Radiocesium in North San Francisco Bay and Baja California coastal surface waters

Radiocesium, 137Cs, and rare earth elements (REEs) were determined in suspended material and dissolved fractions of waters across the salinity gradient in North San Francisco Bay (estuary). We describe the variation of this conservative isotope tracer with salinity and sediment load. REE data are used to differentiate marine and terrigenous source terrains for suspended material and dissolved fractions. We estimate that about 1-4 x 10(10) Bq of 137Cs migrates annually on suspended material through the North Bay. In addition, 137Cs concentrations were measured in surface waters off Baja California. Combined in situ water density (sigma(t)) and 137Cs data distinguish between California Current and Gulf of California water, and delineate areas of upwelling, where nutrient-rich, deep Pacific Intermediate water, with little or no 137Cs, is brought to the surface off promontories along Baja California.     

A FINITE ELEMENT MODEL OF CONTAMINANT MOVEMENT IN GROUNDWATER1

ABSTRACT. Transient, two-dimensional solutions are developed which describe the movement and distribution of a conservative substance in a stream-aquifer system. The solutions are obtained by solving sequentially the groundwater flow and mass transport equations. A variational approach in conjunction with the finite element method is used to solve the groundwater flow equation. Galerkin's approach coupled with the finite element method is used to solve the mass transport equation. Linear approximated triangular elements and a centered scheme of numerical integration are employed to calculate the hydraulic head distribution and the concentration of solute in the flow region. The linear approximation used to define the concentration function within each element is not appropriate for cases involving steep concentration gradients. For such cases, higher order approximations are necessary to assure the continuity of gradients across interelemental boundaries. Numerical examples that illustrate the applicability of the model are presented.     

WATER RESOURCES AND HUMAN HEALTH: THE VIEWPOINT OF MEDICAL GEOGRAPHY1

ABSTRACT: Medical geography studies both areal patterns of human health and disease and the environmental and cultural factors that contribute to such conditions. In such studies water resources are of major importance, not only because they are essential for life and their scenic beauty is of inspirational value, but also because they are involved, directly or indirectly, in more than 80 percent of all disease. The direct involvements result from various disease causing agents sometimes found in surface or ground water organic ones such as bacteria, worms, etc., which are known as pathogens, and inorganic ones such as trace elements and synthetic toxic chemicals. Surface waters may have indirect effects also, for they may serve as habitats or breeding places for organisms that do not themselves cause human disease but that serve as vectors or hosts for such pathogens. This paper will discuss these various roles of water resources in both endemic and epidemic disease occurrences and ways in which various human activities domestic, economic, recreational, or religious — increase or reduce our exposure to such diseases.     

Chemical pollution: Transfer of chemical elements to the aboverground phytomass of herbaceous plants

Changes in the species composition and a decrease in species diversity and total plant biomass along the gradient of soil pollution with heavy metals have been shown. Data on the concentrations of chemical elements (Zn, Cu, Cd, Pb, Co, Ni, Mn, Cr, and Fe) in the aboveground organs of herbaceous plants and the biomass of each species make it possible to estimate the role of higher producers in the incorporation of chemical elements into biogenic cycles in background zones and under conditions of chemical pollution. Plants of the composite family (Asteraceae) play the main role in accumulation of chemical elements. The results obtained indicate that natural ecosystems have mechanisms limiting excessive accumulation of chemical elements into the aboveground plant biomass.     

Development and Validation of the Total HUman Model for Safety (THUMS) Toward Further Understanding of Occupant Injury Mechanisms in Precrash and During Crash

Objective: Active safety devices such as automatic emergency brake (AEB) and precrash seat belt have the potential to accomplish further reduction in the number of the fatalities due to automotive accidents. However, their effectiveness should be investigated by more accurate estimations of their interaction with human bodies. Computational human body models are suitable for investigation, especially considering muscular tone effects on occupant motions and injury outcomes. However, the conventional modeling approaches such as multibody models and detailed finite element (FE) models have advantages and disadvantages in computational costs and injury predictions considering muscular tone effects. The objective of this study is to develop and validate a human body FE model with whole body muscles, which can be used for the detailed investigation of interaction between human bodies and vehicular structures including some safety devices precrash and during a crash with relatively low computational costs.

Methods: In this study, we developed a human body FE model called THUMS (Total HUman Model for Safety) with a body size of 50th percentile adult male (AM50) and a sitting posture. The model has anatomical structures of bones, ligaments, muscles, brain, and internal organs. The total number of elements is 281,260, which would realize relatively low computational costs. Deformable material models were assigned to all body parts. The muscle–tendon complexes were modeled by truss elements with Hill-type muscle material and seat belt elements with tension-only material. The THUMS was validated against 35 series of cadaver or volunteer test data on frontal, lateral, and rear impacts. Model validations for 15 series of cadaver test data associated with frontal impacts are presented in this article. The THUMS with a vehicle sled model was applied to investigate effects of muscle activations on occupant kinematics and injury outcomes in specific frontal impact situations with AEB.

