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排序方式: 共有466条查询结果,搜索用时 46 毫秒
391.
Resilience to global food supply catastrophes 总被引:1,自引:0,他引:1
392.
Graham S. Ohmsen 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1443-1451
ABSTRACT The primary production of Pb via the sinter plant-blast furnace method resulted in a large number of Pb and other phases, reflecting the complex reactions occurring within each of the processes. Optical microscopy and X-ray diffraction (XRD) techniques have been used to characterize fugitive emissions and dusts generated during sintering, smelting, Cu drossing, refining, and slag fuming at a primary Pb-Zn smelter. The results displayed a complex array of phases, with the mineralogy of the dusts and fume reflecting conditions of the particular metallurgical operation. The principal Pb species followed a transformation from PbS through PbSO4 and PbO to Pb° (metal) from raw materials to the refinery. The fugitive emissions generated by the blast furnace were of a finer size with more complex chemistry than fugitive material from other source areas. XRD identified a mixture of PbS, ZnO, and ZnS, associated with one or more of the Cl-bearing phases Pb(OH)Cl, PbCl2, Pb4O3Cl2, Na3Pb2(SO4)3Cl, Pb10(SO4)Cl2O8, Pb4SCl6, and Pb7S2Cl10. The presence of Cl-bearing phases in the fume has possible health implications. 相似文献
393.
Jorge Velásquez-Tibatá Paul Salaman Catherine H. Graham 《Regional Environmental Change》2013,13(2):235-248
Climate change is expected to cause shifts in species distributions worldwide, threatening their viability due to range reductions and altering their representation in protected areas. Biodiversity hotspots might be particularly vulnerable to climate change because they hold large numbers of species with small ranges which could contract even further as species track their optimal habitat. In this study, we assessed the extent to which climate change could cause distribution shifts in threatened and range-restricted birds in Colombia, a megadiverse region that includes the Tropical Andes and Tumbes-Choco-Magdalena hotspots. To evaluate how climate change might influence species in this region, we developed species distribution models using MAXENT. Species are projected to lose on average between 33 and 43 % of their total range under future climate, and up to 18 species may lose their climatically suitable range completely. Species whose suitable climate is projected to disappear occur in mountainous regions, particularly isolated ranges such as the Sierra Nevada de Santa Marta. Depending on the representation target considered, between 46 and 96 % of the species evaluated may be adequately represented in protected areas. In the future, the fraction of species potentially adequately represented is projected to decline to 30–95 %. Additional protected areas may help to retain representativeness of protected areas, but monitoring of species projected to have the largest potential declines in range size will be necessary to assess the need of implementing active management strategies to counteract the effects of climate change. 相似文献
394.
395.
Settlement patterns and the relationship between meroplanktonic larvae and settlement in decapods were studied on the Scottish
east coast. Artificial settlement substrates (ASS), deployed at two locations (sandy vs. rocky sea substrates), were employed
to collect megalopae and newly settled juveniles. Abundance of meroplanktonic larvae was used as an indicator of larval supply.
The results showed a clear seasonality in settlement rates, and in some cases, significant differences between sites were
detected. Nevertheless, the interference of the ASS with the surrounding habitat limits the study of spatial variability in
settlement rates. Significant cross-correlation was found between the abundance of megalopae and juveniles in the collectors
and planktonic larval abundance a month earlier. For individual species, this relationship was observed only in Pisidia longicornis. Complexities caused by the great variety of pre- and post-settlement processes, alongside effects of secondary dispersals
of early juveniles may have obscured the relationship between meroplanktonic larvae and juveniles in other species. 相似文献
396.
The impact of granivores on coastal dune seed reserves may be high, increasing along a landward gradient from the littoral
zone as the structural complexity of the habitat increases. Seasonal removal rates of non-native seeds by nocturnal and diurnal
vertebrates and ants from experimental seed trays in two habitats within the Alexandria Coastal Dunefield, South Africa, were
determined. Overall, seed removal was higher in the dune-field bush-pocket habitat than the landward thicket habitat. Nocturnal
vertebrates were the most important seed removers within bush-pockets. The importance of nocturnal vertebrates decreased in
the thicket and there was a shift in the dominant seed removers to diurnal vertebrates. Seed removal by ants and diurnal vertebrates
did not differ significantly between the bush-pockets and thicket while that of nocturnal vertebrates showed a significant
change. This can be ascribed to the abundance of the omnivorous murid rodentGerbillurus paeba exilis in the bush-pockets which is absent from thicket vegetation. 相似文献
397.
Bridget L. Elliott Graham I. H. Kerley Anton McLachlan 《Journal of Coastal Conservation》2000,6(1):79-88
Dune hummocks (small aeolian dunes formed by sand deposition in and around pioneer plants) are the smallest vegetated dune
unit; they occur along the entire South African coastline but are poorly studied. Structural properties and distribution of
the two main hummock-forming plants:Arctotheca populifolia (a pioneer species with fast growth rate and rapid turnover) andGazania rigens (a later colonizer with slower growth) were investigated. A marked vegetation succession exists across the floor of the slack
as a result of the migration of transverse dune ridges across the slack.Arctotheca hummocks were initiated on the newly exposed eastern margin of the slack, and were replaced about midway across the width
of the slack byGazania hummocks. Hummocks increased in size with distance from the eastern side of the slack.Gazania hummocks attain a greater vegetation height, support a greater vegetation complexity and mass, and attain a larger maximum
size thanArctotheca hummocks. Succession, defined as both the replacement of plant species as well as site modification within the plants over
time, was evident. Since the growth form and dynamics determine (1) the ability of plants to trap wind-borne soil and detritus,
(2) the shape of the hummocks, and (3) the habitat complexity available to spiders and insects, the ecology of the hummocks
is probably determined largely by the vegetation characteristics of the hummock-forming plants. 相似文献
398.
