Subfossil and modern diatom plankton and the paleolimnology of Rotsee (Switzerland) since 1850

The diatom biostratigraphy of the topmost sediment meter of Rotsee, Central Switzerland, is characterized by a major change fromCyclotella comensis-dominated toStephanodiscus hantzschii/S. parvus-dominated assemblages. A comparison between old phytoplankton samples, taken between 1910–1930, and subfossil diatom assemblages is used for dating the upper 35 cm of the core. There is evidence that the change in dominant diatoms occurred in 1919/20, thus before the opening of an artificial inlet in 1922, and is due to increasing eutrophication. Furthermore, the sedimentary carbonate content can be used as a good indicator for past phytoplankton productivity in Rotsee.     

高压技术在深海沉积物兼性嗜压菌的筛选和鉴定中的应用

通过自行改进的高压培养罐及高压设备,对深海沉积物进行可培养微生物的筛选,获得6株具有较强耐受压力的细菌.16SrDNA的测序结果表明这些细菌分别属于6个不同的菌属.压力生长试验的结果表明这6株细菌在40MPa的条件下仍然具有较强的生长能力,属于兼性嗜压菌.对不同压力下生长的细菌做显微镜检,结果显示,除了一株芽孢杆菌在40MPa下的菌体形态发生了明显的变化外,其它5株细菌在压力条件下的菌体的分裂均没有受到明显的影响.     

Hydrogen isotope of individual n-alkanes from modern sediments and their application to environments

Hydrogen isotopes are commonly fractionated to a much greater extent and as a result display larger variations in δ values, In terms of the hydrogen isotope ratios of individual n-alkanes of 16 samples of modern sediments selected from four different locations in the southern part of Gansu, China, the δD values for most of the n-alkanes varied from -150‰-300‰, Variations in δD also occurred between different ranges of n-alkanes, effects of environmental changes on the hydrogen isotopic compositions of individual n-alkanes have been detected. Besides the δD values of n-alkanes, the δD values of lipids including pristane （Pr）, phytane （Ph） were also examined, by the combination of D/H ratios with molecular fingerprinting, Our results further support the notion that hydrogen isotopes of n-alkanes from modern sediments can act as paleoclimatic and paleoenvironmental proxies and provide invaluable new sources of information in the research of paleoenvironment reconstruction.     

南极长城湾沉积物中的自然金

作者在南极长城湾沉积物中首次发现金矿化、自然金和含金的碲、铋、锑化合物。本文着重报导了自然金特征、成色、共生矿物和物质来源等问题。     

Artificial Maturation of Organic Matter from Recent Venezuelan Sediments

Laboratory simulation of the catagenesis of organic matter in sedimentary rocks has been used to provide an understanding of the processes involved in petroleum generation. Several of these studies have focused on the thermal evolution of organic matter (OM) present in Recent sediments. This study examines the geochemical characteristics and experimental thermal evolution of primary organic matter from two organic facies that are thought to be major contributors to Venezuelan hydrocarbon source rocks. A third facies, generally considered unimportant for petroleum formation, is used to contrast the experimental results. Hydrous pyrolysis maturation experiments were performed for three intermediate temperatures. The products of the final 330°C stage are shown in this paper because they best illustrate the changes in the OM during catagenesis. Results from the hydrous pyrolysis experiments show that at 280°C and higher all three samples yield liquid hydrocarbons similar in composition to natural crudes and the transformed organic matter is similar to kerogen that occurs in natural source rocks. Chromatograms from the saturated fraction of extracts at 330°C are similar to natural crudes with respect to n-alkane distribution and abundance of beta; and beta;alpha; hopanes. The only difference seems to be the relative abundance of 22R over 22S isomers, which indicates immature oil. This is in contrast to indications from the R _o and T _max parameters measured on the accompanying kerogen.     

