塔克拉玛干沙漠腹地沙尘暴过程大气颗粒物浓度及影响因素分析   总被引：1，自引：0，他引：1  

刘新春  钟玉婷  何清  艾力·买买提明 《中国沙漠》2011,31(6):1548-1553

利用Grimm1.108、Thermo RP 1400a、TSP以及CAWS-600等仪器,对2008年4月17日至23日发生在塔克拉玛干沙漠腹地的1次强沙尘暴过程的颗粒物质量浓度进行连续观测,结合天气资料分析得出:①Grimm1.108颗粒物分析仪监测结果表明,日平均浓度出现两个峰值区,主峰值出现在20日,次峰值出现在18日,而小时平均浓度高值区主要集中4月19日至20日,21日中午存在1个峰值区,其他时段浓度相对较低。②强沙尘暴发生时的分钟观测数据表明,随着风速的逐渐增强,沙尘暴强度逐渐增强,不同粒径颗粒物浓度达到最大值,>0.23 μm颗粒物总浓度为39 496.5 μg·m-3,>20.0 μm颗粒物总浓度为5 390.7 μg·m-3,随后浓度逐渐下降。③PM10和TSP的浓度变化同样反映沙尘天气的过程和强度,沙尘暴前期大气中颗粒物浓度远低于强沙尘暴期间,随沙尘天气减弱,颗粒物浓度明显下降。④沙尘天气过程中大气颗粒物浓度变化具有以下规律：晴天<浮尘天气<浮尘、扬沙天气<沙尘暴天气。风速大小直接影响大气中颗粒物浓度,风速越大颗粒物浓度越高。气温、相对湿度和气压是影响沙尘暴强度的重要因素,也间接影响大气中颗粒物浓度的变化。  相似文献   

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李伟伟  沈云中 《大地测量与地球动力学》2010,30(6):57-59

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Blasius方程中临界值的分析估计     

陆中会  胡敏 《成都信息工程学院学报》2010,25(3):333-335

证明了流体力学边界层理论中著名的Blasius方程的一个新性质,它在二维平板流的研究中具有重要的作用,由此建立它的积分形式,并给出方程中的临界值βc的分析估计。  相似文献   

The fluvial flux of particulate organic matter from the UK: the emission factor of soil erosion   总被引：1，自引：0，他引：1       下载免费PDF全文

Fred Worrall  Tim P. Burt  Nicholas J.K. Howden 《地球表面变化过程与地形》2016,41(1):61-71

Soil erosion has been identified as a potential global carbon sink since eroded organic matter is replaced at source and eroded material is readily buried. However, this argument has relied on poor estimates of the total fate of in‐transit particulates and could erroneously imply soil erosion could be encouraged to generate carbon stores. These previous estimates have not considered that organic matter can also be released to the atmosphere as a range of greenhouse gases, not only carbon dioxide (CO₂), but also the more powerful greenhouse gases methane (CH₄) and nitrous oxide (N₂O). As soil carbon lost by erosion is only replaced by uptake of CO₂, this could represent a considerable imbalance in greenhouse gas warming potential, even if it is not significant in terms of overall carbon flux. This work therefore considers the flux of particulate organic matter through UK rivers with respect to both carbon fluxes and greenhouse gas emissions. The results show that, although emissions to the atmosphere are dominated by CO₂, there are also considerable fluxes of CH₄ and N₂O. The results suggest that soil erosion is a net source of greenhouse gases with median emission factors of 5.5, 4.4 and 0.3 tonnes CO_2eq/yr for one tonne of fluvial carbon, gross carbon erosion and gross soil erosion, respectively. This study concludes that gross soil erosion would therefore only be a net sink of both carbon and greenhouse gases if all the following criteria are met: the gross soil erosion rate were very low (<91 tonnes/km²/yr); the eroded carbon were completely replaced by new soil organic matter; and if less than half of the gross erosion made it into the stream network. By establishing the emission factor for soil erosion, it becomes possible to properly account for the benefits of good soil management in minimizing losses of greenhouse gases to the atmosphere as a by‐product of soil erosion. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

