双酚A及其类似物对哺乳动物和鱼类神经毒性效应及机制研究进展

双酚A及其类似物双酚S、双酚F、双酚AF和卤代双酚A等双酚类化合物广泛用于生产聚碳酸酯塑料和环氧树脂,生产量大且目前在各种环境介质、食品及人体内均有检出。近年来,研究发现很多神经疾病的发生与双酚类化合物的暴露密切相关,有关双酚A及其类似物的神经毒性日益受到国内外研究者关注。本研究从对动物行为、神经发育、神经递质含量及神经递质代谢等方面综述了双酚类化合物的神经毒性效应及作用机制,为今后进一步探究双酚A类似物的神经毒性作用及其安全性评价提供更多的理论参考。     

Preindustrial, historical, and fertilization simulations using a global ocean carbon model with new parameterizations of iron limitation, calcification, and N2 fixation

The Canadian Model of Ocean Carbon (CMOC) has been developed as part of a global coupled climate carbon model. In a stand-alone integration to preindustrial equilibrium, the model ecosystem and global ocean carbon cycle are in general agreement with estimates based on observations. CMOC reproduces global mean estimates and spatial distributions of various indicators of the strength of the biological pump; the spatial distribution of the air-sea exchange of CO₂ is consistent with present-day estimates. Agreement with the observed distribution of alkalinity is good, consistent with recent estimates of the mean rain ratio that are lower than historic estimates, and with calcification occurring primarily in the lower latitudes. With anthropogenic emissions and climate forcing from a 1850-2000 climate model simulation, anthropogenic CO₂ accumulates at a similar rate and with a similar spatial distribution as estimated from observations. A hypothetical scenario for complete elimination of iron limitation generates maximal rates of uptake of atmospheric CO₂ of less than 1 PgC y⁻¹, or about 11% of 2004 industrial emissions. Even a ‘perfect’ future of sustained fertilization would have a minor impact on atmospheric CO₂ growth. In the long term, the onset of fertilization causes the ocean to take up an additional 77 PgC after several thousand years, compared with about 84 PgC thought to have occurred during the transition into the last glacial maximum due to iron fertilization associated with increased dust deposition.     

Dissolved iron in the Australian sector of the Southern Ocean (CLIVAR SR3 section): Meridional and seasonal trends

We report measurements of dissolved iron (dFe, <0.4 μm) in seawater collected from the upper 300 m of the water column along the CLIVAR SR3 section south of Tasmania in March 1998 (between 42°S and 54°S) and November–December 2001 (between 47°S and 66°S). Results from both cruises indicate a general north-to-south decrease in mixed-layer dFe concentrations, from values as high as 0.76 nM in the Subtropical Front to uniformly low concentrations (<0.1 nM) between the Polar Front and the Antarctic continental shelf. Samples collected from the seasonal sea-ice zone in November–December 2001 provide no evidence of significant dFe inputs from the melting pack ice, which may explain the absence of pronounced ice-edge algal blooms in this sector of the Southern Ocean, as implied by satellite ocean-color images. Our data also allow us to infer changes in the dFe concentration of surface waters during the growing season. South of the Polar Front, a comparison of near-surface with subsurface (150 m depth) dFe concentrations in November–December 2001 suggests a net seasonal biological uptake of at least 0.14–0.18 nM dFe, of which 0.05–0.12 nM is depleted early in the growing season (before mid December). A comparison of our spring 2001 and fall 1998 data indicates a barely discernible seasonal depletion of dFe (0.03 nM) within the Polar Frontal Zone. Further north, most of our iron profiles do not exhibit near-surface depletions, and mixed-layer dFe concentrations are sometimes higher in samples from fall 1998 compared to spring 2001; here, the near-surface dFe distributions appear to be dominated by time-varying inputs of aerosol iron or advection of iron-rich subtropical waters from the north.     

海洋中铁的来源、形态和对初级生产力的限制作用

在海洋中,铁和Ｎ、Ｐ等主营养盐一样,也是一种限制浮游植物初级生产力的重要因素。由于铁是一种化学活性较高的元素,所以海水中铁的存在形态、来源及沉降会直接影响其生物可利用性。目前人们一般采用预富集／原子吸收法（ＡＡＳ）或是借助于电分析技术（如催化极谱）来测定海水中的铁。     

Interaction of glucose and cellulose with hydrogen sulphide and polysulphides

This paper describes simulation experiments in which glucose and cellulose were reacted with polysulphide and hydrogen sulphide at ambient temperatures in an aqueous environment. Organic sulphur containing compounds were formed that yield several thiophenes upon pyrolysis/evaporation. The experiments show that interaction of carbohydrates with hydrogen sulphide or polysulphides is a possible way for carbohydrates to react in very recent sediments. From the results of this study it can be concluded that carbohydrate carbon can be preserved in sediments in a form that is resistant to microbial attack and that will have a greater potential for survival during diagenesis than the carbohydrate precursor.     