莱州湾沉积有机碳储量及海洋健康评估

海洋沉积碳储量在全球碳循环中发挥着重要作用,而海湾作为海洋的重要组成部分,近几十年来由于受人类活动影响有机碳循环发生了明显变化,对碳储备能力的响应同样不可忽视,但却鲜有报道。研究区域位于莱州湾(37°~38°N,118.9°~120.3°E),是渤海三大海湾之一。利用39个表层沉积物和其6根沉积箱式柱状样(站位为6154、6174、6184、6194、7211和7214,柱长在17~39cm之间)对海湾有机碳储量进行评估。同时,通过计算海洋健康指数(OHI)十个目标之一的碳储(carbon storage)来评估海洋健康状况。结果表明,莱州湾表层沉积物1cm的有机碳储量平均为0.3t/ha,在研究区域的中部、东部和北部偏高,莱州湾东南部、区域西北部以及黄河口处有机碳储量偏低。莱州湾0~20cm有机碳储量为20.6t/ha,低于我国表层土壤0~20cm有机碳储量29.7t/ha以及浙江、云南、海南和重庆等省市。莱州湾碳储(carbon storage)得分为37,远低于中国平均值51以及世界平均水平75。

     

Heavy metal pollution of coastal river sediments, north-eastern New South Wales, Australia: lead isotope and chemical evidence

 Heavy metal and metalloid concentrations within stream-estuary sediments (<180-μm size fraction) in north-eastern New South Wales largely represent natural background values. However, element concentrations (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn) of Hunter River sediments within the heavily industrialized and urbanized Newcastle region exceed upstream background values by up to one order of magnitude. High element concentrations have been found within sediments of the Newcastle Harbour and Throsby Creek which drains into urbanized and light industry areas. Observed Pb enrichments and low ²⁰⁸Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁶Pb/²⁰⁴Pb ratios are likely caused by atmospheric deposition of Pb additives from petrol and subsequent Pb transport by road run-off waters into the local drainage system. Sediments of the Richmond River and lower Manning, Macleay, Clarence, Brunswick and Tweed River generally display no evidence for anthropogenic heavy metal and metalloid contamination (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn). However, the rivers and their tributaries possess localized sedimentary traps with elevated heavy metal concentrations (Cu, Pb, Zn). Lead isotope data indicate that anthropogenic Pb provides a detectable contribution to investigated sediments. Such contributions are evident at sample sites close to sewage outlets and in the vicinity of the Pacific Highway. In addition, As concentrations of Richmond River sediments gradually increase downstream. This geochemical trend may be the result of As mobilization from numerous cattle-dip sites within the region into the drainage system and subsequent accumulation of As in downstream river and estuary sediments. Received: 5 September 1997 · Accepted: 4 November 1997     

Holocene environmental change in South Georgia: Evidence from lake sediments

The Holocene environmental history of South Georgia is important because of the island's location in the Southern Westerlies in an oceanic zone of the world devoid of high resolution terrestrial records. This is the first attempt to interpret a palaeoenvironmental record from lake sediments in South Georgia. It is based on a wide variety of analyses undertaken on cores from two lakes. Both are in the same, unglaciated, drainage basin, but one is at 80 m above sea-level and near the altitudinal limit for vegetation growth, whereas the other is at 25 m and within the zone of continuous vegetation cover. Results from both lakes indicate shifts of vegetation boundaries, which, together with evidence for changing biotic productivity within the lakes themselves, are interpreted as indicating climatic changes. Radiocarbon dates on the main changes identify a climatic optimum, beginning before 5620 ± 290 ¹⁴C yr BP, and ending at around 4815 ± 330 ¹⁴C yr BP, when conditions in the upper part of the catchment were more conducive to plant growth than they are today. The record obtained from the lower lake was shorter, but indicates two periods of harsher climate relative to the present since 4000 yr BP. This interpretation of the lake evidence agrees with other dated evidence of environmental change from peat sections, glacial stratigraphy and geomorphology in South Georgia. Together the work allows an overall reconstruction of environmental change in the Holocene.     

山东半岛北部滨浅海区表层沉积物铝物源鉴别

Surface sediment samples in the near shore area of the north Shandong Peninsula are collected for grain size and element analyses. The results indicate that the surface sediments in the study area are primarily composed of the silt-sized components similar to the Huanghe River. The total concentration of aluminum varies from 5.57% to7.37%(average(6.33 ± 0.40)%), and its spatial distribution is mainly controlled by the grain size. Correlations between the ratio of aluminum to titanium concentration and aluminum concentration, titanium concentration and the mean grain size indicate that aluminum in the near shore surface sediments is affected majorly by the terrigenous source, and partially by the anthropogenic source. The ratios of aluminum to titanium concentrations are larger than the background value of loess matter at some stations due to the existence of excess aluminum associated with human activities. Thus, the sources of aluminum should be identified firstly when aluminum is used as an index of terrigenous matter even in the near shore area dominated by terrigenous deposits.