Pathways of multiple inflows into a stratified reservoir: Thomson Reservoir, Australia

The interaction of multiple inflows entering a reservoir (Thomson Reservoir, Australia) is investigated with a field experiment and three-dimensional numerical model simulations. The focus of the study is the mixing and transport patterns within the reservoir of the inflowing water. Data from the field experiment showed the existence of multiple inflows intruding horizontally into the reservoir immediately below the thermocline and selectively propagating into the reservoir at a depth determined by the individual density of each inflow. The results serve to show that inflows slot into a stratified reservoir in an orderly fashion, their depth dependent on the separation of inflow densities and reservoir bed, with minimal mixing between intrusions. Inflows thus do not take their nutrient load into the reservoir as a whole, but rather slot their load into an intrusion layer at an appropriate depth. Nutrients brought in via inflows become accessible only when vertical mixing, either directly at the base of the surface layer, or indirectly via the benthic boundary layer flux, transports the intrusion waters into the surface layer.     

Spatio-temporal occurrences and mineralogical–geochemical characteristics of airborne dusts in Khuzestan Province (southwestern Iran)

Dust storms in Khuzestan province (Iran) are causing problems in industries and human health. To mitigate the impact of those phenomena, it is vital to know the physical and chemical characteristics of airborne dusts. In this paper, we give an overview of the spatio-temporal occurrences and geochemical characteristics of airborne dusts in Khuzestan. Meteorological data from 10 stations in Khuzestan during 1996–2009 indicate (a) an average of 47 dust storm days per year, (b) a lowest annual average of 13 dust storm days in 1998, (c) a highest annual average of 104 dust storm days in 2008, and (d) an average increase of two dust storm days per year. Above-average number of dust storm days usually occurred in the cities of Dezful, Ahvaz, Masjed-e-Soleiman, Abadan and Bostan, whereas below-average number of dust storm days usually occurred in the cities of Mahshahr, Ramhormoz, Behbahan, Shoushtar and Izeh. XRD analyses of airborne dust samples collected in 2008 and 2009 show that the mineralogy of airborne dusts is dominated by calcite, followed by quartz and then kaolinite, with minor gypsum. SEM analyses of the samples indicate that airborne dusts have rounded irregular, prismatic and rhombic shapes. The sizes of airborne dusts vary from 2 to 52 μm, but 10 to 22 μm are the dominant sizes. The smallest and largest dust particles are clays, sulfates or carbonates. XRF and ICP analyses of the samples show that the most important oxide compositions of airborne dusts are SiO₂, Al₂O₃, Fe₂O₃, CaO and MgO. Estimates of enrichment factors (EF) for all studied elements show that Mn, Hf, U, Sc, K, V and Sr, with EF < 10, are of natural origin, whereas Na, Ni, Co, Ba and Cr, with EF > 10, are of anthropogenic origin. Flat REE patterns with depletion in Th, V, Nb, Zr and enrichment in Al, Rb, Sr and Mn indicate that airborne dusts in Khuzestan come from the same source, which is likely an eroded sedimentary environment outside Iran. In general, airborne dusts in Khuzestan are geochemically similar to airborne dusts elsewhere in the world.     

大亚湾核电站周围海域水生生物人工放射性核素辐射剂量率的蒙特卡罗计算

为了定量研究核电站液态流出物对水生生物的辐射,建立了核电站周围海域水生生物辐射剂量模型,用MCNP程序对大亚湾l1种辐射参考生物的人工核素辐射剂量率进行了计算．生物体建模时采用2个椭球体模型,分别模拟全身和器官团．选取了对生物影响最大的9种人工核素作为源项逐一模拟．最后以”’Cs、”Sr、…“Ag三种核素为例,根据其海水中的比活度计算出生物的吸收剂量率．结果表明在正常工况下大亚湾水生生物受到的辐射剂量是安全的,而且生物浓缩核素的内照射贡献了98％以上的辐射剂量．即使是在非正常工况下,海水中放射性核素含量升高,但只要比活度尚未超过海水水质标准的比活度限值,水生生物受到的剂量（最大剂量约3．420mGy／a）仍然是安全的．本研究结果可用于评价核电站对海域生态环境的景;响。以及水生物种的辐射防护工作．     

