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Aeolian sand cover on a granite peninsula (Hammeren, Bornholm, Baltic Sea) formed in three episodes during the past 11,600 years 花岗岩半岛(波罗的海,博恩霍尔姆岛,哈默伦)上的风化沙覆盖层在过去 11 600 年间分三次形成
IF 3.1 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2024-10-16 DOI: 10.1016/j.aeolia.2024.100944
Aeolian sand covers a significant part of the granite peninsula Hammeren on northernmost Bornholm in the Baltic Sea. The coastline of Hammeren is rocky and apart from one relative wide and sandy pocket beach at the east coast only few, small and gravelly pocket beaches exist. The aeolian deposits form three sand covers that stretch inland from the east and northwestern facing coasts of Hammeren. The largest sand cover forms a rising sand plain that cover the granitic landscape up to 700 m inland and reaches up to 60 m above sea level. Historical sources mention aeolian sand movement around CE 1775 in the middle of the Little Ice Age, but until this study no absolute age control has been available to confirm these observations. Luminescence dating of selected sample sites indicates that aeolian sand movement took place in three episodes. The first episode was in the last part of the Younger Dryas at about 11,500 BP, the second episode was in the Danish Late Bronze Age at about 2700 BP, and the youngest episode was indeed during the Little Ice Age around 200 BP (CE 1750). These episodes with aeolian activity all fall during relatively cold climatic intervals and add support to previous studies indicating a link between cold climates an increased storminess in Northwest Europe including the southern Baltic Sea region.
在波罗的海博恩霍尔姆岛(Bornholm)最北端的花岗岩半岛哈默伦(Hammeren)上,有很大一部分地区都覆盖着风化沙。哈默伦半岛的海岸线多岩石,除了东海岸有一个相对宽阔的袋状沙滩外,只有几个小的砾质袋状沙滩。风化沉积物形成了三个沙层,从哈默伦的东海岸和西北海岸向内陆延伸。最大的沙层形成了一个隆起的沙原,覆盖了内陆 700 米的花岗岩地貌,最高处达海拔 60 米。历史资料提到,在小冰河时期中期,即公元 1775 年左右曾出现过风沙运动,但在本研究之前,还没有绝对的年代对照来证实这些观察结果。对选定样本地点进行的荧光测年表明,风沙运动分为三个阶段。第一段发生在小干纪末,约公元前 11500 年;第二段发生在丹麦青铜时代晚期,约公元前 2700 年;最年轻的一段发生在小冰河时期,约公元前 200 年(公元 1750 年)。这些有风化活动的事件都发生在相对寒冷的气候间歇期,为之前的研究提供了支持,这些研究表明寒冷气候与西北欧(包括波罗的海南部地区)风暴增加之间存在联系。
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引用次数: 0
Speculation on an early Pleistocene origin of the Parker dunes of southwest Arizona, USA 关于美国亚利桑那州西南部帕克沙丘早更新世起源的推测
IF 3.1 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2024-10-11 DOI: 10.1016/j.aeolia.2024.100943
The Parker Dunes in western Arizona, USA represent the largest dune system in the Sonoran Desert. This study presents a simple 10Be-26Al cosmogenic burial age of 1.90 ± 0.20 Ma, obtained from well cuttings 240–270 m deep in Butler Valley, just east of the dune field. Given the large errors associated with burial dating, we can only speculate that this oldest known aeolian sediment within the Parker Dunes is roughly concurrent with the Bat Cave flood event ca. 2.1 Ma of the nearby Colorado River, as well as regional climatic aridity during the early Pleistocene. Since older dune deposits may be present at other locations in the Parker Dunes, its origin dates back to at least the early Pleistocene. The more important, broader implication rests in highlighting the underutilized potential of well cuttings as a sediment source for cosmogenic burial dating in aeolian research.
美国亚利桑那州西部的帕克沙丘是索诺拉沙漠中最大的沙丘系统。本研究从沙丘区东部巴特勒山谷 240 至 270 米深的钻孔中获得了简单的 10Be-26Al 宇宙成因埋藏年龄,即 1.90 ± 0.20 Ma。鉴于埋藏年代测定存在较大误差,我们只能推测帕克沙丘内已知最古老的风化沉积物与附近科罗拉多河约 2.1 Ma 的蝙蝠洞洪水事件以及更新世早期的区域气候干旱大致同时发生。由于帕克沙丘的其他位置可能存在更古老的沙丘沉积,因此其起源至少可以追溯到更新世早期。更重要、更广泛的意义在于,它强调了在风化研究中,作为宇宙成因埋藏年代测定的沉积物来源,井碴的潜力未得到充分利用。
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引用次数: 0
Transport and deposition of microplastics and microrubbers during a dust storm (Sarakhs, northeast Iran) 沙尘暴期间微塑料和微橡胶的迁移和沉积(伊朗东北部萨拉赫斯)
IF 3.1 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2024-09-30 DOI: 10.1016/j.aeolia.2024.100942
Dust storms are important vehicles for the erosion and translocation of geogenic material in arid and semi-arid climates but little is known about their role in transporting microplastics (MPs). In this study, local soils (n = 20) and dusts deposited from a storm (n = 41) have been sampled from a remote region of northeastern Iran (Sarakhs) and the quantities and characteristics of MPs and microrubbers (MRs) determined using established techniques. In dusts, MPs and MRs were detected in 33 and 17 cases, respectively, with respective median and maximum concentrations of 0.48 and 23.0 MP g−1 and 0.50 and 6.48 MR g−1 and depositional fluxes of up to about 12 MP m−2 h−1 and 7 MR m−2 h−1. In soils, MPs and MRs were detected in ten and eight cases, respectively, with respective median and maximum concentrations of 0.25 and 1.90 MP g−1 and 3.27 and 14.3 MR g−1. Overall, the ratio of MPs in dusts to soils relative to MRs in dusts to soils was about 20, reflecting the greater mobility of the former type of particle. This can be attributed to the ready suspension and more favourable aerodynamic properties of fibrous MPs compared with fragmented MRs. A comparison of MPs in dusts and soils suggests a preferential long-range transport of fibres with certain characteristics (e.g., long, red and constructed of polypropylene), with HYSPLIT back trajectory modelling suggesting secondary (e.g., soil) sources to the south and southwest. Dust storms are important regional transporters of atmospheric MPs and MRs whose role is predicted to increase as desertification and the demands for potable water and plastics rise.
沙尘暴是干旱和半干旱气候条件下侵蚀和转移地质材料的重要载体,但人们对沙尘暴在迁移微塑料(MPs)方面的作用却知之甚少。本研究从伊朗东北部偏远地区(萨拉赫斯)采集了当地土壤(n = 20)和暴风雨沉积的尘埃(n = 41)样本,并采用成熟技术测定了微塑料和微橡胶(MRs)的数量和特征。在粉尘中,分别检测到 33 和 17 个 MPs 和 MRs,其浓度中位数和最大值分别为 0.48 和 23.0 MP g-1 和 0.50 和 6.48 MR g-1,沉积通量分别高达约 12 MP m-2 h-1 和 7 MR m-2 h-1。在土壤中,分别检测到 10 个 MPs 和 8 个 MRs,浓度中位数和最大值分别为 0.25 MP g-1 和 1.90 MP g-1 以及 3.27 MR g-1 和 14.3 MR g-1。总体而言,粉尘和土壤中的 MP 与粉尘和土壤中的 MR 之比约为 20,反映出前一类颗粒的流动性更大。这可归因于纤维状 MPs 易于悬浮,而且与碎裂的 MRs 相比,纤维状 MPs 具有更有利的空气动力学特性。对尘埃和土壤中的 MPs 进行比较后发现,具有某些特征(如长、红色和聚丙烯结构)的纤维更倾向于长程飘移,而 HYSPLIT 的后向轨迹建模则表明其次要来源(如土壤)在南部和西南部。沙尘暴是大气中 MPs 和 MRs 的重要区域传播者,随着荒漠化的加剧以及对饮用水和塑料需求的增加,预计沙尘暴的作用会越来越大。
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引用次数: 0
Characterizing variability in geochemistry and mineralogy of western US dust sources 美国西部尘源的地球化学和矿物学变异特征
IF 3.1 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2024-09-21 DOI: 10.1016/j.aeolia.2024.100941
Dust events originate from multiple sources in arid and semi-arid regions, making it difficult to quantify source contributions. Dust geochemical/mineralogical composition, if the sources are sufficiently distinct, can be used to quantify the contributions from different sources. To test the viability of using geochemical and mineralogical measurements to separate dust-emitting sites, we used dust samples collected between 2018 and 2020 from ten National Wind Erosion Research Network (NWERN) sites that are representative of western United States (US) dust sources. Dust composition varied seasonally at many of the sites, but within-site variability was smaller than across-site variability, indicating that the geochemical signatures are robust over time. It was not possible to separate all the sites using commonly applied principal component analysis (PCA) and cluster analysis because of overlap in dust geochemistry. However, a linear discriminant analysis (LDA) successfully separated all sites based on their geochemistry, suggesting that LDA may prove useful for separating dust sources that cannot be separated using PCA or other methods. Further, an LDA based on mineralogical data separated most sites using only a limited number of mineral phases that were readily explained by the local geologic setting. Taken together, the geochemical and mineralogical measurements generated distinct signatures of dust emissions across NWERN sites. If expanded to include a broader range of sites across the western US, a library of geochemical and mineralogical data may serve as a basis to track and quantify dust contributions from these sources.
在干旱和半干旱地区,尘埃事件有多种来源,因此很难量化来源的贡献。如果尘埃的地球化学/矿物成分来源足够明确,则可用于量化不同来源的贡献。为了测试使用地球化学和矿物学测量来区分沙尘排放源的可行性,我们使用了 2018 年至 2020 年期间从 10 个国家风蚀研究网络(NWERN)站点收集的沙尘样本,这些站点是美国西部沙尘源的代表。在许多站点,尘埃成分随季节而变化,但站点内的变化小于站点间的变化,这表明地球化学特征随时间变化是稳健的。由于粉尘地球化学特征存在重叠,因此无法使用常用的主成分分析(PCA)和聚类分析将所有地点分开。不过,线性判别分析(LDA)成功地根据地球化学特征将所有地点区分开来,这表明线性判别分析可用于区分无法用 PCA 或其他方法区分的尘源。此外,基于矿物学数据的 LDA 只使用了有限的几种矿物相来分离大多数地点,而这些矿物相很容易用当地的地质环境来解释。综合来看,地球化学和矿物学测量得出了西北地区各站点灰尘排放的不同特征。如果将范围扩大到美国西部更广泛的地点,那么地球化学和矿物学数据库就可以作为跟踪和量化这些来源的粉尘贡献的基础。
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引用次数: 0
Automatic identification of saltating tracks driven by strong wind in high-speed video using multiple statistical quantities of instant particle velocity 利用粒子瞬时速度的多个统计量自动识别高速视频中由强风驱动的盐渍化轨迹
IF 3.1 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2024-09-21 DOI: 10.1016/j.aeolia.2024.100940

