生物质燃烧颗粒物有机示踪化合物的测定和应用

使用气相色谱-质谱法对2002年7月-2003年7月的北京市大气粗、细颗粒物样品中的左旋葡聚糖等糖类化合物进行了测定。结果表明，左旋葡聚糖主要存在于细颗粒中，可以作为示踪化合物来研究生物质燃烧现象。生物质燃烧对北京市大气颗粒物有较重要的贡献。对应于12％-40％的PM2.5有机碳和10％-33％的PM10有机碳。北京市在2002年10月和11月受到明显的生物质燃烧的影响，可能由于农田秸杆焚烧和秋季落叶焚烧。2003年5月7日颗粒物样品受到直线距离约为1000km以外的内蒙古自治区呼伦贝尔市大兴安岭林区森林大火烟雾的影响。生物质燃烧事件具有突发性，可以长距离传输；生物质作为农村生物燃料的使用其燃烧排放具有经常性和持久性的特征。     

ESR dating of palaeolithic calcite: A comparison between powder and monocrystal spectra with thermal annealing

Evolution of ESR spectra with thermal annealing at different temperatures is studied for a monocrystal calcite taken in the Orgnac III site. Up to 20 ESR lines are recognized from the angular dependence of these lines. These lines are compared with the ESR lines observed for powder and rotating monocrystal calcites.The h1 line (g = 2.0057) and h3 line (g = 2.0007) are isotropic or nearly isotropic and are due to the electrons trapped in the amorphous region formed by fission tracks or alpha-ray recoil nuclei. The h2 line (g = 2.0021) is a composite of several different lines.     

Transport in a 2-D saturated porous medium: A new method for particle tracking

A new method for solving the transport equation based on the management of a large numbe of particles in a discretized 2-D domain is presented. The method uses numerical variables to represent the number of particles in a given mesh and is more complex than the 1-D problem. The first part of the paper focuses on the specific management of particles in a 2-D problem. The method also would be valid for three dimensions as long as the medium can be modeled similar to a layered system. As the particles are no longer tracked individually, the algorithm is fast and does not depend on the number of particles present. The numerical tests show that the method is nearly numerical dispersion free and permits accurate calculations even for simulations of low-concentration transport. Because each mesh is considered as a closed system between two successive time steps, it is easy to add adsorption phenomenon without any problem of numerical stability. The model is tested under conditions that are extremely demanding for its operating mode and gives a good fit to analytical solutions. The conditions in which it can be used to best advantage are discussed.     

Petrogenesis of the amphibole-rich veins from the Lherz orogenic lherzolite massif (Eastern Pyrenees, France): a case study for the origin of orthopyroxene-bearing amphibole pyroxenites in the lithospheric mantle

The Lherz orogenic lherzolite massif (Eastern French Pyrenees) displays one of the best exposures of subcontinental lithospheric mantle containing veins of amphibole pyroxenites and hornblendites. A reappraisal of the petrogenesis of these rocks has been attempted from a comprehensive study of their mutual structural relationships, their petrography and their mineral compositions. Amphibole pyroxenites comprise clinopyroxene, orthopyroxene and spinel as early cumulus phases, with garnet and late-magmatic K₂O-poor pargasite replacing clinopyroxene, and subsolidus exsolution products (olivine, spinel II, garnet II, plagioclase). The original magmatic mineralogy and rock compositions were partly obscured by late-intrusive hornblendites and over a few centimetres by vein–wallrock exchange reactions which continued down to subsolidus temperatures for Mg–Fe. Thermobarometric data and liquidus parageneses indicate that amphibole pyroxenites started to crystallize at P ≥ 13 kbar and recrystallized at P < 12 kbar. The high Al^VI/Al^IV ratio (>1) of clinopyroxenes, the early precipitation of orthopyroxene and the late-magmatic amphibole are arguments for parental melts richer in silica but poorer in water than alkali basalts. Their modelled major element compositions are similar to transitional alkali basalt with about 1–3 wt% H₂O. In contrast to amphibole pyroxenites, hornblendites only show kaersutite as liquidus phase, and phlogopite as intercumulus phase. They are interpreted as crystalline segregates from primary basanitic magmas (mg=0.6; 4–6 wt% H₂O). These latter cannot be related to the parental liquids of amphibole pyroxenites by a fractional crystallization process. Rather, basanitic liquids mostly reused pre-existing pyroxenite vein conduits at a higher structural level (P ≤ 10 kbar). A continuous process of redox melting and/or alkali melt/peridotite interaction in a veined lithospheric mantle is proposed to account for the origin of the Lherz hydrous veins. The transitional basalt composition is interpreted in terms of extensive dissolution of olivine and orthopyroxene from wallrock peridotite by alkaline melts produced at the mechanical boundary layer/thermal boundary layer transition (about 45–50 km deep). Continuous fluid ingress allowed remelting of the deeper veined mantle to produce the basanitic, strongly volatiles enriched, melts that precipitated hornblendites. A similar model could be valid for the few orthopyroxene-rich hydrous pyroxenites described in basalt-hosted mantle xenoliths. Received: 15 September 1999 / Accepted: 31 January 2000     

