mantoglou 《Advances in water resources》2009

Pumping optimization of coastal aquifers involves complex numerical models. In problems with many decision variables, the computational burden for reaching the optimal solution can be excessive. Artificial Neural Networks (ANN) are flexible function approximators and have been used as surrogate models of complex numerical models in groundwater optimization. However, this approach is not practical in cases where the number of decision variables is large, because the required neural network structure can be very complex and difficult to train. The present study develops an optimization method based on modular neural networks, in which several small subnetwork modules, trained using a fast adaptive procedure, cooperate to solve a complex pumping optimization problem with many decision variables. The method utilizes the fact that salinity distribution in the aquifer, depends more on pumping from nearby wells rather than from distant ones. Each subnetwork predicts salinity in only one monitoring well, and is controlled by relatively few pumping wells falling within certain control distance from the monitoring well. While the initial control area is radial, its shape is adaptively improved using a Hermite interpolation procedure. The modular neural subnetworks are trained adaptively during optimization, and it is possible to retrain only the ones not performing well. As optimization progresses, the subnetworks are adapted to maximize performance near the current search space of the optimization algorithm. The modular neural subnetwork models are combined with an efficient optimization algorithm and are applied to a real coastal aquifer in the Greek island of Santorini. The numerical code SEAWAT was selected for solving the partial differential equations of flow and density dependent transport. The decision variables correspond to pumping rates from 34 wells. The modular subnetwork implementation resulted in significant reduction in CPU time and identified an even better solution than the original numerical model.  相似文献   

A continuous,real-time water quality monitoring system for the coral reef ecosystems of Nanwan Bay,Southern Taiwan     

Kwee Siong Tew  Ming-Yih Leu  Jih-Terng Wang  Chia-Ming Chang  Chung-Chi Chen  Pei-Jie Meng 《Marine pollution bulletin》2014

The coral reef ecosystems of Nanwan Bay, Southern Taiwan are undergoing degradation due to anthropogenic impacts, and as such have resulted in a decline in coral cover. As a first step in preventing the continual degradation of these coral reef environments, it is important to understand how changes in water quality affect these ecosystems on a fine-tuned timescale. To this end, a real-time water quality monitoring system was implemented in Nanwan Bay in 2010. We found that natural events, such as cold water intrusion due to upwelling, tended to elicit temporal shifts in coral spawning between 2010 and 2011. In addition, Degree Heating Weeks (DHWs), a commonly utilized predictor of coral bleaching, were 0.92 and 0.59 in summer 2010 and 2011, respectively. Though this quantity of DHW was below the presumed stress-inducing value for these reefs, a rise in DHWs in the future may stress the resident corals.  相似文献   

Glyphosate persistence in seawater     

Philip Mercurio  Florita Flores  Jochen F. Mueller  Steve Carter  Andrew P. Negri 《Marine pollution bulletin》2014

Glyphosate is one of the most widely applied herbicides globally but its persistence in seawater has not been reported. Here we quantify the biodegradation of glyphosate using standard “simulation” flask tests with native bacterial populations and coastal seawater from the Great Barrier Reef. The half-life for glyphosate at 25 °C in low-light was 47 days, extending to 267 days in the dark at 25 °C and 315 days in the dark at 31 °C, which is the longest persistence reported for this herbicide. AMPA, the microbial transformation product of glyphosate, was detected under all conditions, confirming that degradation was mediated by the native microbial community. This study demonstrates glyphosate is moderately persistent in the marine water under low light conditions and is highly persistent in the dark. Little degradation would be expected during flood plumes in the tropics, which could potentially deliver dissolved and sediment-bound glyphosate far from shore.  相似文献   

Occurrence,distribution and partitioning of nonionic surfactants and pharmaceuticals in the urbanized Long Island Sound Estuary (NY)     

Pablo A. Lara-Martín  Eduardo González-Mazo  Mira Petrovic  Damià Barceló  Bruce J. Brownawell 《Marine pollution bulletin》2014

