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Response of tenuous clay-polysaccharide flocs to hydrodynamic shearing 粘性粘土-多糖絮团对流体动力剪切的响应
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-09-20 DOI: 10.1016/j.ijsrc.2024.08.004
Li He , Hang Yin , Yongkang Wu , Wei Sun , Guoping Zhang
The response of suspended tenuous clay-polysaccharide flocs to hydrodynamic shearing was investigated in the laboratory via particle size analyses to understand the molecular-scale interactions between clay minerals and polysaccharides and their hydrodynamic behavior such as size kinetics, re-flocculation/breakdown, and shear strengths of the hybrid flocs. While the studied suspensions had a fixed clay concentration of 0.4 g/L, an array of other parameters was varied to reflect the complexity of clay-polysaccharide systems, including four types of clay minerals with varying layer charges and swellability (i.e., kaolinite, illite, and sodium- (Na-) and calcium- (Ca-) montmorillonites), two exopolymers of dissimilar polarities (i.e., xanthan and guar), six polysaccharide (P) to clay (C) weight ratios (i.e., P/C = 0, 1, 2, 5, 10, and 20 wt%), and three hydrodynamic shearing rates of 187, 429, and 1,100 1/s (i.e., corresponding to laminar, transitional, and turbulent flows, respectively). Results show that the clay-polysaccharide floc sizes are sensitive to the shear stress and also vary with different clay-polysaccharide systems. Four discrete particle groups were identified by statistical analyses, consisting of primary particle (PP), flocculi (FL), microfloc (MiF), and macrofloc (MaF), which exhibit distinct stabilities to shearing. The MaF is much weaker than MiF and can easily breakdown, as indicated by the decrease in MaF fraction with increasing shearing, while the MiF is the dominant particle group in transitional and turbulent flows. The fractions of PP and FL generally increase with shearing rate. Based on floc survivability in different flow conditions, the MaF's upper and lower bound shear strengths were estimated to be 0.95 and 0.17 Pa, respectively. The strongest MaF with a maximum shear strength of 0.95 Pa is formed in the clay-guar suspensions at a P/C of 10 wt%. Anionic xanthan only forms flocs with kaolinite with little surface charges, but cannot induce clay-polysaccharide flocs for illite and Ca/Na-montmorillonite with negative surface charges due to electrostatic repulsion. In contrast, neutral guar generates flocs with all 4 clay minerals due to the formation of hydrogen bonds, and MaF compounds usually are absent in turbulent flow (except kaolinite with a small fraction of MaF). These results further demonstrate the essential role of polysaccharide's polarity in dictating the flocculation dynamics, and, hence, sediment transport behavior. Practical implications of the findings are discussed in terms of the emerging technological applications of clay-polymer systems as well as the transport and modeling of natural aquatic cohesive sediment in biofilm-bearing waters.
