生物标志化合物与相关的全球变化   总被引：20，自引：9，他引：20  

谢树成  梁斌  郭建秋  易轶  R.P.Evershed  D.Maddy  F.M.Chambers 《第四纪研究》2003,23(5):521-528

在各种地质体中广泛分布的生物标志化合物在全球变化研究中有着广泛应用,特别是在海洋和湖泊沉积物中,研究工作已涉及到古植被、古温度、古降水量、古大气CO₂浓度和古季风等的恢复.文章介绍利用气相色谱仪、气相色谱-质谱联用仪、气相色谱-热转换-同位素比质谱仪分析了一个长40cm泥炭岩芯(约222年)的生物标志化合物的分布及其单体氢同位素.结果显示,不管是生物标志化合物的分布,还是其单体稳定同位素特征都记载了气候(温度)的变化.正构脂肪酸的碳优势指数(CPI值)、正构烷烃C23/C31比值、正构烷烃C23的δD值与温度有很好的对应关系.  相似文献   

The role of sediment specific gravity and availability on cluster evolution     

A. N. Papanicolaou  K. Strom  A. Schuyler  N. Talebbeydokhti 《地球表面变化过程与地形》2003,28(1):69-86

The objective of this experimental study was to account for the role of sediment availability and specific gravity on cluster formation and cluster geometric characteristics (spacing and size). To isolate the effects of sediment availability and specific gravity on cluster evolution, mono‐sized spheres were used to simulate the cluster evolutionary cycle. Overall, twelve experimental runs were carried out in the laboratory flume. Six of these tests were performed by using glass spheres (specific gravity, SG = 2·58) and the other six by employing an equal combination of glass and Teflon spheres (SG = 2·12) of the same diameter to evaluate the role of specific gravity on cluster evolution. The three sediment availability conditions that were investigated here simulated isolated gravel elements, pool–riffle sequences and densely packed gravel‐bed. An advanced image analysis technique was employed to track the evolution of cluster microforms and provide quantitative information about the size and shape of clusters and the number of clusters per unit area. The results of this study showed that: (1) sediment availability affects the architecture and size of cluster microforms; and (2) clusters consisting of mono‐sized sediments start disintegrating at twice the incipient conditions. By performing complementary tests for the isolated gravel elements case, it was found that the evolutionary cycle of individual clusters could be described as follows, in order of increasing stress: no cluster→two particle cluster→comet→triangle→rhomboid→break up. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

地下水计算参数的测定与估计   总被引：16，自引：1，他引：16       下载免费PDF全文

金光炎  汪家权 《水科学进展》1997,8(1):16-24

叙述了浅层地下水资源评价中几个常用参数(给水度、降雨入渗补给系数和潜水蒸发系数)的测定和估计方法,并结合实例进行剖析.通过分析,得到几点新的认识:(1)给水度值同注水的方式有关,在实际情况中,由于农田表层土壤疏松,且有作物影响,因而其最大值会出现在地表附近;(2)用抽水试验法测定给水度,其值因孔而异;(3)降雨入渗补给系数与土壤结构和给水度的关系密切,一般随着埋深的增加,该系数随之减小;(4)不同季节和不同作物,潜水蒸发系数不同,表现在计算公式上的参数也不相同.  相似文献   

Runoff Scaling in Large Rivers of the World     

Hugo A. Loiciga 《The Professional geographer》1997,49(3):356-364

Runoff and precipitation scaling with respect to drainage area is analyzed for large river basins of the world, those with mean annual runoff in excess of 10 k³/yr. The usefulness of the specific runoff (runoff per unit drainage area, m/yr) to categorize runoff scaling laws across the complete spectrum of climatic and hydrologic conditions is evaluated. It is found that (1) runoff scales with drainage are in those river basins with specific runoff in excess of 0.15 m/yr (r² = 0.88); (2) runoff scaling with drainage area shows remarkably high statistical correlation (r²= 0.97) in river basins with specific runoff equal to or larger than 1.0 m/yr; (3) runoff does not Inc.rease with Inc.reasing drainage area in river basins with specific runoff below 0.15 m/yr, where no discernible statistical association was found between runoff and drainage area; and (4) precipitation depth (m/yr) is inversely proportional to drainage area raised to a fractional exponent in river basins with specific runoff in excess of 0.15 m/yr.  相似文献   

刃具斜切入破岩的试验与研究          下载免费PDF全文

石永泉 《探矿工程》1996,(2):33-35,42

介绍了刃具斜切入破岩的试验装置及试验结果，推导出了跃进载荷的计算公式，并对试验结果进行了理论分析，探讨了影响刃具侵入岩石难易的因素和影响破岩比功大小的因素。  相似文献   

义马新安煤矿特大型奥灰突水的治理     

高建中  傅月之 《煤田地质与勘探》1997,(Z1)

采用“上阻、中栏、下堵”的立体堵水方法，封堵了义马新安煤矿1995年11月5日发生的特大型（4257m3／h）奥灰突水通道，解放被淹矿井，堵水效果良好。  相似文献   

SMBR中污染物处理效率随污泥浓度变化的数学模型     

陈兆波  任南琪  呼冬雪  王爱杰 《地球科学进展》2004,(Z1)

