火山岩型铀矿床的基本特征、研究进展与展望

火山岩型铀矿床主要分布在环太平洋带、阿尔卑斯-喜马拉雅山带、俄罗斯西伯利亚地台南部,形成于白垩纪、古近纪和新近纪等三个时期。其形成过程主要包括铀从源岩中萃取出、热液流体的运输、以及物理化学环境的变化导致铀的沉淀。铀的源岩一般是中酸性-酸性岩石,通常呈碱性、准铝质至过铝质,富硅质、富钾、贫钙,富集U、F、Nb、Ta、Zr、Th和Rb等元素,而亏损Mg、Fe、Ti、P、Ba、Sr、La和Eu等元素;与之有关的火山岩和次火山岩多数显示出A型花岗岩特征。铀通常赋存于副矿物或火山玻璃中,因此,铀源岩发生蚀变、副矿物发生蜕晶化是成矿物质释放的关键。火山岩型铀矿床中铀主要以碳酸盐和氟络合物离子形式迁移,铀的迁移形式对其沉淀机制有着重要影响。成矿流体通常是大气降水和岩浆水的混合,成矿温度集中在100～350℃、盐度一般小于15%NaCleqv。铀沉淀机制主要包括还原作用、pH值升高和沸腾作用。火山岩型铀矿床常伴生Mo、Be、Ag、Cu、Pb、Zn、Hg和F等元素。未来火山岩型铀矿成因机制的研究应加强成矿物质来源、铀与伴生元素成因关系研究,这不仅有助于提高对火山岩型铀矿床成矿过程的认识,也可为勘查找矿工作提供理论帮助。     

渤海西北部海域表层水体中PAHs的分布、来源及风险评价

利用气相色谱质谱仪(GC/MS)测定曹妃甸、山海关及沧州渤海新区表层海水样品中16种优先控制PAHs.结果表明,三个地区近岸海域表层海水中∑PAHs含量分别为14.1-226ng/L、29.9-229ng/L和97.4-254ng/L;平均含量分别为108ng/L、102ng/L和204ng/L.沧州渤海新区近岸∑PAHs含量高于曹妃甸和山海关近岸的含量,且检出的PAHs种类多.与其它国家和地区表层水体样品中PAHs含量相比较,本研究区域表层海水中PAHs含量处于中等水平.高低分子量比值和异构体比值分析表明,渤海西北部海域表层海水中PAHs主要来源于石油污染,此外,生物质及煤的燃烧也有一定贡献.应用商值法对研究区域表层海水中PAHs的生态风险进行评价,结果发现生态风险非常小.     

森林凋落叶分解过程中单萜烯排放研究进展

对森林凋落叶分解过程中排放单萜烯气体的研究方法、种类、来源、排放量及影响因素进行综述。森林凋落叶分解过程中单萜烯气体排放的研究方法主要是在实验室控制条件下对凋落叶进行培养模拟分解并同步采集分析单萜烯气体样品,或者在野外采用分解袋法对凋落叶进行现场分解后带回实验室采集测定单萜烯气体样品;凋落叶排放的单萜烯目前检测到的有1...     

2012年7月21日北京特大暴雨的多尺度特征

本文采用观测和NCEP分析场资料对2012年7月21日发生在北京地区的特大暴雨过程的天气形势、水汽来源和中尺度对流系统的特征进行了研究。结果如下:“7.21”北京暴雨过程是高低空与中低纬系统共同配合的结果,暴雨发生在“东高西低”的环流形势下,低涡、切变线、低槽冷锋和低空急流为此次过程的主要影响天气系统;孟加拉湾至西太平洋地区热带辐合带(ITCZ)活跃,其中热带气旋的活动有利于水汽向东亚大陆输送,此次暴雨过程中华北地区的水汽源地包括孟加拉湾和我国东部的渤海、黄海等,低层的水汽主要来自东部,中层的水汽主要来自孟加拉湾;北京的强降雨有两段,第1段降雨虽然发生在冷锋前,但有明显冷空气的侵入,并与地形和东风的作用有关,第2段降雨对流的组织和增强与冷锋强迫相关。在有利环境下,中尺度对流系统频繁发生发展,持续时间长,且稳定少动是此次特大暴雨形成的重要原因。     

大连湾和杭州湾表层沉积物中多氯联苯和有机氯农药及风险评价

对大连湾与杭州湾沉积物样品中多氯联苯(Polychlorinated Biphenyls,PCBs)和有机氯农药(Organochlorine Pesticides,OCPs)进行了分析测定。结果表明,大连湾和杭州湾沉积物中PCBs的含量为0.72~14.87 ng/g和0.76~3.86 ng/g,其中3、4、5氯联苯比例较高,其和超过总含量的70%;OCPs的含量为2.98~32.23 ng/g和1.61~4.71 ng/g,其中主要成分为六六六(Hexachlorocyclohexanes,HCHs)和滴滴涕(Dichlorodiphenyldichloroethylenes,DDTs)。大连湾和杭州湾表层沉积物中HCHs主要来自农业使用,而且大连湾有新的DDTs输入,杭州湾表层沉积物中的DDTs则主要来自历史残留。生态风险评价的结果表明,PCBs几乎不会对研究区域产生生态风险,OCPs对杭州湾也不会造成潜在的生态风险,但大连湾的OCPs处于中等风险水平,应当引起关注。     