在实验室中通过粒度分析研究了悬浮的粘性粘土多糖絮团对水动力剪切的反应,以了解粘土矿物和多糖之间的分子尺度相互作用及其水动力行为,如混合絮团的粒度动力学、再絮凝/破裂和剪切强度。虽然所研究的悬浮液的粘土浓度固定为 0.4 克/升,但为了反映粘土-多糖系统的复杂性,还改变了一系列其他参数,其中包括四种具有不同层电荷和溶胀性的粘土矿物(即高岭石、伊利石和高岭土)、高岭石、伊利石、钠(Na-)和钙(Ca-)蒙脱石)、两种极性不同的外聚合物(即黄原胶和瓜尔胶)、六种多糖(P)与粘土(C)的重量比(即P/C=0、1、2、5、10 和 20 wt%),以及 187、429 和 1,100 1/s 三种流体动力剪切速率(即分别对应层流、过渡流和湍流)。结果表明,粘土-多糖絮体的大小对剪切应力很敏感,而且随粘土-多糖体系的不同而变化。通过统计分析确定了四个离散的颗粒组,包括原生颗粒(PP)、絮凝体(FL)、微絮凝体(MiF)和大絮凝体(MaF),它们对剪切的稳定性各不相同。MaF 比 MiF 弱得多,很容易破裂,MaF 部分随着剪切力的增加而减少就说明了这一点,而 MiF 则是过渡流和湍流中的主要颗粒群。PP 和 FL 的比例通常会随着剪切速率的增加而增加。根据絮体在不同流动条件下的存活率,估计 MaF 的上下限剪切强度分别为 0.95 和 0.17 Pa。最大剪切强度为 0.95 Pa 的最强 MaF 是在 P/C 为 10 wt%的粘土-瓜耳悬浮液中形成的。阴离子黄原胶只能与表面电荷较少的高岭石形成絮团,但由于静电排斥作用,不能诱导表面带负电荷的伊利石和Ca/Na-蒙脱石形成粘土-多糖絮团。相反,中性瓜尔胶由于形成氢键而与所有 4 种粘土矿物产生絮凝体,而 MaF 化合物在紊流中通常不存在(含有少量 MaF 的高岭石除外)。这些结果进一步证明了多糖的极性在决定絮凝动力学,进而决定沉积物迁移行为方面的重要作用。本文从粘土-聚合物系统的新兴技术应用以及含生物膜水域中天然水生粘性沉积物的输运和建模两个方面讨论了这些发现的实际意义。
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引用次数: 0
Source identification of heavy metal contamination in beach sediments of the ancient city of Phaselis in Antalya, Türkiye 图尔基耶安塔利亚法塞利斯古城海滩沉积物中重金属污染的来源鉴定
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-09-14 DOI: 10.1016/j.ijsrc.2024.09.003
Ozge Ozer Atakoglu , Emirhan Berberoglu , Fusun Yalcin , Serife Gokaydin , Ebru Akkopru , Mustafa Gurhan Yalcin
The ancient city of Phaselis, which is located along gravel, coarse sandy, and sandy beaches, is a popular area visited by thousands of domestic and foreign tourists every year, and has been selected as the study area. Sediment samples collected from 57 different locations in the ancient city of Phaselis were analyzed using an X-ray fluorescence (XRF) spectrometer, and the major, trace, and rare earth element contents of the samples were revealed. The heavy metals arsenic (As), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), tin (Sn), stronsium (Sr), and zinc (Zn) were used in the pollution index calculations. Distribution maps revealed that heavy metal concentrations reached higher levels, especially in the eastern part of the study area. Therefore, it is recommended to plant rooted macrophytes that can absorb the heavy metals Cr and Ni and perform phytoremediation of the sediment in the region.
法塞里斯古城位于砾石滩、粗沙滩和沙滩沿岸,是每年有成千上万国内外游客到访的热门地区,因此被选为研究区域。研究人员使用 X 射线荧光光谱仪(XRF)对从法塞利斯古城 57 个不同地点采集的沉积物样本进行了分析,揭示了样本中主要元素、痕量元素和稀土元素的含量。重金属砷(As)、钴(Co)、铬(Cr)、铜(Cu)、镍(Ni)、铅(Pb)、锡(Sn)、锶(Sr)和锌(Zn)被用于污染指数计算。分布图显示,重金属浓度达到较高水平,尤其是在研究区域的东部。因此,建议在该地区种植能吸收重金属铬和镍的根系大型植物,对沉积物进行植物修复。
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引用次数: 0
Source-oriented health risk assessment of heavy metals in a soil-river continuum in northwest China 中国西北地区土壤-河流连续体中重金属的源导向健康风险评估
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-09-06 DOI: 10.1016/j.ijsrc.2024.09.001
Enqi Yang , Qingzheng Wang , Zepeng Zhang , Wenyan Shao , Haiping Luo , Xiong Xiao , Fei Ni , Jimin Mi , Xiazhong Sun , Qingyu Guan
Heavy metals can easily accumulate in soil and river sediment due to their non-degradability, which seriously endangers the balance of the ecosystem and human health. Thus, research on heavy metals in soil-river composite ecosystems has great significance for risk mitigation. As a seasonal river in a semi-arid region (Yuzhong county) in northwest China, the Wanchuan River supports nearly 500,000 people, but has been polluted by the heavy metals from industrial wastes and sewage discharges. To protect precious water resources and soil ecosystems, it is urgent to do heavy metal research in the Wanchuan River basin. Towards this end, the current study collected samples of soil and river sediment in this basin, and analyzed the distribution characteristics, health risks, and pollution sources of heavy metals, based on the pollution index evaluation method, health risk assessment, a geostatistical model, and the positive matrix factorization (PMF) model. The research