车辆碾压作用下戈壁地表起尘浓度   总被引：1，自引：1，他引：0  

孟小楠  严平  王振亭  董苗  王勇 《中国沙漠》2019,39(1):80-87

通过野外观测车辆碾压作用下戈壁地表PM₁₀释放浓度，探讨其主要影响因素。针对戈壁区砾石、砂砾、砂质和砂土4种路面类型，应用TSI粉尘仪多次重复观测车辆碾压产生的PM₁₀浓度，进而阐明碾压次数、车速和地表水分等因素对起尘浓度的影响。结果表明：4种路面的平均起尘浓度依次为5.339、9.089、16.944、50.251 mg·m^-3，是自然状态下的5~50倍；起尘浓度随碾压次数增多而增大，其中砂土路情况下的增长最显著；随土层厚度的增大呈现出幂函数的增长趋势；降雨后路面起尘浓度显著减小，且降雨量会影响降雨后起尘浓度的变化趋势。最后提出了针对性的建议和措施以减弱车辆碾压导致的戈壁地表起尘。  相似文献   

Meltwater discharge during the Holocene from the Wilkes subglacial basin revealed by beryllium isotope analysis of marine sediments     

Bethany Behrens  Yosuke Miyairi  Adam D. Sproson  Masako Yamane  Yusuke Yokoyama 《第四纪科学杂志》2019,34(8):603-608

Understanding Antarctic Ice Sheet dynamics related to global climate change is of scientific and societal interest as the future behaviour of the ice sheet under the currently changing climate is unknown. We present beryllium‐10 (¹⁰Be) analysis of a high‐resolution marine sediment core from the Adélie Basin near the eastern Wilkes Land margin, which is susceptible to marine ice sheet instability due to the low‐lying nature and down‐sloping trough of the Wilkes Subglacial Basin. Combined with a newly constructed age model using compound specific radiocarbon dates, the data reveal three events associated with high meteoric ¹⁰Be at ca. ~10 ka, ca. ~6.5 ka and from ca. ~4 ka. We interpret these high meteoric ¹⁰Be events to be derived from the deposition of ¹⁰Be released from the ice sheet during meltwater discharge. In particular, the shift to higher meteoric ¹⁰Be concentration at~4 ka may correspond to changes in climate patterns at this time. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献   

Identifying slope processes over time and their imprint in soils of medium‐high mountains of Central Europe (the Karkonosze Mountains,Poland)          下载免费PDF全文

Jaroslaw Waroszewski  Markus Egli  Dagmar Brandová  Marcus Christl  Cezary Kabala  Malgorzata Malkiewicz  Jakub Kierczak  Bartłomiej Glina  Paweł Jezierski 《地球表面变化过程与地形》2018,43(6):1195-1212

Soils in mountainous areas are often polygenetic, developed in slope covers that relate to glacial and periglacial activities of the Pleistocene and Holocene and reflect climatic variations. Landscape development during the Holocene may have been influenced by erosion/solifluction that often started after the Holocene climatic optimum. To trace back soil evolution and its timing, we applied a multi‐methodological approach. This approach helped us to outline scenario of soil transformation. According to our results, some aeolian input must have occurred in the late Pleistocene. During that time and the early Holocene, the soils most likely had features of Cryosols or Leptosols. Physico‐chemical and mineralogical analyses have indicated that the material was denudated (between late Boreal to the Atlantic) from the ridge and upper‐slope positions forming a colluvium at mid‐slope positions. Later, during the Sub‐Boreal, mass wasting of the remains of silt material deposited at the end of the Pleistocene age on the ridge top seems to have occurred. In addition, the cool and moist conditions caused the deposition of a colluvium at the lower‐slope positions. The next phase was characterized by the transformation of Leptosols/Cambisols into Podzols at upper‐slope or shoulder positions and to Albic Cambisols at mid‐slope positions. During the Sub‐Boreal period, Stagnosols started to form at the lower part of the slope catena. Overall, the highest erosion rates were calculated at the upper‐slope position and the lowest rates at mid‐slope sites. Berylium‐10 (¹⁰Be) data showed that the Bs, BC/C were covered during the Holocene by a colluvium with a different geological composition which complicated the calculation of erosion or accumulation rates. The interpretation of erosion and accumulation rates in such multi‐layered materials may, therefore, be hampered. However, the multi‐methodological reconstruction we applied shed light on the soil and landscape evolution of the eastern Karkonosze Mountains. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Deglaciation history at the Alpine-Mediterranean transition (Argentera-Mercantour,SW Alps) from 10Be dating of moraines and glacially polished bedrock     

