Relationships between hydrosedimentary processes and occurrence of mercury-resistant bacteria (merA) in estuary mudflats (Seine, France)     

Ramond JB  Berthe T  Lafite R  Deloffre J  Ouddane B  Petit F 《Marine pollution bulletin》2008,56(6):1168-1176

The Seine estuary (France) is one of the world's macrotidal systems that is most contaminated with heavy metals. To study the mercury-resistant bacterial community in such an environment, we have developed a molecular tool, based on competitive PCR, enabling the quantification of Gram-negative merA gene abundance. The occurrence of the Gram-negative merA gene in relation with the topology (erosion/deposit periods) and the mercury contamination of three contrasted mudflats was investigated through a multidisciplinary approach and compared with a non-anthropized site (Authie, France). The higher abundance of the Gram-negative merA gene in the Seine estuary mudflats indicates a relationship between the degree of anthropization and the abundance of the merA gene in the mudflat sediments. In the Seine mudflats, the maxima of abundance are always located in fresh sediment deposits. Therefore, the abundance is closely related with the hydrosedimentary processes, which thus seem to be determining factors in the occurrence of the Gram-negative merA gene in the surface sediments of the Seine's mudflat.  相似文献   

Degassing patterns of Tungurahua volcano (Ecuador) during the 1999–2006 eruptive period,inferred from remote spectroscopic measurements of SO₂ emissions     

S.R. Arellano  M. Hall  P. Samaniego  J.-L. Le Pennec  A. Ruiz  I. Molina  H. Yepes 《Journal of Volcanology and Geothermal Research》2008

This paper presents the results of 7 years (Aug. 1999–Oct. 2006) of SO₂ gas measurements during the ongoing eruption of Tungurahua volcano, Ecuador. From 2004 onwards, the operation of scanning spectrometers has furnished high temporal resolution measurements of SO₂ flux, enabling this dataset to be correlated with other datasets, including seismicity. The emission rate of SO₂ during this period ranges from less than 100 to 35,000 tonnes/day (t d^− 1) with a mean daily emission rate of 1458 t d^− 1 and a standard deviation of ± 2026 t d^− 1. Average daily emissions during inferred explosive phases are about 1.75 times greater than during passive degassing intervals. The total amount of sulfur emitted since 1999 is estimated as at least 1.91 Mt, mostly injected into the troposphere and carried westwards from the volcano. Our observations suggest that the rate of passive degassing at Tungurahua requires SO₂ exsolution of an andesitic magma volume that is two orders of magnitude larger than expected for the amount of erupted magma. Two possible, and not mutually exclusive, mechanisms are considered here to explain this excess degassing: gas flow through a permeable stagnant-magma-filled conduit and gas escape from convective magma overturning in the conduit. We have found that real-time gas monitoring contributes significantly to better eruption forecasting at Tungurahua, because it has provided improved understanding of underlying physical mechanisms of magma ascent and eruption.  相似文献   

1994-2006年长江三角洲和东北平原酸性气体浓度变化     

徐晓斌  林伟立  颜鹏  张忠华  俞向明 《气候变化研究进展》2008,4(04):195-201

利用长江三角洲和东北平原地区大气本底站的二氧化硫（SO2）和氮氧化物（NOx）历史资料和近期取得的观测数据,探讨两个地区人为排放对这些气候相关酸性气体的不同贡献。从两种酸性气体过去和现在的浓度水平,估算了它们在两个地区的增长率,比较了NOx与SO2比值的不同变化趋势。结果表明,早在20世纪90年代中期,长江三角洲酸性气体污染水平已经较高,其后主要是NOx浓度显著升高,从而使该地区成为硫和氮污染并重的地区;东北平原酸性气体过去浓度很低,但这些气体以很高的速率增长,虽然目前浓度水平仍然比较低,但未来形势不容乐观。  相似文献   

柳林泉域岩溶水特点与地质背景条件分析   总被引：7，自引：3，他引：4  

高宝玉  梁永平  王维泰 《中国岩溶》2008,27(3):209-214

柳林泉域作为我国北方典型的单斜 - 顺置式岩溶水资源系统 ,岩溶水在循环过程中表现出与其它泉域共性的同时 ,也存在一些非常奇特的特征: ( 1)由于泉域内断层、褶皱轴和区域隔水顶板的阻水作用 ,造成了岩溶地下水在主径流方向上的二级排泄与三次富集; ( 2)由于泉域中部王家会阻水性背斜轴的倾覆所形成的地下潜流断面梯形形态 ,导致了泉水流量衰减幅度与阻水断面上游区岩溶地下水位下降幅度的不匹配; ( 3)由于泉域南、北翼岩溶地下水循环路径和所处的地球化学背景不同 ,导致了分布在三川河两岸相距不足 300m 的泉水水化学特征表现出很大的差异性 ; ( 4)由于岩相建造地处中奥陶世古膏盐湖东部边缘 ,泉域西部中硬石膏溶解不仅形成了岩溶热水 ,而且还使得柳林泉成为“锶矿泉水”。 上述特征都是由柳林泉域特定的地质结构、地球化学环境和岩相古地理条件所决定的。   相似文献   