results show that the contents of heavy metals in soil and river sediment were equivalent. However, contamination levels of heavy metals in stream sediment fell below that in soil. The results from the PMF model pointed out that natural sources contributed remarkably to the contents of heavy metals in soil, while industrial sources had the highest contribution to the contents of heavy metals in river sediment. According to the health risk assessment, among all selected metals, Cr brought about the highest carcinogenic risk, while As generated the highest non-carcinogenic risk. Source-oriented health risk assessment showed that natural sources (37%) and agricultural sources (50%), respectively, contributed most to the non-carcinogenic risks and carcinogenic risks induced by soil metals. Industrial sources contributed most both to the non-carcinogenic risks (46%) and carcinogenic risks (37%) induced by river sediment metals. The current research may offer theoretical bases for heavy metal pollution treatment in the soil-river continuum.
由于重金属的难降解性,重金属很容易在土壤和河流沉积物中积累,严重危害生态系统的平衡和人类健康。因此,研究土壤-河流复合生态系统中的重金属对降低风险具有重要意义。作为中国西北半干旱地区(榆中县)的一条季节性河流,万川河养育了近 50 万人口,但却受到了工业废料和污水排放所产生的重金属污染。为了保护珍贵的水资源和土壤生态系统,在万川河流域开展重金属研究迫在眉睫。为此,本研究采集了该流域的土壤和河流沉积物样品,基于污染指数评价法、健康风险评估、地质统计模型和正矩阵因子化(PMF)模型,分析了重金属的分布特征、健康风险和污染源。研究结果表明,土壤和河流沉积物中的重金属含量相当。但是,河流沉积物中的重金属污染水平低于土壤中的污染水平。PMF 模型的结果表明,自然来源对土壤中重金属含量的贡献显著,而工业来源对河流沉积物中重金属含量的贡献最大。根据健康风险评估,在所有选定的金属中,铬的致癌风险最高,而砷的非致癌风险最高。以来源为导向的健康风险评估显示,自然来源(37%)和农业来源(50%)分别对土壤金属的非致癌风险和致癌风险贡献最大。在河流沉积物金属诱发的非致癌风险(46%)和致癌风险(37%)中,工业来源的贡献最大。目前的研究可为土壤-河流连续过程中的重金属污染治理提供理论依据。
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引用次数: 0
Defining and characterizing the phenomenon of river-bottom tearing scour (RBTS): A case study of the Middle Yellow River 河底撕裂冲刷(RBTS)现象的定义和特征:黄河中游案例研究
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-09-03 DOI: 10.1016/j.ijsrc.2024.09.002
Enhui Jiang , Junhua Li , Yongtao Cao , Yanhui Liu , Yuanjian Wang , Qiang Wan , Li Pan
River-bottom tearing scour (RBTS) in natural rivers refers to the incipient motion and transport processes of clay blocks formed by fine cohesive sediment after deposition and consolidation in riverbeds. The RBTS phenomenon can lead to significant channel erosion and changes in river planview morphology, and has, thus, attracted the attention of hydrologists and engineers. In the study, a new determination measure (K) for the occurrence of a RBTS event is derived based on the theoretical expression for the critical incipient velocity of the clay block, K=α2(CL+2λ22), which is a combination of the coefficients of the velocity (i.e., α is a local velocity coefficient), lift force (i.e., CL is the lift coefficient), and clay block size (i.e., λ2 is the ratio of block thickness to length). Furthermore, to explain river behavior during a RBTS event, the Fugu, Xiaobeiganliu, and Weihe river reaches in the Middle Yellow River (MYR) were selected as study areas. Analysis of hydrological data from 1950 to 2023 in the examined reaches implies that a single discharge or sediment threshold cannot predict the occurrence of RBTS. The cross-sectional erosion and deposition volume (CEDV) and the migration intensity of the channel thalweg (MI) also were calculated at the section and reach scales for the examined reaches during the RBTS events. It was observed that RBTS typically causes significant channel erosion originating from the most upstream portion of the study reach with CEDV values ranging from 61 to 6034 m2, while MI values during the RBTS events were close to the multi-year average for the study reach. Finally, a flume experiment simulating RBTS was done to discuss and verify the threshold value of K. Field survey and experimental results indicated that RBTS occurs if K > 0.5, thus, providing theoretical support for the prediction and prevention of RBTS.
