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51.
Local surface travel needs in the Peoples Republic of China (mainlandChina) have traditionally been met largely by nonpolluting bicycles. A majorautomobile manufacturing/importing effort has begun in the country over thelast decade, and planning documents indicate that the Chinese may strive toacquire more than 100 million vehicles early in the next century. By analogywith large automotive fleets already existing in the western world, bothregional and global scale pollution effects are to be expected from theincrease. The present work adopts the latest projections of Chinese automobilemanufacture and performs some quantitative assessments of the extent ofpollution generation.Focus for the investigation is placed upon the oxidant ozone. Emissions of theprecursor species nitrogen oxides and volatile organics are constructed basedon data for the current automotive sector in the eastern portion of the UnitedStates. Ozone production is first estimated from measured values forcontinental/oceanic scale yields relative to precursor oxidation. Theestimates are then corroborated through idealized two dimensional modeling ofthe photochemistry taking place in springtime air flow off the Asian land massand toward the Pacific Ocean. The projected fleet sizes could increase coastaland remote oceanic ozone concentrations by tens of parts per billion (ppb)in the lower troposphere. Influences on the tropospheric aerosol system andon the major greenhouse gas carbon dioxide are treated peripherally. Nitrogenoxides created during the vehicular internal combustion process willcontribute to nitrate pollution levels measured in the open Pacific. Thepotential for soot and fugitive dust increases should be considered as theautomotive infrastructure develops. Since the emerging Chinese automotivetransportation system will represent a substantial addition to the globalfleet and all the carbon in gasoline is eventually oxidized completely, asignificant rise in global carbon dioxide inputs will ensue as well.Some policy issues are treated preliminary. The assumption is made thatalterations to regional oxidant/aerosol systems and to terrestrial climate areconceivable. The likelihood that the Chinese can achieve the latest vehiclefleet goals is discussed, from the points of view of new production, positivepollution feedbacks from a growing automobile industry, and known petroleumreserves. Vehicular fuel and maintenance options lying before the Chinese areoutlines and compared. To provide some perspective on the magnitude of theenvironmental changes associated with an Asian automotive buildup, recentestimates of the effects of future air traffic over the Pacific Rim aredescribed.  相似文献   
52.
Payne, R. J., Lamentowicz, M. & Mitchell, E. A. D. 2010: The perils of taxonomic inconsistency in quantitative palaeoecology: experiments with testate amoeba data. Boreas, 10.1111/j.1502‐3885.2010.00174.x. ISSN 0300‐9483. A fundamental requirement of quantitative palaeoecology is consistent taxonomy between a modern training set and palaeoecological data. In this study we assess the possible consequences of violation of this requirement by simulating taxonomic errors in testate amoeba data. Combinations of easily confused taxa were selected, and data manipulated to reflect confusion of these taxa; transfer functions based on unmodified data were then applied to these modified data sets. Initially these experiments were carried out one error at a time using four modern training sets; subsequently, multiple errors were separately simulated both in four modern training sets and in four palaeoecological data sets. Some plausible taxonomic confusions caused major biases in reconstructed values. In the case of two palaeoecological data sets, a single consistent taxonomic error was capable of changing the pattern of environmental reconstruction beyond all recognition, totally removing any real palaeoenvironmental signal. The issue of taxonomic consistency is one that many researchers would rather ignore; our results show that the consequences of this may ultimately be severe.  相似文献   
53.