Yann Rolland  Romain Darnault  Régis Braucher  Didier Bourlès  Carole Petit  Stéphane Bouissou  ASTER Team 《地球表面变化过程与地形》2020,45(2):393-410

Estimating the extent and age of the last glacial maxima as well as the chronology of glacial recessions in various environmental contexts is key to source-to-sink studies and paleoclimate reconstructions. The Argentera-Mercantour massif is located at the transition between the Alps and the Mediterranean Sea, therefore, its deglaciation chronology can be compared to the sediment budget of the Var River basin. Based on 13 new cosmic-ray exposure (CRE) beryllium-10 (¹⁰Be) datings performed on moraines and polished crystalline bedrocks and 22 reassessed ¹⁰Be CRE ages from similar altitude nearby steep basement surfaces, and from a lake sediment core, we can constrain the deglaciation chronology of the Argentera-Mercantour massif. These data allow for the first time to fully reconstruct the deglaciation history at the scale of the entire massif in agreement with a major glacier recession at c. 15 ka, at the onset of Bølling transition between the Oldest and Older Dryas. Main deglaciation of the upper slopes [2700–2800 m above sea level (a.s.l.)] occurred after the Last Glacial Maximum (LGM) at 20.8–18.6 ka, followed by the main deglaciation of the lower slopes (2300 m a.s.l.) at 15.3–14.2 ka. Finally, the flat polished surfaces above 2600 m a.s.l. and the zones confined within narrow lateral valleys were likely affected by progressive ice melting of remaining debris covered glaciers and moraine erosion following the Younger Dryas re-advance stage between 12 and 8–9 ka. At lower elevations, the Vens Lake located at 2300 m a.s.l., allows evidence of the onset of lake sedimentation at c. 14 ka and a transition towards a vegetated environment that mainly occurred before 8 ka. Moraine final stabilization at 5 ka might reflect denudation acceleration during the Holocene humid phase. This contribution reveals a glacier–climate relationship more sensitive to warming phases in the southern Alps highlighted by a major decrease of glaciers after c. 15 ka. This major deglaciation is correlated with a 2.5-fold decrease of sediment discharge of rivers into the Mediterranean Sea. © 2019 John Wiley & Sons, Ltd.  相似文献   

Climatic and structural controls on Late-glacial and Holocene rockfall occurrence in high-elevated rock walls of the Mont Blanc massif (Western Alps)     

Xavi Gallach  Julien Carcaillet  Ludovic Ravanel  Philip Deline  Christophe Ogier  Magali Rossi  Emmanuel Malet  David Garcia-Sellés 《地球表面变化过程与地形》2020,45(13):3071-3091

In the Mont Blanc massif (European Western Alps), rockfalls are one of the main natural hazards for alpinists and infrastructure. Rockfall activity after the Little Ice Age is well documented. An increase in frequency during the last three decades is related to permafrost degradation caused by rising air temperatures. In order to understand whether climate exerts a long-term control on rockfall occurrence, a selection of paleo-rockfall scars was dated in the Glacier du Géant basin [>3200 m above sea level (a.s.l.)] using terrestrial cosmogenic nuclides. Rockfall occurrence was compared to different climatic and glacial proxies. This study presents 55 new samples (including replicates) and 25 previously-published ages from nine sampling sites. In total, 62 dated rockfall events display ages ranging from 0.03 ± 0.02 ka to 88.40 ± 7.60 ka. Holocene ages and their uncertainties were used to perform a Kernel density function into a continuous dataset displaying rockfall probability per 100 years. Results highlight four Holocene periods of enhanced rockfall occurrence: (i) c. 7–5.7 ka, related to the Holocene Warm Periods; (ii) c. 4.5–4 ka, related to the Sub-boreal Warm Period; (iii) c. 2.3–1.6 ka, related to the Roman Warm Period; and (iv) c. 0.9–0.3 ka, related to the Medieval Warm Period and beginning of the Little Ice Age. Laser and photogrammetric three-dimensional (3D) models of the rock walls were produced to reconstruct the detached volumes from the best-preserved rockfall scars (≤0.91 ± 0.12 ka). A structural study was carried out at the scale of the Glacier du Géant basin using aerial photographs, and at the scale of four selected rock walls using the 3D models. Two main vertical and one horizontal fracture sets were identified. They correspond respectively to alpine shear zones and veins opened-up during long-term exhumation of the Mont Blanc massif. Our study confirms that climate primarily controls rockfall occurrence, and that structural settings, coincident at both the massif and the rock wall scales, control the rock-wall shapes as well as the geometry and volume of the rockfall events. © 2020 John Wiley & Sons, Ltd.  相似文献   