This work deals with the environmental distribution of nonionic surfactants (nonylphenol and alcohol ethoxylates), their metabolites (NP, nonylphenol; NPEC, nonylphenol ethoxycarboxylates; and PEG, polyethylene glycols) and a selection of 64 pharmaceuticals in the Long Island Sound (LIS) Estuary which receives important sewage discharges from New York City (NYC). Most target compounds were efficiently removed (>95%) in one wastewater treatment plant monitored, with the exception of NPEC and some specific drugs (e.g., hydrochlorothiazide). Concentrations of surfactants (1.4–4.5 μg L⁻¹) and pharmaceuticals (0.1–0.3 μg L⁻¹) in seawater were influenced by tides and sampling depth, consistent with salinity differences. Surfactants levels in suspended solids samples were higher than 1 μg g⁻¹, whereas only most hydrophobic or positively charged pharmaceuticals could be found (e.g., tamoxifen, clarithromycin). Maximum levels of target compounds in LIS sediments (PEG at highest concentrations, 2.8 μg g⁻¹) were measured nearest NYC, sharply decreasing with distance from major sewage inputs.  相似文献   

Contribution of electrical resistivity tomography to the study of detrital aquifers affected by seawater intrusion–extrusion effects: The river Vélez delta (Vélez-Málaga, southern Spain)     

J. Martínez  J. Benavente  J.L. García-Arstegui  M.C. Hidalgo  J. Rey 《Engineering Geology》2009,108(3-4):161-168

The coastal aquifer of the Plio-Quaternary delta sediment deposits of the Vélez river (province of Málaga, Spain) presents a highly irregular basement morphology and widely varying fill thickness (10–80 m between neighbouring sectors). The basin, which is tectonically controlled, is filled with lutite facies alternating with channel-filling rudites. This detrital aquifer is affected by seasonal seawater intrusion–extrusion processes due to increasing withdrawal of groundwater for human consumption and irrigation during dry periods.A study was performed to improve the hydrogeological knowledge of this coastal aquifer system. The study examined the morphology of the impervious substratum, the facies distribution and the position of the seawater wedge. For this purpose, an Electrical Resistivity Tomography (ERT) geophysical technique was used and the tomographic data were calibrated using geological observations and borehole studies. An analysis was carried out to compare the direct information obtained from the 35 boreholes with the indirect data corresponding to the four electrical tomography profiles. In the study, over 9660 resistivity data points were processed.The ERT profiles perfectly corroborated the information derived from the boreholes. The profiles made it possible to detect thickness changes, lithological changes and the presence of faults. Moreover, from a hydrogeologic standpoint, this research technique is capable of detecting the position of the phreatic level and, in coastal aquifers such as the one examined in this study, the possible horizontal or vertical penetration of seawater intrusion. Therefore, the electrical geophysical prospecting based on ERT can be highly useful in areas lacking sufficient geological information and/or mechanical borehole data.  相似文献   

ICP-OES标准加入法准确测定海水中的硼     

孙玲玲  宋金明  于颖  孙萱  温廷宇 《海洋科学》2017,41(6):55-60

硼作为海水中的重要组分,其准确测定对海洋环境生物地球化学过程研究具有重要意义。海水中硼的常用测定方法具有前处理步骤繁琐、耗时长、样品易被污染、灵敏度低等缺点,不适于大批量海水样品的准确测定。为剔除海水高盐基体效应及干扰,本文运用电感耦合等离子体发射光谱法(ICP-OES),将海水样品进行稀释,采用标准加入法建立工作曲线,对海水中硼含量进行准确测定。正交实验显示,ICP-OES最佳工作条件为射频功率1400 W,雾化气流量0.7 L/min,观测高度14 mm,进样泵速1.5 m L/min。标准加入法标准曲线相关系数大于0.999,相对标准偏差为0.76%~1.27%,加标回收率为94.6%~101.8%,方法检出限为1.073μg/L。实际的海水样品分析表明,该方法可消除海水基体干扰,减少测定误差,并且前处理操作简单快速,化学试剂用量少,回收率高,精密度好,灵敏度高,可用于海水及其它高盐样品中硼含量的准确测定。  相似文献   

Hydrochemical changes in a small tropical island’s aquifer: Manukan Island, Sabah, Malaysia   总被引：1，自引：0，他引：1  

