Magnetic properties of urban soil profile and their significance for traffic pollution-Case study of the capital airport expressway in Beijing     

Mingjie Shen  Shouyun Hu  Uli. Blaha  Haitao Yan  Wolfgang. R?sler  Ewin. Appel  Viktor. Hoffmann 《Frontiers of Earth Science》2008,2(4):400-407

An expressway-side soil profile 22 cm long was sampled from the grassland of the expressway linking Beijing and the Capital International Airport. Magnetic measurements, geochemical and multivariate statistic analyses were performed on the soil samples. The results reveal that the soil profile can be divided into two parts with significant difference in magnetic proxies and heavy metal concentration. The uppermost soil horizon (0–8 cm) represents the pollution-rich layer with higher concentration of ferrimagnetic phases and metallic elements. The values of xare very high with an average of 141.60 × 10⁻⁸ m³·kg⁻¹ in the layer. We explain that the anthropogenic dust input from traffic is the predominant cause for strong signals of magnetic phases and heavy metals. Below the profile depth of 8 cm, there is minor pollution in the soil with lower concentration of magnetic minerals and heavy metals compared to the natural background values. χ remains quite stable and relatively low with an average of 49.44 × 10⁻⁸ m³·kg⁻¹. S-ratio also generally decreases with depth, and it changes from 0.93 in the 0–8 cm layer to 0.87 below the depth of 8 cm. It indicates that the soil samples are overwhelmingly predominated by ferrimagnetic minerals in the upper part soil, while the contribution of imperfect antiferromagnetic components is stronger in the lower part. Rock magnetic experiments show MD magnetite as the main magnetic carrier both in the upper and lower parts. Themagnetic grain size in the upper part is, however, a bit coarser than that in the lower part. Cluster analysis shows a positive correlation between magnetic properties (χ, ARM, SIRM) and heavy metal pollutants of Pb, Zn, Cu. Fuzzy C-means cluster analysis can clearly help divide the soil profile into two different layers and distinguish their characteristics. It can be concluded that these magnetic concentration-related parameters can be used as proxies for pollution investigation in a fast, sensitive, low-cost and highly efficient approach to screening heavy metal pollution. __________ Translated from Quaternary Sciences, 2007, 27(6): 1113-1120 [译自:第四纪研究]  相似文献   

Sulfur isotope biogeochemistry of the Proterozoic McArthur Basin     

David T. Johnston  James Farquhar  Yanan Shen  Andrew L. Masterson 《Geochimica et cosmochimica acta》2008,72(17):4278-4290

Previous geochemical and biomarker studies of the late Paleo-Mesoproterozoic propose a stratified world, with strongly reducing (possibly sulfidic) deep-ocean conditions overlain by an oxygenated surface-ocean and atmosphere. To investigate such a scenario, we look to the structure of the biogeochemical sulfur cycle. We present sulfur (³²S, ³³S, ³⁴S, and ³⁶S in sulfides) isotope data from the McArthur Basin (Barney Creek, Reward, Velkerri, and McMinn formations) that allows for a direct evaluation of the surface biosphere. We are interested in investigating the types of information that can be gained by including ³³S and ³⁶S. When the ³⁴S/³²S fractionations are small, the inclusion of ³³S and ³⁶S provides little additional information, but does provide ancillary evidence for relative isotopic homogeneity (with the internal consistency of ³³S/³²S and ³⁶S/³²S). When the ³⁴S/³²S fractionations are large, direct information about the fractionation mechanisms can be obtained, with the potential to distinguish the biological from abiological processes. For example, the reconstruction of the Roper Group suggests that seawater sulfate concentrations were high enough to buffer against spatial heterogeneities. Overall, our findings agree with previously proposed redox structure of the Proterozoic ocean, highlight contributions from the oxidative sulfur cycle, and outline a new tool for interpreting the state of the surface sulfur cycle.  相似文献   

