Organochlorine pesticides in soil and air at and around a compound contaminated site: vertical distribution,soil–air exchange and risk evaluation

The control of soil pollution in China has become an issue, and in this study, a compound contaminated site was selected and focus on the site and its nearby environment, organochlorine pesticides (OCPs) were investigated in both soil (top and deep soil) and air samples. The main pollutants in top soils at site are dichlorodiphenyltrichloroethane (DDTs, 0.05–104 mg/kg d.w., avg: 14.5 mg/kg d.w.) and hexachlorobenzene (HCB, 0.02–4.85 mg/kg d.w., avg: 0.72 mg/kg d.w.) which is in accordance with its production history. As for the deep soils, ΣOCPs at site were found concentrated at workshops especially the technical pesticide workshop (5.29–22.1 mg/kg d.w., avg: 9.15 mg/kg d.w.) and the history DDTs’ workshop (4.00–64.8 mg/kg d.w., avg: 20.4 mg/kg d.w). Around site, OCPs were mainly concentrated at layers of −20 cm and the −40 cm and decreased with distance being far away, at 5000 m, the ΣOCPs was comparable with normal agriculture soil (22.1−91.4 ng/g d.w., avg: 55.4 ng/g d.w.). ΣOCPs in the air samples ranged 64.6–823 ng/m³ (avg: 459 ng/m³) at site and 9.93–176 ng/m³ (avg: 50.8 ng/m³) around site which are all dominated with DDTs and HCHs. Soil–air exchange fugacity was calculated to judge the transportation of the OCPs and the results showed soils at the site and its nearby areas (within 5000 m) are releasing most of the OCPs into air, and accordingly through evaluation, inhalation was found to be the major source for human health risk, which is a great threat to the workers at site and the nearby residents.

     

通过滑面应力状态评价滑坡稳定性

以黄河上游某大型滑坡为例,研究了有限元法在评价滑坡稳定性中的应用。具体操作过程是：建立滑坡的有限元模型,求出滑面上的应力状态,计算滑面上总的抗滑力与总的滑动力之比,最后评价滑坡的稳定性。通过对黄河上游某大型滑坡比较研究发现,采用有限元法比传递系数法得出的稳定性系数高0．07,这种差异属允许差异范围。采用有限元法计算该滑坡在天然与地震两种条件下的稳定性系数分别为1．14和1．1,可以认为滑坡在两种条件下的稳定性较好。该方法原理正确、操作简单、结果可信度高,有一定的适用价值。     

基于手机位置数据的地震灾情指标选择

选取四川阿坝州九寨沟县MS7.0地震、新疆博尔塔拉州精河县MS6.6地震、四川广元市青川县MS5.4地震作为案例分析,绘制活跃Wi Fi数量、无线网络联网设备数量、汇总在线设备数量、活跃基站数量等4种地震灾情指标在地震发生前后数量变化的折线图。根据与地震前1天变化情况的对比分析,验证地震灾情指标的可用性,选取出效果好的指标,这对进一步研究震后快速获取极震区位置、影响场方向等具有重要意义。     

Adsorption characteristics of copper ion on nanoporous silica

Adsorption by nanoporous media is critically involved in many fundamental geological and geochemical processes including chemical weathering,element migration and enrichment,environmental pollution,etc.Yet,the adsorption behavior of metal ions on nanoporous materials has not been systematically investigated.In this study,MCM-41 material with a monodisperse pore size(4.4 nm)and a large BET specific surface area(839 m^2/g)was hydrothermally prepared and used as a model silica adsorbent to study the adsorption characteristics of Cu^2+as a representative metal ion.The Cu^2+adsorption capacity was found to increase with increasing suspension pH in the range from 3 to 5 and to decrease in the presence of NaNO3.At 25℃,pH=5,and a solid-to-liquid ratio of 5 g/L,the adsorption capacity was determined to be 0.29 mg/g,which can be converted to a dimensionless partition coefficient of 45,indicating a strong enriching effect of nanoporous silica.The adsorption isotherm and kinetic data were fitted to several commonly used thermodynamic,kinetic,and diffusion models.The adsorption mechanism was also studied by Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy and synchrotron-based X-ray absorption spectroscopy.The results suggest that Cu2+ion adsorption is an entropy-driven endothermal process,possibly involving both outer-sphere and inner-sphere complexes.     

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CICE5.0与BCC_CSM2.0模式的耦合及对北极海冰的模拟评估

本文将美国Los Alamos国家实验室发展的最新海冰模式CICE5.0引入国家气候中心气候系统模式BCC_CSM2.0,替代原有的海冰模式SIS,形成一个新的耦合模式。在此基础上,评估新耦合模式对1985-2009年北极海冰的模拟性能,检验引入CICE5.0后对耦合模式中北极海冰、海洋和大气模拟结果的改进。结果表明,引入CICE5.0后,模式能较好地模拟出北极海冰的空间分布、季节以及年际变化特征。相比于旧版本耦合模式,新耦合模式模拟的北极多年冰增多、一年冰减少,同时,海冰增厚、海冰流速减慢,模拟效果得到显著改进,对波弗特涡流模拟的改善尤为明显。进一步分析发现,相比于SIS,CICE5.0对北极海冰特别是海冰厚度模拟性能的提升,在耦合进入BCC_CSM2.0后,会触发冰-温的正反馈机制,改进了模式对海平面气压场、表层气温和海表温度的模拟,由此进一步提高了模式对北极海冰的模拟能力。     

