Distribution and bioaccumulation of polychlorinated biphenyls and organochlorine pesticides residues in sediments and Manila clams (Ruditapes philippinarum) from along the Mid-Western coast of Korea

The distribution and bioaccumulation features of PCBs, DDTs, and HCHs were investigated in the sediments and Manila clams collected from along the Mid-Western coast of Korea. The measured concentrations of ΣPCBs, ΣDDTs and ΣHCHs were 1.08–3.5, 0.12–0.35 and 0.090–0.30 ng g⁻¹ dw in sediment, and 33–390, 7.4–46 and 6.3–27 ng g⁻¹ lipid in Manila clam, respectively. Their levels were found to be relatively lower than those of other contaminated areas and the consumption of Manila clam from these areas seems to be safe for human health according to calculated lifetime cancer risk and hazard indices. The ΣPCBs and ΣDDTs concentrations in sediments showed a significant relationship to those in clams. The significant correlation was observed between BSAF in clams and K_ow for each PCB congeners and DDT metabolites. These findings support that the PCBs and DDTs levels, which are highly hydrophobic chemicals, in clam reflect the sediment pollution through bioaccumulation.     

回转椭球电场问题一种新解法

讨论关于回转椭球静态场求解的一般方法，借助回转椭圆坐标系，静态场问题的一般解可以用实宗量和虚宗量勒让德函数以及余弦函数形式表出，使得结果更为简明和系统化。所得结果可以直接应用到椭球导体电场、尖端效应、介质椭球极化以至双极化雷达测量降水问题等，具有相当具体的实用价值。     

Comparative study on CO_2 emissions from different types of alpine meadows during grass exuberance period

1IntroductionTherisingatmosphericgreenhousegaseswerebelievedtobetheprimarycauseofglobalclimatechange(Tettetal.,1999;Crowley,2000).Amongthegreenhousegases,theconcentrationofatmosphericcarbondioxidehasincreasedfrom280ppmsincepre-industrialtimestocurrent355ppm,whichaccountedfor50%ofthetotalgreenhouseeffect(Nefteletal.,1985;Friedlietal.,1986;Rodhe,1990;Fanetal.,1998).ElevatedCO2hasamarkedeffectonterrestrialecosystemprocesses(Melilloetal.,1996).TheQinghai-TibetPlateau,thelargestgeomorphologica…     

Characteristics of atmospheric dust deposition in snow on Glacier No. 4, Mt Bogeda, China

Wind-blown mineral dust derived from the crustal surface is an important atmospheric component affecting the Earth’s radiation budget. Deposition of dust particles was measured in snow on the Glacier No. 4, Mt Bogeda, in the eastern Tian Shan, China. The mean number concentration of dust particles with 0.57 < d < 26 μm in the snowpack is 279 × 10³ mL^?1, with a mean mass concentration of 1,480 μg kg^?1. Dust number size distribution showed the dominant particles with d < 2 μm, while volume size distribution showed single-modal structures having volume median diameters from 3 to 25 μm. Results were compared with the data from other sites in the Tian Shan and various northern hemisphere sites. A backward trajectory model was also employed to examine the transport process of dust particles in this region. Most of the air mass originated from the southern and northwestern regions, e.g., the Taklimakan and Gurbantunggut deserts in springtime, during the Asian dust period, which may bring plentiful aerosol dust particles from the sandy deserts. Transport of dust from western Chinese deserts to adjacent mountains is in agreement with a growing body of evidence on the importance of dust inputs to alpine regions.     

西藏“一江两河”中部流域地区土地沙漠化防治目标,对策与治沙工程布局

西藏“一江两河”中部流域地区是我国沙漠化强烈发展的地区之一。根据“一江两河”综合开发部署和沙漠化的实际状况，制定了本区沙漠化防治的目标、对策和治沙工程布局。“八·五”、“九·五”期间治理沙漠化土地８．４６万ｈａ。治沙工程实施后，综合效益指数将比１９９０年提高３３．７％，系统功能状况与效益水平在整体上提高１／３。     

若干特殊地表风蚀的风洞实验研究

经风洞模拟实验,本文对四种特殊地表在净风和挟沙风情况下的风蚀特性,进行了定量的研究。揭示了原始地表结构受人为破坏后,其抗风蚀能力急剧降低的特点。探讨了风成沙粒配、戈壁风蚀平衡与风蚀有关的几个问题。     

土钉与锚杆联合支护在深基坑工程中的应用

结合深圳市星海阁办公楼的工程实例,从周边环境对深基坑支护的特殊要求及复杂的地质条件出发,论述了采用土钉与锚杆联合支护形式的依据.介绍了在深基坑支护施工中采取的具体措施后期效果.同时分析了这种联合支护结构形式的力学特点,通过将两者联合使用,可实现锚杆支护结构水平侧移小和土钉支护结构受力合理的优点.且土钉与锚杆联合支护,使得上部锚杆和中下部的土钉墙两者形成了统一的受力整体,共同抵抗荷载和变形.     

城市群演化的空间过程及土地利用优化配置

城市群演化包含了诸多内容 ,如人口、产业、城市类型、城市职能等 ,而空间过程是最直接、最综合的表现。     

Geospatial spreadsheets with microscale air quality visualization and synchronization for supporting multiple-scenario visual collaboration

A major obstacle of the interdisciplinary communications for decision-making is that each participant prefers the solution from their own area because current collaboration systems cannot effectively mediate among many alternatives. If a visual collaboration system could display multiple alternatives in a single visual presentation, users would be able to compare alternatives with only a few variables, where all other parameters are fixed, at least from a visual perspective. In this study, we developed a visualization tool to support a microscale air quality (MSAQ) management group, the members of which often need to compare the effects of many alternative control methods. The main achievements of this study are: (1) three-dimensional (3D) visualization of the MSAQ using a 3D city model and (2) development of a geospatial spreadsheet (GS) to facilitate visual comparisons, thereby improving decision-making by making it easy to compare differences based on realistic visual display items. A questionnaire-based survey showed that use of the GS could generate a shared perspective and provide a spatiotemporal context for the participants, thereby making it easy to compare, mediate and reach decisions when confronted with many alternatives.