Effect of indigenous bacteria on geochemical behavior of arsenic in aquifer sediments from the Hetao Basin, Inner Mongolia: Evidence from sediment incubations   总被引：5，自引：0，他引：5  

Huaming Guo  Xiaohui Tang  Suzhen Yang  Zhaoli Shen 《Applied Geochemistry》2008,23(12):3267-3277

Incubation studies were carried out using 5 freshly collected sediments from shallow aquifers of the Hetao Basin, Inner Mongolia. The aquifer sediments covering a range of redox conditions, as indicated by their deep grey to yellow color were mixed with degassed artificial As solution or degassed deionized water at a ratio of solid to water of about 1:10 (wt./wt.). Suspensions which were either amended with glucose or autoclaved, were incubated in parallel with unamended suspensions. Five microcosm cultures of unamended sediments gradually release the equivalent of 0.03–0.30 μg/g As to the dissolved phase. The addition of glucose as a potential electron donor results in a marked stimulation in the mobilization of As (0.71–3.81 μg/g) in the amended incubations for all sediments. The quantity of As released accounts for 60–70% of As bound to Fe/Mn oxides in the original sediments. The microbially mediated mobilization of As with the organic nutrient as an electron donor is strongly associated with the As bound to Fe/Mn oxides, as well as the exchangeable As. During the incubations amended with glucose, 2–4% of the sediment Fe is released. The results suggest that the introduction of labile dissolved organic C into the yellowish sediment aquifers with As-free groundwater would reduce a significant proportion of the Fe(III) oxyhydroxides mediated by anaerobic bacteria respiration and increase groundwater As concentrations.  相似文献   

Combined effects of heavy metal and polycyclic aromatic hydrocarbon on soil microorganism communities   总被引：2，自引：0，他引：2  

Linkui Cao  Guoqing Shen  Yitong Lu 《Environmental Geology》2008,54(7):1531-1536

Soil contaminated sites contain a variety of pollutants, especially heavy metals and polycyclic aromatic hydrocarbons (PAHs). Interactions between heavy metals have been relatively well studied, but little is known about interactions between heavy metals and PAHs. The combined effect of heavy metals and PAHs on soil microorganism was studied in laboratory conditions and evaluated by random denaturing gradient gel electrophoresis. We extracted DNA directly from contaminated soils and then amplified the V3 sequences of the 16S rDNA. The results showed that with different culture time, the gene diversity of the single and combined contaminated soil differed as well. After 15 days of culture, the microorganisms were stimulated and accommodated. After 45 days of cultivation, the quantities of the soil microorganisms were affected. It is concluded that some of the microorganisms utilize phenanthrene as important carbon resources. Microorganisms directly isolated from soil could reflect the diversity of soil microorganism and population distribution conditions.  相似文献   

Application of allochthonous organic carbon and phosphorus forms in the interpretation of past environmental conditions   总被引：2，自引：0，他引：2  

Changwei Lü  Jiang He  Huimin Sun  Hongxi Xue  Ying Liang  Saruli Bai  Ying Sun  Lili Shen  Qingyun Fan 《Environmental Geology》2008,55(6):1279-1289

Organic matter in sediments, for instance, carbon, nitrogen and phosphorus, can be used to reconstruct the paleoecological and pollution history of lakes and their catchment basins. In this paper, the contents of allochthonous organic carbon (allochthonous OC) and autochthonous organic carbon (autochthonous OC) in sediment cores taken from Wuliangsuhai Lake and Daihai Lake in northern China are quantified by using a binary model, and phosphorus forms in the sediment cores from the two lakes are extracted by sequential extraction techniques. The results indicate that the palaeoenvironment and paleoclimate of Daihai Lake and its catchment basin in the recent 250 years can be well reconstructed based on the content of allochthonous OC. The climate was relatively humid and warm in the period of 1865–2005, while relatively dry and cold in the period of 1765–1865. The sedimentary information of allochthonous OC in the 22–42-cm portion of the sediment cores in Daihai Lake corresponds to the final cold fluctuation of the Little Ice Age that occurred since the Middle Holocene. The difference of phosphorus forms in the sediment cores between the two lakes indicates that phosphorus input to the lakes and the correlation between phosphorus forms and distribution and the changes of environment are influenced by the eutrophication mechanisms and environmental conditions of the two lakes.  相似文献   