天然河流中的河底撕裂冲刷(RBTS)是指细粘性泥沙在河床中沉积和固结后形成的粘土块的初始运动和迁移过程。RBTS 现象可导致严重的河道侵蚀和河道平面形态变化,因此引起了水文学家和工程师的关注。在本研究中,根据粘土块临界初速度的理论表达式 K=α2(CL+2λ22),推导出了发生 RBTS 事件的新判定指标 (K),该指标是速度系数(即 α 是局部速度系数)、升力(即 CL 是升力系数)和粘土块大小(即 λ2 是粘土块厚度与长度之比)的组合。此外,为了解释 RBTS 事件期间的河流行为,黄河中游(MYR)的府谷、小北干流和渭河河段被选为研究区域。对研究河段 1950 年至 2023 年水文数据的分析表明,单一的排水量或泥沙阈值无法预测 RBTS 的发生。在 RBTS 事件期间,还计算了所研究河段的断面侵蚀和沉积量(CEDV)以及河道干流的迁移强度(MI)。结果表明,RBTS 通常会从研究河段的最上游造成严重的河道侵蚀,CEDV 值从 61 到 6034 平方米不等,而 RBTS 事件期间的 MI 值接近研究河段的多年平均值。最后,通过模拟 RBTS 的水槽实验来讨论和验证 K 的临界值。实地调查和实验结果表明,如果 K > 0.5,则会发生 RBTS,从而为预测和预防 RBTS 提供了理论支持。
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引用次数: 0
TOC 技术选择委员会
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-08-26 DOI: 10.1016/S1001-6279(24)00085-4
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引用次数: 0
Soil erosion susceptibility prediction using ensemble hybrid models with multicriteria decision-making analysis: Case study of the Medjerda basin, northern Africa 利用集合混合模型和多标准决策分析进行土壤侵蚀易感性预测:北非梅杰达盆地案例研究
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-08-24 DOI: 10.1016/j.ijsrc.2024.08.003
Asma Bouamrane , Hamouda Boutaghane , Ali Bouamrane , Noura Dahri , Habib Abida , Mohamed Saber , Sameh A. Kantoush , Tetsuya Sumi
Soil erosion is considered one of the most prevalent natural hazards in semiarid regions, leading to the instability of ecosystems and human life. The main purpose of this research was to investigate and analyze soil erosion susceptibility maps in the Medjerda basin in northern Africa. This study utilizes four ensemble models based on the analytical hierarchy process (AHP) multicriteria decision-making analysis, namely, deep learning neural network AHP (DLNN-AHP), frequency ratio AHP (FR-AHP), Monte Carlo AHP (MC-AHP), and fuzzy AHP (F-AHP). Eight predictor variables were considered as inputs to the model, namely, the slope degree, digital elevation model (DEM), topographic wetness index (TWI), distance to river (DFR), distance to road (DFRD), normalized difference vegetation index (NDVI), rainfall erosivity (R), factor and soil erodibility factor (K). Soil erosion inventory maps were developed from field surveys and satellite images. The dataset was randomly divided into 70% for training and 30% for testing. The performances of the utilized models were compared using a receiver operating characteristic (ROC) curve. The results highlighted that all the models utilized exhibited good performance, with DLNN-AHP (93.1%) exhibiting slight superiority, followed by FR-AHP (90.9%), F-AHP (88.9%), and MC-AHP (88.5%). Among the influencing factors, the distance to the river and rainfall erosivity had the most significant impacts on the incidence of soil erosion. Moreover, the current findings revealed that 38.3% of the study area is extremely highly susceptible to soil erosion. The results of this study can aid in developing decision-support tools for planners and managers aiming to mitigate the adverse effects of soil erosion.