海洋气团对沿海城市大气环境影响与识别研究     

石红旗  王霄曈  张昊阳  石博欣  张睿 《海洋科学》2018,42(12):100-108

本研究通过识别海洋气团特征及沿海城市大气受到海洋气团的影响方式与程度,为评价沿海城市空气环境质量提供科学依据。以青岛市为例,收集大气气溶胶样品中放射性核素~(210)Pb、40K数据及采集时段当地大气颗粒物数据;分析~(210)Pb活度浓度与气溶胶颗粒物浓度变化;对当地当时大气气团进行溯源分析。研究表明:(1)研究期间青岛沿岸地区2015年4月至2016年6月与2016年6月至2017年6月大气污染特征显著不同,前者~(210)Pb活度浓度与污染颗粒物浓度显著相关,而后者~(210)Pb活度浓度与污染颗粒物无相关关系;(2)穿越海洋的陆地气团呈现出高活度浓度、低颗粒物浓度的特征;来自海洋气团的气溶胶呈现出低活度浓度、低颗粒物浓度的特征;(3)海洋气团气溶胶中~(210)Pb活度浓度较低。临近大陆的海洋(黄海、东海)上层大气受到大陆气团的影响,其海洋气团的特征有所减弱。~(210)Pb活度浓度、颗粒物浓度(PM2.5)可作为判断海洋气团的指标,识别"来自海洋的气团"与"经过海洋的气团"。  相似文献   

Paired 10Be sampling of polished bedrock and erratic boulders to improve dating of glacial landforms: an example from the Western Alps     

Charlotte Prud'homme  Riccardo Vassallo  Christian Crouzet  Julien Carcaillet  Jean-Louis Mugnier  Joaquin Cortés-Aranda 《地球表面变化过程与地形》2020,45(5):1168-1180

Cosmogenic nuclide dating of glacial landforms may lead to ambiguous results for ice retreat histories. The persistence of significant cosmogenic concentrations inherited from previous exposure may increase the apparent exposure ages for polished bedrocks affected by limited erosion under ice and for erratic boulders transported by glaciers and previously exposed in high-altitude rock walls. In contrast, transient burying by moraines, sediments and snow decreases the apparent exposure age. We propose a new sampling strategy, applied to four sites distributed in the Arc and Arve valleys in the Western Alps, to better constrain the factors that can bias exposure ages associated with glacial processes. We used the terrestrial cosmogenic nuclide ¹⁰Be (TCN) to estimate the exposure time from paired sampling of depth profiles in polished bedrock and on overlying erratic boulders. For a given sampling site, the exposure ages for both the polished bedrock and boulder are expected to be the same. However, in six cases out of seven, boulders had significantly higher ¹⁰Be surface concentrations than those of the associated polished surfaces. In present and past glacial processes, the ¹⁰Be distribution with depth for boulders and bedrocks implies the presence of an inheritance concentration of ¹⁰Be. Our study suggests that ¹⁰Be concentrations in erratic boulders and in polished bedrocks provide maximum and minimum exposure ages of the glacial retreat, respectively. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Fluvial dynamics and 14C-10Be disequilibrium on the Bolivian Altiplano     

Kristina Hippe  Tiemen Gordijn  Vincenzo Picotti  Irka Hajdas  John D. Jansen  Marcus Christl  Christof Vockenhuber  Colin Maden  Naki Akçar  Susan Ivy-Ochs 《地球表面变化过程与地形》2019,44(3):766-780

