共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
早白垩世泥炭地净初级生产力及其控制因素--来自二连盆地吉尔嘎郎图凹陷6号煤的证据 总被引：2，自引：0，他引：2
现代泥炭地中蕴藏着巨量的碳,泥炭地生产力的高低会影响全球碳循环及全球气候变化。前人对全新世以来泥炭地生产力做了大量研究,但对前第四纪的“深时”阶段的泥炭地生产力则极少涉及,其主要原因是缺少精确的定年方法。以二连盆地吉尔嘎郎图凹陷早白垩世6号煤为例,利用地球物理测井信号进行频谱分析并获得煤层中米兰科维奇旋回周期参数（123 ka（偏心率）:38.1 ka（斜率）:22.1 ka（岁差））,将米兰科维奇旋回作为“深时”地层时间的“度量”工具,计算出6号煤层碳的聚集速率为35.1~38.9 g C/（m2·a）,进一步推算出其所代表的泥炭地的碳聚集速率为46.2~51.2 g C/（m2·a）,净初级生产力（NPP）为231~256 g C/（m2·a）。将该计算结果与全新世同一纬度带泥炭地生产力水平比较,并结合前人研究成果综合分析影响因素,得出早白垩世泥炭地生产力水平主要受温度和大气中二氧化碳含量控制,而这两种因素又与气候相关联,则泥炭地生产力的研究可能对进一步了解古气候提供帮助。 相似文献
3.
以河北省石津灌区为研究对象,以2007-2009年两季冬小麦生育期为研究时段,基于Hydrus-1D和Modflow模型模拟分析了井渠结合灌溉模式下冬小麦的净入流量水分生产率和净灌溉水分生产率的尺度效应(作物、田间、分干、干渠和灌区尺度)。结果表明:①从作物尺度到灌区尺度,损失水量越来越多,使得净入流量水分生产率和净灌溉水分生产率分别减少了9.49%和16.59%;②由于研究区地下水埋深较大,冬小麦生育期内渗漏补给地下水库的重复利用水量很小,而净灌溉水分生产率因为考虑了这一小部分重复利用水量,比传统的灌溉水分生产率有了小幅提升;③在多年时间尺度上,由于渗漏水量能够全部进入地下水库被重复利用,净入流量水分生产率随尺度增大而增大,而不同空间尺度的净灌溉水分生产率也比冬小麦生育期时间尺度上提高37%~65%。 相似文献
4.
Biodiversity and ecosystem functions in wetlands: A case study in the estuary of the Seine River, France 总被引：1，自引：0，他引：1
O. Chabrerie I. Poudevigne F. Bureau M. Vinceslas-Akpa S. Nebbache M. Aubert A. Bourcier D. Alard 《Estuaries and Coasts》2001,24(6):1088-1096
The integrity of estuarine wetlands is maintained by physical connections between river and sea to floodplain. Their ecological importance can be assessed through plant biodiversity and such ecosystem functions as primary productivity and nitrate removal capacity. Multivariate analysis were used to establish a hierarchy of environmental factors related to the vegetation structure and diversity. Four different measures of plant diversity (both structural and functional) were made on a Seine River wetland. Key functions of estuarine floodplain (productivity and denitrification capacity) were either measured directly or assessed using remotely sensed data. The richest plant communities correspond to mesophilous grasslands which have an intermediate position between natural and anthropogenic disturbance regimes. These species assemblages occur in ecosystems presenting both a regular productivity in time and space and the highest denitrification potentiality. 相似文献
5.
利用测井资料进行天然气储层产能的评价与预测 总被引：6，自引：0，他引：6
以鄂尔多斯某区块石盒子组第一段为主要研究层段,以测井数据体为实际利用资料,通过对测井数据资料的聚类分析,建立了对应产层的评价参数,以多参数聚类分析方法建立了天然气储层产能评价和预测的标准模式,从而达到从定性到定量对天然气储层的产能进行评价和预测的目的.分析结果表明,该区块目的层段的产能级别可分为两类,一类的产能级别较差,其无阻流量小于5 000 m3/d,达不到国家工业气流标准,无开采价值;而另一类的产能级别较好,其无阻流量大于5 000 m3/d,多在10 000 m3/d以上,具备一定的开采价值.研究验证该方法是一种行之有效的方法. 相似文献
6.