水土流失被认为是半干旱地区最普遍的自然灾害之一,会导致生态系统和人类生活的不稳定。本研究的主要目的是调查和分析非洲北部梅杰达盆地的土壤侵蚀易感性地图。本研究采用了四种基于分析层次过程(AHP)多标准决策分析的集合模型,即深度学习神经网络 AHP(DLNN-AHP)、频率比 AHP(FR-AHP)、蒙特卡罗 AHP(MC-AHP)和模糊 AHP(F-AHP)。八个预测变量被视为模型的输入变量,即坡度、数字高程模型(DEM)、地形湿润指数(TWI)、河流距离(DFR)、道路距离(DFRD)、归一化植被差异指数(NDVI)、降雨侵蚀率()、因子和土壤可侵蚀性因子()。土壤侵蚀清单图是根据实地调查和卫星图像绘制的。数据集随机分为 70% 用于训练,30% 用于测试。使用接收器工作特征曲线(ROC)对所使用模型的性能进行了比较。结果表明,所有使用的模型都表现出良好的性能,其中 DLNN-AHP(93.1%)略胜一筹,其次是 FR-AHP(90.9%)、F-AHP(88.9%)和 MC-AHP(88.5%)。在影响因素中,河流距离和降雨侵蚀性对水土流失发生率的影响最为显著。此外,目前的研究结果表明,38.3% 的研究区域极易发生水土流失。这项研究的结果有助于为规划者和管理者开发决策支持工具,以减轻水土流失的不利影响。
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引用次数: 0
Formation condition for concave-bank deposition in the meanders of the Middle Yangtze River and its application 长江中游河道凹岸沉积的形成条件及其应用
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-08-22 DOI: 10.1016/j.ijsrc.2024.06.005
Xin Liu , Junqiang Xia , Shanshan Deng , Meirong Zhou , Koen Blanckaert
In what kind of meanders concave-bank deposition (CBD) can occur remains an open question. This study investigated the characteristics and major influencing factors of CBD in the meanders of the Middle Yangtze River (MYR), and proposed a formation condition for CBD. Concave-bank deposition occurred in 10 of 23 meanders in the MYR, including two types: counter point bar (CPB) and concave-bank bench (CBB). CPB occurred in both mildly-curved and sharp bends, while CBB only occurred in sharp bends. Hydrodynamic conditions and sediment supply are two major factors controlling the formation of CBD. The incoming sediment load remained in an amount of 0.68 × 108 t/y at Jianli and 0.77 × 108 t/y at Luoshan after Three Gorges Project operation, therefore, CBD development was not limited by a lack of sediment and instead is mainly dependent on the hydrodynamic conditions in the MYR. Flow separation zones were observed in the typical CBD-type bends of the MYR, which indicated that CBD was the result of flow separation or recirculation. An adverse longitudinal water surface gradient is the necessary condition for the formation of concave-bank flow separation. Therefore, a formation condition for CBD was proposed based on this assumption, which considered the combined effects of channel resistance, riverbed slope, channel widening, and curvature. CBD happens when the channel widening and curvature terms are greater than the channel resistance and longitudinal channel slope terms. The proposed condition was verified based on the data of the 23 bends in the MYR and 26 bends in 12 other rivers. The results indicated that more than 85% of the bends were correctly identified. Therefore, the proposed formation condition provided considerably high accuracy.