以一体式膜生物反应器(SMBR)对生活污水进行处理,研究不同水力停留时间(HRT)条件下污泥浓度对有机物去除率的影响,并对所得试验数据进行曲线拟合,建立有机物去除率与污泥浓度的数学模型。试验结果表明:在溶解氧(DO)浓度为2.0～3.0mg/L的条件下,HRT为3h、2h和1h时,有机物去除率(η)随着污泥浓度的增大而增大,但当污泥浓度增大到6000mg/L时,η增大趋势逐渐减小,并趋于稳定。有机物去除率与污泥浓度的数学模型表明:有机物去除率(η)与水力停留时间(τ)、进水COD浓度(S_o)和污泥负荷率(N_s)等主要运行参数有关,并可以通过调节运行参数τ、S_o和N_s来达到所需要的COD去除率。  相似文献   

Removal of Cu(Ⅱ) from Wastewater Using Acidified Sewage Sludge Ash     

Gan Yiqun  Wang Yanxin  Zhang Congjun 《中国地质大学学报(英文版)》2004,15(3)

Sewage sludge ash (SSA), the waste generated in sewage sludge incineration, was obtained from Wuhan Sewage Treatment Plant and used as a low-cost sorbent for removing Cu(Ⅱ) from wastewaters. The sorbent was first modified with 5 % sulfuric acid to increase its sorption capacity. The specific surface area, porosity, cation-exchange capacity (CEC) and pHZPC of the sorbent were measured. Batch experiments were made to study the effect of contact time, solution pH value and temperature on sorption. Both Langmuir and Freundlich models well described the Cu(Ⅱ) sorption process, with correlation coefficient (R2) values of 0.993 4 and 0.989 9 respectively. And the sorption process follows the Lagergren first order kinetic model. The equilibrium sorption capacity of acidified SSA to Cu(Ⅱ) is estimated to be 7.78 mg/g under optimal conditions.  相似文献   

Channel Bed Mobility Downstream from the Elwha Dams,Washington*     

Molly Pohl 《The Professional geographer》2004,56(3):422-431

Dams are a major source of fragmentation and degradation of rivers. Although substantial research has been conducted on the environmental impacts of large structures in the United States, smaller dams have received less attention. This study evaluated the impact of two dams of moderate size, the Elwha Dams, on the downstream channel system using field data collection at river cross‐sections. The relationship of average boundary shear stress (τ_o) to critical shear stress (τ_cr) served as the basis for determining channel bed material mobility under the two‐year and ten‐year flood events. The channel had the greatest channel bed mobility at the natural cross‐section upstream from the dams, low bed mobility between the structures, and an increase in channel bed mobility in the low gradient river segment near the mouth of the river. Low bed mobility tended to be associated with a lack of channel system complexity, including reduction or loss of bars and low alluvial terraces and their associated young riparian communities. Although these run‐of‐the‐river dams do not modify streamflow greatly, the loss of sediment from the channel system has had a substantial impact on bed mobility and geomorphic and biotic complexity of the Elwha River.  相似文献   

A long‐term study of stable isotopes as tracers of processes governing water flow and quality in a lowland river basin: the upper Thames,UK          下载免费PDF全文

W. George Darling  Michael J. Bowes 《水文研究》2016,30(13):2178-2195

A long‐term study of O, H and C stable isotopes has been undertaken on river waters across the 7000‐km² upper Thames lowland river basin in the southern UK. During the period, flow conditions ranged from drought to flood. A 10‐year monthly record (2003–2012) of the main River Thames showed a maximum variation of 3‰ (δ¹⁸O) and 20‰ (δ²H), although interannual average values varied little around a mean of –6.5‰ (δ¹⁸O) and –44‰ (δ²H). A δ²H/δ¹⁸O slope of 5.3 suggested a degree of evaporative enrichment, consistent with derivation from local rainfall with a weighted mean of –7.2‰ (δ¹⁸O) and –48‰ (δ²H) for the period. A tendency towards isotopic depletion of the river with increasing flow rate was noted, but at very high flows (>100 m³/s), a reversion to the mean was interpreted as the displacement of bank storage by rising groundwater levels (corroborated by measurements of specific electrical conductivity). A shorter quarterly study (October 2011–April 2013) of isotope variations in 15 tributaries with varying geology revealed different responses to evaporation, with a well‐correlated inverse relationship between Δ¹⁸O and baseflow index for most of the rivers. A comparison with aquifer waters in the basin showed that even at low flow, rivers rarely consist solely of isotopically unmodified groundwater. Long‐term monitoring (2003–2007) of carbon stable isotopes in dissolved inorganic carbon (DIC) in the Thames revealed a complex interplay between respiration, photosynthesis and evasion, but with a mean interannual δ¹³C‐DIC value of –14.8 ± 0.5‰, exchange with atmospheric carbon could be ruled out. Quarterly monitoring of the tributaries (October 2011–April 2013) indicated that in addition to the aforementioned factors, river flow variations and catchment characteristics were likely to affect δ¹³C‐DIC. Comparison with basin groundwaters of different alkalinity and δ¹³C‐DIC values showed that the origin of river baseflow is usually obscured. The findings show that long‐term monitoring of environmental tracers can help to improve the understanding of how lowland river catchments function. Copyright © NERC 2015. Hydrological Processes © 2015 John Wiley & Sons, Ltd.  相似文献