Sorption and Desorption of Copper and Cadmium in a Contaminated Soil Affected by Soil Amendments          下载免费PDF全文

Ping Li  Man Lang  Xing‐Xiang Wang  Tao‐Lin Zhang 《洁净——土壤、空气、水》2016,44(11):1547-1556

  相似文献   

科尔沁沙地植物功能性状的尺度变异及关联   总被引：1，自引：1，他引：0  

周欣  左小安  赵学勇  刘川  吕朋 《中国沙漠》2016,36(1):20-26

调查了科尔沁沙地流动沙丘、半固定沙丘和固定沙丘18个样地的物种组成,测定了28种植物的叶面积(LA)、比叶面积(SLA)和叶干物质含量(LDMC)等3个植物功能性状,并用性状梯度分析法对3个功能性状在群落水平上的变化进行了分解,研究了沙丘固定过程中的植物功能性状的尺度变异及其与生境变化的关系。结果表明:(1)随着沙丘的固定,群落平均LA逐渐增大,群落平均SLA及LDMC在半固定沙丘上最小;(2)群落平均SLA的生态位宽度随着沙丘固定程度依次减小,流动、半固定沙丘植物群落的适应能力较固定沙丘更强;(3)沙丘固定过程中物种性状值的变化与群落内共生植物种性状间变异的关联相比于群落间性状的变异更密切。沙丘固定导致了物种LA与LDMC较强的正相关关系,两性状在群落间的依赖性比群落内的强。物种在群落内和群落间采取不同的策略来适应沙丘固定过程生境的变化。  相似文献   

Estimation of tail dependence coefficient in rainfall accumulation fields     

Amir Aghakouchak  Grzegorz Ciach  Emad Habib 《Advances in water resources》2010

Extreme rainfall events are of particular importance due to their severe impacts on the economy, the environment and the society. Characterization and quantification of extremes and their spatial dependence structure may lead to a better understanding of extreme events. An important concept in statistical modeling is the tail dependence coefficient (TDC) that describes the degree of association between concurrent rainfall extremes at different locations. Accurate knowledge of the spatial characteristics of the TDC can help improve on the existing models of the occurrence probability of extreme storms. In this study, efficient estimation of the TDC in rainfall is investigated using a dense network of rain gauges located in south Louisiana, USA. The inter-gauge distances in this network range from about 1 km to 9 km. Four different nonparametric TDC estimators are implemented on samples of the rain gauge data and their advantages and disadvantages are discussed. Three averaging time-scales are considered: 1 h, 2 h and 3 h. The results indicate that a significant tail dependency may exist that cannot be ignored for realistic modeling of multivariate rainfall fields. Presence of a strong dependence among extremes contradicts with the assumption of joint normality, commonly used in hydrologic applications.  相似文献   

WA-PLS diatom-based pH, TP and DOC inference models from 42 lakes in the Abitibi clay belt area (Québec, Canada)     

Mihaela Enache  Yves T. Prairie 《Journal of Paleolimnology》2002,27(2):151-171

The relationship between surficial sediment diatom species and measured environmental variables was explored in lakes from the Abitibi region of western Quebec. Diatom assemblages in 42 lakes were identified and their relationship with measured environmental variables was examined using multivariate statistical methods. Canonical correspondence analysis with forward selection and Monte Carlo permutation tests revealed that the three environmental variables pH, TP and DOC each accounted for statistically significant fractions of the variation in diatom taxa. A training set with 164 modern diatom taxa was used to derive transfer functions for lake-water pH, TP and DOC using weighted-averaging-partial-least-squares (WA-PLS) techniques. The models were developed to infer lake water pH, TP and DOC within the ranges 4–8 for pH, 2.75–30.0 g l^–1 for TP, and 2.9–18.5 mg l^–1 for DOC. These quantitative inference models may now be used to help identify and estimate the effects of natural disturbances on the biogeochemistry of Abitibi lakes during their historical development.  相似文献   

Fractal Reconstruction with Unorganized Geochemical Data     

Li Changjiang  Zhao Nailiang  Ma Tuhua 《Mathematical Geology》2002,34(7):809-829

Fractal geometry is receiving increased attention as a model for many natural phenomena. In this paper, we address two issues in dealing with unorganized 3-D measured data using fractal geometry: extraction of fractal characters and fractal surface (geochemical landscapes) reconstruction. We start from a set of randomly measured 3-D data on a plane. After classification and concentration of the input data, we present methods for estimating the fractal dimension and texture deviation as fractal characters, and then an improved subdivision scheme is developed to reconstruct fractal surface on the basis of the extracted fractal characters. We demonstrate both characterization and reconstruction with irregularly measured geochemical data from 1767 stream sediment samples in the middle district (450km² in area) of Zhejiang, China.  相似文献   

Elemental δ13C at Allen's Cave,Nullarbor Plain,Australia: assessing post‐depositional disturbance and reconstructing past environments     