Fluids in deeply subducted continental crust: Petrology, mineral chemistry and fluid inclusion of UHP metamorphic veins from the Sulu orogen, eastern China   总被引：10，自引：0，他引：10  

Ze-Ming Zhang  Kun Shen  Yong-Sheng Liu  Cao Shi 《Geochimica et cosmochimica acta》2008,72(13):3200-3228

The complex vein associations hosted in southern Sulu ultrahigh-pressure (UHP) eclogites contain quartz ± omphacite (or jadeite) ± kyanite ± allanite ± zoisite ± rutile ± garnet. These minerals have chemical compositions similar to those of host eclogites. Inclusions of polycrystalline quartz pseudomorphs after coesite were identified in vein allanite and garnet, and coesite inclusions were found in vein zircon. These facts suggest that the veins together with host eclogites have been subjected to synchronous UHP metamorphism. The vein minerals contain relatively high concentrations of rare earth elements (REE), high-field-strength elements (HFSE) and transition metal elements (TME). A kyanite-quartz vein has a whole-rock composition similar to adjacent UHP metamorphic granitic gneisses. Abundant primary multi-solid fluid inclusions trapped within UHP vein minerals contain complex daughter minerals of muscovite, calcite, anhydrite, magnetite, pyrite, apatite, celestite and liquid and gas phase of H₂O with solids up to 30-70% of the inclusion volume. The presence of daughter minerals anhydrite and magnetite indicates the subduction fluids were oxidizing, and provides a possible interpretation for the high oxygen fugacity of subduction zone magmas. These characteristics imply that the UHP vein minerals were crystallized from supercritical silicate-rich aqueous fluids that were in equilibrium with peak-UHP minerals, and that the fluids in deeply subducted continental crust may contain very high concentrations of silicate as well as HREE, HFSE and TME. Such fluids might have resulted in major fractionation between Nb and Ta, i.e. the UHP fluids have subchondritic Nb/Ta values, whereas the host eclogites after extraction of the fluids have suprachondritic Nb/Ta values. Therefore, voluminous residual eclogites with high Nb/Ta ratios may be the complementary suprachondritic reservoir capable of balancing the subchondritic depleted mantle and continental crust reservoirs.  相似文献   

Holocene environmental and climatic changes inferred from Wulungu Lake in northern Xinjiang, China   总被引：7，自引：0，他引：7  

Xingqi Liu  Ulrike Herzschuh  Ji Shen  Qingfen Jiang  Xiayun Xiao 《Quaternary Research》2008,70(3):412-425

Sedimentological, geochemical and palynological data from Wulungu Lake in northern Xinjiang, China, are used to reconstruct environmental and climate changes since 9550 cal yr BP. High abundance of Sparganium and Poaceae, low Md (median diameter) and δ¹³C_organic values indicate aridity between 9550 and 6730 cal yr BP. High Md and δ¹³C_organic values, and the prevalence of desert-steppe and steppe vegetation between 4200 and 560 cal yr BP, indicate that effective moisture increased after 6730 cal yr BP, peaking at 4200 and 560 cal yr BP. Low Md values, a negative excursion of δ¹³C_org, and the transition from steppe to desert vegetation since 560 cal yr BP reflect a decrease in effective moisture during the latest Holocene. Late Holocene human activities were indicated by sharp increase in the abundance of Pediastrum then. Variations in carbonate contents indicate that temperature was generally high between 9550 and 7740 cal yr BP, low between 7740 and 6730 cal yr BP, intermediate between 6730 and 560 cal yr BP, and low during the last 560 yr. Regional comparison indicates that the Asian monsoon did not extend to Wulungu Lake and westerlies were the main factor in determining the moisture availability during the Holocene.  相似文献   

