Evaluation of geochemical impact of tsunami on Pichavaram mangrove ecosystem,southeast coast of India   总被引：1，自引：0，他引：1  

Rajesh Kumar Ranjan  AL. Ramanathan  Gurmeet Singh 《Environmental Geology》2008,55(3):687-697

The 26 December 2004-tsunami has deposited sediments in the Pichavaram mangrove ecosystem, east coast of India. Ten surface and three core sediment samples were collected within 30 days of the event and analyzed for nutrients. Water samples were also analyzed to see the impact of tsunami on the geochemical behavior of nutrients. An increase in the concentration of various nutrients namely nitrate and phosphate was observed. The geochemistry of the mangrove forest was observed to be influenced by a number of factors like rapid increase of aquaculture farms, agricultural practices and the anthropogenic discharge from the nearby-inhabited areas. Further the sediment column was disturbed due to energetic tsunami waves, which has caused a sheer increase in the dissolved oxygen in water. As a result, the change in the redox potential has resulted in change in the nutrients absorbed/associated with the sediments. In addition, role of retreating water after tsunami on the nutrient geochemistry was also evaluated.  相似文献   

Geostatistical estimation of chemical contamination in stream sediments: The case study of Vale das Gatas mine (northern Portugal)     

A.R. Salgueiro  P. Freire vila  H. Garcia Pereira  J.M. Santos Oliveira 《Journal of Geochemical Exploration》2008,98(1-2):15

Based on an environmental geochemistry case study carried out in the neighbourhood of a W–Sn abandoned mine, the pollution in stream sediments was modelled through a Global Contamination Index. Such an index permits one to summarize the combination of deleterious elements in a single variable, obtained by the projection of samples onto the first axis of a PCASD (Principal Components Analysis of Standardized Data) applied to the entire n × p matrix containing the available concentrations of p = 16 elements in the set of n = 220 collected samples.In order to provide a sound basis for a coherent planning of the remediation process which will be put in operation in the affected area, it is necessary to balance the costs of reclaiming with the probabilities of exceeding the upper limits accepted for concentrations of environmentally harmful elements in sediments. Given these limits, they are back-transformed in the index values, providing a practical threshold between ‘clean’ and ‘contaminated’ samples. On the other hand, the minimum dimension of the cell to be reclaimed is restrained by the selected remediation process to be applied in the affected area. Hence, to meet the constraints of such a remediation process, it is required to estimate the probabilities of exceeding the index threshold in technologically meaningful sub-areas. For this end, the Indicator Block Kriging technique was applied, producing a series of maps where sub-areas to be reclaimed can be spotted for different probability levels. These maps, on which the decision making remediation agency can rely for its cost-benefit analysis, take into account both the spatial structure of ‘clean’ vs. ‘contaminated’ samples and the constraints of the reclaiming process.  相似文献   

藏南地区中生代硅质岩的地球化学特征及其成因意义   总被引：6，自引：1，他引：5  

周永章  付伟  杨志军  何俊国  聂凤军  李文  赵文霞 《岩石学报》2008,24(3)

藏南地区中生代硅质岩包括蛇绿岩套硅质岩(与蛇绿岩共生)和非蛇绿岩套硅质岩两大类.本文重点分析日喀则地区彭错林、夏鲁以及泽当地区的罗布莎、江孜盆地宗卓组及四个剖面的硅质岩.其中,彭错林、夏鲁和罗布莎硅质岩与蛇绿岩共生,江孜盆地宗卓组为非蛇绿岩套硅质岩.分析表明:(1)藏南地区硅质岩剖面地球化学特征鲜明,具有一致性和多样性特点;(2)与蛇绿岩共生的彭错林、夏鲁、罗布莎硅质岩普遍具有高Si、高Fe、低Al特征,大部分微量元素相对于克拉克值亏损,稀土元素总量低,经北美页岩标准化后,Ce异常明显或不明显,重稀土相对轻稀土富集.硅质泥岩的∑REE要明显高于硅质岩;(3)非蛇绿岩套宗卓组硅质岩SiO2含量稍低,Al2O3、TiO2则相反.V、Th、Hf、Ta等不相容元素上亏损程度较小,部分样品含量可接近克拉克值.稀土总量相对较高,页岩标准化配分模式上体现为弱Ce正异常,负Eu异常,轻重稀土分异不明显的平坦型曲线图;(4)地球化学特征指示了,藏南地区硅质岩多数具有明显的热水沉积成因属性,同时有正常陆源组分的加入.其中,夏鲁硅质岩的热水沉积地球化学特征较为典型,而宗卓组硅质岩则表现出受陆源物质加入的影响显著的地球化学特点.  相似文献   