鄂尔多斯盆地下古生界奥陶系碳酸盐岩生烃能力研究 总被引：2，自引：0，他引：2
产率比是有机质在某一成熟度下的气态烃类产物的产率与其最终气态烃产率的百分比,对相同类型有机质的不同阶段的产率比进行分析可建立该类型有机质的产率比与成熟度的关系.元素平衡法是指有机质及其生成物、残留物间存在的一种物质平衡关系.应用产率比法和元素平衡法对鄂尔多斯盆地下古生界奥陶系碳酸盐岩的生烃能力进行了讨论,指出下古生界奥陶系泥质碳酸盐岩具有一定的生烃能力,其气态烃最终产率可达420～430 m3/T*有机碳,相当于Ⅱ型干酪根的生烃能力;纯碳酸盐岩的生烃能力相对较低,气态烃产率只有120 m3/T*有机碳. 相似文献
7.
Artificial sediment enhancement using a thin layer of dredged material has been suggested as a means to increase elevation
and create soil conditions conducive to increased marsh structure and function in deteriorating marshes. Using a chronosequence
approach, we examined the effects of sediment enhancement in deteriorating marsh and open-water pond habitats located in six
brackish marshes. Sediment enhancement of both marsh and interior pond sites had significant, immediate, and long-lasting
effects on physical soil properties and nutrient status with increased bulk density and inorganic nitrogen. Vegetative cover
and productivity response were minimal for deteriorating vegetated marshes with the short-term response data showing no significant
impact of sediment enhancement and long-term trends indicating decreasing productivity over time. In contrast, trajectory
models of vegetative cover and productivity in interior pond sites showed increases over time indicating that, for restoration
of interior ponds, sediment enhancement may prove valuable. The use of trajectory models emphasizes the need for long-term
monitoring to determine restoration success of projects. 相似文献
8.
用硫酸钠生产烧碱,是对硫酸钠资源开发利用的一种新尝试。将路布兰法制纯碱和苛化法制烧碱有机地结合起来,设计了一条工艺流程路线;通过对各步反应的温度、时间及反应物之间的比例与其产率之间关系的研究,摸索出最佳的反应条件,并对硫酸钠在烧碱工业中的应用前景作了初步的探讨。 相似文献
9.
地球微生物过程与潜在烃源岩的形成: 钙质微生物岩 总被引：2，自引：0，他引：2
钙质微生物岩是各种微生物生命活动引起的特殊的碳酸盐建造, 主要集中发育在前寒武纪及显生宙等重大地质转折期, 在我国华北及华南地区有着广泛的分布.微生物岩中大量微生物化石的存在反映当时的海洋具有很高的初级生产力.明显偏低的钼同位素值显示在前寒武纪相当长的时期里, 海洋底部处于缺氧状态.Th/U值的急剧降低和黄铁矿在浅水台地区的广泛出现显示二叠纪大绝灭后, 海洋环境也同样呈现缺氧的还原状态.高生产力和还原的沉积环境为生物有机质的埋藏及烃源岩的形成创造了条件.前寒武纪及晚泥盆世微生物岩中沥青的发现, 进一步增加了钙质微生物岩作为潜在碳酸盐型烃源岩的可能性. 相似文献
10.
Shale gas production has gradually achieved high and stable output, which makes it possible to make up for the shortage of oil and gas energy as an alternative energy source. Shale reservoir is compact, with well-developed nano-pore, and has the characteristics of adsorption and desorption, diffusion and slippage. At the same time, there are a large number of natural cracks, bedding and foliation. Hydraulic fractures expand irregularly after volume fracturing in horizontal wells. The whole system has multi-field coupling and cross-scale flow effects. Productivity prediction of shale gas is difficult and uncertain, which restricts the efficient development and evaluation of shale reservoirs. In this paper, the development status of productivity numerical models for shale gas horizontal wells is reviewed in consideration of the multi-scale transport characteristics of shale gas. These models include dual media capacity models, multiple media capacity models, and complex seam productivity models. It is considered that the dual medium and multi-media productivity models weaken the large permeable flow area and channel provided by the complex seam network system after shale reservoir lamination, and cannot comprehensively characterize the full-scale coupled transport characteristics of shale gas. The numerical model for productivity prediction of shale gas horizontal wells based on complex fracture network provides a multi-scale flow embedded fracture network system, which solves the problem of systematic flow without losing the ability to accurately characterize each scale flow. It is necessary to obtain the complex fracture network morphological characterization which conforms to reservoir geological characteristics, rock mechanical behavior and fluid-solid coupling mechanism. Fracture network characterization is the key to the productivity prediction of shale gas horizontal wells. 相似文献
11.
