澄碧河水库上游流域气候变化特征及其影响分析

运用数理统计方法,对广西澄碧河水库上游流域气候变化特征进行分析,结果表明:水库降水量的变化以减少为主,春季、秋季和主汛期降水量的减幅均较大;平均气温均呈显著增高趋势,其中冬季增幅最大;蒸散量的变化均呈减少趋势.并探讨了气候变化对澄碧河水库上游流域的影响,总体来看,弊大于利;提出了水库应对气候变化的若干措施和建议.     

Use of magnetic measures to assess soil redistribution following deforestation in hilly region

Limited information is available about the use of magnetic susceptibility property to determine soil redistribution in hilly areas of the semi-arid regions. This study was conducted to evaluate the use of magnetic properties to determine soil redistribution along a hill slope following deforestation. The study area is located in the Quaternary hilly region of Lordegan district in west Iran. Ten transects were established in two land uses that included natural Querqus forested and cultivated lands. Soil samples were collected at different positions along the slope and magnetic properties (χlf, χhf, SIRM, ARM, and χfd) and selected physico-chemical properties were determined. The results (based on the χfd, SIRM/ARM) showed that the magnetic susceptibly in the calcareous materials is pre-dominantly derived during the pedogenic processes and the superparamagnetic particles which were transported to lower positions of hill slope following deforestation. The results confirmed that this methodology could be applied for monitoring soil redistribution along the slope in calcareous hilly areas in the semi-arid regions.     

井地大地电磁非线性共轭梯度二维反演研究

本文提出并验证了地下大地电磁测深数据的正、反演算法和程序,为井地大地电磁测深和井地可控源音频大地电磁测深这一前沿研究课题提供了地球物理解释方法.使其更加完善和有效.在Rodi(2001)发表的大地电磁场二维NLCG反演理论和算法的基础上,推导了井地大地电磁场二维NLCG反演算法,改编反演的代码,开发出二维NLCG反演程...     

Chemical characterization of naturally weathered oil residues in the sediment from Yellow River Delta, China

With its close proximity to Shengli Oilfield, China’s second largest oilfield, the Yellow River Delta is at high risk for crude oil contamination. The massive oil discharge in oilfield may offer a chance for a natural experiment to investigate compositional changes of oil residues and study the stability of source- and weathering-dependent molecular parameters in oil residues after spills. The results demonstrate that the conventional diagnostic ratios, such as C₂₉20S/(20S + 20R), C₂₉/C₃₀H, C₃₀βα/αβ, C₃₁22S/(22S + 22R), C₂-DBTs/C₂-PHENs, C₃-DBTs/C₃-PHENs, DBT/MCHRY, CHRY/PHENs, are also valid for oil source identification even after extensive weathering of spilled oils in terrestrial environment, although some exceptions were encountered for extensively weathered sample. Moreover, the ratios of selected specific biomarkers (the oleanane index, the gammacerane index) have been developed and assessed as source indicators. Finally, we find that some maturity parameters based on alkyl naphthalenes and methyl phenanthrenes in petroleum geochemistry, such as the methylnaphthalene ratios (TMNr, TeMNr, PMNr), the methylphenanthrene ratios (MPI-1, MPDF), can be applied for the source identification and correlation at their lightly to moderately weathered stage.     

Simulation of yielding and stress–stain behavior of shanghai soft clay

In this paper, a simple bounding surface plasticity model is used to reproduce the yielding and stress–strain behavior of the structured soft clay found at Shanghai of China. A series of undrained triaxial tests and drained stress probe tests under isotropic and anisotropic consolidation modes were performed on undisturbed samples of Shanghai soft clay to study the yielding characteristics. The degradation of the clay structure is modeled with an internal variable that allows the size of the bounding surface to decay with accumulated plastic strain. An anisotropic tensor and rotational hardening law are introduced to reflect the initial anisotropy and the evolution of anisotropy. Combined with the isotropic hardening rule, the rotational hardening rule and the degradation law are incorporated into the bounding surface formulation with an associated flow rule. Validity of the model is verified by the undrained isotropic and anisotropic triaxial test and drained stress probe test results for Shanghai soft clay. The effects of stress anisotropy and loss of structure are well captured by the model.     

Shear Strength Criteria for Unsaturated Soils

Shear strength is one of the fundamental properties of unsaturated soils. It has been found to change with matric suction. Various shear strength equations have been proposed for predicting the shear strength versus suction relationship for unsaturated soils. Some of these equations are based on regression analysis of experimental data, while some are embodied in more complex stress–strain constitutive models. In this paper, a variety of shear strength equations are examined and compared with respect to their fit of experimental data. Data for specimens prepared from initially slurry conditions as well as data for initially compacted soil specimens are analysed. The advantages and limitations associated with various proposed shear strength equations are discussed in this paper.     

Research on the water use efficiency and foliar nutrient status of <Emphasis Type="Italic">Populus euphratica</Emphasis> and <Emphasis Type="Italic">Tamarix ramosissima</Emphasis> in the extreme arid region of China

Seasonal variations in foliar stable carbon composition (δ¹³C) and nitrogen (N), phosphorus (P) and potassium (K) concentrations of Populus euphratica Olivier and Tamarix ramosissima Ledeb, as well as correlations between foliar δ¹³C values and N, P and K concentrations were studied in the Ejina oasis in the lower reaches of the Heihe River, northwestern China. Foliar δ¹³C values, and P and K concentrations significantly differed between species. Foliar δ¹³C signatures in T. ramosissima were significantly more enriched than those in P. euphratica, but P and K concentrations of P. euphratica were higher. The seasonal variations and patterns of these were similar. The total foliar δ¹³C values and N, P and K concentrations in both P. euphratica and T. ramosissima showed a descending trend. There were significantly positive correlations between foliar δ¹³C values and N and P concentration of both P. euphratica and T. ramosissima. For the relationship between foliar δ¹³C and K concentration, there appeared oppositely positive and negative correlations in P. euphratica and T. ramosissima, respectively, but they were not significant. The simple positive correlations of δ¹³C–P% and δ¹³C–N% suggested that N and P in P. euphratica and T. ramosissima behave in a similar manner. This study also showed that there were nutrient deficiencies; N and P nutriments were the co-limiting factors in P. euphratica, while it was P nutriment in T. ramosissima.     

Transformations of organic carbon and its impact on lead weathering in shooting range soils

Five soil samples collected from shooting ranges in 1998 were stored under a closed condition for 5 years. In addition to SEM and XRD investigations, the total organic carbon content (TOC), inorganic carbon content (TIC), δ¹³C and δ¹⁸O of carbonates and δ¹³C of plant remains were analyzed. The concentrations of total carbon contents, the sum of TOC and TIC, remained the same within the 5 years storage, whereas the TOC and TIC contents decreased and increased, respectively. The TIC increase is associated with a decreased TOC, suggesting a conversion of organic carbon into inorganic carbon. Such a conversion is evidenced by the presence of primary lead carbonates and carbon isotopic composition of lead carbonates. It can be concluded that soil organic matters play an important role in the process of bullets weathering and controls migration of the elevated lead in the soil.     

环渤海地区经济增长与环境污染关系分析——基于环境库兹涅茨曲线

发达国家的发展历史表明,经济发展与环境污染存在一定的关系,在经济发展的初级阶段,经济的快速增长可能以牺牲环境为代价.环渤海地区经济增长与环境污染的矛盾尤为突出.文章运用环境库兹涅茨曲线原理和模型,分析了环渤海地区经济增长与环境污染之间的关系.研究发现,在过去一段时间内,环渤海地区的环境污染状况与经济收入也基本符合倒“U...