The evolution of saltating tracks driven by strong wind remains unknown due to the low accuracy or recall rates of saltating particle tracking algorithms (SPTs). Manual identification of saltating tracks becomes a primary bottleneck because of low efficiency, restricting the development of new SPTs with high accuracy. Herein, we proposed an optimized tree model for automatically identifying saltating tracks in the high-speed video under strong wind through establishing the dataset with multiple statistical quantities of instant saltating velocity (MSQV) and the workflow embracing the Tree-structured Parzen Estimator (TPE). The optimized Categorical Boosting model by the D3 dataset (CatBoost-D3) could be considered the best classifier among the tree models, owning the higher accuracy (0.9352), precision (0.9348), recall (0.9352), F1-score (0.9350) and area under an receiver operating characteristics curve (AUC, 0.9730), and lower time cost. The best performances were associated with the ensemble effect of critical and secondary features, distinct from the previous finding which revealed only the effect of critical features on enhancing AUC value. Additionally, one observed that the present model was comparable to other optimized tree model by the dataset with double-class and outperformed the other tree model by the dataset with multi-class. The present work offers a new avenue for identifying hop trajectories and tracking sand particle flow via machine learning in the future, and a new channel for reunderstanding the relationship between midair collision and saltation under strong wind through automatic identification of saltating tracks.

