Assessment of risk of PCDD/Fs and dioxin-like PCBs in marine and freshwater fish in Pearl River Delta, China

Fish consumption is known to be beneficial to human health. However since the age of industrialization, the released/disposed chemical pollutants into water systems make fish a source of various environmental toxicants to humans. In oceanic cities with heavy industrial activities, fish products contribute the greatest proportion of exposure to pollutants. In this study, risks and potential effects of dioxins to health of coastal populations in the Pearl River Delta were assessed. Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (PCBs) were measured in common fish species purchased at local markets. Concentrations of total dioxins in fish ranged from 0.481 to 9.05 pg TEQ/g wet weight were similar to the lesser concentrations reported for fish from other countries. The greatest concentrations of dioxins were measured in mandarin fish, a carnivorous freshwater fish. Exposure of murine primary leydig and ovarian cells to 2,3,7,8-tetrachlorinated dibenzo-p-dioxins (2,3,7,8-TCDD) reduced the synthesis of progesterone, testosterone and/or estrogen. The reductions were probably via inhibitory effects on the expression of the steroidogenic enzymes, steroidogenic acute regulatory protein (StAR) and cytochrome P450 side-chain cleavage enzyme (P450scc). Based on these reproductive parameters, the concentrations of dioxins and dioxin-like residues represent a moderate health risk due to consumption of fish.     

Toxicities of antifouling biocide Irgarol 1051 and its major degraded product to marine primary producers

Irgarol 1051 (2-methythiol-4-tert-butylamino-6-cyclopropylamino-s-triazine) is an algaecide commonly used in antifouling paints. It undergoes photodegradation which yields M1 (2-methylthio-4-tert-butylamino-6-amino-s-triazine) as its major and most stable degradant. Elevated levels of both Irgarol and M1 have been detected in coastal waters worldwide; however, ecotoxicity effects of M1 to various marine autotrophs such as cyanobacteria are still largely unknown. This study firstly examined and compared the 96 h toxicities of Irgarol and M1 to the cyanobacterium Chroococcus minor and two marine diatom species, Skeletonema costatum and Thalassiosira pseudonana. Our results suggested that Irgarol was consistently more toxic to all of the three species than M1 (96 h EC50 values: C. minor, 7.71 microug L(-1) Irgarol vs. > 200 microg L(-1) M1; S. costatum, 0.29 microg L(-1) Irgarol vs. 11.32 microg L(-1)M1; and T. pseudonana, 0.41 microg L(-1) Irgarol vs. 16.50 microg L(-1)M1). Secondly, we conducted a meta-analysis of currently available data on toxicities of Irgarol and M1 to both freshwater and marine primary producers based on species sensitivity distributions (SSDs). Interestingly, freshwater autotrophs are more sensitive to Irgarol than their marine counterparts. For marine autotrophs, microalgae are generally more sensitive to Irgarol than macroalgae and cyanobacteria. With very limited available data on M1 (i.e. five species), M1 might be less toxic than Irgarol; nonetheless this finding warrants further confirmation with additional data on other autotrophic species.     

Seasonal changes in imposex and tissue burden of butyltin compounds in Thais clavigera populations along the coastal area of Mirs Bay, China

We assessed the current status of tributyltin (TBT) contamination of Thais clavigera (Gastropoda) along the coastal area of Mirs Bay, China for the first time. The snail samples were collected from 10 different sites in the summer (June) and winter (December) of 2006, respectively. They were analyzed for imposex status, i.e. relative penis size index (RPSI) and vas deferens sequence index (VDSI), followed by quantification of butyltins in their tissues. Most of the collected females suffered from imposex, but the level of butyltin contamination varied with the distance from Yantian Port, which is currently the fourth busiest container port in the world. The tissue concentration of TBT varied with season. For a particular site, the winter samples in general contained much higher concentration of TBT than the summer samples. RPSI, VDSI and organotin concentrations were higher in T. clavigera collected from sites closer to the Port, such as the Seafood Street and Kat O. Both RPSI and VDSI were positively correlated with the tissue burden of tributyltin. VDSI exhibited little seasonal variability, whereas RPSI showed marked seasonal variability, with lower values in the summer samples. The current results will serve as an important reference for long-term monitoring of butyltin contamination in this area.     

近年中国夏季降水变化特征分析

利用台站观测资料和卫星观测换算资料,分析了近年（2002-2004年）中国夏季日内降水量变化统计学特征,其结果是较为一致的。对于东部大部分地区,日内最强降水易出现在下午到傍晚,对于西部大部分地区易出现在夜晚到清晨。夏季降水以对流降水为主,降水大的地区对应潜热通量也大。由于受观测资料的限制,计算结果有待更多的观测资料来验证。     

The effects of intermediate principle stress on the mechanical behavior of transversely isotropic rocks: Insights from DEM simulations

