Synchronous pattern of moisture availability on the southern Tibetan Plateau since 17.5 cal. ka BP – the Tangra Yumco lake sediment record

A possible asynchronicity of the spatial and temporal moisture availability on the Tibetan Plateau has been a controversial subject of discussion in recent years. Here we present the first attempt to systematically investigate possible spatial and temporal variations in moisture availability by examining two lakes, Tangra Yumco and Nam Co, on an east–west transect on the southern Tibetan Plateau using identical proxies for palaeoenvironmental reconstruction. In this study, an independent record from Tangra Yumco was analysed applying a multi‐proxy approach to reconstruct variations in moisture availability since the Lateglacial. Results were subsequently compared with previously published records from Nam Co and additional records from Tso Moriri (northwestern Himalaya) and Naleng Co (southeastern Tibetan Plateau). Our results show that Tangra Yumco was at least partially ice covered prior to 17.1 cal. ka BP. A temperature rise after 17.1 cal. ka BP probably resulted in thawing of the permafrost. At 16.0 cal. ka BP moisture availability increased, representing an initial monsoonal intensification. Warmer conditions between 13.0 and 12.4 cal. ka BP and cooler conditions between 12.4 cal. ka BP and the onset of the Holocene reflect the Bølling‐Allerød and Younger Dryas. At the onset of the Holocene moisture availability rapidly increased, with moisture highest prior to 8.5 cal. ka BP when temperatures were also highest. After 8.5 cal. ka BP the moisture availability gradually decreased and showed only minor amplitude variations. These findings are consistent with the records from large lakes like Nam Co, Tso Moriri, and Naleng Co, revealing a synchronous pattern of moisture availability on the southern Tibetan Plateau.     

Probability of received-power fluctuation of an optical system in the turbulent atmosphere

The probability of received-power fluctuation in the turbulent atmosphere is discussed with a simple and yet reasonable model for a direct-detection optical system. Good agreement was found between the theore-tical results and the field experiment. Thus the analysis in this paper may be taken as a guide for the design of atmospheric optical system.     

贵州晴隆中二叠统大厂层砾岩成因研究

贵州晴隆中二叠统大厂层中—上部产出一套呈囊状、透镜状分布的砾岩层。对大厂层砾岩沉积序列、结构、构造特征和矿物组合进行研究,结果表明:沉积序列为"反粒序",砾岩成分单一,基本为玄武质,是由峨眉山玄武岩直接改造而成,未发育河道相沉积特征;大厂层砾石具特殊的"泥化边"构造,是玄武岩在海水中大量水解的直接证据,填隙物中的青磐岩化矿物组合表明砾岩遭受了低温热液的改造。填隙物具有接近凝灰岩的Zr/Hf(30.7~43.4,均值38.0),揭示玄武岩在改造形成砾石的过程中有火山碎屑(火山灰)参与成岩;砾石和填隙物相对玄武岩贫Na(Na2O)富K(K2O),三者具有相似的稀土配分模式,其中∑REE呈规律性变化(玄武岩最高,砾石次之,填隙物中最低)。沉积背景分析认为,峨眉地幔柱作用使地壳发生了差异抬升,抬升一侧暴露遭受剥蚀形成不整合面,相对沉降一侧继续接受沉积,大厂层正是峨眉山玄武岩前锋带在局限海盆边缘(沉降侧),于茅口灰岩之上继续沉积的产物。大厂层砾岩形成机制是:炽热玄武岩流在海水中急剧爆裂,同时火山碎屑参与沉积,形成的玄武岩前积层(淬碎熔岩角砾)及凝灰岩,沉积在茅口组灰岩之上;在后期的演化过程中,炽热玄武岩冷凝收缩,柱状节理发育,在潮汐流和沿岸流的相互作用下不断磨蚀形成大厂层砾岩。     

长输管道局部腐蚀体积型缺陷逐次评价

局部腐蚀包括缝隙腐蚀、应力腐蚀、腐蚀磨损、氢腐蚀,H2S应力腐蚀和氢腐蚀是长输管道最容易发生的一种局部腐蚀方式。针对长输管道易发生局部腐蚀的特点,参考其他管道评价方法,根据现场管道的安全状况,提出了适用于现场的含局部腐蚀体积型缺陷管道的三步评价法。该方法不需要考虑管道的腐蚀裕量,简化公式,便于现场计算。     