In Louisiana, salt marshes are being created in an effort to offset the large loss of such habitat that has occurred over the last 50 yr. Primary productivity is an important function and indicator of success for salt marsh creation and restoration projects. The aim of this study was to determine whether the aboveground and belowground productivity of the dominant salt marsh grassSpartina alterniflora in created marshes in southwest Louisiana began to approximate productivity levels in natural marshes, over time. Net annual aboveground primary productivity (NAPP) was measured by a harvest technique, while the ingrowth core method was used to estimate net annual belowground primary productivity (NBPP). NAPP levels were similar to those found in other, Louisiana salt marshes, while NBPP levels were similar to or higher than the reported range forS. alterniflora studied along the Atlantic and Gulf of Mexico coasts. NAPP tended to decrease as the created marshes aged, but the levels in the oldest, 19 year old, created marsh were still well above values measured in the, natural marshes. It was estimated that it would take 35 yr after marsh creation for NAPP in the created marshes to become equivalent to that in natural marshes. NBPP in the created marshes became equivalent to levels found in the natural marshes after 6–8 yr, but then belowground production increased with marsh age, reaching an asymptote that surpassed natural marsh levels. Equivalency in primary productivity has not been reached in these marshes. Elevation also affected productivity, as higher elevational sites with greater topographic heterogeneity had significantly lower aboveground and belowground biomass levels than those with elevations closer to mean sea level. This underscores the need to construct marshes so that their mean elevation and degree of topographic heterogeneity are similar to natural marshes. 相似文献
12.
《地学前缘(英文版)》2015,6(6)
The western continental margin of India is one of the highly productive regions in the global ocean.Primary productivity is induced by upwelling and convective mixing during the southwest and northeast monsoons respectively.Realizing the importance of high primary productivity,a sediment core was collected below the current oxygen minimum zone(OMZ) from the southwestern continental margin of India.This was dated by AMS radiocarbon and as many as 60 paleoclimate/paceoceanographic proxies,such as particle size,biogenic components,major,trace and rare earth elements(REEs) which were measured for the first time to determine sources of sediment,biogeochemical processes operating in the water column and their variations since the last glacial cycle.R-mode factor analysis of comprehensive data indicates that the dominant regulator of paleoproductivity is the southwest monsoon wind induced upwelling.Other paleoproductivity related factors identified are the marine biogenic component and biogenic detritus(as an exported component from the water column added to the bottom sediment).All paleoproductivity components increased significantly during the marine isotope stage-1(MIS-1)compared to those accumulated from MIS-4 to MIS-2.The second group of factors identified are the terrigenous sediments with heavy minerals like zircon and ilmenite.The terrigenous sediment,in particular,increased during MIS-2 when the sea-level was lower;however,the heavy mineral component fluctuated over time implying pulsed inputs of sediment.The diagenetic fraction and reducing component are the third group of factors identified which varied with time with increased accumulation during the MIS transitions.The primary productivity along the southwestern continental margin of India seems to have been controlled principally by the upwelling during the southwest monsoon season that was weaker from MIS-4 to MIS-2,as relative to that during the MIS-1.In contrast,increased glacial productivity noticed in sediments deposited below the current oxygen minimum zone(OMZ) along the north of the study area that can be linked to entrainment of nutrients through the intensified convective mixing of surface water during the northeast monsoon.The sequestration of greenhouse gases by the western continental margin of India was higher during glacial than interglacial cycles. 相似文献
13.