Chemical characterization and multivariate analysis of atmospheric PM<Subscript>2.5</Subscript> particles

The new European Council Directive (PE-CONS 3696/07) frames the inhalable (PM₁₀) and fine particles (PM_2.5) on priority to chemically characterize these fractions in order to understand their possible relation with health effects. Considering this, PM_2.5 was collected during four different seasons to evaluate the relative abundance of bulk elements (Cl, S, Si, Al, Br, Cu, Fe, Ti, Ca, K, Pb, Zn, Ni, Mn, Cr and V) and water soluble ions (F⁻, Cl⁻, NO₂ ⁻, NO₃ ⁻, SO₄ ²⁻, Na⁺, NH₄ ⁺, Ca²⁺ and Mg²⁺) over Menen, a Belgian city near the French border. The air quality over Menen is influenced by industrialized regions on both sides of the border. The most abundant ionic species were NO₃ ⁻, SO₄ ²⁻ and NH₄ ⁺, and they showed distinct seasonal variation. The elevated levels of NO₃ ⁻ during spring and summer were found to be related to the larger availability of the NO_x precursor. The various elemental species analyzed were distinguished into crustal and anthropogenic source categories. The dominating elements were S and Cl in the PM_2.5 particles. The anthropogenic fraction (e.g. Zn, Pb, and Cu) shows a more scattered abundance. Furthermore, the ions and elemental data were also processed using principal component analysis and cluster analysis to identify their sources and chemistry. These approach identifies anthropogenic (traffic and industrial) emissions as a major source for fine particles. The variations in the natural/anthropogenic fractions of PM_2.5 were also found to be a function of meteorological conditions as well as of long-range transport of air masses from the industrialized regions of the continent. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The Pliocene Yafo Formation in Israel: Hydrogeologically inert or active?

For several decades the “Saqiye beds” (later renamed Yafo Formation) underlying the Coastal Plain aquifer (Kurkar Group) aquifer of Israel, were regarded as an extremely thick, tectonically undisturbed, and absolutely impervious aquiclude. Following intensive groundwater exploitation from the overlying Kurkar Group aquifer, brackish and saline waters were locally encountered in the lower parts of this aquifer and always at the contact with the underlying Yafo Formation aquiclude. The present study revealed that this aquiclude is not a uniform and impervious rock unit, but rather an alternation of pervious and impervious strata within the Yafo Formation containing highly pressured fluids of different — mostly high — salinities. The permeable beds are at an angular unconformity and in direct contact with the overlying Kurkar Group aquifer. The Yafo Formation and the underlying and overlying rock units are dislocated by numerous fault systems, which facilitate accessibility of brines into the Kurkar Group aquifer. The mobilization of the saline fluids and their injection into the Kurkar Group aquifer could be due either to diffusion of saline fluids occurring in the permeable horizons of the Petah Tiqva Member through the clays of the Yafo Formation or to their upconing following intensive pumping in the Coastal Plain aquifer. It could have also been caused by up-dip movement of saline water as the result of overpressure generated by major accumulation of gas in the permeable horizons. Another possible mechanism could be hydraulic contact with pressurized brines up-flowing along fault zones from deep-seated Jurassic or Cretaceous reservoirs. The squeezing of saline interstitial water from the clays of the Yafo Formation into the overlying Kurkar Group aquifer, is of secondary importance for groundwater salinization (its input is comparable with salt input from rain).     

Nouveaux éléments sur la structure et le fonctionnement hydrogéologique du plateau basaltique de l'Aubrac (Massif central,France). Première évaluation des potentialités en eau souterraine

In volcanic areas, the quality of the geological data at the various scales is of paramount importance for the estimation of aquifer potentialities and thus for groundwater exploitation. Geological and hydrogeological investigation (synthesis of existing data, field geological observations, reconstruction of the infra-volcanic morphology, stream gauging, field hydrogeology, etc.) have been performed on the 450-km² Aubrac basaltic plateau (Massif Central, France). These results allow us to specify the hydrological structure and functioning of this volcanic plateau that were quite unknown before. It is mainly constituted by the piling up of lava flows resting on a plutonic and metamorphic substratum. This volcanic unit constitutes an aquifer of regional importance whose groundwater resources are currently underexploited. These results allow us to delineate zones and strategies for priority hydrogeological prospecting. To cite this article: P.-Y. Bourlier et al., C. R. Geoscience 337 (2005).     

Industrial sources of CO2 emissions in Poland in the light of underground storage possibilities

Industrial sectors responsible for large part of CO₂ emissions in Poland are characterized from the point of view of possibilities of sequestration of this gas by underground storage. On the basis of official statistics and data obtained from local administration and individual plants, attempt was made to evaluate the magnitude of emissions from selected categories, sub-categories and sectors of the industry (in accordance with methodology of IPCC), concentration of CO₂ in combustion gases and those emitted by industry, and to identify major point sources of emission of this gas in Poland. A special attention was paid to those sectors of industry that may be the first to act as a source of carbon dioxide for sequestration by underground storage in the nearest future. To cite this article: R. Tarkowski, C. R. Geoscience 337 (2005).