Historical trends of mercury and spheroidal carbonaceous particle deposition in sub-alpine lakes in the Great Basin,United States

The geochemistry of lake sediments was used to identify anthropogenic factors influencing aquatic ecosystems of sub-alpine lakes in the western United States during the past century. Sediment cores were recovered from six high-elevation lakes in the central Great Basin of the United States. The proxies utilized to examine the degree of recent anthropogenic environmental change include spheroidal carbonaceous particle (SCP), mercury (Hg), and sediment organic content estimated using loss-on-ignition. Chronologies for the sediment cores, developed using ²¹⁰Pb, indicate the cores span the twentieth century. Mercury flux varied between lakes but all exhibited increasing fluxes during the mid-twentieth century. The mean ratio of modern (post-A.D. 1985) to preindustrial (pre-A.D. 1880) Hg flux was 5.2, which is comparable to the results from previous studies conducted in western North America. Peak SCP flux for all lakes occurred between approximately A.D. 1940 and A.D. 1970, after which time the SCP flux was greatly reduced. The reduction in SCP input is likely due to better controls on combustion sources. Measured Hg concentrations and calculated sedimentation rates suggest atmospheric Hg flux increased in the early 1900s, from A.D. 1920 to A.D. 1990, and at present. Atmospheric deposition is the primary source of the anthropogenic inputs of Hg and SCPs to these high elevation lakes. The input of SCPs, which is largely driven by regional sources, has declined with the implementation of national pollution control regulations. Mercury deposition in the Great Basin has most likely been influenced more by regional inputs.     

City of the Spectacle: White Night Melbourne and the politics of public space

Public policy frequently is utilised as a medium to facilitate or restrict access to public space, and to privilege economic priorities. In this context urban arts festivals are used as a means to generate dominant narratives of place and use of public space. Urban arts festivals generate spaces of spectacle and wonder, and are often used as marketing strategies to revitalise urban economies and differentiate cities one from another on the global stage, engendering a commodification of place. The present paper explores this tension through an examination of the role of urban arts festivals in spatial politics. White Night Melbourne is the first Australian iteration of the Nuit Blanche International, an international network of all-night arts festivals. It is used as a case study to explore the impact of an urban arts festival on the spatial politics of Melbourne. A theoretical basis is established using the frame of Guy Debord's ([1967] 1994) The Society of the Spectacle, as well as the concepts of ‘assemblage’ and ‘expressivity’.     

Microsimulation of large-scale evacuations utilizing metrorail transit

Public transit plays an important role in emergency evacuations, particularly for areas where public transit serves as a major commute mode for commuters. Microsimulation techniques provide great flexibility in assessing different scenarios in emergency situations. Combining GIS-based network analysis with microsimulation techniques, this study developed a framework to simulate emergency evacuations using rail transit. Applying the framework to a hypothetical attack on the Pentagon, this study investigated the performance of the Washington Metropolitan Area Transit Authority’s Metrorail for large-scale evacuations. A network-based analysis was performed to estimate the number of riders in association with each metro line and station. Using VISSIM, a multi-mode micro-simulation software package, this study integrated a pedestrian model with a Metrorail transit model to evaluate the performance of the Metrorail in the hypothetical evacuations. The simulation results suggested that if the potential of Metrorail transit is effectively utilized, it could be very useful resource during a large-scale evacuation. This study demonstrated the great potential and flexibility of microsimulation techniques for evaluating complex evacuation scenarios and strategies. The framework and approach used in this study can be applied to analyze other similar situations and help develop effective evacuation plans.     

TRACKING THE BABY BOOM,THE BABY BUST,AND THE ECHO GENERATIONS: HOW AGE COMPOSITION REGULATES US MIGRATION*

US regional and state migration data from the 1940s–80s, when members of the baby boom generation aged into their years of peak labor force mobility, suggest ways in which changing age composition regulates geographical mobility and interregional migration. Labor supply pressure plays a key role in the dynamics of the national migration system. A “delayed mobility” effect in the 1980s similar to the delayed fertility of the baby boom cohorts appears to be a result of the depressed rates of mobility experienced by members of this generation when they flooded regional labor markets with record numbers of entrants in the 1970s. Recent temporal shifts in age-specific volumes of interregional migration help predict the future pace of migration based upon the projected age distribution of the nation.     