论ICT时代的地图学复兴     

郭仁忠  应申 《测绘学报》2017,46(10):1274-1283

在ICT技术推动下,地图学的发展迎来空前的挑战,本文针对当前地图学的发展面临的问题和转变,深入分析传统地图学的限制——物理空间的传统约束,面向现代地图的形式松散化,从现实与虚拟、外表与内里、纸质与电子等8个方面论述现代地图学信息空间的数字自由,并针对数字时代和大数据的发展机遇和需求,拓展地图学框架,同化新兴元素,推动地图学复兴。  相似文献   

GPS positioning algorithm for a spinning vehicle with discontinuous signals received by a single-patch antenna     

Qiang Shen  Miao Li  Ru Gong 《GPS Solutions》2017,21(4):1491-1502

A GPS positioning algorithm is studied and applied to locate a spinning vehicle on which a single-patch antenna is mounted. Because the antenna is directional and the received signal is periodically discontinuous, the bits and frames cannot be synchronized to assemble the transmission time of the satellite signals. The characteristics of the signals received by a single-patch antenna are described. The means by which the tracking loop works with these discontinuous signals are analyzed and simulated. Aiming at spinning projectiles, the positioning algorithm forming differencing with respect to a reference satellite is applied to locate the spinning vehicle by using code phases obtained in the tracking of the discontinuous signals. Experiments were carried out, and the results showed that the positioning algorithm works properly on the spinning vehicle. The results revealed that the positioning error of the algorithm applied to a spinning vehicle is close to that of the conventional positioning method applied to a non-spinning vehicle.  相似文献   

同型半胱氨酸水平与脑梗死患者MTHFR基因C677T多态性之间的相关性研究     

王国保  沈群弟  吕丹萍 《寒旱区科学》2017,9(5):154-158

目的 探讨研究同型半胱氨酸（homocysteine,Hcy）水平与脑梗死患者亚甲基四氢叶酸还原酶（MTHFR）基因C677T的多态性之间的相关性。方法 选择2012年2月~2015年8月期间在笔者医院住院就诊的450例脑梗死患者作为研究组,其中糖尿病患者181例,非糖尿病患者269例,另外选择285例笔者医院门诊部健康的体检人员作为对照组,分别采用焦磷酸测序的方法检测分析MTHFR基因C677T的多态性,并分析各基因型与Hcy水平之间的相关性。结果 脑梗死组与健康对照组的MTHFR基因型分布之间的差异具有统计学意义（P<0.05）,脑梗死组T基因的频率明显比对照组高,差异有统计学意义（χ²=13.67,P=0.00）。脑梗死组患者的Hcy浓度明显高于健康对照组,差异有统计学意义（t=12.71,P=0.00）。脑梗死组患者各MTHFR基因型患者的Hcy水平之间比较,差异有统计学意义（F=17.68,P=0.00）。非糖尿病脑梗死患者的Hcy水平明显高于糖尿病脑梗死患者,差异有统计学意义（t=2.97,P=0.00）,非糖尿病组TT型的Hcy浓度明显高于糖尿病组,CC型的Hcy浓度明显低于糖尿病组,差异均有统计学意义（t=5.67,2.18;P=0.00,0.03）。糖尿病性脑梗死患者和非糖尿病脑梗死患者中,MTHFR基因为TT型的Hcy水平明显高于CC型和CT型,差异均有统计学意义（P<0.05）,而CC型和CT型的Hcy水平之间比较差异无统计学意义（P>0.05）。结论 脑梗死患者比健康人的MTHFR基因C677T的T等位基因频率高,且脑梗死患者的MTHFR基因C677T为TT基因型时血清中Hcy的水平更高,由此判断TT基因型可能是脑梗死发生的危险因素。  相似文献