由于盐化粒子跟踪算法(SPT)的准确率或召回率较低,强风驱动的盐化轨迹的演变情况仍不为人所知。由于效率低,人工识别盐化轨迹成为一个主要瓶颈,限制了高精度新型 SPT 的发展。在此,我们通过建立具有多个瞬时盐化速度统计量(MSQV)的数据集和包含树状结构帕尔森估计器(TPE)的工作流程,提出了一种优化的树状模型,用于自动识别强风下高速视频中的盐化轨迹。根据 D3 数据集优化的分类提升模型(CatBoost-D3)被认为是树状模型中最好的分类器,它具有更高的准确度(0.9352)、精确度(0.9348)、召回率(0.9352)、F1 分数(0.9350)和接收器工作特性曲线下面积(AUC,0.9730),以及更低的时间成本。最佳性能与关键特征和次要特征的组合效应有关,这与之前的发现不同,之前的发现只显示了关键特征对提高 AUC 值的影响。此外,我们还观察到,在双类数据集上,本模型与其他优化树模型不相上下,而在多类数据集上,本模型的表现优于其他树模型。本研究为今后通过机器学习识别跳跃轨迹和跟踪沙粒流提供了新的途径,也为通过自动识别盐化轨迹重新理解强风下半空碰撞与盐化之间的关系提供了新的渠道。
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引用次数: 0
Regional differences in the grain size characteristics of surface sediments from typical barchan dunes in arid zones 干旱地区典型巴查沙丘表层沉积物粒度特征的地区差异
IF 3.1 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2024-07-22 DOI: 10.1016/j.aeolia.2024.100939