Lisa A. Graham Sheri L. Belisle Paul Rieger 《Atmospheric environment (Oxford, England : 1994)》2009,43(12):2031-2044
Nitrous oxide (N2O) emissions measurements were made on light duty gasoline and light duty diesel vehicles during chassis dynamometer testing conducted at the Environment Canada and California Air Resources Board vehicle emissions laboratories between 2001 and 2007. Per phase and composite FTP emission rates were measured. A subset of vehicles was also tested using other driving cycles to characterize emissions as a function of different driving conditions. Vehicles were both new (<6500 km) and in-use (6500–160,000 km) and were tested on low sulfur gasoline (<30 ppm) or low sulfur diesel (<300 ppm). Measurements from selected published studies were combined with these new measurements to give a test fleet of 467 vehicles meeting both US EPA and California criteria pollutant emissions standards between Tier 0 and Tier 2 Bin 3 or SULEV. Aggregate distance-based and fuel-based emission factors for N2O are reported for each emission standard and for each of the different test cycles. Results show that the distinction between light duty automobile and light duty truck is not significant for any of the emission standards represented by the test fleet and the distinction between new and aged catalyst is significant for vehicles meeting all emission standards but Tier 2. This is likely due to the relatively low mileage accumulated by the Tier 2 vehicles in this study as compared to the durability requirement of the standard. The FTP composite N2O emission factors for gasoline vehicles meeting emission standards more stringent than Tier 1 are substantially lower than those currently used by both Canada and the US for the 2005 inventories. N2O emission factors from test cycles other than the FTP illustrate the variability of emission factors as a function of driving conditions. N2O emission factors are shown to strongly correlate with NMHC/NMOG emission standards and less strongly with NOX and CO emission standards. A review of several published reports on the effect of gasoline sulfur content on N2O emissions suggests that additional research is needed to adequately quantify the increase in N2O emissions as a function of fuel sulfur. 相似文献
399.
Territoriality is an emerging concept of importance in organizations. Unfortunately, there does not exist currently a valid measure of territoriality with which to conduct research on territoriality in organizations. I developed a theoretically driven four-factor measure of territoriality. Six hundred and sixty-three people working in office settings completed an online survey about their territorial behaviors. Using confirmatory factor analysis I found that the four-factor structure had acceptable fit. I also found preliminary evidence of construct validity. Collectively, the results support the validity of the measure, thus providing an instrument for studying territoriality in organizations. I then discuss specific implications of this measure for both research and practise. 相似文献
400.
Provenancing anthropogenic Pb within the fluvial environment: developments and challenges in the use of Pb isotopes 总被引:1,自引:0,他引:1
Bird G 《Environment international》2011,37(4):802-819
The potentially deleterious presence of ore-derived Pb within riverine environments has been a long-term impact of industrial and anthropogenic activity in general. The surface drainage network has been widely established as a key transport mechanism and storage environment for anthropogenically-derived Pb and other potentially harmful trace metals. Lead isotopes ((204)Pb, (206)Pb, (207)Pb, (208)Pb) have been utilized as a geochemical tracer of Pb origin in a variety of environmental media, notably in atmospheric aerosols. However, given the relative complexity of dispersal processes within riverine environments, the use of Pb isotopes as geochemical tracers has been relatively limited and it is only relatively recently that a growing body of research has applied Pb isotopes to provenancing fluvially-dispersed Pb. This paper seeks to synthesize the developments in the use of Pb isotopes within riverine environments. In doing so it outlines the Pb-isotope fingerprinting technique and associated analytical developments, and assesses the application of Pb isotopes in establishing the origin and dispersal mechanisms of anthropogenically- and geogenically-derived Pb at a range of temporal and spatial scales. Of particular importance are the approaches quantifying source inputs using Pb isotopic signatures and the challenges faced, and options available in quantifying source inputs at the catchment scale; where Pb may be sourced from a variety (n=>2) of sources. The Pb isotopic signature of contemporary riverine Pb loads is shown to reflect a spatially complex influence of mineralization chemistry, anthropogenic activity as well as the hydro-morphological controls exerted upon Pb release, dispersal and storage. In relation to this, the long-term environmental legacy, and its influence upon Pb fingerprinting studies, of tetra-ethyl Pb, sourced from the combustion of leaded-petrol is also discussed. Finally, this paper places the use of Pb isotopes in the context of recently developed Cu and Zn isotopic fingerprinting techniques and assesses the role of Pb, Cu and Zn isotopes in a multi-proxy approach to geochemical tracing. 相似文献