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   

国家地缘脆弱性探索——缅甸案例及对中国地缘战略启示   总被引：3，自引：1，他引：2  

李飞  成升魁  于会录  秦奇  刘晓洁  徐增让  吴良  张丹  李欣  初冬梅 《地理科学进展》2016,35(6):737-746

当今国际地缘政治经济格局正处于剧烈变动中,并对缅甸地缘环境的复杂性及地缘脆弱性产生深刻影响。缅甸所在的大湄公河次区域日益成为世界重要地缘政治力量博弈前沿和焦点。系统研究缅甸国家地缘脆弱性,对于中国西部大开发、“一带一路”及周边地缘环境建设具有重要战略意义。本文基于地缘政治及人地关系地域系统等学科理论,规范分析与实证分析相结合,从暴露性、敏感性和适应性等方面构建了国家地缘脆弱性研究框架,系统探索了缅甸典型的国家地缘脆弱性特征。资源环境禀赋、内部地域结构等引致的经济政治体系、社会文化传承等方面是缅甸脆弱性的本底特征,而缅甸与中国的地缘关系及决策则从根本上影响其地缘战略位态。缅甸地缘政治脆弱性及其与中国的相互依赖使之成为西方“U型封堵大陆战略”的薄弱点和今后角逐的着力点,也是中国解围破局重要的地缘战略出口。近期中国应通过“一带一路”孟中印缅经济走廊建设,大力加强中缅之间政治、经济、文化等各方面友好关系。  相似文献   

离水停食胁迫对中华鳖(Trionyx sinensis)翻身能力、血清生化、裙边质构及脏器相关功能酶活力的影响     

郑嘉豪  申屠琰  徐英杰  李有志  朱卫东  王志铮 《海洋与湖沼》2023,54(6):1737-1745

中华鳖(Trionyx sinensis)历来有活品消费的习惯,离水停食是其批量销售环节必须承受的胁迫。因此,探究离水停食对其商品价值的影响过程与机制,对于明确其活体销售货架期具有重要指导价值和现实意义。以2020年5月20日同池起捕后离水停食处理0 d(S₀实验组)、4 d(S₄实验组)、8 d(S₈实验组)、12 d(S₁₂实验组)、16 d(S₁₆实验组)的雄性商品鳖[平均体质量(546.86±94.70) g]为研究对象,在常温条件下较系统开展了离水停食对其翻身能力、血清生化、裙边质构及脏器酶活力的影响研究。结果表明:(1)实验鳖连续翻身次数呈S₄≈S₈>S₀≈S₁₂≈S₁₆,且均主要集中于1 min内;(2)血清TP、ALB、TC、LDL-C均无组间差异(P>0.05),GLU-O呈S₀≈S₄≈S  相似文献   

Comparison of short-term toxicity of 14 common phycotoxins (alone and in combination) to the survival of brine shrimp Artemia salina     

Yuting Zhang  Shanshan Song  Bin Zhang  Yang Zhang  Miao Tian  Ziyi Wu  Huorong Chen  Guangmao Ding  Renyan Liu  Jingli Mu 《海洋学报(英文版)》2023,42(2):134-141

Toxic harmful algal blooms(HABs) can cause deleterious effects in marine organisms, threatening the stability of marine ecosystems. It is well known that different strains, natural populations and growth conditions of the same toxic algal species may lead to different amount of phycotoxin production and the ensuing toxicity. To fully assess the ecological risk of toxic HABs, it is of great importance to investigate the toxic effects of phycotoxins in marine organisms. In this study, the short-te...  相似文献   

C60全珊瑚海水混凝土的钢筋锈蚀行为研究     

李森林  余红发  达波  麻海燕  吴烨  吴彰钰  郭建博 《海洋工程》2021,39(3):135-140

采用线性极化电阻法,测试了C60全珊瑚海水混凝土（coral aggregate seawater concrete,简称CASC）的线性极化曲线、自腐蚀电位（E_corr）和极化电阻（R_p）,研究了不同暴露时间、不同种类钢筋CASC的钢筋腐蚀行为,提出了提升岛礁CASC结构耐久性的建议措施。结果表明：随着暴露时间的延长,CASC的E_corr和R_p均逐渐降低,钢筋的耐蚀性能逐渐减弱。不同种类钢筋CASC耐蚀性能规律为：316不锈钢筋优于有机新涂层钢筋,优于普通钢筋。即使暴露0 d,CASC中普通钢筋仍会发生锈蚀,表明普通钢筋在不附加任何防腐措施的条件下不适用于岛礁CASC结构。综合分析阻锈效果和成本因素,316不锈钢筋的性价比明显低于有机新涂层钢筋,建议岛礁CASC工程优先选用有机新涂层钢筋。  相似文献   