In southwestern Alberta, Canada, a westward-rising last-glacial-maximum continental ice limit has been identified. This limit is defined by the upper elevation of Canadian Shield erratics deposited by last-glacial-maximum continental ice along the flanks of prominent ridges and buttes within the region. The interpolation between ice-limit data points has produced two distinct slope profiles: 2.9 m/km to the east, and 4.2 m/km to the west of Mokowan Butte. Three hypotheses are proposed to explain this westward rise of the last-glacial-maximum continental ice limit: (1) regional tectonic uplift, (2) glacio-isostatic uplift, and (3) continental ice-flow convergence due to topographic obstacles and interaction with montane ice. Inferred long-term rates of tectonic uplift and glacio-isostatic modelling show that these two mechanisms account for less than 25% of the observed absolute elevation increase of the limit between the Del Bonita uplands and Cloudy Ridge in southwestern Alberta. The remaining rise in elevation of the continental ice-sheet margin in this region is thought to result from continental ice-flow convergence due to the combined effects of the regional topography and interaction with montane glaciers to the west. The steeper rise in the former continental ice surface west of Mokowan Butte can be explained by the topographic obstruction and interaction with montane glaciers in the area of the Rocky Mountain front.  相似文献   
54.
Most people have heard of the Rock of Gibraltar, yet few know anything of its geology. Recent studies now interpret the Rock as a partly overturned mass of Jurassic limestone, thrust into position during continent-continent collision by about 15–20 million years ago, and shaped largely by shoreline processes active during Pleistocene tectonic uplift. The Rock's geology has implications for currently developing interpretations of the geological evolution of the western Mediterranean region and for the fast-growing development of Gibraltar's urban environment.  相似文献   
55.
In a remarkable and yet largely unheralded piece off legislation, the New Zealand government has reshaped national provisions for earthquake insurance. Three major sets off issues emerge from the 1993 Earthquake Commission Act and warrant detailed investigation. The A ct will encourage significant changes in patterns of regional development in New Zealand, it heralds a simultaneous globalisation and localisation of earthquake risk through the mechanism of insurance and it gives new regulatory powers to insurers in New Zealand society.  相似文献   
56.
Abstract— The Ocotillo IAB iron meteorite contains small silicate inclusions consisting of olivine, low-Ca pyroxene, chromian diopside, plagioclase, magnesiochromite, apatite, troilite and metal. The ferromagnesian silicates have a small range of Fe/(Fe + Mg) ratios that are not due to zoning. These phases appear to be not well equilibrated. The FeO content of magnesiochromite is lower than values normally seen in silicate assemblages in IAB iron meteorites. The minerals in Ocotillo are generally like silicate assemblages in other IAB meteorites, covering similar composition ranges and exhibiting a metamorphic (granoblastic) texture. An estimate was made of the bulk composition of Ocotillo silicate inclusions. The bulk composition is close to that of ordinary chondrites with the exception of a deficiency in CaO that might be due to a sampling problem associated with the method used to estimate the bulk composition.  相似文献   
57.
This paper presents a revised glacial chronology for the Lahul Himalaya and provides the most detailed reconstruction of former glacier extents in the western Himalayas published to date. On the basis of detailed geomorphological mapping, morphostratigraphy, and absolute and relative dating, three glaciations and two glacial advances are constrained. The oldest glaciation (Chandra glacial stage) is represented by glacially eroded benches and drumlins (the first to be described from the Himalaya) at altitudes of >4300 m and indicates glaciation on a landscape of broad valleys that had minimal fluvial incision. The second glaciation (Batal glacial stage) is represented by highly weathered and disssected lateral moraines and drumlins representing two phases of glaciation within the Batal glacial stage (Batal I and Batal II). The Batal stage was an extensive valley glaciation interrupted by a readvance that produced superimposed bedforms. Optically stimulated luminescence (OSL) dating, indicates that glaciers probably started to retreat between 43400 ± 10300 and 36900 ± 8400 yr ago during the Batal stage. The Batal stage may be equivalent to marine Oxygen Isotope Stage 4 and early Oxygen Isotope Stage 3. The third glaciation (Kulti glacial stage), is represented by well-preserved moraines in the main tributary valleys that formed due to a less-extensive valley glaciation when ice advanced no more than 12 km from present ice margins. On the basis of an OSL age for deltaic sands and gravels that underlie tills of Kulti age, the Kulti glaciation is younger than 36900 ± 8400 yr ago. The development of peat bogs, having a basal age of 9160 ± 70 14C yr BP possibly represents a phase of climatic amelioration coincident with post-Kulti deglaciation. The Kulti glaciation, therefore, is probably equivalent to all or parts of late Oxygen Isotope Stage 3, Stage 2 and early Stage 1. Two minor advances (Sonapani I and II) are represented by small sharp-crested moraines within a few kilometres of glacier termini. On the basis of relative weathering, the Sonapani advance is possibly of early mid-Holocene age, whereas the Sonapani II advance is historical. The change in style and extent of glaciation is attributed to topographic controls produced by fluvial incision and by increasing aridity during the Quaternary. © 1997 John Wiley & Sons, Ltd.  相似文献   
58.
