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51.
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Brian Gulson Karen Mizon Michael Korsch Honway Louie Michael Wu Jenny Stauber J. Michael Davis Alan Taylor 《中国地球化学学报》2006,25(B08):62-62
This is a 4-year longitudinal study to evaluate changes to the environment and exposure of young children associated with the introduction of methylcyclopentadienyl manganese tricarbonyl (MMT) into Australia in 2000. The cohort includes 57 females and 56 males; age range of 0.29 to 3.9 years. Samples are collected every 6 months from children in residences located at varying distances from major traffic thoroughfares in Sydney. Environmental samples: air, house and day care dustfall, soil, dust sweepings and gasoline. Samples from children: blood, urine, handwipes prior to and after playing outdoors, and a 6-day duplicate diet. All samples are analyzed for a suite of 20 elements using ICP-MS. Results are presented for the first three 6-month sampling periods for Pb and Mn. For dustfall accumulation, there was no significant change over the 3 sampling periods (time) for Pb or Mn, and a positive relationship between ‘traffic exposure' (traffic volume and proximity to the road) and Pb but not Mn. For handwipes, Pb and Mn in wipes taken from children after playing outdoors were usually significantly greater than for wipes taken prior to playing. There was no significant association between Pb or Mn in handwipes with traffic exposure. Dustfall accumulation was a significant predictor for Pb in the handwipes, and dust sweepings were a significant predictor of Mn in handwipes. 相似文献
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地方认同是衡量人地情感、理解人与地方认知关系的重要概念,能够反映人地互动的复杂动态关系。企业社区作为重要的城市居住空间,理解居民地方认同对于科学开展城市社区更新、街区振兴与可持续发展具有重要意义。以西安市西北第一印染厂社区为例,采用扎根理论方法,分析社会环境变迁和社区重构影响下,居民个人身份与地方认同的变化及作用机理。研究发现:1)企业社区居民个人身份认同是从单位人向社会人,以及未来作为留守老年群体的转变。2)延续传承的集体记忆维系居民积极式认同,社会交往生疏化和社区管理社会化加剧地方认同弱化,破败的建筑环境和落后的配套设施带来消极式认同。3)居民在生活、成长的企业社区环境和社会互动中构建了自身及对地方的认同,随着外部社会环境与内部居民个体特征而变化。外部社会环境的国企改革、住房改革使企业转轨、社区社会空间转变,加以居住时间差异、个体特征、心理因素与个人经历变化等内部因素,共同塑造居民的地方认同及其变化过程。 相似文献
55.
大别山前寒武纪变质地体基本组成 总被引:5,自引:0,他引:5
本文以新城-圻春断裂为界将大别山前寒武纪变质地体划分为华北陆块南缘和场子陆块北缘两个次级变质地体,两个次级地体不仅在地球物理,构造变形方面明显不同,而且在物质成分上有显著差异,它们有各自独立的变质地层系统,遭受了不同类型的变质作用,有完全不同的岩浆活动图象,上述差异均可指示华北,扬子两古陆碰掸对接时扬子陆块北缘向北俯冲至华北陆块南缘之下,这可能包括两次合作用,从元古代开始至中生代最终结束的长期复杂 相似文献
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A chert-phosphorite unit from the Sugetbrak section in the Tarim Basin was analyzed for rare earth elements (Ce, Eu), redox sensitive proxies, and carbon isotopic compositions (δ13Ccarb and δ 13Corg) in the lower Yurtus Formation of the Early Cambrian period. Redox sensitive element ratios (Th/U, V/Cr, Ni/Co, and V/Sc) were employed to determine the palaeoenvironmental conditions during this period. The ratios indicated that the depositional environment of the chert-phosphorite-black shale unit ranged from suboxic to anoxic. Negative Ce and positive Eu anomalies in the chert-phosphorite assemblages of the studied Yurtus Formation indicated the existence of a redox-stratified ocean, similar to that of South China. Overturn or upward expansion of the deep water-mass probably reached the shallow marine zone after the formation of the Yurtus phosphorites. The characteristics of the negative Ce anomaly may be due to phosphoritic inheritance from the Ce-depleted signature of the overlying water column. Subsequent hydrothermal inputs and reduced detrital supplies of the deep water caused by the upwelling affected certain redox sensitive elements in the sedimentary basin. δ 13Ccarb and δ13Corg negative excursions in the Yurtus chert-phosphorite unit may be related to a transgression phase when episodic basinal upwelling moved 12C- and P-rich waters from the pelagic basin floor to the continental shelf. Although carbon isotopic compositions in the Yurtus chert-phosphorite assemblages may have suffered from diagenetic alteration, they can be used to probe diagenetic conditions. Multi-proxy geochemical studies indicated that the δ 13Ccarb values of the Yurtus chert-phosphorite assemblages might be considered reflections of a predominantly suboxic environment that was subsequently affected by hydrothermal inputs due to the upwelling. 相似文献
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针对当前网络地图服务现状,认为在网络地图服务中引入自适应理论与技术是提升地图服务智能水平与服务质量的一个重要途径.在分析地图可视化领域自适应相关研究基础上,立足于自适应环境和主体多元需求的阶段性改变,梳理与客体相应的自适应因素,提出了网络地图服务自适应层次模型.阐明了该模型中5个自适应层次的关键研究内容及其技术要点,进而探讨了网络地图服务自适应的发展方向. 相似文献
59.
Javier Castro-Larragoitia Utz Kramar Harald Puchelt 《Journal of Geochemical Exploration》1997,58(1):81-91
The Ag---Pb---Zn---Cu---Au mining district of Santa María de La Paz has been extensively exploited for approximately 200 years. Consequences of these activities are several deposits of tailings with high As and heavy metal concentrations, which are completely unstable. The climate is semiarid and as the dumps have no protective cover, material from the dumps is dispersed by strong winds. It is also washed out during seasonally heavy rainfalls. By these processes approximately 100 km2 of surrounding have been contaminated by dump material. The As and heavy metal content of the soils was determined as well as their level in crops (Zea Maize) from agricultural lands in the vicinity of the dumps. In the direction of prevailing winds concentrations up to 1000 ppm Zn, 400 ppm Pb, 16 ppm Cd, 550 ppm Cu and 300 As have been detected in top soils. Using fuzzy cluster analysis the different contamination sources could be identified. Grains of corn from contaminated sites showed no critical concentrations, but leaves which are also used tor fodder, have As-concentrations up to 20 ppm. 相似文献
60.
作物生长岩-土环境中不同存在形态钾素含量动态变化 总被引:1,自引:0,他引:1
以较系统的观测资料,对土壤环境中的缓效态、速效态、水溶态钾素含量的动态变化进行探索.结果表明,缓效态钾的季节性动态变化制约着速效态、水溶态钾的季节性动态变化,但是后两者变化幅度较缓效态钾的大;这种动态变化同时受土壤类型和深度的影响. 相似文献