柴达木盆地昆特依盐湖的地球化学演化与古气候变化   总被引：9，自引：1，他引：9  

韩凤清  黄麒  王克俊  王华安  原力 《海洋与湖沼》1995,26(5):502-508

１９９０年用铀系年代学及古地磁对昆特依盐湖沉积物进行年代测定，探讨该湖区地球化学演化与古气候变化关系。结果表明，该区最老的盐层形成于早更新世晚期（大于７３０ｋａ），大量的盐类沉积则始于３００ｋａ左右；盐湖沉积物中元素含量变化主要受古盐度、矿物、类质同象和吸附控制；沉积物水溶Ｆ／Ｃｌ比值与古盐度成反比关系；该湖２０００ｋａ以来的古环境演变：盐层形成于干冷、偏酸性的氧化环境，泥岩层形成于湿暖、偏碱性的  相似文献   

广东三水盆地晚自垩世—始新世古地磁研究及构造意义     

侯红明  袁友仁  张毅祥  汤贤赞  王保贵 《热带海洋学报》1994,(4)

对广东三水盆地上白垩统三水组、大　山组、古新统莘庄组及始新统　心组、宝月组的系统的古地磁研究结果表明：（１）旋转运动是该区构造运动的主要形式，顺时针旋转盆地拉张发育，这时针旋转盆地挤压衰亡，发育的程度与旋转角度有关；（２）始新世该区旋转方向由顺时针旋转变为道时针旋转，对应于太平洋－库拉板块对欧亚板块作用方向的改变，说明三水盆地的形成发育与太平洋－库拉板块对欧亚板块的作用密切相关；（３）三水盆地所在的华南地块从晚白垩世至始新世在纬向上不存在明显的运动，一直停留在略低于现今纬度的位置上。  相似文献   

套子湾表层沉积物地球化学特征的研究     

程波 《海洋科学进展》1993,(4)

本文对套子湾表层沉积物中的pH、Eh、硫化物、氮、磷、有机质、铜、铅、锌、镉地球化学特征进行了分析研究.并讨论了如下几个关系:①与沉积类型之间的关系;②其相关性与环境的关系。③与矿物的关系;④与水和风等作用的关系;⑤与水化学的关系;⑥重点分析了表层沉积物中化学要素与生物的相互关系。这不仅为该湾的开发治理.生物养殖等提供科学依据.并进一步证明沉积物地球化学.在环境化学和生态学研究等方面的理论意义。  相似文献   

