Pyrite morphology and episodic euxinia of the Ediacaran Doushantuo Formation in South China

The Ediacaran Doushantuo Formation with well-preserved fossil record in South China provides a rare window for our understanding of biological evolution,global carbon cycle,and oceanic redox states.Prominent negativeδ~(13)C anomalies(i.e.,the Shuram excursion)in Ediacaran successions worldwide fundamentally challenge the traditional models of isotopic mass balance.Additionally,conflicting opinions of both oxic and anoxic conditions have been proposed for the deep waters during this period.Here,we present a detailed study of pyrite morphology and carbonate carbon isotope data documented from drill core samples at Songtao County,northeastern Guizhou.Framboid aggregates are the dominant pyrite form in black shale and they can transfer to euhedral crystals through continuous growth of the constituent microcrystals.A positive correlation between microcrystal sizes(d)and framboid diameters(D)is observed,while the different D/d ratios of framboids in argillaceous dolostone and black shale reflect different substrate availability.Electron microprobe analyses reveal no consistent compositional patterns between framboidal and euhedral pyrites.Framboid size distributions of the investigated drill core,in combination with previously published redox data from the intra-shelf Jiulongwan section,shelf margin Zhongling section,and lower slope Wuhe section,suggest that three episodes of marine euxinia have been established throughout the deposition of the Doushantuo Formation.The time lag between the uppermost euxinic interval and the Shuram excursion may arise from the depression of sulfate reduction maintained by other oxidants.     

Finite Element Calculation of Creep Effects on Pile Foundation

The axisymmetric finite element technique is used in this paper to analyze the creep effects on pole foundation. Generalized Kelvin model and Bingham model are proposed to simulate the viscoelastic and viscoelastic behavior of soil respectively. Viscoelastic and viscoelastic strain incremental formulas are derived for interface elements and soil elements around piles and the axisymmetric elastic-viscoelastc-viscoplastic finite element program is compiled. Creep effects on the settlement of poles, the building load carried by raft and the distribution of stresses along piles are analyzed. In addition, the behavior of interface between pile and soil are investigated through experiment.     

判定地下水二维水动力弥散参数的直线图解法

弥散参数的求得，是正确认识地下水污染运移及对其控制的前提。本文根据极值理论和非线性方程线性化手段，导出了浓度和时间变化的线性关系，得出了确定弥散参数的直线图解法。它可以弥补其它方法的不足。借用实际弥散试验资料对其进行了检验，表明所建数学模型与实际模型之间吻合良好，即所求得的参数结果可信。     

Arching effect and displacement on theoretical estimation for lateral force acting on retaining wall

Natural Hazards - A new approach is proposed to evaluate the non-limit active earth pressure in c–φ soil based on the horizontal slices method and limit equilibrium method, which takes...     

大别山北部蛇绿岩的地球化学制约

常量元素,微量元素,稀土元素,Ｎｄ同位素及氧同位素地球化学特征表明,太别山北部变质镁铁－超镁铁质岩带中存在变质的蛇绿岩,它主要由变质橄榄岩,辉长岩（－辉绿岩？）和基性熔岩三部分组成,其中,变质的基性熔岩的亏损地幔模式年龄ｔＤＭ／Ｍａ＝１０３６．８～１２９３．８,εＮｄ（ｔ）＝７．２～７．７,表明它可能代表１０００Ｍａ左右形成于中等扩张速率（２ｃｍ／ａｄ左右）洋盆条件下的洋壳残片。     

Impacts of surface runoff and sediment on nitrogen and phosphorus loss in red soil region of southern China

Surface runoff plays an important role in the process of nitrogen (N) and phosphorus (P) loss. It has two common evaluation indicators, runoff and sediment, which are greatly affected by the contributing factors. To study the impacts of surface runoff and sediment on N and P loss, 36 simulated rainfalls were applied on fields with different conditions (three rainfall intensities, three coverage ratios, and two slopes) at laboratory scale with two replicates. It was found that: (1) loss modulus of both the total nitrogen and total phosphorus decreased with runoff occurrence time; (2) runoff modulus had a closer relationship with undissolved N and P than dissolved N and P; (3) N loss was more affected by runoff than P loss; (4) both N and P loss modulus followed the consistent changes with the sediment content. At last, suggestions were provided to reduce the harm of N and P loss in red soil region of southern China in different areas with different conditions.     

Photodegradation of dimethyl phthalate (DMP) by UV–TiO<Subscript>2</Subscript> in aqueous solution: operational parameters and kinetic analysis

In this paper, the adsorption and degradation phenomenon involved in the photocatalytic degradation of dimethyl phthalates (DMPs) by titanium dioxide (TiO₂) was studied. A variety of operating variables were selected firstly. Then, it was proved that even for such weak adsorption properties molecules as DMP, adsorption was still an important prerequisite for photolysis. A surface-mediated reaction process was proposed that the photodegradation of DMP assisted by TiO₂ particles occurred primarily at the surface of the photocatalyst rather than in the homogeneous phase. According to Langmuir–Hinshelwood model, the adsorption constant determined from the dark adsorption was far less than that obtained in the light condition. Enhanced DMP adsorption on the surface of TiO₂ under irradiation was the possible reason for the improvement of photodegradation efficiency. Under the irradiation of light, a synergistic mechanism of adsorption and photocatalysis was responsible for DMP degradation. The quantitative analysis by adding scavengers indicated that ^·OH radical was primarily responsible for the photodegradation of DMP. It was further verified that ^·OH was produced much more from conduction band electrons rather than valance band holes toward photodegradation of DMP by adding foreign Cu²⁺.     

Investigation of source locations and contributions using an integrated trajectory-source apportionment method with multiple time resolution data

Fine particulate matter (PM_2.5) and volatile organic compounds (VOCs) coexist in ambient air and contribute to adverse health effects in human populations. Thus, it is helpful to identify the contributions of air pollutants from different sources in order to design effective control strategies. Nevertheless, different sampling time schedules for VOCs and PM_2.5 result in difficulties for conventional receptor modeling. Additionally, a receptor model is unable to link the retrieved factors directly with actual source locations. To address these gaps, this study integrated back-trajectory data into an improved source apportionment model suitable for multiple time resolution data to estimate the locations of the regional transport-related factor. Within six potential source regions (PSRs) outlined by the above method, PSR 5 was suggested the primary one located near the industrial regions in the northeastern China. Constrained model results showed that the source contribution estimates with back trajectories passing over the PSRs were 3 and 9% of the selected VOCs and PM_2.5 mass, respectively.     

Thermodynamic analysis of heat transfer in a wellbore combining compressed air energy storage

Compressed air energy storage (CAES) is a potential energy storage technology. The gas phase and short cycle period are two key factors affecting heat transfer loss in the wellbore of CAES. A semi-analytical solution was developed by using the convolution method considering gas movement in this study to describe the transient behavior of heat transfer with a short cycle period. The comparative analysis of the presented solution with two published solutions showed that the solution matched well with the previous solutions under steady state. Parametric studies were carried out to investigate the impact of injection rate, overall heat transfer coefficient and thermal diffusivity of the formation on heat loss in the wellbore. The results indicated that a low overall heat transfer coefficient and thermal diffusivity of the formation with an appropriate injection rate can efficiently reduce the heat loss. A hypothetical case study with a short cycle period of injection and production was conducted to demonstrate the applicability of the developed solution in CAES. The results suggest that the semi-analytical solution is applicable for heat transfer in the wellbore of CAES.