The grain size characteristics of aeolian sediments are the combined result of sand sources, regional airflow regimes, dune morphology, etc., and are essential for understanding the formation and evolution of barchan dunes. Based on field investigations and laboratory experimental data, in this paper, we explored differences in the grain size characteristics of the surface sediments of barchan dunes at the southeastern edge of the Taklimakan Desert (TKLM-SE), the western (QB-W) and southern parts of the Qaidam Basin Desert (QB-S), the sand belt connecting the Badain Jaran Desert and the Tengger Desert (BT-B), and their responses to sand sources, dune morphology, and wind regimes. The main results were as follows: (i) The mean grian size distribution patterns of the windward slope toe to the leeward slope toe through the dune crest/ridge varied with different transects of the barchan dunes and different deserts, showing four types including gradually fining (GF), gradually coarsening (GC), coarsening followed by fining (CF), and fining followed by coarsening (FC). The patterns were GF and CF in the TKLM-SE; GF, GC, and FC in the BT-B; GF, GC, and CF in the QB-W; and GF in the QB-S. (ii) The interdune sediments provided the source material for the formation and development of barchan dunes and their grain size varied in different deserts. The interdune sediments were composed of gravel and very fine sand in the TKLM-SE, while they were composed of medium and fine sand in the QB-W, QB-S, and BT-B. (iii) The windward side of the barchans varied with different wind directions, and dune height affected dune surface airflow velocity and direction, changing the pattern of grain size distribution on the dune surface. The wind regime over a ten-day or half-month scale could explain the variance in the grain size distribution patterns better than that on an annual scale. (iv) Grain size characteristics of dune surface sands changed with dune shape due to changes in the surface airflow velocity and direction and the sediment-carrying capacity of the airflow. With an increasing ratio of dune height to dune width, the grain size of the dune crest sands became coarser. These results help advance our understanding of the grain size characteristics of barchan dunes and regional variabilities in their patterns.

