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991.
Izvestiya, Atmospheric and Oceanic Physics - In recent years, rapid urbanization and population growth have led to an overload of waste in big cities of Vietnam. Waste decomposition is always...  相似文献   
992.
Le  Cong-huan  Li  Yan-e  Huang  Lei  Ren  Jian-yu  Ding  Hong-yan  Zhang  Pu-yang 《中国海洋工程》2021,35(5):779-788
China Ocean Engineering - In the leg-lowering process, the offshore jack-up platform is in a floating state, and the spudcan may collide with the seabed due to the platform motion in waves, thereby...  相似文献   
993.
21世纪被称为"海洋世纪",但由于人类复杂的生产活动,大量的垃圾正有意或无意的被投放入海洋环境中,这将导致全球范围内近岸污染,包括生态环境恶化,生物资源锐减等问题。本研究以天津高沙岭、上海南汇嘴和深圳大铲湾三地的海滩为研究区域,通过对三个海滩垃圾的种类、时空特征及相关性进行统计分析,以期了解中国近海不同海滩的海滩垃圾分布特征,为我国海洋垃圾监测和调查、监督和管理等起到一定的指导作用。结果显示,海滩垃圾不同种类间数量差异较大,三年间垃圾数量大体呈逐年增加的趋势,且不同的海滩,垃圾数量和种类都存在明显差异。  相似文献   
994.
海岸侵蚀是沿海各国面临的共同问题,海滩养护是当前砂质海岸保护的最佳手段,在全球范围内得到广泛应用。本文回顾了海滩养护技术的发展历程,总结了世界范围的海滩养护实践,分析各国海滩养护理念上存在的差异。以研究文献为基础,总结归纳了平面和横向剖面的补砂方式、辅助工程技术和海滩模型预测等方面的海滩养护技术研究进展,并在此基础上提出了海滩养护的未来发展趋势:①针对复杂海岸的海滩养护应用拓展;②基于沉积物管理的海滩养护修复;③从地貌系统到生态系统全面考虑的海滩养护技术;④全球砂源赤字条件下的海滩保护和修复思路。  相似文献   
995.
Forested peatlands are widespread in boreal regions of Canada, and these ecosystems, which are major terrestrial carbon sinks, are undergoing significant transformations linked to climate change, fires and human activities. This study targets millennial‐scale vegetation dynamics and related hydrological variability in forested peatlands of the Clay Belt south of James Bay, eastern Canada, using palaeoecological data. Changes in peatland vegetation communities were reconstructed using plant macrofossil analyses, and variations in water‐table depths were inferred using testate amoeba analyses. High‐resolution analyses of macroscopic charcoal >0.5 mm were used to reconstruct local fire history. Our data showed two successional pathways towards the development of present‐day forested peatlands influenced by autogenic processes such as vertical peat growth and related drying, and allogenic factors such as the occurrence of local fires. The oldest documented peatland initiated in a wet rich fen around 8000 cal. a BP shortly after land emergence and transformed into a drier forested bog rapidly after peat inception that persisted over millennia. In the second site, peat started to accumulate from ~5200 cal. a BP over a mesic coniferous forest that shifted into a wet forested peatland following a fire that partially consumed the organic layer ~4600 cal. a BP. The charcoal records show that fires rarely occurred in these peatlands, but they have favoured the process of forest paludification and influenced successional trajectories over millennia. The macrofossil data suggest that Picea mariana (black spruce) persisted on the peatlands throughout their development, although there were periods of more open canopy due to local fires in some cases. This study brings new understanding on the natural variability of boreal forested peatlands which may help predict their response to future changes in climate, fire regimes and anthropogenic disturbances.  相似文献   
996.
Mitigating and adapting to global changes requires a better understanding of the response of the Biosphere to these environmental variations. Human disturbances and their effects act in the long term (decades to centuries) and consequently, a similar time frame is needed to fully understand the hydrological and biogeochemical functioning of a natural system. To this end, the ‘Centre National de la Recherche Scientifique’ (CNRS) promotes and certifies long-term monitoring tools called national observation services or ‘Service National d'Observation’ (SNO) in a large range of hydrological and biogeochemical systems (e.g., cryosphere, catchments, aquifers). The SNO investigating peatlands, the SNO ‘Tourbières’, was certified in 2011 ( https://www.sno-tourbieres.cnrs.fr/ ). Peatlands are mostly found in the high latitudes of the northern hemisphere and French peatlands are located in the southern part of this area. Thus, they are located in environmental conditions that will occur in northern peatlands in coming decades or centuries and can be considered as sentinels. The SNO Tourbières is composed of four peatlands: La Guette (lowland central France), Landemarais (lowland oceanic western France), Frasne (upland continental eastern France) and Bernadouze (upland southern France). Thirty target variables are monitored to study the hydrological and biogeochemical functioning of the sites. They are grouped into four datasets: hydrology, fluvial export of organic matter, greenhouse gas fluxes and meteorology/soil physics. The data from all sites follow a common processing chain from the sensors to the public repository. The raw data are stored on an FTP server. After operator or automatic processing, data are stored in a database, from which a web application extracts the data to make them available ( https://data-snot.cnrs.fr/data-access/ ). Each year at least, an archive of each dataset is stored in Zenodo, with a digital object identifier (DOI) attribution ( https://zenodo.org/communities/sno_tourbieres_data/ ).  相似文献   
997.