Dissolved titanium distributions in the Mid-Atlantic Bight   总被引：1，自引：0，他引：1  

Stephen A. Skrabal   《Marine Chemistry》2006,102(3-4):218-229

Although titanium is abundant in Earth's crust, its sources and distribution in the ocean are poorly understood. To elucidate its behavior, distributions of dissolved (< 0.2 μm) Ti were determined in surface waters and vertical profiles from the Mid-Atlantic Bight (MAB). Concentrations of Ti decreased from 390 pM at the Delaware Bay mouth to < 100 pM across the Delaware continental shelf. In vertical profiles, small increases in bottom waters suggest a possible flux of Ti from shelf sediments, consistent with previous reports of pore water enrichments of dissolved Ti in MAB sediments. Concentrations in surface waters of the outer shelf and slope ranged between 30 and 140 pM, with most values below 90 pM. Concentrations in a 1000 m vertical profile in the eastern Gulf Stream ranged between 110 and 280 pM, and showed a variable distribution attributed to the mixing of water masses in the outer MAB. A simple model of Ti sources to the MAB suggests that atmospheric deposition of dissolved Ti is comparable to net riverine contributions and therefore must be considered in applications of Ti as a tracer of oceanographic processes.  相似文献   

南沙海区中生界岩相分布及构造特征   总被引：3，自引：0，他引：3       下载免费PDF全文

刘海龄  谢国发  阎贫  刘迎春  郑红波 《海洋与湖沼》2007,38(3):272-278

为了了解南中国海南部南沙群岛陆架-陆坡区中生代地层发育情况,作者通过综合分析该海区钻井、拖网及1987年以来采集的20000多公里的多道反射地震勘探等资料,得到了对该区中生界基本特征的如下新认识:空间分布上,南沙的中生界具有从北部的郑和-礼乐隆起南缘向南增厚的趋势;沉积岩相方面,东部三叠纪时为深海相,侏罗纪为浅海与三角洲相,白垩纪为浅海-内浅海相,而往西南部中生代的海水深度有变深的趋势;中-新生代变形上,在南沙西部的曾母盆地,中生界褶皱为复式的、非协调性的,南沙中部多为舒缓褶皱,东部仅在近巴拉望海槽地带出现小幅度的褶皱。结合围区中生界及特提斯构造域的发育特征,作者提出南沙地块上的海相中生界在大地构造上归属于残留在中特提斯洋北部减薄陆缘地壳上的中特提斯期海相沉积地层,是该海域油气资源勘探不可忽视的对象。  相似文献   

我国西部特殊景观区化探方法研究进展   总被引：5，自引：2，他引：3  

张必敏 《物探与化探》2008,32(5):473-476

西部特殊景观区的化探方法研究一直是中国化探界的一个研究热点和难点.在岩石出露、水系发育地区可以沿用传统的水系沉积物化探方法,但在覆盖景观区,常规化探方法效果并不理想.目前,谢学锦和王学求所提出的深穿透地球化学方法,经过一系列的实验研究,证明其能在覆盖区达到快速有效地圈定战略靶区的作用,具有广泛的应用前景.要做好西部特殊景观区的化探工作,化探科研人员必需采取新方法、新思路,继续系统地开展化探方法技术研究,通过不懈的努力最终找到一套适合中国西部特殊景观区特别是覆盖区的行之有效的化探方法.  相似文献   

鄂尔多斯地块早白垩世构造-热事件:杭锦旗玄武岩的Ar-Ar年代学证据   总被引：8，自引：3，他引：5  

邹和平  张珂  李刚 《大地构造与成矿学》2008,32(3)

在鄂尔多斯地块北部杭锦旗黑石头沟,于下白垩统砂岩之上发现了一层玄武岩。其SiO2(46.93%)较低而碱含量(K2O+Na2O=6.21%)较高,组合指数σ=8.0,含标准矿物Ne,属于碱性橄榄玄武岩。Ar-Ar激光阶段加热定年结果表明,该玄武岩具有126.2±0.4Ma的Ar-Ar年龄。年龄数据表明杭锦旗黑石头沟玄武岩形成于早白垩世,反映鄂尔多斯地块在早白垩世发生了一次构造-岩浆-热事件,这与华北、乃至整个中国东部在早白垩世发生了较普遍的构造-岩浆-热事件具有一致性。这次构造-岩浆-热事件可能引起深部流体自地下深部上涌及在地块内部运移,为各种成矿元素的迁移、沉淀、富集和成矿创造了合适条件。  相似文献