Oxygen isotope composition of phenocrysts from Tristan da Cunha and Gough Island lavas: variation with fractional crystallization and evidence for assimilation

We have measured the δ¹⁸O values of the major phenocrysts (olivine, clinopyroxene and plagioclase) present in lavas from Tristan da Cunha and Gough Island. These islands, which result from the same mantle plume, have enriched radiogenic isotope ratios and are, therefore, prime candidates for an oxygen isotope signature that is distinct from that of MORB. Consistent differences between the δ¹⁸O values of olivine, pyroxene and feldspar in the Gough lavas show that the phenocrysts in the mafic Gough Island lavas are in oxygen isotope equilibrium. The olivines in lavas with SiO₂ <50 wt% have a mean δ¹⁸O value of 5.19‰, consistent with crystallization from a magma having the same oxygen isotope composition as MORB. Phenocrysts in all the Gough lavas show a systematic increase in δ¹⁸O value as silica content increases, which is consistent with closed-system fractional crystallization. The lack of enrichment in δ¹⁸O of the Gough magmas suggests that the mantle source contained <2% recycled sediment. In contrast, the Tristan lavas with SiO₂ >48 wt% contain phenocrysts which have δ¹⁸O values that are systematically ∼0.3‰ lower than their counterparts from Gough. We suggest that the parental mafic Tristan magmas were contaminated by material from the volcanic edifice that acquired low δ¹⁸O values by interaction with water at high temperatures. The highly porphyritic SiO₂-poor lavas show a negative correlation between olivine δ¹⁸O value and whole-rock silica content rather than the expected positive correlation. The minimum δ¹⁸O value occurs at an SiO₂ content of about 45 wt%. Below 45 wt% SiO₂, magmas evolved via a combination of assimilation, fractionational crystallization and crystal accumulation; above 45 wt% SiO₂, magmas appeared to have evolved via closed-system fractional crystallization. Received: 23 November 1998 / Accepted: 27 September 1999     

Decoupling between the middle and upper crust during transpression-related lateral flow: Variscan evolution of the Aston gneiss dome (Pyrenees, France)

We present a structural, AMS, microstructural and kinematic study of the Aston gneiss dome (French Pyrenees), which consists of a core made up of orthogneiss and paragneiss intruded by numerous sills of Carboniferous peraluminous granite. The orthogneiss corresponds to a former Ordovician granitic laccolith. Four Variscan events have been evidenced in this gneiss dome: (i) D1 deformation observed only as relics in the orthogneisses and their country-rocks located above the sillimanite isograd, and characterized by a NS to NE–SW non coaxial stretch associated to top to the south motions (NS convergence); (ii) D2-a deformation observed in the orthogneisses and their country-rocks, mainly migmatitic paragneisses, located below the sillimanite isograd and in the peraluminous granites whatever their structural level, and characterized by an EW to N120°E stretch associated to a top to the east flat shearing (lateral flow in the hot middle crust in a transpressive regime); (iii) D2-b deformation characterized by EW-trending megafolds corresponding to the domes in the middle crust and by EW-trending tight folds with subvertical axial planes in the metasedimentary upper crust; (iv) subvertical medium-temperature mylonitic bands developed by the end of the transpression.The Aston massif is a good example of decoupling between a cold upper crust and a hotter middle crust overheated by a thermal event originated in the upper mantle. This decoupling allowed the lateral flow of the migmatitic middle crust along a direction at high angle with respect to the more or less NS-trending direction of convergence. We suggest that the HT-LP metamorphism developed before the formation of the domes during D2-a, coevally with the emplacement of numerous sills of peraluminous granite, whereas the emplacement of the large calc-alkaline plutons in the upper crust occurred by the end of D2-b. Our data invalidate the previous geodynamical models based on either early or late extensional regime to explain the development of the HT-LP metamorphism. This new interpretation of the dynamics of the Variscan crust of the Pyrenees is consistent with recent studies conducted in Archaean and Palaeoproterozoic hot continental crusts having undergone oblique convergence, and characterized by a competition between vertical thickening and lateral flow induced by the important rheological contrast between two thermally different levels.     

