Stable isotope-guided analysis of biomagnification profiles of arsenic species in a tropical mangrove ecosystem

We performed stable carbon and nitrogen-guided analyses of biomagnification profiles of arsenic (As) species, including total As, lipid-soluble As, eight water-soluble As compounds (arsenobetaine (AB), arsenocholine (AC), tetramethylarsonium ion (TETRA), trimethylarsine oxide (TMAO), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenate (As[V]), and arsenite (As[III])), and non-extracted As in a tropical mangrove ecosystem in the Ba Ria Vung Tau, South Vietnam. Arsenobetaine was the predominant As species (65-96% of water-soluble As). Simple linear regression slopes of log-transformed concentrations of total As, As fractions or individual As compounds on stable nitrogen isotopic ratio (δ15N) values are regarded as indices of biomagnification. In this ecosystem, lipid-soluble As (slope, 0.130) and AB (slope, 0.108) were significantly biomagnified through the food web; total As and other water-soluble As compounds were not. To our knowledge, this is one of the first reports on biomagnification profiles of As compounds from a tropical mangrove ecosystem.     

科尔沁沙地采用人工植被对流沙治理的技术

在科尔沁沙地的流动沙丘上采用不同的人工措施,即铺设秸秆栅栏沙障、草方格和栽植差不嘎蒿,对沙丘的固定作用进行了研究。结果表明三种措施都有利于增加沙丘植物的多样性和生物量,但栽植差不嘎蒿和草方格好于秸秆栅栏沙障;沙丘固定过程中,植物的演替顺序有沙蓬-差不嘎蒿-狗尾草-黄蒿的趋势;植物生物量的形成与土壤湿度关系密切,应用试验数据建立了生物量(Y)与土壤湿度(X)的回归关系方程。Y=-13.7x²+72.5x-11.42 R²=0.824。     

Evidence of subsidence of seamounts in the north-western Pacific

The subsidence of seamounts in the northwestern Pacific is suggested from the unexpected high vesicularity of submarine basaltic rocks which were dredged from great depths. There exists a tendency that the closer the seamount is situated to the trench axis, the greater the amount of subsidence becomes.     

Simple monitoring method for precaution of landslides watching tilting and water contents on slopes surface

A low-cost and simple monitoring method for early warning of landslides is proposed. To detect abnormal deformation of a slope, this method employs a tilt sensor in place of an extensometer on the slope surface. In order to examine the relevance of measuring rotation angle on a slope surface by tilt sensor, model tests were conducted, and rotation on the slope surface was observed together with slide displacement along the surface. The rotation data responded 30 min before failure in a model test, which could be useful as a signal for early warning. However, the behavior of rotation before failure varies from case to case, and thus, criteria to issue warning should be defined more carefully. For a model slope made of uniform loose sand, measurement of slide displacement along the slope surface is sensitive to failure at the toe, while the measurement of rotation on the slope surface is useful to detect the development of progressive failure upward along the slope. Wireless sensor units with microelectromechanical systems (MEMS) tilt sensor and volumetric water content sensor were also examined on a real slope in Kobe City, and a long-term monitoring was attempted. A simple but possible way to define the criteria of judgment to issue warning can be proposed based on combination of data obtained by the tilt sensors and volumetric water content sensors.     

40Ar/39Ar dating on volcanic rocks of the Deccan Traps,India

⁴⁰Ar/³⁹Ar dating results on seven volcanic rocks from four areas of the Deccan Traps, India, suggest that volcanic activity more than 70 Ma ago might have occurred at least in limited areas.In the Igat Puri area, the uppermost flow shows an⁴⁰Ar/³⁹Ar age of 63 Ma, whereas a lower flow has an age of around 82–84 Ma.⁴⁰Ar/³⁹Ar ages of samples from the Bombay area also seem to favor the occurrence of volcanic activity more than 70 Ma ago. One rhyolite dyke from the Osam Hill in the Girnar Hill area shows a well-defined plateau age of 68 Ma, whereas two tholeiitic basalts from the Mahabaleshwar area indicate a total⁴⁰Ar/³⁹Ar age of around 63–64 Ma, though they show the effect of secondary disturbance in the age spectra.The volcanic activity(ies) more than 70 Ma ago may correspond to precursory one(s) for the main volcanic activity around 65 Ma ago in the Deccan Traps.     

Surface microtopography of metamorphic white micas

Gold decoration and platinum-carbon-shadowing techniques of electron microscopy have been applied to study the surface microtopographs of noncleavage (001) faces of porphyroblastic white micas and sericite crystals collected from the chlorite, biotite, and garnet zones in the Shiragayama area in the Sanbagawa metamorphic terrain, Shikoku, Japan. Two different types of surface microtopograph have been observed; parallel step system and saw-tooth step system. The former is interpreted as representing the surface microtopographs formed either by growth or under near equilibrium conditions, the latter either by dissolution or under rigorous kinetic conditions. The former has been observed on porphyroblastic white micas occurring in the middle portion of each metamorphic zone and on all sericite crystals, the latter on most sericites and on porphyroblastic white micas occurring along the boundaries of the neighboring metamorphic zones. It is suggested that the observed variations in the surface microtopographic characteristics are due to Ostwald ripening during a kind of sintering process in which interstitial water plays an essential role, and that the drastic changes along the metamorphic zone boundaries are due to dehydration reactions. Retrogressive metamorphism is considered to have an almost negligible effect, if any, upon the surface microtopographs.     