风化沉积物的粒度特征是沙源、区域气流机制、沙丘形态等因素综合作用的结果,对于了解巴查沙丘的形成和演变至关重要。本文以野外调查和实验室实验数据为基础,探讨了塔克拉玛干沙漠东南边缘(TKLM-SE)、柴达木盆地沙漠西部(QB-W)和南部(QB-S)、连接巴丹吉林沙漠和腾格里沙漠的沙带(BT-B)的沙丘表层沉积物粒度特征的差异,以及它们对沙源、沙丘形态和风向的响应。主要结果如下(i) 从迎风坡坡脚到背风坡坡脚,通过沙丘峰顶/沙脊的平均粒度分布模式随不同的沙丘横断面和不同的沙漠而变化,呈现出四种类型,包括逐渐细化(GF)、逐渐粗化(GC)、粗化后细化(CF)和细化后粗化(FC)。在 TKLM-SE 中,其形态为 GF 和 CF;在 BT-B 中,其形态为 GF、GC 和 FC;在 QB-W 中,其形态为 GF、GC 和 CF;在 QB-S 中,其形态为 GF。(ii) 沙丘间沉积物是形成和发展沙丘的源材料,其粒度在不同沙漠中各不相同。沙丘间沉积物在 TKLM-SE 由砾石和极细沙组成,而在 QB-W、QB-S 和 BT-B 则由中沙和细沙组成。(iii) 沙丘的迎风面随风向的不同而变化,沙丘高度影响沙丘表面气流的速度和方向,从而改变沙丘表面的粒径分布模式。十天或半月尺度的风向比全年尺度的风向更能解释沙粒大小分布模式的差异。(iv) 沙丘表面沙粒大小的特徵會隨沙丘形狀而改變,這是由於沙丘表面氣流速度和方向,以及氣流攜帶沉積物的能力改變所致。随着沙丘高度与沙丘宽度之比的增加,沙丘顶沙的粒度变得更粗。这些结果有助于加深我们对巴钦沙丘粒度特征及其区域变化模式的理解。
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引用次数: 0
Carcinogenic and non-carcinogenic health risks of heavy metals in windborne sediments from a residential area (Case study: Tabas, Iran) 居民区风载沉积物中重金属的致癌和非致癌健康风险(案例研究:伊朗塔巴斯)
IF 3.1 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2024-07-06 DOI: 10.1016/j.aeolia.2024.100938
Hojat Emami , Mahsa Memarzadeh , Fateme Naghizade Asl

Dust particles are considered as a very important way of soil contamination by heavy metals. Therefore, this study was conducted to evaluate the concentration of heavy metals and their health risk in windborne sediments. For this purpose, sediment traps were installed in five dominant wind directions including north, northeast, northwest, west, and southwest, and center of Tabas city (Iran) to collect the suspended sediments in the air. Sediment sampling was conducted monthly from January to December 2021. The concentrations of heavy metals were measured using atomic adsorption method followed by extraction by aqua regia, and the carcinogenic and non-carcinogenic health risks of heavy metals for children and adults were evaluated during different months of the year. According to the results, the maximum and minimum amounts of windborne sediments found in northwest (85.66 gm−2) and west (29.3 gm−2), respectively. Monthly variations in windborne sediments discharge also revealed that the maximum amounts of windborne sediments occurred in September and November 2021 from northeast (125 and 117 mgkg−1, respectively). The maximum concentrations of cadmium (0.82 mg/kg) were found in the west of Tabas, while those of lead (192.72 mg/kg), and nickel (227.34 mg/kg) were obtained in the city center. In addition, the highest carcinogenic and non-carcinogenic risks belonged to nickel and the lowest risks were obtained for lead. Also, the carcinogenic risk of cadmium was higher than lead but lower than nickel. In general, the carcinogenic and non-carcinogenic risks of the studied heavy metals were low (less than 1).

尘埃微粒被认为是重金属污染土壤的一个非常重要的途径。因此,本研究对风载沉积物中的重金属浓度及其健康风险进行了评估。为此,在五个主要风向(包括北风、东北风、西北风、西风、西南风)和塔巴斯市(伊朗)中心安装了沉积物收集器,以收集空气中的悬浮沉积物。沉积物采样从 2021 年 1 月至 12 月每月进行一次。采用原子吸附法测定重金属浓度,然后用王水萃取,并评估了一年中不同月份重金属对儿童和成人的致癌和非致癌健康风险。结果显示,西北部(85.66 gm-2)和西部(29.3 gm-2)的风载沉积物含量最高,最低。风载沉积物排放量的月度变化也显示,2021 年 9 月和 11 月来自东北部的风载沉积物量最大(分别为 125 毫克千克-1 和 117 毫克千克-1)。镉的最高浓度(0.82 毫克/千克)出现在塔巴斯西部,而铅(192.72 毫克/千克)和镍(227.34 毫克/千克)的最高浓度则出现在市中心。此外,镍的致癌和非致癌风险最高,铅的风险最低。此外,镉的致癌风险高于铅,但低于镍。总的来说,所研究的重金属的致癌和非致癌风险都很低(小于 1)。
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引用次数: 0
Characterization of 21 years of dust events across four West Texas regions 德克萨斯州西部四个地区 21 年沙尘事件的特征描述
IF 3.3 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-20 DOI: 10.1016/j.aeolia.2024.100930
M.C. Robinson, K. Ardon-Dryer