南丹铁陨石物态方程用于地核的研究

从南丹铁陨石的物态方程和地球的PREM模型出发,求得内外地核交界面处的物质密度为12.83-13.419/cm~3,温度为5440-5680K;地心处物质密度为13.12-13.73g/cm~3,温度为5660-5990K,推估内地核可能由铁镍合金组成.     

Identification and occurrence of novel C36–C54 3,4-dialkylthiophenes with an unusual carbon skeleton in immature sediments

A series of novel long-chain 3,4-dialkylthiophenes (C₃₆–C₅₄) was identified in a number of sediments ranging from Pleistocene to Cretaceous. The identifications were based on mass spectral characterisation, desulphurisation and mass spectral data of synthesised model compounds. These organic sulphur compounds are probably formed by sulphur incorporation into mid-chain dimethylalkadienes with two methylenic double bonds. These putative precursor lipids are unprecedented and may be considered rather unusual. The distribution of 3,4-dialkylthiophenes in sediments varies considerably with the depositional palaeoenvironment, indicating that these compounds have a potential as molecular markers reflecting changes in palaeoenvironment.     

Relationships among dissolved organic matter,iron, and discharge in a moorland stream

Dissolved organic matter (DOM) and iron in a moorland stream were determined at 8-hour intervals over a 6-month period to examine relationships with streamflow. Regression of both solutes on discharge were positive and explained 50–70 per cent of the variance in the solute data, but better predictions were obtained in both cases when a covariate reflecting temporal variation in the relationships was introduced (explained variance 80–90 per cent). Variations in the regression of Fe on DOM were also identified, indicating differences in the complexing power of DOM for Fe and possible variations in the chemical composition of the DOM.     

Prediction of the abiotic degradability of organic compounds in the troposphere

A statistically relevant correlation between the reaction rate coefficient, k _OH, for the OH radical reaction with 161 organic compounds in the gas phase at 300 K, and the corresponding vertical ionisation energies E _i,v, reveals two classes of compounds: aromatics where –log(k _OH/cm³s^-1)3/2E _i,v(eV)–2 and aliphatics where –log(k _OH/cm³s^-1)4/5E _i,v(eV)+3. The prediction of the rate coefficient, k _OH, for the reaction of OH with organic molecules from the above equations has a probability of about 90%. Assuming a global diurnal mean of the OH radical concentration of 5×10⁵ cm³, the upper limit of the tropospheric half-life of organic compounds and their persistence can be estimated.     

Effect of system variables and particle size on physical characteristics of air sparging plumes

Air was injected through a well in a thin transparent tank filled with saturated glass beads to study how the size and air saturation of air sparging plumes are affected by particle size and gradation; operational parameters such as injection pressure, well depth, injection pressure pulsing; and well outlet configuration. V-shaped air plumes with an apex between 40° and 60° were obtained for all tests. The air pressure required to initiate sparging agreed closely with the sum of the air entry pressure and the hydrostatic pressure, with higher initiation pressures required in the fine and well-graded beads. Higher air flow rates and air saturations were obtained in coarser beads at a given pressure, and the variation in flow rate was consistent with estimated air permeabilities. Peak average air saturations were 28–56% for the coarse-medium beads, 10% for the well-graded beads, and 8% for the fine beads. Air saturation and the radius of influence increased modestly (<40%) as the normalized injection pressure exceeded 0.1. Radius of influence increased by approximately a factor of two as the well depth increased, but leveled off once the ratio of radius of influence to well depth reached 0.60–1.05. Pulsing of injection pressure had no effect on the initiation pressure, air flow rate, or air saturation, but increased the size of the air plume and the radius of influence slightly (<15%). Well outlet configuration had only a slight affect the radius of influence (<10%), air saturation (<10%), or air flow rate (<12%). Dye testing showed that water surrounding the air plume circulated during continuous and pulsed sparging. However, pulsed sparging resulted in greater and more defined circulation of water within and adjacent to the air plume, which should reduce mass transfer limitations during sparging.