南海具有典型边缘海特征,其北部陆坡由于具有高沉积速率的地层剖面,可以用于研究亚轨道尺度气候变化。本研究以南海北部陆坡下部MD12 3432柱状样(19°16.88′N,116°14.52′E,水深2 125 m)为主要研究材料,分析其粗组分百分含量、底栖有孔虫丰度和特定环境指示属种的百分含量与丰度,并结合相关研究结果,运用多指标综合分析,重建了南海北部陆坡MIS 11期(距今约40万年)以来的表层初级生产力和底层水溶解氧含量的演化情况。与之前研究不同,本研究发现MIS11期以来南海北部的古生产力在温暖的间冰期高、在寒冷的冰期低,且主要受控于东亚夏季风影响下低纬地区降水强度的变化。在MIS 7期和MIS 9期可能有较高溶解氧含量的底层水进入南海北部,导致在高生产力的暖期中,喜氧的低生产力指示种Cibicidoides wuellerstorfi丰度增加。 相似文献
14.
Donald K. Grayson 《Quaternary Research》1998,49(3):330-334
Precipitation and net primary productivity are positively correlated in arid environments. Both variables are, in turn, correlated with mammal species richness, but this relationship is not necessarily positive. With increasing precipitation in arid areas of low to moderate productivity, mammal richness increases linearly; as rainfall and productivity increase beyond this point, mammal richness is known to decline in some areas, producing a relationship that has been termed “unimodal” or “humped.” In the Great Basin of the arid western United States, studies of the relationship between rodent species richness and precipitation have revealed only a positive relationship between these two variables. It has, however, been argued that if areas of higher precipitation were to be sampled within this region, the decline phase would become evident. When latest Pleistocene and Holocene small mammal assemblages from the northern Bonneville Basin (central Utah) are examined across a temporal moisture gradient, species richness declines as moisture declines. Since the Great Basin was significantly moister during the latest Pleistocene and Early Holocene than it has been since that time, the unimodal response model does not appear to apply to this region. 相似文献
15.
Phosphorus burial as a function of paleoproductivity and redox conditions in Arabian Sea sediments 总被引：1，自引：0，他引：1
In this study the response of sedimentary phosphorus (P) burial to changes in primary productivity and bottom water oxygen concentrations during the Late Quaternary is investigated, using two sediment cores from the Arabian Sea, one recovered from the continental slope and the other from the deep basin. The average solid-phase P speciation in both cores is similar, authigenic and biogenic (fish debris) apatite make up the bulk of the P inventory (ca. 70%);whereas P adsorbed to iron oxides, organic P, and detrital apatite constitute minor fractions. Postdepositional redistribution has not significantly altered the downcore distribution of total solid-phase P. Phosphorus burial efficiencies are generally lower during periods of increased paleoproductivity. This is caused by (a) partial decoupling of the P export flux, consisting primarily of particulate organic P, and the P burial flux, consisting primarily of biogenic and authigenic apatite; and (b) the lack of increased rates of authigenic CFA formation during periods of higher P deposition. In addition, fluctuations in bottom water oxygen concentrations may have affected P burial in continental slope sediments. The results of this study indicate that higher primary productivity induces more efficient P cycling. On time scales exceeding the oceanic P residence time, this process may induce higher surface water productivity, thus creating a positive feedback loop. In the Arabian Sea, this feedback mechanism may have contributed to changes in sea surface productivity on sub-Milankovitch time scales because P, regenerated on the continental slopes of the Oman and Somalian coastal upwelling zones, is reintroduced into the photic zone relatively fast. 相似文献
16.
The tandem operation of draglines is in use in some of the major Indian opencast coalmines owing to the favourable geo-mining
conditions, technical suitability, efficiency and economic viability. In view of the importance of tandem operation, the present
study has been undertaken in a large Indian opencast coalmine in order to critically investigate the horizontal and vertical
tandem operation of draglines on moderately strong and high sandstone benches (35–42 m), overlying a 15–18 m thick coal seam.
The study has revealed that although the preparation of balancing diagram for planning of dragline operations is the first
and the most important step, its actual implementation is equally important. Marked discrepancies in the productivity parameters
as envisaged by the balancing diagram and as observed in the field studies, have been investigated and reported. The study
also propounds the importance of appraisal of dragline productivity parameters, such as, cycle time, swing angle, seating
position, availability, utilization, etc., in the field scale. Irrespective of the mode of operation (horizontal or vertical
tandem), the study moots the concept of computation of the weighted cycle time and overall cycle time vis-à-vis swing angle
variation for the draglines operating in field. The results drawn from the case study have been discussed in terms of cycle
time computations, annual output computation and evaluation of earthmoving efficiency for the horizontal and vertical tandem
modes of operation. 相似文献
17.