Dust events are caused by strong winds that lift dust particles into the air. Due to surrounding deserts and agriculture, West Texas experiences many dust events. This study examines dust events that occurred between 2000 and 2020 across four locations: Amarillo, Lubbock, Midland, and El Paso. A total of 1,834 dust events were identified across the four locations with an average of 22 dust events annually. 227 dust events were observed in Amarillo, 609 in Lubbock, 545 in Midland, and 453 dust events were observed in El Paso. A slight increasing trend of dust events over time was observed for Amarillo, Lubbock, and Midland while El Paso showed a decreasing trend. Most dust events occurred during the spring to early summer months and they lasted an hour or less. Many dust events occurred during times of drought and periods of La Niña. Separation of the dust events based on the meteorological disturbance that caused them (convective vs. synoptic) showed that synoptic disturbances contribute to >60 % of the dust events, while convective disturbances were responsible for most of the remaining. Synoptic disturbances were predominately in spring while convective disturbances were common in the early summer months. A comparison of meteorological parameters measured during each disturbance shows that synoptic dust events were associated with lower temperatures, dew point, and relative humidity, but with higher wind speeds and gusts.

沙尘暴是由强风将沙尘颗粒吹向空中造成的。由于周围有沙漠和农业,西得克萨斯州经历了许多沙尘事件。本研究考察了 2000 年至 2020 年期间在四个地点发生的沙尘事件:阿马里洛、拉伯克、米德兰和埃尔帕索。四个地点共发现 1834 起沙尘事件,平均每年 22 起。在阿马里洛观测到 227 起沙尘事件,在拉伯克观测到 609 起,在米德兰观测到 545 起,在埃尔帕索观测到 453 起。随着时间的推移,阿马里洛、拉伯克和米德兰的沙尘事件呈轻微上升趋势,而埃尔帕索则呈下降趋势。大多数沙尘事件发生在春季至初夏,持续时间为一小时或更短。许多沙尘事件发生在干旱时期和拉尼娜时期。根据造成沙尘事件的气象扰动(对流扰动和同步扰动)对沙尘事件进行的分类显示,同步扰动造成了 60% 的沙尘事件,而对流扰动则造成了其余大部分沙尘事件。同步扰动主要发生在春季,而对流扰动则常见于初夏季节。对每次扰动期间测量到的气象参数进行比较后发现,同步沙尘事件与较低的温度、露点和相对湿度有关,但与较高的风速和阵风有关。
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引用次数: 0
Reconstructing star dune dynamics using ground penetrating radar – How movement shapes complex surface structures 利用地面穿透雷达重建星形沙丘动态--运动如何塑造复杂的地表结构
IF 3.3 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-18 DOI: 10.1016/j.aeolia.2024.100920
Manuel Herzog , Alexander Schmitt , Olaf Bubenzer

The evolution of large star dunes, because of their remote location, size and surface complexity, is barely recorded and understood. This lack of understanding applies to surface and subsurface features alike. In order to detect the transformation, the detailed subsurface stratigraphy and the relative chronology of large star dunes, we used ground penetrating radar (GPR) on all major arms of a complex star dune of Erg Chebbi, south-eastern Morocco. We used a 350 MHz digital antenna from Geophysical Survey Systems, Inc (GSSI), reaching a depth of 12.5 m to identify main radar facies associated with former downwind dune flanks describing the depositional history. Our results enable the determination of former dune crest positions, their potential past movement and in consequence the construction of the paleo-dune topography. In accordance with simulated historical wind data, we found a potential sediment deficit on the south-eastern side of the dune. This also correlates with surface data describing an oblique form of the star dune and the spatial distribution frequency of its major arms. Our detailed recordings show, for the first time, the complex internal composition of all arms of one large star dune and surface sensitive form-flow interactions. Our results allow the discrimination of deposition phases and therefore, we have constructed a relative chronology as a basis for future sampling and the reconstruction of star dune evolution in general.