在什么样的河曲中会出现凹岸沉积(CBD)仍是一个未决问题。本研究探讨了长江中游河曲凹岸沉积的特征及其主要影响因素,并提出了凹岸沉积的形成条件。在长江中游 23 条河道中,有 10 条河道出现了凹岸沉积,包括两种类型:反点条形沉积(CPB)和凹岸台形沉积(CBB)。CPB 出现在轻度弯曲和急弯处,而 CBB 仅出现在急弯处。水动力条件和泥沙供应是控制 CBD 形成的两个主要因素。三峡工程运行后,监利和罗山的泥沙入库量分别保持在 0.68×10 吨/年和 0.77×10 吨/年,因此,CBD 的发育并不受制于泥沙的缺乏,而主要取决于多年河道的水动力条件。在马家河典型的 CBD 型弯道中观察到了分流区,这表明 CBD 是分流或再循环的结果。不利的纵向水面梯度是形成凹岸分流的必要条件。因此,根据这一假设,考虑到河道阻力、河床坡度、河道加宽和曲率的综合影响,提出了 CBD 的形成条件。当河道加宽和曲率项大于河道阻力和河道纵坡项时,就会出现 CBD。根据马约河 23 个弯道和其他 12 条河流 26 个弯道的数据,对提出的条件进行了验证。结果表明,85% 以上的弯道被正确识别。因此,所提出的形成条件具有相当高的准确性。
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引用次数: 0
Modeling flow resistance and geometry of dunes bed form in alluvial channels using hybrid RANN–AHA and GEP models 利用 RANN-AHA 和 GEP 混合模型模拟冲积河道中的流动阻力和沙丘床面的几何形状
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-08-16 DOI: 10.1016/j.ijsrc.2024.08.002
Riham Ezzeldin, Mahmoud Abd-Elmaboud
Dunes formation in sandy rivers significantly impacts flow resistance, subsequently affecting water levels, flow velocity, river navigation, and hydraulic structures performance. Accurate prediction of flow resistance and dune geometry (length and height) is essential for environmental engineering and river management. The current paper introduces two models to evaluate the flow resistance and geometry of dunes formed in sand-bed channels. The first model, RANN–AHA is a hybrid artificial intelligence model using the recurrent artificial neural network (RANN) linked with the artificial hummingbird optimization algorithm (AHA) to optimize the biases and weights of the neural network model. The second model uses gene expression programming (GEP) as a nonlinear approach based on a genetic algorithm (GA) and genetic programming (GP) to explicitly determine dune characteristics. For both models, the input parameters include flow and sediment characteristics, while Manning's roughness coefficient (nM), and relative dune height, h/H or h/L, were used as output parameters where h is the dune height, H is the flow depth above the dune crest, and L is the dune length. Five different published flume data sets were compiled for the analysis. Sensitivity analysis was done using different combinations of input parameters. It was found that the combination of hydraulic radius divided by median diameter (RH/d50), Reynolds number (Re), Particle densimetric Froude number (F∗), and grain Froude number (FG) yielded the best prediction accuracy for estimating Manning nM and relative height, h/H or h/L, with a root mean square error (RMSE) = 0.00027, 0.0504, and 0.0078 and a correlation coefficient (R) = 0.9989, 0.942, and 0.9272, respectively. Model verification proved that the RANN–AHA model outperformed the GEP model and most of the previous studies available in the literature when predicting the roughness coefficient and dune geometry in sand bed channels.