绿色化学的进展   总被引：11，自引：0，他引：11  

闵恩泽  傅军 《岩矿测试》1999,20(2):81-86

绿色化学是一门从源头上阻止污染的化学,近年来这方面的研究主要是围绕化学反应,原料,催化剂,溶剂和产品的绿色化开展的。根据这条主线,评述了绿色化学的一些主要研究进展。最后,介绍了国内绿色化学的活动。  相似文献   

Depositional and post-depositional controls on magnetic signals from saltmarshes on the north-west coast of Ireland   总被引：3，自引：0，他引：3  

Andrew J. Wheeler  Frank Oldfield  & Julian D. Orford 《Sedimentology》1999,46(3):545-558

Magnetic measurements were carried out on samples from two saltmarshes deposited during the last century on the north-west coast of Ireland. Based on profiles from cliffed saltmarsh edge, mid-marsh and supratidal locations, the processes that affect the generation and persistence of magnetic properties in environments were investigated. This was done to help in understanding the geochemical processes affecting north-west Irish coast saltmarshes and to determine the frequency and provenance of sediment-laden flooding events; hence, disentangling the importance of clastic and organic contributions to saltmarsh growth. Magnetic properties indicate depositional and post-depositional effects varying on both temporal and spatial scales. The interpretations presented here suggest that both biogenic and diagenetic processes have a strong effect on the magnetic properties recorded: in the former case, the growth of magnetotactic bacteria is the main process; in the latter case, it is reductive diagenesis, associated with organic matter decomposition, that is important. The biogenic and diagenetic effects overprint and degrade the detrital magnetic signatures respectively. This suggests that magnetic measurements within the context of north-west Irish coast saltmarshes can provide limited information on clastic sediment input to these environments. Comparisons between sites on the north-west coast of Ireland show similar magnetic properties, despite differences in deposition rates, implying that significant post-depositional alteration of magnetic properties occurs within the first 20–40 years after deposition. Magnetic properties of north-west coast Irish saltmarshes are put into a regional context by comparison with magnetic profiles from similar sites.  相似文献   

陕西韩城寒武系白云岩和石灰岩固硫试验   总被引：3，自引：1，他引：2  

雒昆利  王五一  姚改焕  史江峰  阎黎东 《煤田地质与勘探》1999,27(4):16-18

选用韩城7个分别采自于寒武系白云岩和石灰岩的样品,以10%和25%为基准,加入韩城的高硫煤中,进行固硫试验。研究表明:中、下寒武系白云岩固硫率为10%~15%,石灰岩的固硫率为15%~26%,上寒武统下部白云岩的固硫率为30%~47%。上寒武统中上部的白云岩固硫率为10%~20%。岩石中白云石和方解石的含量相当时,白云岩的固硫率高于石灰岩5~10个百分点。   相似文献   

中国主要类型锑矿床硫同位素组成及地球化学特征   总被引：6，自引：2，他引：4  

张国林  谷湘平 《矿产与地质》1999,13(3):172-178

中国主要类型锑矿床的硫同位素组成范围变化很大,锑矿床中各种矿物（辉锑矿、黄铁矿、闪锌矿、雄黄、方铅矿、重晶石、毒砂、辰砂、脆硫锑铅矿）的δ３４Ｓ值从－３２．７‰变化到＋３４．８‰,极差值高达６７．５‰。各类锑矿床中矿物的硫同位素组成变化各异,说明锑矿床成因较复杂,硫的来源不仅有海水中沉淀的硫酸盐硫,而且还有生物、细菌形式的还原硫和深源硫（岩浆作用、喷流作用等）,从而形成不同类型或成因复杂的锑矿床  相似文献   

Party organisation and democracy – A comparison of Les Verts and the British Green Party     

Florence Faucher 《GeoJournal》1999,47(3):487-496

The environment is the issue most closely identified with the Green movement. However, a commitment to the rejuvenation of political practices has been equally important in the development of their partisan organisations. Green party members share the conviction that democracy is the best way to attain a sustainable society. They aspire to a more participatory politics and have translated their ideals of equality and individual fulfilment into alternative party structures. Many of their practices demonstrate that they share values and attitudes which inspire their behaviours and intra-party regulations. However, Green parties are also influenced by the national structure of political opportunities. The practical arrangements French and British Greens have developed reflect their relative integration within the political system as well as the influence of national political culture on conceptions of equality and participation. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

块状硫化物矿床研究进展评述   总被引：27，自引：4，他引：23  

顾连兴 《地质论评》1999,45(3):265-275

最近十余年来,海底块状硫化物矿床的研究在如下方面有新的进展：矿床类型,矿化和蚀变特征,矿石结构－构造和变形－变质,矿床模式和成矿机制,金属和硫的来源,成矿流体的性质和来源,以及现代海盆地中的成矿作用等。  相似文献