全球温升1.5℃和2.0℃情景下中国降雨诱发地质灾害危险性和人口暴露度评估研究     

林齐根  王磊斌  张家慧 《地球信息科学学报》2023,25(1):177-189

气候变化情景下极端降水事件的频次和强度预估呈增加趋势,这会导致全球部分地区极端降雨诱发地质灾害风险的增加。本文基于中国降雨诱发地质灾害易发性模型和不同地貌分区的累积事件降雨量-降雨历时阈值曲线,采用最新的CMIP6全球气候模式多模式集合结果,基于全球温升目标情景的视角,从地质灾害空间易发性和发生频次两方面,探讨温升情景下中国地质灾害危险性的可能变化及其对暴露人口的潜在影响。结果表明,CMIP6多模式集合预估的多年平均降水在温升1.5℃和2.0℃情景下相比基准时期可能增加5.4%～9.5%,导致中等至极高地质灾害易发区范围预估增加0.33%～0.74%,由于预估的极端降水事件增加,地质灾害发生频次预估增加7.0%～11.2%,进一步综合未来人口空间分布,潜在地质灾害暴露人口可能增加6.20亿人次（18.90%）和4.26亿人次（12.97%）。各地貌分区未来情景下地质灾害危险性预估增加且存在显著的空间异质性,温升2.0℃情景下中等至极高易发性范围相比基准时期增加0.71%～1.28%,地质灾害发生频次预估增加1.2%～15.6%,其中,青藏高原区地质灾害危险性增加最明显。综合考虑未来人口...  相似文献   

高强耐热铝合金钻杆材料优选          下载免费PDF全文

梁健  尹浩  孙建华  李亚红  王成彪  张金昌 《探矿工程》2020,47(4):65-71

铝合金钻杆的使用性能是制约深部钻探技术发展的“瓶颈”。本文综合考虑孔内工况因素和钻杆性能因素,以钻柱组合设计为基础准则,从特深孔钻探工程技术需求出发,开展了高强耐温铝合金钻杆材质选择和评价的试验研究。试验结果表明：2219铝合金固溶时效制度分别为535 ℃/1 h、165 ℃/20 h,2618铝合金固溶时效制度分别为530 ℃/1 h、200 ℃/20 h;2219铝合金在高温长时间暴露后的室温力学性能优于2618铝合金,在高温瞬时条件下的力学性能劣于2618铝合金;2219铝合金中含有Zr,该元素在热暴露过程中起到减缓溶质扩散速率的作用,这对提高热暴露后的剩余强度是有利的。  相似文献   

The effect of long-term aerial exposure on intertidal mudflat erodibility     

Hieu M. Nguyen  Karin R. Bryan  Conrad A. Pilditch 《地球表面变化过程与地形》2020,45(14):3623-3638

Intertidal zones by definition are exposed to air at low tide, and the exposure duration can be weeks (e.g. during neap tides) depending on water level and bed elevation. Here we investigated the effect of varying exposure duration (6 h to 10 days) on intertidal mudflat erosion (measured using the EROMES device), where the effects of water content and biofilm biomass (using chlorophyll-a content as a proxy, Chl-a μg g⁻¹) were taken into account. Sediments were collected between spring and summer (in October 2018, January 2019 and February 2019) from an intertidal site in the Firth of Thames, New Zealand. Longer exposure duration resulted in more stable sediments [higher erosion threshold (Ƭ_cr, N m⁻²) and lower erosion rate (ER, g m⁻² s⁻¹)]. After 10 days, exposure increased Ƭ_cr by 1.7 to 4.4 times and decreased ER by 11.6 to 21.5 times compared with 6 h of exposure. Chl-a and water content changed with exposure duration and were significantly correlated with changes in Ƭ_cr and ER. The stability of sediments after two re-submersion periods following exposure was also examined and showed that the stabilizing effect of exposure persisted even though water content had increased to non-exposure levels. Re-submersion was associated with an increase in Chl-a content, which likely counteracted the destabilizing influence of increased water content. A site-specific model, which included the interplay between evaporation and biofilm biomass, was developed to predict water content as a function of exposure duration. The modelled water content (W_Mod.) explained 98% of the observed variation in water content (W_Obs.). These results highlight how the exposure period can cause subtle changes to erosion regimes of sediments. An understanding of these effects (e.g. in sediment transport modelling) is critical to predicting the resilience of intertidal zones into the future, when sea-level rise is believed to exacerbate erosion in low-lying areas. © 2020 John Wiley & Sons, Ltd.  相似文献   