贵州省铜仁市地质灾害发育分布特征及形成条件浅析   总被引：1，自引：0，他引：1  

麻秋景  黄会 《贵州地质》2009,26(2):154-159

本文针对铜仁市滑坡、崩塌、泥石流等地质灾害发育类型、分布特征及其形成条件进行分析,探讨在山间盆地分布区地质灾害产生的原因及治理措施。  相似文献   

河流活性物质入海通量:初步成果   总被引：2，自引：0，他引：2       下载免费PDF全文

孙彬彬  周国华  魏华铃  刘占元  曾道明 《地学前缘》2009,16(2):361

河流是陆地与海洋相互作用的重要纽带,查明陆地河流活性物质入海通量是当前生态地球化学评价的一项重要任务。文中选择了中国东部入海河流中主要的35条河流,分丰、枯水期系统采集了悬浮物、过滤水、底泥等样品,利用河流径流量参数,计算得到了各河流主要重金属及营养元素的年入海通量及陆地河流年入海总通量,确定了各元素水溶态及悬浮物态迁移入海量的比例,为陆海相互作用研究、浅海生态地球化学评价提供了重要依据。  相似文献   

5.12汶川地震对都汶公路(G213)沿线土地破坏及损失评价     

庄建琦  葛永刚 《地质科技情报》2009,28(2)

5.12汶川地震及其次生山地灾害对灾区的土地资源造成了严重破坏,损失巨大.以重灾区都汶公路沿线为研究对象,通过野外实际调查,利用遥感影像解译和土地利用资料,探讨了地震引起的崩塌、滑坡等次生山地灾害对土地利用的破坏方式和特征,次生山地灾害以移动破坏、淤埋破坏和拉裂破坏3种形式破坏土地资源,并对土地利用损失进行了评估.结果表明:①各种土地利用类型中,淤埋破坏是最主要的破坏形式,占总破坏面积的77.23%,移动破坏面积占总破坏面积的22.77%;②林地和草地破坏呈现出在缓坡地带和陡坡地带破坏比例高,在中间地带破坏比例低的规律,旱地破坏具有随着坡度的增大而加剧的趋势;③研究区内各类土地利用类型总损失价值达76 577.26万元,其中林地损失量最大,占总损失价值的87.18%,是地震引起崩塌、滑坡灾害损失的主要对象.  相似文献   

Compact,concurrent, and contiguous: smart growth and 50 years of residential planning in the Toronto region     

Paul Mitchell Hess  André Sorensen 《Urban geography》2013,34(1):127-151

In this article, we use parcel-based land-use data to analyze 50 years of residential development in the Toronto region. We test two hypotheses: (1) Toronto’s form does not conform to conventional definitions of suburban sprawl and (2) Toronto’s suburban development shows high levels of continuity over time with relatively high densities and mixed housing types. Contrary to recent research suggesting a convergence of urban forms among North American metropolitan regions, Ontario’s robust planning system has created a distinctive, highly consistent pattern of residential development that has, for half a century, achieved many of the core goals of smart growth including relatively compact, contiguous, and concurrent development. This form continues to be automobile dependent, however, and is not producing many of the benefits ascribed to smart growth. Rather than continuing to adopt United States-inspired smart growth policies, a more ambitious set of initiatives will be required to address current regional challenges.  相似文献   

Whither the Jobs: Identifying Concentrations of Employment in Metropolitan Areas     

Todd K. Gardner  Matthew Marlay 《Urban geography》2013,34(6):795-814

Large concentrations of employment have developed outside traditional central business districts. Our research focuses on analyzing the changing distribution of employment in metropolitan areas by using tract-to-tract commuting data from Census 2000 to identify high-employment nodes within large metropolitan areas. We propose a new way to delineate clusters of contiguous high-employment tracts based on the job density in these areas. We then compare outlying employment clusters with traditional central business districts and contrast employment clusters of varying job densities. Our method has several advantages over existing methods of identifying employment clusters: it is conceptually simple, can use publicly available data, relies on a standardized geographic unit applicable across the entire United States, and offers the ability to examine data from multiple census years.  相似文献   

The Spatial Restructuring of Population in Metropolitan Beijing: Toward Polycentricity in the Post-Reform ERA     

《Urban geography》2013,34(7):779-802

Based on data from the third (1982), fourth (1990), and fifth (2000) Population Census of China, this research examines the changing patterns of population distribution in the Beijing metropolitan area in the post-reform era. In the mid-1980s, China launched a series of urban land use reforms aimed toward achieving a market economy. A direct impact of these reforms in Beijing was the restructuring of land uses, evidenced by the relocation of central-city residents to the suburbs to make room for commercial development. This residential suburbanization trend emerged during the 1980s and accelerated in the 1990s. Population change rates varied significantly across subdistricts, and variation was much greater in the 1990s than in the 1980s, indicating an increasingly diverse set of growth trajectories across metropolitan Beijing over time. Various population density functions are tested. The population density pattern is best characterized by a monocentric model in 1982, a dual-centered model in 1990, and a seven-centered model in 2000. This transition in Beijing's urban form toward polycentricity is similar to trends in most Western cities.  相似文献