Progress in isotope paleohydrology using lake sediment cellulose     

Brent B. Wolfe  Matthew D. Falcone  Ken P. Clogg-Wright  Cherie L. Mongeon  Yi Yi  Bronwyn E. Brock  Natalie A. St. Amour  William A. Mark  Thomas W. D. Edwards 《Journal of Paleolimnology》2007,37(2):221-231

Recent advances in sample preparation techniques and mass spectrometry have fostered more routine oxygen isotope analysis of aquatic cellulose in lake sediment cores, a proxy for lake water oxygen isotope history. These methodological developments have significantly increased the feasibility of incorporating this approach into high-resolution, multi-site, and multi-proxy studies, which are frequently necessary to answer complex hydrological, hydroecological and hydroclimatic questions requiring a paleoenvironmental perspective. Direct translation of lake sediment aquatic cellulose oxygen isotope composition into lake water oxygen isotope composition offers appreciable opportunity for quantitative paleohydrological reconstructions, as evidenced by studies conducted over the past 15 years that span Holocene and pre-historical timescales.  相似文献   

The effects of organic removal treatment on the integrity of δ<Superscript>18</Superscript>O measurements from biogenic silica     

Jonathan J. Tyler  Melanie J. Leng  Hilary J. Sloane 《Journal of Paleolimnology》2007,37(4):491-497

Prior to oxygen isotope analysis of biogenic silica by fluorination techniques, sediments must be cleaned of all organic compounds. Despite the expanding volume of research utilising oxygen isotope ratios in biogenic silica in palaeoclimatology, very little is known about the effects of different standard preparation methods for the removal of organic matter on the isotope values. Here we compare a number of methods for the removal of organic matter in order to assess their effectiveness and influence on subsequent isotope measurements. Not all the methods described here effectively removed organic matter, the best treatments were H₂O₂ and ignition in air at 550°C. Ignition in air at 950°C, and heating in vacuum at 250 and 450°C results in marked alteration of isotope values, whereas use of hydrogen peroxide (H₂O₂), nitric acid (HNO₃) and plasma ashing have little or no effect, within the bounds of analytical error. Ignition in air at 550°C was the most effective technique, and induced no alteration of δ¹⁸O_silica, but practical constraints may limit the application of this method routinely. Our findings indicate that considerable caution is required when preparing sediment for isotope analysis of biogenic silica.  相似文献   

青海湖碳酸盐氧同位素环境记录再认识   总被引：1，自引：2，他引：1       下载免费PDF全文

曾承 《盐湖研究》2007,15(1):16-19

青海湖是我国内陆最大的闭流型水体,地处东亚季风和西风的交汇影响区,对区域降水的改变等气候变化反应敏感,其水位变化历史是研究区域季风环境演变极其宝贵和重要的环境档案。青海湖Q14B孔岩芯介壳δ18Oc变化曲线自1991年发表以来,受到国内外同行的广泛关注和继续探讨。依据近年来青海湖气候与环境演变研究的最新研究结果和个人对闭流型湖泊同位素地球化学的认识,对介壳δ18Oc变化曲线进行了重新判读并得出以下结论:14.5~10.5 ka B.P.,青海湖区气候已逐渐从干冷向温湿过渡,季风降水逐渐增加;10.8~10.5 ka B.P.,青海湖处于碳酸盐滩湖环境,湖水深度从几米演变到接近干涸;10.5~9.5 kaB.P.,季风降水增加;9.5~8 ka B.P,湖水位从此前的接近干涸演变到此间的2~8 m,δ18Oc值跌落到一个较低的位置;8~3.5ka B.P,气候条件相对稳定,湖水不断蒸发引起重同位素的富集;3.5~0ka B.P,湖水处于同位素稳定阶段。研究结果还显示,δ18Oc值的短期波动与湖泊水位短期变化关系密切且明显,即水位高低分别对应δ18Oc的低值与高值。δ18Oc值的长期变化与湖泊水位长期变化关系不明显,水位较浅时,二者几乎无关联;水位较深时,水位的长期缓慢下降自然会导致δ18Oc逐渐攀升,而水位的长期缓慢上升也可以伴随δ18Oc逐渐攀升。  相似文献   

Simulation analysis on the regulation of overflow ecological water consumption in arid areas——A case study in the Canmrik ecological area of the mainstream zone of the Tarim River     

CHEN Xi  HUANG Yue  QIAN Jing  LIU HaiLong  FENG XianWei  LIU Ying  BAO AnMing  WANG WeiSheng 《中国科学D辑(英文版)》2007,50(Z1)