59.
Following the Painted Cave Fire of 25 June 1990 in Santa Barbara, California which burned 1214 ha, an emergency watershed protection plan was implemented consisting of stream clearing, grade stabilizers and construction of debris basins. Research was initiated focusing on hydrological response and channel morphology changes on two branches of Maria Ygnacio Creek, the main drainage of the burned area. Research results support the hypothesis that the response of small drainage basins in chaparral ecosystems to wildfire is complex and flushing of sediment by fluvial processes is more likely than by high magnitude debris flows. During the winter of 1990–1991, 35–66 cm of rainfall and intensities up to 10 cm per hour for a five-minute period were recorded with a seasonal total of 100% of average (normal) rainfall (average=63 cm/year). During the winter of 1991–1992, 48–74 cm of rainfall and intensities up to 8 cm per hour were recorded with a seasonal total of 115% of normal. Even though there was moderate rainfall on barren, saturated soils, no major debris flows occurred in burned areas. The winter of 1992–1993 recorded total precipitation of about 170% of normal, annual average intensities were relatively low and again no debris flows were observed. The response to winter storms in the first three years following the fire was a moderate but spectacular flushing of sediment, most of which was derived from the hillslopes upstream of the debris basins. The first significant storm and stream flow of the 1990–1991 winter was transport-limited resulting in large volumes of sediment being deposited in the channel of Maria Ygnacio Creek; the second storm and stream flow was sediment-limited and the channel scoured. Debris basins trapped about 23 000 m3, the majority coming from the storm of 17–20 March 1991. Sediment transported downstream during the three winters following the fire and not trapped in the debris basins was eventually flushed to the estuarine reaches of the creeks below the burn area, where approximately 108 000 m3 accumulated. Changes in stream morphology following the fire were dramatic as pools filled with sediment which greatly smoothed longitudinal and cross-sectional profiles. Major changes in channel morphology occur following a fire as sediment derived from the hillslope is temporarily stored in channels within the burned area. However, this sediment may quickly move downstream of the burned region, where it may accumulate reducing channel capacity and increasing the flood hazard. Ecological consequences of wildfire to the riparian zone of streams in the chaparral environment are virtually unknown, but must be significant as the majority of sediment (particularly gravel necessary for fish and other aquatic organisms) entering the system does so in response to fires. © 1997 John Wiley & Sons, Ltd.  相似文献   
60.
Thermodynamic calculations based on addition of mass balanceequations to the Gibbs Method (Spear, 1986) are used to modelthe cordierite-producing reaction in pelitic gneiss from theMcCullough Range, southern Nevada. Calculations which treatthe model paragenesis as a system open to transfer of H2O areconsistent with textural relations. Results indicate that cordieritegrew by the continuous net-transfer reaction: 0?76 BIO+1?72 SILL+3? 55 QTZ+0?27 PLG+0?005 GRT +0?06Al2R2+–1Si–1[BIO]1?02 KSP+0?76 H2O +0?30 FeMg–1[CRD]+0?15FeMg–1[BIO]+0?0005 FeMg–1[GRT] +0?005 CaNaAl–1Si–1[PLG] with decreasing P, decreasing T, and increasing aH2O The steepretrograde dP/dT path for these low-pressure granulites contrastswith isobaric cooling paths typical of higher pressure granulites,and suggests uplift and erosion were active during Proterozoicgranulite-grade metamorphism in this area.  相似文献   
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