纳米四氧化三铁/离子载体修饰电极检测海水中痕量重金属铅

制备了一种纳米四氧化三铁/离子载体(nano-Fe<,3>O<,4>/ionophore)修饰的玻碳电极,利用阳极溶出伏安法实现了海水中的痕量铅离子的测定.利用纳米四氧化三铁的高比表面积和铅离子载体(ionophore)能够提供与铅离子配合的位点或仅供铅离子通过的空穴,有效地提高了检测重金属离子的灵敏度和选择性.实验结...     

The Bizielle vein (valle de Gistain): A case of iron oxide transformations at the Pyrenees of Spain

The Bizielle vein has some unique features among the Pyrenean alpine veins that allow us to address the question of the nature of iron oxides transformations under low temperature hydrothermal conditions, which is well known to prevailed over wide areas of western Europe between early Triassic to early Cretaceous times. Isotopic studies indicate a deep-seated origin of the ore-forming fluids and suggest that the metals were leached from the Variscan basement (mainly from granites). Isotopic geothermometry and regional evidences point to a 250 °C and reducing fluid, being SH₂ the predominant S specie. Under such conditions, the proposed in situ deposition of hematite is a consequence of Fe carbonates dissolution and oxidation involving dissolution/precipitation processes in the sense of Putnis. Non-redox model is a quite plausible origin for subsequent hematite to magnetite conversion.     

The effect of valence state and site geometry on Cr L3,2 electron energy-loss spectra of Cr-bearing oxidic compounds

Chromium L_3,2 energy loss near-edge structures (ELNES) of nine chromium compounds were measured in a transmission electron microscope to study the effect of valence state and site geometry of chromium on spectral features. The compounds studied represent a set of standards with given valence state and coordination. The chromium coordination is either octahedral or tetrahedral with different degree of distortion. The distortion of polyhedra results in a loss of the fine detail of spectral features in Cr L_3,2 ELNES spectra. The effect of valence state manifests in a systematic chemical shift of the ELNES spectra by about 2 eV per oxidation state for octahedrally coordinated Cr and 0.4–1.4 eV per oxidation state for tetrahedrally coordinated Cr. On the basis of collected Cr L_3,2 ELNES spectra we propose a simple quantification technique for the determination of chromium oxidation state in oxidic compounds which is independent of the coordination.     

Infiltration pattern in a regolith–fractured bedrock profile: field observation of a dye stain pattern

We examined the infiltration pattern of water in a regolith–bedrock profile consisting of two overburdens (OB1 and OB2), a buried rice paddy soil (PS), two texturally distinctive weathered materials (WM1 and WM2) and a fractured sedimentary rock (BR), using a Brilliant Blue FCF dye tracer. A black‐coloured coating in conducting fractures in WM1, WM2 and BR was analysed by X‐ray diffraction and scanning electron microscopy. The dye tracer penetrated to greater than 2 m depth in the profile. The macropore flow and saturated interflow were the major infiltration patterns in the profile. Macropore flow and saturated interflow were observed along fractures in WM1, WM2 and BR and at the dipping interfaces of PS–WM1, PS–WM2 and PS–BR respectively. Heterogeneous matrix flow occurred in upper overburden (OB1) and PS. Compared with OB1, the coarser textured OB2 acted as a physical barrier for vertical flow of water. The PS with low bulk density and many fine roots was another major conducting route of water in the profile. Manganese oxide and iron oxide were positively identified in the black coating material and had low crystallinity and high surface area, indicating their high reactivity with conducting contaminants. Copyright © 2006 John Wiley & Sons, Ltd.     

Carbon co-benefits of tighter SO2 and NOx regulations in China

Air pollution has been recognized as a significant problem in China. In its Twelfth Five Year Plan, China proposes to reduce SO₂ and NO_x emissions significantly, and here we investigate the cost of achieving those reductions and the implications of doing so for CO₂ emissions. We extend the analysis through 2050, and either hold emissions policy targets at the level specified in the Plan, or continue to reduce them gradually. We apply a computable general equilibrium model of the Chinese economy that includes a representation of pollution abatement derived from detailed assessment of abatement technology and costs. We find that China's SO₂ and NO_x emissions control targets would have substantial effects on CO₂ emissions leading to emissions savings far beyond those we estimate would be needed to meet its CO₂ intensity targets. However, the cost of achieving and maintaining the pollution targets can be quite high given the growing economy. In fact, we find that the near term pollution targets can be met while still expanding the use of coal, but if they are, then there is a lock-in effect that makes it more costly to maintain or further reduce emissions. That is, if firms were to look ahead to tighter targets, they would make different technology choices in the near term, largely turning away from increased use of coal immediately.     