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干旱条件下夏玉米耗水分析   总被引：5，自引：1，他引：5  

吕厚荃  杨霏云  钱拴 《气象》2002,28(2):38-41

根据田间试验结果，分析干旱年份夏玉米不同发育阶段耗水状况，对比了不同日降水量对玉米田3米剖面的水分分布状况的影响，讨论了土壤失熵过程中的不同深度的水分的变化以及土壤水对玉米干物质积累的影响，为干旱年份玉米水分的科学管理提供依据。  相似文献   

Climate induced temperature effects on growth performance, fecundity and recruitment in marine fish: developing a hypothesis for cause and effect relationships in Atlantic cod (Gadus morhua) and common eelpout (Zoarces viviparus)     

H. O. Prtner  B. Berdal  R. Blust  O. Brix  A. Colosimo  B. De Wachter  A. Giuliani  T. Johansen  T. Fischer  R. Knust  G. Lannig  G. Naevdal  A. Nedenes  G. Nyhammer  F. J. Sartoris  I. Serendero  P. Sirabella  S. Thorkildsen  M. Zakhartsev 《Continental Shelf Research》2001,21(18-19)

Effects of global warming on animal distribution and performance become visible in many marine ecosystems. The present study was designed to develop a concept for a cause and effect understanding with respect to temperature changes and to explain ecological findings based on physiological processes. The concept is based on a wide comparison of invertebrate and fish species with a special focus on recent data obtained in two model species of fish. These fish species are both characterized by northern and southern distribution limits in the North Atlantic: eelpout (Zoarces viviparus), as a typical non-migrating inhabitant of the coastal zone and the cod (Gadus morhua), as a typical inhabitant of the continental shelf with a high importance for fisheries.Mathematical modelling demonstrates a clear significant correlation between climate induced temperature fluctuations and the recruitment of cod stocks. Growth performance in cod is optimal at temperatures close to 10°C, regardless of the population investigated in a latitudinal cline. However, temperature specific growth rates decrease at higher latitudes. Also, fecundity is less in White Sea than in North and Baltic Sea cod or eelpout populations. These findings suggest that a cold-induced shift in energy budget occurs which is unfavorable for growth performance and fecundity. Thermal tolerance limits shift depending on latitude and are characterized by oxygen limitation at both low or high temperatures. Oxygen supply to tissues is optimized at low temperature by a shift in hemoglobin isoforms and oxygen binding properties to lower affinities and higher unloading potential. Protective stimulation of heat shock protein synthesis was not observed.According to a recent model of thermal tolerance the downward shift of tolerance limits during cold adaptation is associated with rising mitochondrial densities and, thus, aerobic capacity and performance in the cold, especially in eurythermal species. At the same time the costs of mitochondrial maintenance reflected by mitochondrial proton leakage should rise leaving a lower energy fraction for growth and reproduction. The preliminary conclusion can be drawn that warming will cause a northern shift of distribution limits for both species with a rise in growth performance and fecundity larger than expected from the Q₁₀ effect in the north and lower growth or even extinction of the species in the south. Such a shift may heavily affect fishing activities in the North Sea.  相似文献   

Inhibition Concentration of Phenolic Substances under Different Cultivation Conditions. Part I: Phenol Oxidation by Mixed Microbial Population in a Model System     

J. Pca  G. G. S. Martius 《洁净——土壤、空气、水》1996,24(3):127-131

The effects of oxygen supply rate and the presence or absence of nutrients on the kinetics of phenol degradation and oxygen consumption by a mixed microbial population were tested in a model system. The values for the maximum specific rate of phenol degradation (q_Smax), the saturation constant (K_S), and the inhibition concentration (S_CR) were determined for unlimited growth (K_La = 340 h^?1, growth medium) with 1.7 mmol g^?1 h^?1, 65 mg L^?1, and 190 mg L^?1. Under limitation conditions, alterations occur depending on the type of limitation. Nutrient limitations lead to values of 0.8 mmol g^?1 h^?1, 45 mg L^?1, and 160 mg L^?1, and oxygen limitations lead to 1.2 mmol g^?1 h^?1. 30 mg L^?1, and 120 mg L^?1, respectively. The results suggest that with excess oxygen, the rate of phenol degradation was higher and the inhibition effect of phenol was suppressed to some extent. Under the same high oxygen supply rate, the presence of nutrients in the model water significantly supported the phenol degradation rate.  相似文献   