Results and Conclusions: In the validations using 5 series of cadaver test data, force–time curves predicted by the THUMS were quantitatively evaluated using correlation and analysis (CORA), which showed good or acceptable agreement with cadaver test data in most cases. The investigation of muscular effects showed that muscle activation levels and timing had significant effects on occupant kinematics and injury outcomes. Although further studies on accident injury reconstruction are needed, the THUMS has the potential for predictions of occupant kinematics and injury outcomes considering muscular tone effects with relatively low computational costs.     

突发事件情景演化及关键要素提取方法

针对突发事件应急处置难度大的特点,突发事件应急管理模式必须向"情景-应对"转变。从系统复杂性、开放式预先设想以及序贯性三个主要原则的角度理解突发事件情景演化的机理,构建了突发事件情景演化系统模型,并以此为基础设计了突发事件情景网络关键要素的提取方法。该方法以危险源形成、突发事件演化以及应急响应三方面主要内容为情景网络的主体,以三方面主要内容所涉及的影响因素为分支,适当的选取情景网络关键要素并将关键要素分为四类。该方法的提出弥补了情景网络关键要素提取方法理论的空白,为突发事件情景构建提供了理论支持。     

Trace elements in particulate matter of ambient air at petroleum filling stations

Size segregated suspended particulate matter (PM_2.5 and PM_10-2.5) in air at four major petroleum-filling stations in Ile-Ife, Nigeria, were monitored using double staged “Gent” stacked samplers to assess variations in mass loads and elemental concentrations of 25 elements. Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr, Cs, Ta, W, and Pb were determined in both fractions by external ion beam proton-induced X-ray emission technique. Enrichment factors and pollution indices were calculated and results revealed that most elements were anthropogenic in both fractions with concentrations exceeding the World Health Organization guideline standards.     

北京河流水污染现状分析研究

通过总结近年来北京河流中氮磷、有机质和重金属等方面的研究成果,结果表明北运河水系各河段水质均较差,劣Ⅴ类水质的河流长度超过80％,城市河流污染特征明显,主要污染指标为耗氧型有机污染物和氨氮,重金属污染较轻,悬浮物中的重金属占较大的比重;永定河水系枯水期氮污染较重,主要是硝态氮超标,以颗粒态磷为主要形式的磷污染较轻,重金属含量大都低于地表水Ⅲ类标准;潮白河水系水质较好,各水质指标除个别断面外大都满足中Ⅲ类水标准,重金属含量大都符合Ⅰ～Ⅲ类水标准。     

微波消解－ICP－MS法测定土壤中稀土元素的研究

建立了电感耦合等离子体质谱（ ICP－MS）测定土壤中稀土元素的分析方法。采用HNO3＋HF酸体系用微波消解对土壤样品进行处理,以混合内标（ In、Bi）校正基体干扰和信号漂移,用ICP－MS对其中的16种稀土元素进行了测定。在优化的实验条件下,16种稀土元素标准曲线的相关系数r＞0．9999,检出限为0.012 ng／ml～0.069 ng／ml,加标回收率为84.0％～110％,相对标准偏差（n＝6）RSD均小于3.5％。该方法可用于四种不同类型土壤中稀土元素含量的测定。     

基于两种样品前处理方法对比研究小冬克玛底冰川雪坑中痕量元素

通过对唐古拉山小冬克玛底冰川雪坑中非季风季节沉积的雪样分别进行酸化处理和消解处理后,利用高分辨扇形磁场等离子体质谱仪(ICP-SFMS)测试了样品中19种痕量元素(Ba、U、Sr、Rb、Tl、Mo、Cs、Pb、Sb、V、Cr、Mn、Fe、Co、Al、Cu、Ti、Li、As)的酸化浓度和总浓度.研究结果表明,痕量元素浓度的变化范围较大,元素Al的最大/最小浓度比为326(酸化浓度)和465(总浓度),元素Pb相应比值为27和48.雪冰中痕量元素的总浓度一般大于该元素的酸化浓度,其中,元素Pb、Fe、Sb、Ba、Al、Ti的酸化浓度占总浓度的平均比值分别为91%、76%、60%、52%、33%和21%.一般地,样品中不溶微粒含量越大,酸化浓度占总浓度的比值越小;不溶微粒含量越小,则相反.对痕量元素的富集系数(EF)分析表明,各元素总浓度EF均值小于酸化浓度EF均值,揭示了用酸化浓度计算EF存在对痕量元素人为来源影响的高估.人类排放是小冬克玛底冰川中痕量元素的来源之一,对于元素Mo和Sb,人类排放估计是主要来源.利用后向轨迹模型模拟出小冬克玛底冰川雪冰中痕量元素在非季风季节主要来源于青藏高原西部及中亚中东地区.