金万富  何广静  陈乐 《热带地理》2020,40(3):515-524
利用空间分析和数理统计等方法探究了1984—2016年中国高尔夫球场数量时空演变、影响因素和扩散模式。结果表明:1)球场数量变化经历了低速增长期、稳定增长期、加速增长期和紧缩期;2)球场空间分布范围经历了扩张期和收缩期,向北、向西扩散较为明显;3)目前球场主要分布在经济发展水平较高且外向型经济突出的长三角、珠三角和环渤海地区;4)人均GDP、人口规模、区域开放程度、交通优势度、气候类型和土地资源稀缺性与球场空间分布均呈显著正相关,其中交通优势度相关系数最大;5)高尔夫球场空间扩散模式兼具接触性扩散和等级性扩散。  相似文献   
998.
Groundwater transit time is an essential hydrologic metric for groundwater resources management. However, especially in tropical environments, studies on the transit time distribution (TTD) of groundwater infiltration and its corresponding mean transit time (mTT) have been extremely limited due to data sparsity. In this study, we primarily use stable isotopes to examine the TTDs and their mTTs of both vertical and horizontal infiltration at a riverbank infiltration area in the Vietnamese Mekong Delta (VMD), representative of the tropical climate in Asian monsoon regions. Precipitation, river water, groundwater, and local ponding surface water were sampled for 3 to 9 years and analysed for stable isotopes (δ18O and δ2H), providing a unique data set of stable isotope records for a tropical region. We quantified the contribution that the two sources contributed to the local shallow groundwater by a novel concept of two‐component lumped parameter models (LPMs) that are solved using δ18O records. The study illustrates that two‐component LPMs, in conjunction with hydrological and isotopic measurements, are able to identify subsurface flow conditions and water mixing at riverbank infiltration systems. However, the predictive skill and the reliability of the models decrease for locations farther from the river, where recharge by precipitation dominates, and a low‐permeable aquitard layer above the highly permeable aquifer is present. This specific setting impairs the identifiability of model parameters. For river infiltration, short mTTs (<40 weeks) were determined for sites closer to the river (<200 m), whereas for the precipitation infiltration, the mTTs were longer (>80 weeks) and independent of the distance to the river. The results not only enhance the understanding of the groundwater recharge dynamics in the VMD but also suggest that the highly complex mechanisms of surface–groundwater interaction can be conceptualized by exploiting two‐component LPMs in general. The model concept could thus be a powerful tool for better understanding both the hydrological functioning of mixing processes and the movement of different water components in riverbank infiltration systems.  相似文献   
999.
北极海冰消融情景下东北航道通航性能演变分析   总被引:2,自引:1,他引:1  
全球气候增暖,导致北极海冰消融加速,冰上丝绸之路的开通逐渐提上日程。本文针对2030—2070年俄罗斯8个重要港口通过东北航道到达白令海峡的通航性能,采用6种CMIP5气候模式在2种排放情景下的海冰数据,以及PC6破冰船和普通商船2种船型,分别对最优航线、通航时长、可通航里程以及通航成本4项要素进行研究。主要结论为:① 随着时间变化,各条最优通航线路逐渐集中有序,普通商船的通航能力显著提高,到2070年拥有和PC6近似相等的通航能力;② 俄港口到白令海峡间的运输时长每过10 a下降14 h,其中圣彼得堡港运输时长下降最为显著。到2070年,俄港口与白令海峡的经度差每增加1°,该港口的运输时长下降0.4 h;③ 未来50 a,东北航道可通航里程平均每隔10 a增加166 km,其中圣彼得堡港可通航里程的变化模式和平均变化模式最为相近;④ 从北冰洋港口出发的航线通航成本每10 a下降1万美元,商船在高浓度排放情景下总通航成本的下降幅度最明显。结合海冰变化情况,俄中西部港口具有巨大的资源运输潜力。本文量化并评估了东北航道在未来海冰消融情景下的通航性能演变态势,为东北航道通航以及北极港口贸易情况提供了理论和数据支撑。  相似文献   
1000.
地形对黄土高原滑坡的影响   总被引:4,自引:0,他引:4  
高分辨率地形与影像数据的缺乏已成为研究地表现象、特征与过程的重要瓶颈。低成本无人机设备和摄影测量技术的发展,打开了地学领域获取高分辨率数据的大门,大大提高了地质灾害野外调查与灾害编目的精度与效率。本文通过无人机野外调查和遥感室内目视解译,构建了一个包含307个黄土滑坡属性的数据库。在此基础上,通过数字地形分析和数理统计等方法,总结归纳了黄土滑坡样本数据的分布规律,探讨了地形对黄土滑坡分布的影响,阐述了地形相对高差对最长滑动距离、滑坡周长、滑坡面积的影响,提出了基于传统经验公式拟合的滑坡规模快速预测公式。结果表明:① 滑坡规模—频率分布具有明显的规律性,不同最大长度、最大宽度和周长的黄土滑坡数量分布均呈现正偏态分布,而不同面积的滑坡数量分布则服从幂函数分布;② 地形对黄土滑坡发育控制作用明显,不同地形高差、平均坡度、坡形的斜坡单元滑坡发育数量差异较大;③ 地形相对高差与滑坡的最长滑距、周长和面积的拟合曲线很好地符合幂律分布规律,但不同地形区的拟合效果有所差异,黄土丘陵区拟合效果最好,黄土高原全区次之,黄土台塬区最差;④ 本文建立的黄土滑坡规模快速预测模型,为黄土滑坡灾害调查提供了经验公式支撑。  相似文献   
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