The discrete element method (DEM) is used to study the response of anisotropic rocks under true triaxial testing. Numerical samples of seven different bedding orientations (β = 0^o, 15^o, 30^o, 45^o, 60^o, 75^o, and 90^o) are created. Six series of test simulations (σ₃ = 0, 10, 30, 50, 70, and 100 MPa) are conducted on each sample, with five different σ₂ values, varied from σ₃ to σ₁. The effects of anisotropy and intermediate stress on the peak strength, brittle-ductile transition, and degree of anisotropy are subsequently explained through underlying micromechanics. Results show a “fan-shaped” variation of the peak strength with σ₂, displaying an ascending-then-descending trend. An increasing brittleness with σ₂ is observed at lower confining pressures for all, but medium anisotropy angles. For higher confining pressures, increasing ductility with σ₂ is seen for every anisotropy angle. A U-shaped variation of peak strength with anisotropy angles is noted that flattens under high intermediate stress. Hence, for numerical models of Posidonia shale under normalized σ₂ higher than 0.76, the anisotropy effect is found to be negligible. Micromechanical analyses reveal that the stress asymmetry, suppression of weak plane action as well as the localization and coalescence of microcracks in the intact rock matrix, due to σ₂, are the contributors towards the obtained trends. Since existing failure criteria do not weigh in these features in geotechnical assessments, this paper helps future studies by providing a deeper understanding of these effects and a comprehensive data set for the analyses of anisotropic rocks under polyaxial stress conditions.     

UBV observations of short-period close binary V392 Orionis

The eclipsing binary V392 Ori was observed photoelectrically, from November 1984 to January 1985, inUBV bands using the P34B photometer attached to the 0.91 m reflector at the McDonald Observatory. Four-hundred eighty-six observations in each band were obtained. Six primary and 4 secondary minimum were observed during this period. The light curves show a typical Beta Lyrae-type variation instead of an Algol-type light curve reported earlier.     

《坤輿万国全图》与《利玛窦中国札记》中外译本考疑

金尼阁编译的《利玛窦中国札记》多种欧洲文字版本之间存在翻译差异,而300年后出版的英译本和中译本与原文存在严重错漏。600页的札记,利玛窦只用不到两页的篇幅叙述测绘《坤輿万国全图》一事,连实际比例尺的描述也不清楚。利玛窦承认没有见过其他的版本,"六幅版"地图出现在南京或北京,个别欧洲文字翻译版本不一,《坤輿万国全图》究竟是在南京还是北京完成的也有疑问。《利玛窦中国札记》用的是中国传统的测绘术语,指出地图的错误是针对西方地图而不是中国地图。《坤輿万国全图》中一半的中文地名,当时欧洲地图没有对应。1593年,利玛窦尚未制作《坤輿万国全图》,"六幅版"中文世界地图已出现在南京。因此,《坤輿万国全图》原本早已存在,《坤輿万国全图》应是郑和时代(1405—1433)大航海的成果,中国的地图学,不是西学东渐,甚至有可能是中国的世界地理与地图学流传到西方。世界地图史应该还原中国对地理大发现与地图学的贡献。     

EFFECT OF DUNE MIGRATION ON SCOUR AT BRIDGE PIERS

This paper examines the effect of dune migration on local scour around bridge piers. Experiments show that local scour depths fluctuate in response to the translation of dunes past the scour hole. The scour depths measured in a model study conducted in live-bed conditions contain both scour due to the pier and that due to dunes. The con' tribution from scour due to the dunes may form a significant fraction of the total scour depth measured in model investigations. Therefore, it is imperative to separate these two components of scour for analysis and comparison. The study proposes that an equilibrium or time-average scour depth normalized using pier diameter be used for analysis, and the contribution from dunes to the total scour depth be added independently. Dune size, in the absence of field or measured data, may be estimated using published predictive curves. Comparisons between computed and measured scour depths show a good correlation, and 90% of all the data tested fall within a scatter of 15%.     

Vibration isolation by trenches in continuously nonhomogeneous soil by the BEM

Vibration isolation of structures from ground-transmitted waves by open trenches in isotropic, linearly elastic or viscoelastic soil with a shear modulus varying continuously with depth is numerically studied. Both an exponential and a linear shear modulus variation with depth are used in this work. Waves produced by the harmonic motion of a rigid surface machine foundation are considered. The problem is solved by the frequency domain boundary element method employing the Green's function of Kausel-Peek-Hull for a thin layered half-space. Thus only the trench perimeter and the soil-foundation interface need essentially to be discretized. The proposed methodology is first tested for accuracy by solving two Rayleigh wave propagation problems in nonhomogeneous soil with known analytical solutions and/or for which experimental results are available. Then the method is applied to vibration isolation problems and the effect of the inhomogeneity on the wave screening effectiveness of trenches is studied.     

Non-linear steady state vibration and dynamic snap through of shallow arch beams

The non-linear steady state vibration of shallow arch beams is studied by a finite element method based on the principle of virtual work. Both the free and forced periodic vibrations are considered. The axial and flexural deformations are coupled by the induced axial force along the beam element. The spatial discretization is achieved by the usual finite element method and the steady state nodal displacements are expanded into a Fourier series. The harmonic balance method gives a set of non-linear algebraic equations in terms of the vibrating frequency and the Fourier coefficients of nodal displacements. The non-linear algebraic equations are solved by the Newtonian algorithm iteratively. The combined algorithm is called the incremental harmonic balance method. The importance of the conditions of completeness and balanceability is presented. Since the non-linearity is essentially softening, different orders of internal resonances between two modes can occur repeatedly. Isolated response curves are possible and are connected to the bifurcation of a particular excited mode.