青藏高原古人类的艺术创作——基于中更新世手脚印形态分析

在第二次青藏科考过程中,作者在西藏自治区拉萨市邱桑村的古泉华沉积上新发现了由5个手印和5个脚印组成 “岩面艺术” （parietal art）。对这一“岩面艺术”进行解剖学测量、3D 模型模拟、铀系测年和手脚印形态分析后,得到以下认识：① “岩面艺术”是在泉华没有成岩之前由古人类有意压上去的;② “岩面艺术”所在岩层的U/Th年代为226~169 ka B.P.,这其中包含一个手指印岩层的表面直接年龄（207~188 ka B.P.）;③ 这一发现是迄今为止发表的古人类在青藏高原上活动的最早记录之一,也为古人类适应高寒、低氧环境提供了新的证据;④ 此岩面艺术是目前世界上已知的最古老的艺术,上面的手印也是古人类留下的最早的手印;⑤ 这一原始的岩面艺术表明,创作它的古老人种可能具有一定的认知和空间感知能力,此岩面艺术的发现也将有可能改写人类艺术史,并且加深我们对已消失的古人类认知水平的认识。     

Mid-infrared, spatially resolved spectroscopy of the nucleus of the Circinus galaxy

High spatial resolution spectroscopy at 8–13 μm with T-ReCS on Gemini-S has revealed striking variations in the mid-infrared emission and absorption in the nucleus of the Circinus galaxy (hereafter Circinus) on subarcsecond scales. The core of Circinus is compact and obscured by a substantial column of cool silicate dust. Weak extended emission to the east and west coincides with the coronal line region and arises from featureless dust grains which are probably heated by line emission in the coronal emission zone. The extended emission on the east side of the nucleus displays a much deeper silicate absorption than that on the west, indicating significant columns of cool material along the line of sight and corresponding to an additional extinction of   A_V ∼ 25 mag  . Emission bands from aromatic hydrocarbons are not subject to this additional extinction, are relatively weak in the core and in the coronal line region, and are much more spatially extended than the continuum dust emission; they presumably arise in the circumnuclear star-forming regions. These data are interpreted in terms of an inclined disc-like structure around the nucleus extending over tens of parsecs and possibly related to the inner disc found from observations of water masers by Greenhill et al..     

Record of Late Pleistocene Glaciation and Deglaciation in the Southern Cascade Range. I. Petrological Evidence from Lacustrine Sediment in Upper Klamath Lake, Southern Oregon

Petrological and textural properties of lacustrine sediments from Upper Klamath Lake, Oregon, reflect changing input volumes of glacial flour and thus reveal a detailed glacial history for the southern Cascade Range between about 37 and 15 ka. Magnetic properties vary as a result of mixing different amounts of the highly magnetic, glacially generated detritus with less magnetic, more weathered detritus derived from unglaciated parts of the large catchment. Evidence that the magnetic properties record glacial flour input is based mainly on the strong correlation between bulk sediment particle size and parameters that measure the magnetite content and magnetic mineral freshness. High magnetization corresponds to relatively fine particle size and lower magnetization to coarser particle size. This relation is not found in the Buck Lake core in a nearby, unglaciated catchment. Angular silt-sized volcanic rock fragments containing unaltered magnetite dominate the magnetic fraction in the late Pleistocene sediments but are absent in younger, low magnetization sediments. The finer grained, highly magnetic sediments contain high proportions of planktic diatoms indicative of cold, oligotrophic limnic conditions. Sediment with lower magnetite content contains populations of diatoms indicative of warmer, eutrophic limnic conditions. During the latter part of oxygen isotope stage 3 (about 37–25 ka), the magnetic properties record millennial-scale variations in glacial-flour content. The input of glacial flour was uniformly high during the Last Glacial Maximum, between about 21 and 16 ka. At about 16 ka, magnetite input, both absolute and relative to hematite, decreased abruptly, reflecting a rapid decline in glacially derived detritus. The decrease in magnetite transport into the lake preceded declines in pollen from both grass and sagebrush. A more gradual decrease in heavy mineral content over this interval records sediment starvation with the growth of marshes at the margins of the lake and dilution of detrital material by biogenic silica and other organic matter.     

Integrated and Participatory Research Approaches towards Sustainable Livelihoods and Ecosystems in Mountainous Regions

Mountainous regions cover about 27 per cent of the world’s land surface and are home to some 22 per cent of the global population (UNEP 2002). A much greater number of people depend on mountain environments for a wide range of services, including clean water, energy, timber, biodiversity, recreation, and protection from environmental hazards, such as landslides and floods. At the same time, mountain areas are extremely vulnerable ecosystems and under continuous threat of environmental degrad…