Elastic properties of garnet solid-solution series

The elastic constants of sixteen garnet specimens of wide variety in chemical composition are accurately determined by means of the rectangular parallelpiped resonance method. The dependence of the elastic properties on chemical composition is analyzed using the present data and those for seven garnets investigated by other authors. The property X_i of a garnet solid solution i is given by a linear addition law in terms of the mole fraction n_ij of component j; X_i = Σn_ijX_j where the X_j's are the properties of the end-members j (j = pyrope, almandine, spessartine, grossular and andradite). The X_j's are determined for density ρ, bulk modulus K, and shear moduli C_s = (C₁₁ ? C₁₂)/2 and C₄₄. No systematic deviation is observed from the linear addition law for the elastic moduli nor for other quantities such as the elastic wave velocities. The extrapolated elastic moduli (Mbar) of the end-members are:

     

30.

Thermal equation of state of majorite with MORB composition     

Yu Nishihara  Ichiro Aoki  Eiichi Takahashi  Ken-ichi Funakoshi 《Physics of the Earth and Planetary Interiors》2005,148(1):73-84

In situ synchrotron X-ray diffraction experiments were conducted using the SPEED-1500 multi-anvil press at SPring-8 on majoritic garnet synthesized from natural mid-ocean ridge basalt (MORB), whose chemical composition is close to the average of oceanic crust, at 19 GPa and 2200 K. Pressure-volume-temperature data were collected using a newly developed high-pressure cell assembly to 21 GPa and 1273 K. Data were fit to the high-temperature Birch-Murnaghan equation of state, with fixed values for the ambient cell volume (V₀ = 1574.14(4) Å³) and the pressure derivative of the isothermal bulk modulus (K^′T = 4). This yielded an isothermal bulk modulus of K_T0 = 173(1) GPa, a temperature derivative of the bulk modulus (∂K_T/∂T)_P = −0.022(5) GPa K⁻¹, and a volumetric coefficient of thermal expansivity α = a + bT with values of a = 2.0(3) × 10⁻⁵ K⁻¹ and b = 1.0(5) × 10⁻⁸ K⁻². The derived thermoelastic parameters are very similar to those of pyrope. The density of subducted oceanic crust compared to pyrolitic mantle at the conditions in Earth's transition zone (410-660 km depth) was calculated using these results and previously reported thermoelastic parameters for MORB and pyrolite mineral assembledges. These calculations show that oceanic crust is denser than pyrolitic mantle throughout the mantle transition zone along a normal geotherm, and the density difference is insensitive to temperature at the pressures in lower part of the transition zone.     

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	Almandine	Pyrope	Spessartine	Grossular	Andradite
$\text{K}$	1.779 ± 0.008	1.730 ± 0.009	1.742 ± 0.009	1.691 ± 0.008	1.379 ± 0.017
$\text{C}{}_{\mathrm{<mtext>s</mtext>}}$	0.981 ± 0.004	0.925 ± 0.004	0.964 ± 0.004	1.106 ± 0.004	0.979 ± 0.007
$\text{C}{}_{\mathrm{<mtext>44</mtext>}}$	0.958 ± 0.005	0.919 ± 0.005	0.937 ± 0.005	1.017 ± 0.006	0.827 ± 0.010

Thermal equation of state of majorite with MORB composition

In situ synchrotron X-ray diffraction experiments were conducted using the SPEED-1500 multi-anvil press at SPring-8 on majoritic garnet synthesized from natural mid-ocean ridge basalt (MORB), whose chemical composition is close to the average of oceanic crust, at 19 GPa and 2200 K. Pressure-volume-temperature data were collected using a newly developed high-pressure cell assembly to 21 GPa and 1273 K. Data were fit to the high-temperature Birch-Murnaghan equation of state, with fixed values for the ambient cell volume (V₀ = 1574.14(4) Å³) and the pressure derivative of the isothermal bulk modulus (K^′T = 4). This yielded an isothermal bulk modulus of K_T0 = 173(1) GPa, a temperature derivative of the bulk modulus (∂K_T/∂T)_P = −0.022(5) GPa K⁻¹, and a volumetric coefficient of thermal expansivity α = a + bT with values of a = 2.0(3) × 10⁻⁵ K⁻¹ and b = 1.0(5) × 10⁻⁸ K⁻². The derived thermoelastic parameters are very similar to those of pyrope. The density of subducted oceanic crust compared to pyrolitic mantle at the conditions in Earth's transition zone (410-660 km depth) was calculated using these results and previously reported thermoelastic parameters for MORB and pyrolite mineral assembledges. These calculations show that oceanic crust is denser than pyrolitic mantle throughout the mantle transition zone along a normal geotherm, and the density difference is insensitive to temperature at the pressures in lower part of the transition zone.