Determining sediment transfer times is key to understanding source-to-sink dynamics and the transmission of environmental signals through the fluvial system. Previous work on the Bolivian Altiplano applied the in situ cosmogenic ¹⁴C-¹⁰Be-chronometer to river sands and proposed sediment storage times of ~10–20 kyr in four catchments southeast of Lake Titicaca. However, the fidelity of those results hinges upon isotopic steady-state within sediment supplied from the source area. With the aim of independently quantifying sediment storage times and testing the ¹⁴C-¹⁰Be steady-state assumption, we dated sediment storage units within one of the previously investigated catchments using radiocarbon dating, cosmogenic ¹⁰Be-²⁶Al isochron burial dating, and ¹⁰Be-²⁶Al depth-profile dating. Palaeosurfaces appear to preserve remnants of a former fluvial system, which has undergone drainage reversal, reduction in catchment area, and local isostatic uplift since ~2.8 Ma. From alluvium mantling the palaeosurfaces we gained a deposition age of ~580 ka, while lower down fluvial terraces yielded ≤34 ka, and floodplains ~3–1 ka. Owing to restricted channel connectivity with the terraces and palaeosurfaces, the main source of channel sediment is via reworking of the late Holocene floodplain. Yet modelling a set of feasible scenarios reveals that floodplain storage and burial depth are incompatible with the ¹⁴C-¹⁰Be disequilibrium measured in the channel. Instead we propose that the ¹⁴C-¹⁰Be offset results from: (i) non-uniform erosion whereby deep gullies supply hillslope-derived debris; and/or (ii) holocene landscape transience associated with climate or human impact. The reliability of the ¹⁴C-¹⁰Be chronometer vitally depends upon careful evaluation of sources of isotopic disequilibrium in a wide range of depositional and erosional landforms in the landscape. © 2018 John Wiley & Sons, Ltd.  相似文献   

Late Pleistocene climate of the northern Iberian Peninsula: New insights from palaeoglaciers at Fuentes Carrionas (Cantabrian Mountains)     

Ramn Pellitero  Jos M. Fernndez‐Fernndez  Nstor Campos  Enrique Serrano  Alfonso Pisabarro 《第四纪科学杂志》2019,34(4-5):342-354

New ¹⁰Be dates for glacial landforms in the Fuentes Carrionas area (Cantabrian Mountains, nothern Spain) are presented. Mapped and dated landforms in Fuentes Carrionas made possible a palaeoglacier reconstruction for four glacial stages. Results were compared to other nearby palaeoenvironmental proxies, so a final approximation on the mean annual temperature and annual precipitation that caused the four glacial advance stages is proposed. Glaciers reached their maximum extension at 36 ka, in a cold and dry environment. A second advance stage took place between 18.5 and 19.5 ka, during the Last Glacial Maximum (LGM), when glaciers advanced in a wet environment, with positive rainfall anomalies. A third glacial advance was dated during the Oldest Dryas, in which climate shifted to extremely cold and dry conditions. Finally, a last stage has been identified and proposed to the Younger Dryas, in which precipitation anomalies are negligible. Our results confirm some of the previously made palaeoglacial and palaeoenvironmental inferences for the Iberian Peninsula, as well as provide valuable and accurate anomalies, which are useful for climate modelling.  相似文献   

黄河北煤田10号煤煤层气储层物性及特征研究     

罗怡鑫  李莹  王怀洪  尹露生  孔凡顺  王东东 《中国煤炭地质》2021,(1)

煤层气是一种备受国家重视和开发利用的非常规清洁能源,煤层气储层物性的研究对煤层气资源的评价与开发具有重要意义。以黄河北煤田煤层气开发资料为基础,结合区域地质特征,应用煤层气地质理论对煤田内10号煤煤层气储层物性特征进行了研究。研究发现:10号煤层宏观煤岩类型以半亮煤为主,煤中有机显微组分以镜质组为主,无机显微组分以黏土为主;煤的变质程度比较高,整体进入成熟阶段;10号煤层储层孔裂隙发育、渗透率较低;10煤层对甲烷的吸附能力较强;10号煤层储层压力为2.16~4.20MPa,压力梯度为0.418~0.797MPa/100m,为低压储层至常压储层;黄河北煤田呈单斜构造,10号煤层埋藏深度较深,含水性较好,有利于煤层气保存。  相似文献