锡的地球化学性质与华南晚白垩世锡矿成因     

隋清霖  祝红丽  孙赛军  陈登辉  赵晓健  王钊飞 《岩石学报》2020,36(1):23-34

锡在地质过程中表现出亲氧、亲硫和亲铁三重特性。在地幔岩浆过程中,锡是一种中等不相容的金属元素。锡成矿主要与酸性岩浆活动有关,其地球化学性质决定了其成矿主要受源区性质、氧逸度以及挥发分含量、岩浆结晶分异等因素控制。高度结晶分异可使锡在岩浆中进一步富集,是锡成矿相关花岗岩的普遍特征;锡为变价元素,岩浆体系氧逸度影响源区中锡的迁移能力和分离结晶过程中锡的元素行为,还原性岩浆体系有利于锡富集成矿。富含F、Cl和B等挥发组分对锡元素的迁移和富集起积极的作用。全球锡矿床分布与俯冲带关系密切,特提斯和环太平洋构造域是主要蕴藏区。重要的锡成矿事件表现出区域性和阶段性的特征。结合锡的地球化学特性以及锡矿分布特征,我们认为最有利锡成矿的动力学机制是俯冲板片后撤机制。俯冲板片后撤引发深部软流圈地幔上涌,导致强烈的壳幔相互作用,形成低氧逸度、富F、Cl和B等花岗岩,有利于锡成矿。对于华南晚白垩世锡成矿事件,新特提斯洋俯冲板片发生后撤是其成矿地球动力学背景。  相似文献   

Electricity consumption patterns within cities: application of a data-driven settlement characterization method     

Pranab K. Roy Chowdhury  Jeanette E. Weaver  Eric M. Weber  Dalton Lunga  St. Thomas M. LeDoux  Amy N. Rose 《International Journal of Digital Earth》2020,13(1):119-135

ABSTRACT

Urban areas presently consume around 75% of global primary energy supply, which is expected to significantly increase in the future due to urban growth. Having sustainable, universal energy access is a pressing challenge for most parts of the globe. Understanding urban energy consumption patterns may help to address the challenges to urban sustainability and energy security. However, urban energy analyses are severely limited by the lack of urban energy data. Such datasets are virtually non-existent for the developing countries. As per current projections, most of the new urban growth is bound to occur in these data-starved regions. Hence, there is an urgent need of research methods for monitoring and quantifying urban energy utilization patterns. Here, we apply a data-driven approach to characterize urban settlements based on their formality, which is then used to assess intra-urban urban energy consumption in Johannesburg, South Africa; Sana’a, Yemen; and Ndola, Zambia. Electricity is the fastest growing energy fuel. By analyzing the relationship between the settlement types and the corresponding nighttime light emission, a proxy of electricity consumption, we assess the differential electricity consumption patterns. Our study presents a simple and scalable solution to fill the present data void to understand intra-city electricity consumption patterns.  相似文献   

Palaeomonsoon and palaeoproductivity records of δ18O, δ{13}C and CaCO3 variations in the northern Indian Ocean sedimentsC and CaCO3 variations in the northern Indian Ocean sediments     

A. Sarkar  R. Ramesh  S. K. Bhattacharya  N. B. Price 《Journal of Earth System Science》2000,109(1):157-169

δ¹⁸ O and δ¹³C of G.sacculifer have been measured in five cores from the northern Indian Ocean. In addition, high resolution analysis (1 to 2 cm) was performed on one core (SK-20-185) for both δ¹⁸O and gd¹³C in five species of planktonic foraminifera. CaCO₃ variation was measured in two cores. The results, presented here, show that

–	• the summer monsoon was weaker during 18 ka and was stronger during 9 ka, relative to modern conditions;
–	• δ13C variations are consistent with independent evidence that shows that during the last glacial maximum (LGM; 18 ka) the upwelling was reduced while during 9 ka it was vigorous;
–	• calculation of CaCO3 flux shows that the LGM was characterized by low biogenic productivity in the Arabian Sea while during the Holocene productivity increased by ∼65%, as a direct consequence of the changes in upwelling. Similar changes (of lesser magnitude) are also seen in the equatorial Indian Ocean. The amount of terrigenous input into the Arabian Sea doubled during LGM possibly due to the higher erosion rate along the west coast.
–	• δ18O values indicate that the Arabian Sea was saltier by 1 to 2%o during LGM. The northern part was dominated by evaporation while in the equatorial part there was an increased precipitation.

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