不同地理环境下"空间贫困陷阱"分异机制比较——基于大别山与黄土高原的实证

脱贫攻坚战的打赢使贫困治理的目光转向缓解相对贫困,脱贫人口与相对贫困人口的重合性决定了集中连片特困地区仍将是我国解决贫困问题的主战场。以大别山区的新县和黄土高原地区的延长县为例,以贫困发生率为因变量,从“人”、“业”、“地”3个维度选取自变量,综合运用空间自相关和地理探测器等方法,解析不同地理环境下贫困空间分异模式与作用机制。结果表明：大别山区贫困空间集聚为点状和团块状相间分布为主,黄土高原地区则以团块状为主。大别山区“地”和“业”2个维度对空间贫困作用显著,黄土高原地区则“人”、“业”、“地”3个维度相对均衡。承载空间“地”的资源丰度带来的生存压力不同两地贫困形成机制的差异所在,黄土高原地区基于足够的生存资源,在相对封闭的空间中形成3个维度的负向循环累积,而大别山区在资源匮乏作用下,个体生存理性抉择下选择外出务工,从而打破贫困累积的循环。     

Study on the relationship between speciation of heavy metals and their ecotoxicity

Heavy metal is a main pollutant in the marine ecosystem, so study on the effect of heavy metal on phytoplankton is important. Algae (Chaetoceros sp.,Dunaliella sp.,Dicrateria zhanjiangenis Hu. var. sp.) were laboratory cultured to observe the effect of heavy metals on their growth. The effect of different metal ion concentration, the detoxication effect of complexation agents and the growth of algae in different media and different nutrition levels were studied to evaluate the effect of metal speciation. It is proved that trace amount of heavy metals can stimulate the growth of algae cells but that high concentration is lethal. The sequence of toxicity is Cd²⁺>Zn²⁺>Pb²⁺. In ordinary nutrition conditions, the detoxication sequence of complexation agents toChaetoceros sp. is EDTA >sodium salicylate>sodium oxalate >sodium citrate>sulfanilic acid>O-phenanthroline. This is in good conformity with the stability constant sequence of these agents with copper and good evidence that toxicity of metal ion is related to its activity and not to its total concentration. Project supported by the Fund of Excellent Young Teachers of State Educational Commission of China.     

青藏高原北部冰前湖沉积记录的中晚全新世冰川活动

青藏高原的冰川为亚洲地区大多数人口提供了重要的水资源,研究青藏高原的冰川活动历史有助于预估未来气候变化条件下的冰川响应。本文通过对羌塘腹地布若错沉积物岩芯的粒度、元素以及总有机碳等指标进行分析,重建了该流域中晚全新世以来的冰川活动历史。结果表明,布若错流域在5.2~4.0 cal.ka B.P.期间,冰川退缩,气候相对温暖;然而,4.0 cal.ka B.P.以来环境逐渐变干,印度季风持续减弱;随着3.2 cal.ka B.P.左右大规模的冰川前进,布若错流域进入新冰期,并受到较强西风的影响,气候寒冷干旱;1.3 cal.ka B.P.以来,流域内冰川仍然维持着较大规模,然而湖面却略有升高,可能反映了西风带来了一定的降水。此外,该流域存在4次显著的冰川前进事件,它们分别发生在3.6~3.4 cal.ka B.P.、3.2~2.3 cal.ka B.P.、1.9~1.7 cal.ka B.P.和0.4~0.1 cal.ka B.P.。这4次冷期与青藏高原其他古气候记录对应较好,这种频繁发生的冷事件可能与太阳辐射的长期衰减以及太阳活动的周期性变化有关,热带辐合带的持续南退是季风持续减弱的重要原因;此外,中晚全新世北大西洋的气候变化通过增强的西风环流对该流域产生影响。     

Laboratory Investigation into the Evaporation of Natural-Gas Condensate Oils: Hints for the Sanchi Oil Spill

The Sanchi oil tanker collision in the East China Sea on January 6th, 2018 has caused worldwide attention due to its uniqueness. A considerable amount of h     

黔西南中晚二叠世大厂层火山热水沉积成矿作用

贵州晴隆大厂锑矿区赋矿地层大厂层为一套以硅化为主的火山碎屑岩沉积建造,因其别具特色的岩石组合、特殊的构造位置,以及含有金、锑、萤石、硫铁矿等矿产资源而备受地学界关注。晴隆大厂锑矿床90%以上的锑矿体和金矿化体均位于大厂层之中,因此,研究大厂层的形成和演化过程及其对锑、金成矿的控制作用或影响机理显得尤为重要。沉积岩相学研究表明,大厂层主要包括火山岩相(火山溢流相、淬碎角砾岩相、沉凝灰岩相、空落集块岩相和熔结凝灰岩相)和热液沉积岩相(热水沉积相、热水喷流相和热水交代相)。中—晚二叠世(约260 Ma)的溢流玄武岩、基性火山喷发和海底热水喷流活动是大厂层的主要物源供给者。元素地球化学研究表明,大厂层在沉积过程的热水喷流沉积作用提供了Sb、As、Au、Ag、Pb等成矿元素,并形成成矿元素的初始"富集体"。综合研究认为,中—晚二叠世的热水喷流沉积活动在时间上与右江盆地印支期低温热液成矿事件(200～250 Ma)在时空上基本一致,为印支期成矿事件在右江盆地北缘的响应。