Macrozoobenthic community structure in a large shallow lake: Disentangling the effect of eutrophication and wind-wave disturbance     

《Limnologica》2016

Biological communities in shallow lakes are often subject to the combined effects of eutrophication and wind-wave disturbance. However, their relative importance in regulating macrozoobenthic community assembly has not been well addressed. In the present study, a monthly sampling of macrozoobenthos and environmental parameters was conducted at ten sites from December 2012 to November 2013 in Lake Hongze, the fourth largest freshwater lake in China, which has undergone serious water quality deterioration over the past few decades. A total of 30 taxa were recorded during the 12 sampling occasions, including 6 chironomids, 6 bivalves, 4 gastropods, 4 oligochaetes, 4 polychaetes, 4 crustaceans and 2 other aquatic insects. The mean abundance and biomass of total macrozoobenthos varied greatly among the ten sites and presented distinctive taxonomic composition between the protected bays and the offshore zone. Three eutrophication parameters (including permanganate index (COD_Mn), chlorophyll a, and total phosphorus in surficial sediments) and three wind-wave variables (including Secchi depth, turbidity, and mean effective fetch) were highly related to spatial variation of macrozoobenthic assemblages. When eutrophication variables were controlled, there was a significant correlation between community similarity and wind-wave disturbance condition, and vice versa. Variation partitioning showed that wind wave disturbance explained 15.9% of the variation in benthic community composition, slightly lower than that explained by eutrophication (17.9%). These results indicate that wind-wave disturbance is as important as eutrophication in regulating benthic community structure in this large shallow lake. Wind-wave disturbance imposed opposite effects on benthic community relative to eutrophication, and were more prominent in the offshore zone weakening the role of eutrophication.  相似文献   

Schmidt‐hammer exposure‐age dating (SHD) of snow‐avalanche impact ramparts in southern Norway: approaches,results and implications for landform age,dynamics and development          下载免费PDF全文

John A. Matthews  Lindsey J. McEwen  Geraint Owen 《地球表面变化过程与地形》2015,40(13):1705-1718

Schmidt‐hammer exposure‐age dating (SHD) was applied to the problem of dating the diachronous surfaces of five distal river‐bank boulder ramparts deposited by snow avalanches plunging into the Jostedøla and Sprongdøla rivers in the Jostedalsbreen region of southern Norway. Approaches to local high‐precision linear age calibration, which controlled in different ways for boulder roundness, were developed. The mean age (SHD_mean) and the maximum age (SHD_max) of surface boulders were estimated for whole ramparts, crests and distal fringes. Interpretation was further assisted by reference to R‐value distributions. SHD_mean ages (with 95% confidence intervals) ranged from 520 ± 270 years to 5375 ± 965 years, whereas SHD_max ages (expected to be exceeded by <5% of surface boulders) ranged from 675 to 9065 years. SHD ages from the Jostedøla ramparts tended to be older than those associated with the Sprongdøla, rampart crests were younger than the respective distal fringes, and use of relatively rounded boulders yielded more consistent SHD ages than angular boulders. The SHD_mean ages indicate differences in recent levels of snow‐avalanche activity between ramparts and provide insights into rampart dynamics as boulders are deposited on rampart crests and, in smaller numbers, on the distal fringes. SHD_max ages provide minimum age estimates of rampart age (i.e. the time elapsed since the ramparts began to form) and suggest that at least some of the ramparts have been developing since the early Holocene. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献