A. Z. Aris  M. H. Abdullah  K. W. Kim  S. M. Praveena 《Environmental Geology》2009,56(8):1721-1732

Small islands groundwater are often exposed to heavy pumpings as a result of high demand for freshwater consumption. Intensive exploitation of groundwater from Manukan Island’s aquifer has disturbed the natural equilibrium between fresh and saline water, and has resulted increase the groundwater salinity and leap to the hydrochemical complexities of freshwater–seawater contact. An attempt was made to identify the hydrochemical processes that accompany current intrusion of seawater using ionic changes and saturation indices. It was observed that the mixing between freshwater–seawater created diversity in geochemical processes of the Manukan Island’s aquifer and altered the freshwater and seawater mixture away from the theoretical composition line. This explained the most visible processes taking place during the displacement.  相似文献   

Application of major and trace elements as well as boron isotopes for tracing hydrochemical processes: the case of Trifilia coastal karst aquifer,Greece     

G. Panagopoulos 《Environmental Geology》2009,58(5):1067-1082

The Trifilia karst aquifer presents a complex hydrochemical character due to the intricate geochemical processes that take place in the area. Their discernment was achieved by using the chemical analyses of major, trace elements and boron isotopes. Major ion composition indicates mixing between seawater and freshwater is occurring. Five hydrochemical zones corresponding to five respective groundwater types were distinguished, in which the chemical composition of groundwater is influenced mainly due to the different salinization grade of the aquifer. The relatively increased temperature of the aquifer indicates the presence of hydrothermal waters. Boron isotopes and trace elements indicate that the intruding seawater has been hydrothermally altered, as it is shown by the δ¹¹B depleted signature and the increased concentrations of Li and Sr. Trace elements analyses showed that the groundwater is enriched in various metallic elements, which derive from the solid hydrocarbons (bitumens), contained in the carbonate sediments of the Tripolis zone. The concentration of these trace elements depends on the redox environment. Thus, in reductive conditions As, Mn, Co and NH₄ concentrations are high, in oxidized conditions the V, Se, Mo, Tl and U concentration increases while Ni is not redox sensitive and present high concentration in both environments.  相似文献   

A modeling study of seawater intrusion in Alabama Gulf Coast,USA   总被引：4，自引：0，他引：4  

Jin Lin  J. Blake Snodsmith  Chunmiao Zheng  Jianfeng Wu 《Environmental Geology》2009,57(1):119-130

A numerical model of variable-density groundwater flow and miscible salt transport is developed to investigate the extent of seawater intrusion in the Gulf coast aquifers of Alabama, USA. The SEAWAT code is used to solve the density-dependent groundwater flow and solute transport governing equations. The numerical model is calibrated against the observed hydraulic heads measured in 1996 by adjusting the zonation and values of hydraulic conductivity and recharge rate. Using the calibrated model and assuming all the hydrogeologic conditions remain the same as those in 1996, a predictive 40-year simulation run indicates that further seawater intrusion into the coastal aquifers can occur in the study area. Moreover, the predicted intrusion may be more significant in the deeper aquifer than the shallower ones. As the population continues to grow and the demand for groundwater pumping intensifies beyond the 1996 level, it can be expected that the actual extent of seawater intrusion in the future would be more severe than the model prediction. Better strategies for groundwater development and management will be necessary to protect the freshwater aquifers from contamination by seawater intrusion.

Jin LinEmail:

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Adsorption behaviour of dibutyl phthalate on marine sediments   总被引：1，自引：0，他引：1  

Xu XR  Li XY 《Marine pollution bulletin》2008,57(6-12):403-408

Laboratory experiments were carried out to investigate the adsorption behaviour of dibutyl phthalate (DBP) on marine sediments collected from five different sites in Victoria Harbour, Hong Kong. DBP adsorption can be well described by the Langmuir isotherm. The maximum DBP adsorption capacity (Q(max)) of the marine sediments ranges from 53 to 79 mg g(-1), which has a positive correlation with their organic content. Around 90% of the organic can be removed from the sediments with treatment by H(2)O(2) oxidation, and the Q(max) then decreases to a range between 13 and 22 mg g(-1). The black carbon content of the sediments has a much greater DBP adsorption capacity than does the natural organic matter of the sediments. The amount of DBP adsorbed on the sediments increases as the salinity of the marine water increases.  相似文献