多沙河流中沙丘的形成会严重影响水流阻力,进而影响水位、流速、河流航运和水工建筑物的性能。准确预测流动阻力和沙丘几何形状(长度和高度)对于环境工程和河流管理至关重要。本文介绍了两个模型,用于评估沙床河道中形成的沙丘的流动阻力和几何形状。第一个模型 RANN-AHA 是一个混合人工智能模型,使用循环人工神经网络 (RANN) 与人工蜂鸟优化算法 (AHA) 相结合来优化神经网络模型的偏置和权重。第二个模型使用基因表达编程(GEP)作为基于遗传算法(GA)和遗传编程(GP)的非线性方法,明确确定沙丘特征。对于这两个模型,输入参数包括水流和沉积物特征,而曼宁粗糙度系数()和沙丘相对高度/或/则被用作输出参数,其中为沙丘高度,为沙丘顶上的水流深度,为沙丘长度。为进行分析,汇编了五个不同的已公布水槽数据集。使用不同的输入参数组合进行了敏感性分析。结果发现,水力半径除以中值直径 (/)、雷诺数 (Re)、颗粒密度测量弗劳德数 (∗) 和颗粒弗劳德数 ()的组合在估算曼宁和相对高度 / 或 / 时具有最佳预测精度,均方根误差 (RMSE) 分别为 0.00027、0.0504 和 0.0078,相关系数 () 分别为 0.9989、0.942 和 0.9272。模型验证证明,RANN-AHA 模型在预测沙床河道的粗糙度系数和沙丘几何形状时,优于 GEP 模型和大多数先前的文献研究。
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引用次数: 0
Soil erosion risk assessment of the Lakhmess watershed (northwestern Tunisia) via the SEAGIS model: Inferred prioritization of risky sub-watersheds 通过 SEAGIS 模型对 Lakhmess 流域(突尼斯西北部)进行土壤侵蚀风险评估:推断风险子流域的优先次序
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-08-10 DOI: 10.1016/j.ijsrc.2024.08.001
Afef Marghmi , Lilia Ben Cheikha , Amina Mabrouk El Asmi , Moncef Gueddari
Water erosion in Tunisian semi-arid regions causes harmful effects by silting reservoirs and reducing agricultural lands and soil fertility. Several factors are involved in the erosion process: rain erosivity, soil fragility, and degraded land cover on steep slopes associated with the intensification of inappropriate human practices. Thus, identifying erosion vulnerable sub-watersheds based on the assessed soil loss rate is very important to apply suitable conservation measures. The current research aimed to prioritize risky areas in the Lakhmess watershed, north-west Tunisia via the Soil Erosion Assessment using Geographical Information System (SEAGIS) model. To prioritize sub-watersheds vulnerable to soil erosion and sediment yield, the Lakhmess watershed, covering an area of 162 km2, was divided into 16 sub-watersheds (L1–L16), according to the hydrographic network. Then, the mean annual soil erosion rate and the mean annual sediment yield in the watershed were estimated by integrating the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) in the SEAGIS model and their spatial distribution was determined. The obtained results indicate that the estimated average annual soil erosion rate is 4.2 t/ha/y and the annual sediment yield is 2.6 t/ha/y. Maner's SDR model was selected as the best model for estimating SY, with standard error, standard deviation, and coefficient of variation values of 0.75%, 0.01, and 0.45%, respectively. The prioritization of the Lakhmess sub-watersheds based on the estimated soil loss rate reveals that among the 16 sub-watersheds, three sub-watersheds (L10, L12, and L15) were identified as being in a very high priority soil erosion class. The high soil erosion rate and sediment yield in these sub-watersheds is explained by the steep slope and a high rainfall erosivity factor. Six sub-watersheds (L2, L4, L5, L6, L7, and L16) were found to belong to a very low priority soil erosion class, as they are characterized by a very gentle slope, which appears to be an extremely determining factor. These findings constitute a basis for decision makers to plan effective conservation measures to conserve agricultural lands, soil, and water resources in northwestern Tunisia.