大型星沙丘由于位置偏远、面积巨大、表面复杂,其演变过程几乎没有记录和了解。这种缺乏了解的情况同样适用于地表和地下特征。为了探测大型星形沙丘的变化、详细的地下地层和相对年代学,我们在摩洛哥东南部 Erg Chebbi 复杂星形沙丘的所有主要臂上使用了地面穿透雷达 (GPR)。我们使用了地球物理勘测系统公司(GSSI)生产的 350 MHz 数字天线,雷达探测深度达 12.5 米,以确定与描述沉积历史的前下风沙丘侧翼相关的主要雷达面。我们的研究结果有助于确定前沙丘峰的位置及其过去可能发生的移动,从而构建古沙丘地形。根据模拟的历史风力数据,我们发现沙丘东南侧可能存在沉积物不足的情况。这也与描述星形沙丘斜面形态的地表数据及其主要沙臂的空间分布频率相关。我们的详细记录首次显示了一个大型星沙丘所有沙臂的复杂内部组成以及表面敏感的形态-流动相互作用。我们的研究结果可以区分沉积阶段,因此,我们构建了一个相对年表,作为未来取样和重建星沙丘演变的基础。
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引用次数: 0
The influence of backdune morphology on air flow dynamics through an excavated foredune notch 后沙丘形态对通过开挖前沙丘缺口的气流动力学的影响
IF 3.3 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-15 DOI: 10.1016/j.aeolia.2024.100929
Duc Nguyen , Sarah Wakes , Mike Hilton

On many metropolitan and developed coasts foredunes are narrow, vegetated, highly stable and confined by hinterland development. Such foredunes are most likely to erode, rather than landward migration, in response to ongoing eustatic sea-level rise. Foredune notching may be undertaken on such coasts to facilitate sand transport through the foredune zone and accomplish degrees of foredune landward migration; however, the efficacy of this method has not been examined in relation to the backdune topography, which in many instances takes the form of a dyke or similar infrastructure.

Computational Fluid Dynamics (CFD) is used to investigate how the space behind a notch, and the slope of the seaward face of the backdune topography, modifies near-surface wind through foredune notches. Incident winds are simulated parallel to the notch long axis and the effects of changing backdune morphology on the secondary winds through the notch are examined. Swale widths between 3 and 53 m and hinterland gradients between 0° and 90° are examined.

Air flow through the notch is strongly influenced by the morphology of backdune infrastructure. Wind speed increases through the notch as the spacing behind the notch increases and the slope of the hinterland topography decreases. An increase in spacing reduces the landward extension of wind recirculation in the lee of the notch. To maximise notch efficiency and sediment accumulation in the lee of the foredune the minimum spacing should be 8 and 30 m when the slope of the backdune infrastructure is 20° and 90°, respectively.

在许多大都市和发达海岸,前沙丘狭窄、植被丰富、高度稳定,并受到腹地开发的限制。随着海平面的持续上升,这些前沙丘最有可能被侵蚀,而不是向陆地迁移。在这样的海岸上可能会对前沙丘进行缺口处理,以促进沙粒通过前沙丘区并实现一定程度的前沙丘向陆地迁移;然而,这种方法的有效性还没有与后沙丘地形相关的研究,后沙丘地形在许多情况下是堤坝或类似基础设施的形式。计算流体动力学(CFD)用于研究缺口后的空间和后沙丘地形向海面的坡度如何改变穿过前沙丘缺口的近地表风。模拟的入射风平行于缺口长轴,并研究变化的背风沙丘形态对穿过缺口的次生风的影响。对 3 米到 53 米之间的沼泽宽度以及 0° 到 90° 之间的腹地坡度进行了研究。随着缺口后间距的增加和腹地地形坡度的减小,通过缺口的风速也会增加。间距的增大减少了风在缺口附近的再循环向陆地的延伸。为了最大限度地提高缺口效率和前沙丘附近的沉积物堆积,当后沙丘基础设施的坡度分别为 20° 和 90° 时,最小间距应分别为 8 米和 30 米。
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Aeolian Research
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