Dye adsorption on electrochemical exfoliated graphene oxide nanosheets: pH influence,kinetics and equilibrium in aqueous solution

Graphene oxide nanosheets were synthesized by electrochemical exfoliation. X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectrometry and Fourier transform infrared spectrometry were used to characterize crystal structure, particle size, thickness and function groups of the nanosheets. The nanosheets were examined for adsorption of methyl orange, an anionic dye, in aqueous solution at different pHs and temperatures. The maximum adsorption capacity of methyl orange on graphene oxide nanosheets obtained from the Langmuir isotherm was 138.69 mg/g at pH 2.0, which is larger than that of other carbonaceous adsorbents. The large adsorption affinity of graphene oxide nanosheets to methyl orange might be due to the presence of hydrogen bonding and π–π interaction between methyl orange and graphene oxide nanosheets. Adsorption kinetics followed a pseudo-second-order kinetic model, and the isotherm adsorption results were fitted with Langmuir isotherm model in a monolayer adsorption manner. The thermodynamic studies indicated that the adsorption reaction was a spontaneous physisorption process.     

The diagenetic geochemistry and contamination assessment of iron,cadmium, and lead in the sediments from the Shuangtaizi estuary,China

Sediment and pore water samples have been collected from the coastal tidal flat in the Shuangtaizi estuary, China, in order to investigate the geochemical behavior of iron, cadmium, and lead during diagenesis and to assess the degree of contamination. The calculated enrichment factors and geoaccumulation indices for separate elements show that anthropogenic activities have had no significant influence on the distribution of Fe and Pb in the study area, whereas the distribution of Cd has been closely influenced in this way. The high percentage of exchangeable Cd (average of 56.34%) suggests that Cd represents a potential hazard to benthic organisms in the estuary. The calculated diffusive fluxes of metals show that the most mobilized metal is Fe (9.22 mg m^?2 a^?1), followed by Cd (0.54 mg m^?2 a^?1) and Pb (0.42 mg m^?2 a^?1). Low Fe²⁺ contents in surface pore water, alongside high chromium-reducible sulfur contents, and low acid-volatile sulfur, and elemental sulfur contents at 0–25 cm depth in sediments show that Fe²⁺ is formed by the reduction of Fe oxides and is transformed first to a solid phase of iron monosulfides (FeS) and eventually to pyrite (FeS₂). The release of adsorbed Pb due to reductive dissolution of Fe/Mn oxides during early diagenesis could be a source of Pb²⁺ in pore water. From the relatively low total organic carbon contents measured in sediments (0.46–1.28%, with an average of 0.94%) and the vertical variation of Cd²⁺ in pore water, sulfide or Fe/Mn oxides (instead of organic matter) are presumed to exert a significant influence on carrying or releasing Cd by the sediments.     

A distributed parameter model of a frame pin‐supported wall structure

Many reinforced‐concrete frames collapse via a soft‐story mechanism during severe earthquakes. Such collapses are mainly attributed to concentrated deformation in a soft story. Deformation control is thus important in preventing collapse. The frame pin‐supported wall structure is a type of rocking structure that releases constraints at the bottom of the wall. Previous research has obtained good results for the deformation control of this type of structure. However, the interior forces and strength demands of the pin‐supported wall have not been systematically explored. In this paper, a distributed parameter model is developed to investigate the strength demand of the wall in a frame pin‐supported wall structure. In the model, the pin‐supported wall is simplified as a bending beam and the frame is simplified as a shear beam. The two beams are joined by distributed shear connectors, so that the shear force can be transferred at any location on the interface. The model can be solved using differential equations based on equilibrium and compatibility. The accuracy of the model is verified using SAP2000 (Computers and Structures Inc., Berkeley, CA, USA). Displacement distribution of the structure and distributions of the moment and shear force within the pin‐supported wall are obtained for two typical external force profiles. It is found that the pin‐supported wall can effectively reduce the drift concentration factor. Distributions of the displacement, moment, and shear force are closely correlated with the relative stiffness of the wall and frame. Finally, recommendations on the stiffness and strength of a pin‐supported wall are made. Copyright © 2015 John Wiley & Sons, Ltd.     

Land cover mapping using time series HJ-1/CCD data

It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolution and finer resolution data. The first category uses time series of data to retrieve the variation of land surface for classification, which are usually used for coarser resolution data with high temporal frequency. The second category uses fine spatial resolution data to classify different land surface. With the launch of Chinese satellite constellation HJ-1in 2008, four 30 m spatial resolution CCDs with about 360 km coverage for each one onboard two satellites made a revisit period of two days, which brought a new type of data with both high spatial resolution and high temporal frequency. Therefore, by taking the spatiotemporal advantage of HJ-1/CCD data we propose a new method for finer resolution land cover mapping using the time series HJ-1/CCD data, which can greatly improve the land cover mapping accuracy. In our two study areas, the very high resolution remote sensing data within Google Earth are used to validate the land cover mapping results, which shows a very high mapping accuracy of 95.76% and 83.78% and a high Kappa coefficient of 0.9423 and 0.8165 in the Dahuofang area of Liaoning Province and the Heiquan area of Gansu Province respectively.