C. S. M. Turney  M. I. Bird  R. G. Roberts 《第四纪科学杂志》2001,16(8):779-784

The degree to which post‐depositional disturbance can be assessed in archaeological sequences is critical for the development of robust chronologies for such deposits. A common approach is the identification of conjoined artefacts distributed through the sequence as a measure of disturbance following deposition, although this method is relatively labour intensive and does not provide a continuous record of disturbance through the entire sequence. Here we present δ¹³C values for different size fractions (<125 and >125 µm) of chemically resistant charcoal distributed through a sedimentary profile at Allen's Cave, South Australia. The curves generated from both size fractions parallel one another, indicating minimal disturbance through the entire profile and providing greater confidence in the luminescence and radiocarbon chronologies reported previously for the site. In addition, the elemental δ¹³C values provide an indication of greater aridity (compared with present) persisting in this area from ca. 45 to 12 ka, consistent with other proxy records. The onset of the Holocene is marked by a shift to wetter conditions, probably as a result of post‐glacial marine transgression and closer proximity to the coastline. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

黑斑口虾蛄生态因子的试验观察     

吴琴瑟  赵延霞 《广东海洋大学学报》1997,(2)

选用活力强、体长10cm左右的黑斑口虾蛄，进行海水盐度、水温、pH值等生态因子试验。结果表明：其生存的海水盐度为6．02％～38．64％，适宜的盐度是24．20‰～29．51‰；生存的水温为10～35℃，适宜的水温为22～30℃；存活的PH6～10，适宜的PH7～9。主要以摄食贝类、鱼类及虾类为生。  相似文献   

Climatic significance of δ <Superscript>18</Superscript>O records from an 80.36 m ice core in the East Rongbuk Glacier,Mount Qomolangma (Everest)     

Zhang?Dongqi?Email author  Qin?Dahe  Hou?Shugui  Kang?Shichang  Ren?Jiawen  Paul?A?Mayewski 《中国科学D辑(英文版)》2005,48(2):266-272

The δ ¹⁸O variations in an 80.36 m ice core retrieved in the accumulation zone of the East Rongbuk Glacier, Mount Qomolangma (Everest), is not consistent with changes of air temperature from both southern and northern slopes of Himalayas, as well as these of the temperature anomalies over the Northern Hemisphere. The negative relationship between the δ ¹⁸O and the net accumulation records of the ice core suggests the “amount effect” of summer precipitation on the δ ¹⁸O values in the region. Therefore, the δ ¹⁸O records of the East Rongbuk ice core should be a proxy of Indian Summer Monsoon intensity, which shows lower δ ¹⁸O values during strong monsoon phases and higher values during weak phases.  相似文献   

Relationships Between Fundamental Seismic Hazard Parameters for the Different Source Regions in Turkey     

Yusuf?BayrakEmail author  Ahmet?Yilmaztürk  Serkan??ztürk 《Natural Hazards》2005,36(3):445-462

Turkey has been divided into eight different seismic regions taking into consideration the tectonic environments and epicenters of the earthquakes to examine relationships of the modal values (a/b), the expected maximum magnitudes (M_max) and the maximum intensities (I_max). For this purpose, the earthquakes for the time period 1900–1992 from the Global Hypocenter Data Base CD-ROM prepared by USGS, and for the time period 1993–2001 from the PDE data and IRIS data are used. Concerning the relationships developed between different magnitude scales and between surface wave magnitudes (M_S) and intensity for different source regions in Turkey, we have constructed a uniform catalog of M_S. We have estimated the values of M_max and I_max using the Gumbel III asymptotic distribution. Highest a-values are observed in the Aegean region and the lowest b-values are estimated for the North Anatolian Fault. Maximum values of a/b, M_max and I_max are related to the eastern and western part of the North Anatolian Fault and the Aegean Arc. The lowest values of all parameters are observed near the Mid Anatolian Fault system. Linear relationships have been calculated between a/b, M_max and I_max using orthogonal regression. If one of the three parameters is computed, two other parameters can be calculated empirically using these linear relationships. Hazard maps of M_max and I_max values are produced using these relationships for a grid of equally spaced points at 1°. It is observed that the maps produced empirically may be used as a measure of seismic hazard in Turkey.  相似文献   

Quantitative estimates of recent environmental changes in the Canadian High Arctic inferred from diatoms in lake and pond sediments   总被引：4，自引：0，他引：4  

Antoniades  Dermot  Douglas  Marianne S. V.  Smol  John P. 《Journal of Paleolimnology》2005,33(3):349-360

Diatoms were examined in three lacustrine sediment records from Alert, northern Ellesmere Island, and from Isachsen, Ellef Ringnes Island. Diatom assemblages changed markedly since the mid-19th century following relatively stable community composition that spanned centuries to millennia. Three different assemblages, primarily composed of Fragilaria pinnata, Diadesmis spp., or Pinnularia spp., dominated the pre-1850 period at the three sites, but were replaced with different, more diverse assemblages in recent sediments. These species shifts occurred in the mid- to late-19th century in the Isachsen sites, and in the mid- to late-20th century in our Alert site. This difference in timing appears to be a result of the different sensitivities of lakes and ponds to environmental change, rather than of site-specific chemical properties. Reconstructions of pH using diatom inference models indicated increases from 0.5 to 0.8 pH units at these sites over this period of assemblage change. The diatom-inferred pH record from Alert showed agreement with measured climate data from Alert over the last 30 years. These marked community changes suggest that these sensitive high arctic sites have recently crossed important ecological thresholds due to environmental change, most likely related to recent warming.  相似文献