生物的生产量以及被保存的沉积有机质是烃源岩形成的重要条件。多细胞生物出现并广泛地生活于扬子地区伊迪卡拉纪陡山沱期晚期的浅海中,生物之间相互依赖和共存的多层次化和复杂化生态系统的建立,使陡山沱期成为扬子地区生命演化和发展重要时期。陡山沱期的黑色泥(页)岩在沉积时为富含水份的粥性沉积物,同时当时海洋中的氧化-还原界面较浅,生物遗体可迅速地被沉积物所覆盖而形成烃源岩。伊迪卡拉纪陡山沱期是化学、气候和环境变化的剧烈时期,也是扬子地区生命演化、有机质生产力发展和烃源岩形成的一个重要时期。 相似文献
18.
A terrestrial scenario for the Cretaceous-Tertiary boundary collapse of the marine pelagic ecosystem
In this paper, we present an expansion of the model for marine ecosystem collapse at the Cretaceous-Tertiary boundary presented by Brinkhuis and Zachariasse (1988). A long-term sea-level drop at the end of the Cretaceous culminated in a short-term regressive pulse at K-T time. Deep-water production was curtailed, minimizing the vertical advection of nutrients and oxygen in the oceans. Consequently, a productivity crisis developed, which could only be survived by cosmopolitan shallow-dwellers, and the Oxygen Minimum Zone (OMZ) expanded. No sustained Oceanic Anoxic Event followed the K-T boundary event, since productivity had dropped to extremely low values. At K-T time, however, the short-term expansion of the OMZ, invoked by the combination of minimized oxygen advection and abrupt mass mortality, caused dysoxic conditions even to reach up to the shelves, as can be deduced from sedimentological, chemical and faunistic observations. 相似文献
19.
韦恒叶 《沉积与特提斯地质》2012,32(2):76-88
海洋表层初级生产力大小以及水体氧化还原条件是古海洋和古气候研究的重要内容,而元素地球化学是研究初级生产力以及氧化还原条件最常用的手段。主量元素Fe和Si是限制生物的营养元素,痕量金属元素Cu、Ni和Zn是微营养元素,而营养条件是沉积生产力的限制因素,因此这些元素的含量能反映初级生产力大小。Ba和Mo是随有机质一起沉淀下来的,与水体的有机碳通量有关,也是古生产力大小的指标。对氧化还原敏感的痕量金属元素含量（如Cr、V和U）以及元素比值（如V/（V＋Ni）、V/Cr、Ni/Co、U/Th和V/Sc）常用来重构水体的氧化还原条件。 相似文献
20.
通过对ODP184航次1147/1148站位约4MaB.P.以来沉积物中来源于定鞭金藻的生物标志化合物的研究,对南海北部晚上新世以来的古海洋生产力、表层海水温度及CO2分压的变化情况进行了探讨.定鞭金藻生产力与硅藻生产力一样在0.9MaB.P.以前比较稳定地保持在较低水平,而0.9MaB.P.后定鞭金藻生产力较高,且呈现冰期低间冰期高的波动,硅藻生产力则呈现持续升高的趋势.由C37烯酮不饱和度指标获得的南海北部4MaB.P.以来表层海水的UK′37温度与浮游有孔虫壳体δ18O具有较好的相关性,且能显示出0.9MaB.P.来的19个氧同位素期,表明将U37K′37温标应用到晚第四纪以前基本上是可行的.由δ13C37:2计算的表层海水pCO2显示,晚上新世的pCO2要高于300μL/L,而第四纪的pCO2尽管存在波动,却基本上在300μL/L以下.计算出的晚第四纪的pCO2十分稳定,与同期的大气pCO2历史变化不一致.这可能与计算中简单地假定某些参数(如生长速率)为常数有关,这些参数在第四纪冰期间冰期旋回中可能有较大变化. 相似文献