Subseabed disposal of radioactive waste: effects of consolidational fluid flow

Subseabed disposal of radioactive waste applies a multiple-barrier concept with the sediment being the most important barrier for preventing a release of nuclides into the biosphere. While many investigations have been carried out to analyze the risk potential in this type of disposal, the effects of sediment consolidation and associated fluid flow have not fully been taken into consideration. Here, possible effects of consolidational fluid flow in the penetrator disposal option and possible consequences to the transport of nuclides in the sediment are analyzed. Results of numerical experiments demonstrate that consolidation contributes to the transport of radioactive nuclides released from containers buried in the sediment and to the release of nuclides at the sediment-water interface. Both depend on geological conditions and to a large extent on possible alterations of hydraulic conductivity i of the sediment in the vicinity of the entry path of a penetrator.Symbols c concentration ml m^–3 - c _a concentration of adsorbed solute mg kg^–1 (relative to dry weight of sorbing substance) - c _in solute concentration of source q mg m^–3 - c ₀ initial concentration mg m^–3 - ID dispersion tensorm ²s^–1 - ID ^* diffusion tensor m²s^–1 - D coefficient of dispersion m²s^–1 - d ₀ coefficient of molecular diffusion m²s^–1 - d coefficient of effective diffusion m²s^–1 - g gravity m²s^–1 - h piezometric pressure m - k hydraulic conductivity m²s^–1 - m mass kg - p pressure Pa - q source/sink m³s^–1 - S ₀ specific surface m²m^–3 - t time s - v velocity m s^–1 - x, z cartesian coordinates m - compressibiliy of sediment m²N^–1 - _L longitudinal dispersivity m - effective porosity (decimal fraction) - density kg m^–3 - _s density of sediment kg m^–3 - _w density of water kg m^–3 - decay constant per s - kinematic viscosity m²s^–1     

地理学基本规律及其对社会发展的影响

地理学是自然科学与社会科学的汇合,是一门独立科学,有特定的功能和演变规律。地理学的基本规律包括有地域分异规律、地域综合规律和地域发展规律等。研究地理学的基本规律有助于认识许多复杂的历史事件和社会活动,对构建社会建设的总体思想和区域发展战略有重要指导意义。     

300°～500℃锌在含氯、氟溶液中的溶解度

实验在300°～500℃,1Kb,用C-CO_2 Ni-NiO作缓冲剂控制fo_2条件下对ZnS在不同浓度、不同pH值的NaCl-H_2O和NaF-H_2O体系中的溶解度进行研究,同时对ZnCl_2在临界条件不同浓度NaCl溶液中迁移能力进行实验,通过实验结果热力学计算和分析,讨论了温度、介质种类、溶液浓度、pH值等影响Zn溶解度的各种主要因素:确定500C 1kb,Zn在含Cl溶液中主要以ZnCl_2~0形式存在.其标准生成自由能△G_(1.ZnCl_2~0)~0 =161.902kJ/mol;F~-对ZnS比Cl~-对ZnS的溶解能力大,在临界条件均一相中、ZnCl_2~0全部汽化迁移,依据实验数据,建立了Zn溶解度函数关系,使特定条件下的实验数据更具普遍意义.     

论经济地理研究中的运输化问题

本文提出运输化是工业化的重要特征,也是伴随工业化而发生的一种经济过程,经济发展的运输化过程受一定客观规律的支配。应当重视运输化进程与生产力布局、经济空间结构改善之间的关系,把对不同区域运输化发展水平及运输化进一步走向的分析,与经济发展规划结合起来。     

人口地理学的研究进展

本文系统回顾了国外及我国人口地理学的发展过程和研究现状与趋势，并指出了我国的人口地理学研究与西方发达国家之间存在的主要差距，以及我国人口地理学今后发展的主要方向。     

区域客流分布模型的研究

通过O-D调查虽可以取得区域之间的客流量,但因需要投入大量的人力和资金,不可能进行经常性和全覆盖的调查,而且从抽样调查得出分析结果往往有一段时滞。因此,寻求区域之间客流联系的一般规律,利用有限的客流统计资料,借助数学模型来模拟和预测区域间的客流联系成为取得客流分布的一种重要手段。本文通过中国省区之间客流联系和辽宁省内客流联系的分析,对区域客流联系的模型和方法进行了研究。     

珠三角外围地区农村回流劳动力的就业选择及影响因素

在农村劳动力持续外流的同时,农村地区的劳动力存在着弱回流,农村回流劳动力对乡村振兴与重构极为重要。基于珠三角外围地区不同地域类型的15个村的问卷调查资料,采用Logistic回归模型,对农村回流劳动力的就业选择特征及非农就业的影响因素进行综合分析。研究发现：① 外出务工的工资性收入的资本积累,是返乡从事零售、杂货、服装和个体修理等个体经营的基础,非农就业在空间选择上倾向于中心镇或县（区）。② 农村人口外流致使农村地域的人地关系发生显著变化,农地生计保障性功能弱化,农地规模经营的租种成本降低,部分农村回流劳动力选择从事农业生产,主要以种植经济果林、药材为主,助推了农用地非粮化。③ 农村回流劳动力的非农就业受到个人特征、家庭特征、村庄特征等多元因素影响。在个人特征方面,年龄越小、受教育程度越高的回流者从事非农职业的倾向性越大;在家庭特征方面,家庭务农人数与务工人数越少、农田面积越小的回流劳动力倾向于从事非农职业;在村庄特征方面,不同县域的农村劳动力就业倾向差异较大,距离县城越近的农村劳动力从事非农职业的几率越大。县域村镇体系的中心地发展与规划建设是乡村转型发展的关键地域节点。