突尼斯半干旱地区的水土流失造成水库淤塞、农田减少和土壤肥力下降等有害影响。水土流失过程涉及多个因素:雨水的侵蚀性、土壤的脆弱性以及与人类不当行为加剧有关的陡坡土地覆盖退化。因此,根据评估的土壤流失率确定易受侵蚀的次级流域对于采取适当的保护措施非常重要。目前的研究旨在通过使用地理信息系统(SEAGIS)模型进行土壤侵蚀评估,确定突尼斯西北部拉赫梅斯流域风险区域的优先次序。为了确定易受土壤侵蚀和泥沙产生影响的子流域的优先次序,根据水文地理网络,将面积为 162 千米的拉赫梅斯流域划分为 16 个子流域(L1-L16)。然后,利用 SEAGIS 模型中的修订通用土壤流失方程(RUSLE)和泥沙输移比(SDR),估算了流域的年平均土壤侵蚀率和年平均泥沙输移量,并确定了它们的空间分布。结果表明,估计年平均土壤侵蚀率为 4.2 吨/公顷/年,年泥沙产量为 2.6 吨/公顷/年。Maner 的 SDR 模型被选为估算 SY 的最佳模型,其标准误差、标准偏差和变异系数值分别为 0.75%、0.01 和 0.45%。根据估算的土壤流失率对拉克梅斯分流域进行优先级排序后发现,在 16 个分流域中,有 3 个分流域(L10、L12 和 L15)被确定为土壤侵蚀优先级极高的流域。这些次级流域的土壤侵蚀率和泥沙产量较高的原因是坡度陡峭和降雨侵蚀系数较高。六个次级流域(L2、L4、L5、L6、L7 和 L16)被认定为属于极低优先级的土壤侵蚀等级,因为它们的特点是坡度非常平缓,这似乎是一个极其重要的决定因素。这些发现为决策者规划有效的保护措施提供了依据,以保护突尼斯西北部的农田、土壤和水资源。
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引用次数: 0
Sustainable systems engineering by CFD modeling of lateral intake flow with flexible gate operations to improve efficient water supply 可持续系统工程,通过 CFD 对横向取水口水流进行建模,采用灵活的闸门操作,提高供水效率
IF 3.5 2区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-08-01 DOI: 10.1016/j.ijsrc.2024.05.003

Lateral intakes are very important for diverting a portion of the river flow and providing the proper flow depth. In cases where small dams are used to operate and control the river's water level for the intake and to meet downstream water needs, the opening and closing of the dam gates before the construction of the intake and during its operation are important. In the current study, the problem of reducing the water head in the intake basin of the Hemmat dam pumping station, especially in the seasons of low water and the accumulation of sediment in the intake inlet of the Hemmat dam located in the Khuzestan province of Iran, has been investigated. Focusing on different arrangements of opening and closing gates, using a spur dike and flow rates of 143, 100, 62, 32, and 12 m3/s to investigate velocity changes and the depth of flow at the water inlet, computational fluid dynamics (CFD) simulations were done. With the spur dike, the water intake efficiency is increased by 384% compared to the project's current state (operation without any flow control structure), and the hydraulic conditions resulting in sedimentation are eliminated. The flow depth of the water intake channel, with the spur dike, increases by 10% compared to the condition without it. It is worth mentioning that gate management also affects water supply efficiency. The results of the current study are a good example of the successful application of computer simulations for sustainable systems engineering.

侧向取水口对于分流部分河水和提供适当的水流深度非常重要。在使用小型水坝来操作和控制河流水位以满足取水口和下游用水需求的情况下,取水口建造前和运行期间水坝闸门的开启和关闭非常重要。本研究调查了降低 Hemmat 大坝泵站取水口流域水头的问题,尤其是在低水位季节和位于伊朗胡齐斯坦省的 Hemmat 大坝取水口泥沙淤积的情况下。针对不同的闸门启闭方式,利用支堤和 143、100、62、32 和 12 米/秒的流速,对进水口的流速变化和水流深度进行了计算流体动力学(CFD)模拟。与工程现状(无任何流量控制结构的运行)相比,采用支堤后,取水效率提高了 384%,并消除了导致沉积的水力条件。与没有支堤的情况相比,有支堤的取水渠道水深增加了 10%。值得一提的是,水闸管理也会影响供水效率。本次研究的结果是将计算机模拟成功应用于可持续系统工程的典范。
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引用次数: 0
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International Journal of Sediment Research
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