冷锋天气大气边界层内臭氧及 氮氧化物的观测研究

利用北京325 m气象塔作为高空平台,于1997年10月观测到一次冷锋过程大气边界层内O3及NOx体积分数的变化,研究了O3及NOx体积分数与气象要素之间的关系,着重讨论了冷锋过境前后O3及NOx的体积分数变化及其与输送过程的关系。研究表明:北京大气边界层中下层存在明显的O3体积分数垂直梯度,O3的垂直输送与风速及温度梯度密切相关。冷锋过程有利于高层O3向低层输送,使O3体积分数垂直梯度明显减小,并使NOx体积分数显著降低。     

Characterization of corrosion products in the permeable reactive barriers

 The impact of geochemical processes and microbial activity has been a major concern for the long-term performance of reactive iron barriers because corrosion products and precipitates during the water treatment with reactive materials will decrease the reactivity and permeability of the iron bed. This study characterizes corrosion products in reactive iron barrier as well as evaluates the effect of the iron corrosion products and precipitates on iron wall performance during contaminated-water treatment under varying conditions. Major phases in the reactive iron barrier include iron oxides, carbonates, iron sulfides, and elemental sulfur, depending on the degree of iron oxidation, groundwater chemistry, and microbial activity. Detailed geochemical and mineralogical characteristics are imperative for long-range predictions of the reactive iron wall performance on water treatment because the surface coating materials reduce the effectiveness of the zero-valent iron media. Received: 17 September 1999 · Accepted: 11 April 2000     

http://www.sciencedirect.com/science/article/pii/S1674987113000078

A sequence of gabbros showing isotropic,layered and fine-grained textures is exposed in the Nalaqing mine at the southern tip of the～260 Ma Panzhihua intrusion,SW China.The field relations,structure,texture and mineralogy of the rocks indicate that the sequence represents the transition between the Lower zone and Middle zone of the intrusion.Isotropic gabbros characteristic of the Lower zone pass upward to layered gabbros of the Middle zone through a～5 m-thick microgabbro sheet,within and close to which small-scaled, concordant Fe-Ti oxide ore horizons are identified.Strong fractionation between HFSE and REE in a subset of samples is ascribed to cumulus titanomagnetite into which HFSE are preferentially incorporated over REE,as reflected in the parallel relations between Nb/La,Hf/Sm and Ti/Ti^*.Both the isotropic and layered gabbros display cumulate textures and have similar mineral compositions(Mg^# of clinopyroxene =～76-79 and An_59-61),isotopic compositions[(⁸⁷Sr/⁸⁶Sr)i = 0.7044-0.7045 andε_Nd（t） = +2.4 to +3.9]and trapped liquid contents inferred from Zr abundance（～17-34 ppm）.However,there are substantial variations in elemental abundances（V,Cr and PGE） and ratios（Ti/V,La/Yb,Ba/Y and Cu/Pd） between the two types of gabbros,features that cannot be explained by cumulate formation from a common magma in a closed system.The microgabbros generally resemble high-Ti Emeishan basalts in major element compositions,but their low trace element abundances indicate some lost of residual liquid is inevitable despite rapid nucleation and cooling.Combined with available data and observations,we propose a model involving in-situ crystallization,followed by magma recharge and closed-system fractionation to explain the formation of texturally distinctive gabbros at Nalaqing and the evolution of the lower part of the Panzhihua intrusion.     

淋溶条件下石英砂柱中铁锰氧化物的形成特点

用不同浓度铁锰离子混合溶液对石英砂柱进行40次淋溶实验,研究砂柱中铁锰氧化物的形成状况.结果表明,淋出液中铁锰离子浓度与其pH值随着淋溶次数的增加呈现先降低后升高的趋势;各处理所形成的铁锰氧化物含量之间存在极显著差异,淋溶液中铁锰离子浓度越大,形成的铁锰氧化物含量越高,当淋溶液中铁锰摩尔浓度比即c(Fe2+)/c(Mn2+)为2∶1时最有利于铁锰氧化物的形成;随着淋溶次数的增加,铁锰氧化物含量的增长逐渐减慢;不同层次铁锰氧化物含量差异显著,下层(20～30 cm)含量明显高于其它层次;各阶段(每淋溶10次为一阶段)不同形态(非晶形态、晶形态)铁锰氧化物含量间的相关性存在差异,铁锰氧化物尤其是非晶形态的相对比例(Fe/Mn)随着淋溶次数的增加逐渐增大.     

Spectral response of different eroded soils in subtropical china: A case study in Changting County,China

Hyper-spectral data is widely used to determine soil properties. However, few studies have explored the soil spectral characteristics as response to soil erosion. This study analysed the spectral response of different eroded soils in subtropical China, and then identify the spectral characteristics and soil properties that better discriminate softs with different erosion degrees. Two methods were compared： direct identification by inherent spectral characteristics and indirect identification by predictions of critical soft properties. Results showed that the spectral curves for different degrees of erosion were similar in morphology, while overall reflectance and characteristics of specific absorption peaks were different. When the first method is applied, some differences among different eroded groups were found by integration of associated indicators. However, the index of such indicators showed apparent mixing and crossover among different groups, which reduced the accuracy of identification. For the second method, the correlation between critical soil properties, such as soil organic matter （SOM）, iron and aluminium oxides and reflectance spectra, was analysed. The correlation coefficients for the moderate eroded group were primarily between -0.3 to -0.5, which were worse than the other twogroups. However, the maximum value of R2 was obtained as 0.86 and 0.94 for the non-apparent eroded and the severe group. Furthermore, these two groups also showed some differences in the spectral response of iron complex state （Fep）, Aluminium amorphous state （Alo） and the modelling results for soil organic matter （SOM）. The study proved that it is feasible to identify different degrees of soil erosion by hyperspectral data, and that indirect identification by modelling critical soil properties and reflectance spectra is much better than direct identification. These results indicate that hyper-spectral data may represent a promising tool in monitoring and modelling soil erosion.