Sites occupancy of Fe3+ in Garfield Nontronite: A spectroscopic study

New data on the structure of Garfield nontronite have been produced by the use of different spectroscopic techniques: Mössbauer spectroscopy, optical spectroscopy, X-ray absorption edges and EXAFS and NMR. The tetrahedral iron content is found to be no higher than 1 percent. All iron atoms belong to the octahedral sheet excluding the possibility of the presence of non crystallized phases. Some ambiguities remain about the coherence of the octahedral sheet because of the presence of two doublets in the Mössbauer spectrum and at least two lineshapes in NMR spectra of OH which correspond to different environments.     

It starts at home? Climate policies targeting household consumption and behavioral decisions are key to low-carbon futures

Through their consumption behavior, households are responsible for 72% of global greenhouse gas emissions. Thus, they are key actors in reaching the 1.5 °C goal under the Paris Agreement. However, the possible contribution and position of households in climate policies is neither well understood, nor do households receive sufficiently high priority in current climate policy strategies. This paper investigates how behavioral change can achieve a substantial reduction in greenhouse gas emissions in European high-income countries. It uses theoretical thinking and some core results from the HOPE research project, which investigated household preferences for reducing emissions in four European cities in France, Germany, Norway and Sweden. The paper makes five major points: First, car and plane mobility, meat and dairy consumption, as well as heating are the most dominant components of household footprints. Second, household living situations (demographics, size of home) greatly influence the household potential to reduce their footprint, even more than country or city location. Third, household decisions can be sequential and temporally dynamic, shifting through different phases such as childhood, adulthood, and illness. Fourth, short term voluntary efforts will not be sufficient by themselves to reach the drastic reductions needed to achieve the 1.5 °C goal; instead, households need a regulatory framework supporting their behavioral changes. Fifth, there is a mismatch between the roles and responsibilities conveyed by current climate policies and household perceptions of responsibility. We then conclude with further recommendations for research and policy.     

Early Permian extensional shearing of an Ordovician granite: The Saint-Eutrope “C/S-like” orthogneiss (Montagne Noire,French Massif Central)

Dating the magmatic events in the Montagne Noire gneiss dome is a key point to arbitrate between the different interpretations of the Late Carboniferous–Early Permian tectonics in this southern part of the Variscan belt. The Saint-Eutrope orthogneiss crops out along the northern flank of the dome. We show that the protolith of this orthogneiss is an Ordovician granite dated at 455 ± 2 Ma (LA-ICP-MS U-Pb dating on zircon). This age is identical to that previously obtained on the augen orthogneiss of the southern flank, strongly suggesting that both orthogneiss occurrences have the same Ordovician protolith. The Saint-Eutrope orthogneiss experienced intense shearing along the Espinouse extensional detachment at ca. 295 Ma (LA-ICP-MS U-Pb-Th on monazite), an age close to that determined previously on mica by the ³⁹Ar-⁴⁰Ar method and contemporaneous with the emplacement age of the syntectonic Montalet granite farther to the west. This normal sense shearing reworked previous fabrics related to Variscan thrusting that can be still observed in the augen orthogneiss of the southern flank, and is responsible for the spectacular “C/S-like” pattern of the Saint-Eutrope orthogneiss. This work also shows that care is needed when dealing with C/S-type structures, since they can develop not only in syntectonic intrusions, but also in orthogneisses affected by an intense secondary deformation, at decreasing temperature.