The origins of rare earths in metalliferous sediments of the Troodos Massif. Cyprus

The ferromanganoan umbers which overlie the uppermost pillow lavas of the Troodos Massif, Cyprus, are strongly enriched in REE relative to normal pelagic clays. Together, the umbers, related ferruginous sediments, and the ochres which are associated with massive cupriferous sulphides located within the lavas, all show light REE enrichment. There is a marked negative Ce anomaly which is characteristic of seawater. Field and chemical data suggest that the REE were incorporated into ferruginous precipitates derived from deep leaching of tholeiitic lavas by seawater. All the metalliferous sediments can be interpreted as related events in the evolution of the Troodos ocean ridge. In contrast, REE patterns of bentonitic clays above the umbers indicate a predominantly continental derivation.     

上覆水pH值和总磷浓度对含铁盐的高砷沉积物中砷迁移转化的影响

含铁盐的高砷沉积物中,上覆水p H值和总磷浓度的变化对砷迁移的影响尚不明确.以含铁盐的高砷沉积物为研究对象,通过实验观测其暴露在不同p H值的上覆水及经过不同初始p H值、不同初始总磷浓度的溶液淋洗后,沉积物中砷的迁移规律.结果表明:当沉积物暴露在p H=10和11的上覆水时,分别在第11 d和第6 d后,沉积物中的砷溶出速度突然增大,说明当沉积物处于强碱性上覆水环境中,碱性越强,砷的溶出速度越快、溶出量越大.从室内实验条件的角度来看,上覆水的碱化有可能会增加沉积物中砷溶出的风险.而上覆水p H值在4~8之间时,上覆水的酸碱度对沉积物砷的迁移影响较小.此外,当上覆水总磷浓度不高于0.5 mg/L时,磷的竞争吸附对砷的迁移影响较小.     

Hydrothermal sediments associated with a relict back-arc spreading center in the Shikoku Basin, recovered from the Nankai accretionary prism, Japan

The hemipelagic mudrocks of the Nankai accretionary prism, Japan, contain hydrothermal deposits associated with a relict spreading center in the Shikoku Basin. Initial work on core samples from Ocean Drilling Program site 808 found several samples with elevated concentrations of calcium, magnesium, iron and manganese, at depths of between 1060 and 1111 m below sea floor. However, the origin of these sediments was uncertain, due to a lack of data. There was no recorded evidence of whether these elevated concentrations were present throughout this interval of core, or if they were present as discrete layers with the background hemipelagic mudrocks in between. In the present study the core was resampled, and the sediments with anomalous chemical compositions were found to be present in discrete layers. This fact, along with a detailed interpretation of their geochemistry, has allowed them to be identified as hydrothermal sediments, associated with the relict spreading center in the Shikoku Basin. The lower (older) two layers display a chemical composition typical of umbers, while the upper (younger) two layers are metalliferous mudrocks typical of deposits found further from the spreading center.     

轮叶黑藻(Hydrilla verticillata)对沉积物-水界面微观剖面理化参数的影响

水生植物是湖泊生态系统的重要组成部分,沉积物-水界面是湖泊生态系统中营养盐循环的重要界面,因而研究水生植物对沉积物-水界面微观剖面的影响具有重要意义.本文利用轮叶黑藻作为研究对象,研究了来自于香溪河、太湖和东湖3个样点的沉积物及上覆水中N、P等理化性质,并利用微电极研究轮叶黑藻对3种沉积物-水界面微观剖面是否有影响.实验结果表明:轮叶黑藻生长迅速.增长率因沉积物不同而不同,有一定的耐污能力;轮叶黑藻使水体和沉积物中总氮、总磷含量减少,对水体和底泥有一定的净化作用;轮叶黑藻可使水体溶解氧升高,并使沉积物有氧层厚度增加,改变沉积物的氧化还原电位;轮叶黑藻可能改变了根际微环境中微生物的数量和种类,而使沉积物和上覆水中的pH、N₂O和H2S等发生变化.     

运河(杭州段)沉积物磷释放的模拟试验

采用室内模拟的方法研究了扰动情况下运河（杭州段）表层沉积物磷的释放对上覆水的影响以及投加石灰、投加三气氛发化铁、连续曝气、换水清洗等措施对沉积物磷释放的控制效果,研究表明,在扰动、开放体系条件下,运河（杭州段）沉积物磷释放导致的上覆水总磷浓度在释放初期最高,随时间逐渐下降,表现出净吸附,采集于有机污染较重河段的沉积物磷释放能力显著高于总磷含量较高但以重金属污染为主的河段的沉积物,上覆水投加石灰最终导致沉积物磷释放量的增加,投加三氯化铁显著降低了上覆水总磷浓度,上覆水连续曝气降低了上覆水的平衡磷浓度、换水清洗对上覆水磷浓度的降低效果是有限的,然而上述措施均未能将上覆水总磷浓度控制在V类水的浓度限定值以下,因此,就上覆水TP的浓度指标而言,运河（杭州段）沉积物的内源释放对其影响很大。     

太湖底泥悬浮中营养盐释放的波浪水槽试验

波浪水槽中研究了小波掀沙(波高8.77cm,波周期0.8s)和大波掀沙(波高12.31cm和13.29cm,波周期1.0s)对太湖沉积物悬浮及N、P营养盐释放的作用规律.结果显示:小波掀沙时,底泥并未发生大量悬浮,SS浓度最高时仅13.6mg/L;大波掀沙时,底泥大规模悬浮,SS浓度最高达达245.2mg/L水体悬浮物、营养盐浓度变化滞后波高变化1h以上.当波高改变1h后,水体悬浮物、N、P营养盐浓度才改变到相应的平衡浓度.除总磷浓度显著提高外,小波掀沙对水体N、P浓度的影响很小,大波掀沙则显著提高了水体总氮、总溶解氮、总磷、总溶解磷、氨氮(NH4 -N)、溶解性活性磷(SRP),其中NH4 -N、SRP最大增幅达30％和20％.小波和大波掀沙过程中,水体溶解氧浓度均持续增加,掀沙2h后增高2mg/L,溶解性有机碳持续下降,2h后下降33％-51％.试验结果表明,掀沙过程中水体充氧及颗粒物的絮凝、吸附作用可能是限制NH4 -N、SRP浓度增高的重要因素之一.     

滇池表层沉积物铵态氮吸附特征

为研究滇池内源污染特征,2013年利用GIS软件针对滇池全湖布设36个采样点,采集表层沉积物,研究滇池表层沉积物铵态氮(NH_4+-N)吸附特征,同时分析沉积物的理化性质对NH_4+-N吸附特性的影响.结果表明:滇池表层沉积物对NH_4+-N的吸附量在前2 h之内呈增长趋势,吸附速率较大,之后沉积物对NH_4+-N的吸附量不随时间变化而变化,基本达到平衡,最大吸附速率均发生在0~5 min内;不同区域表层沉积物NH_4+-N最大吸附速率平均值表现为:外海南部湖心区外海北部草海,最大吸附量平均值表现为:湖心区外海南部外海北部草海,吸附效率平均值表现为:外海北部草海湖心区外海南部;沉积物对NH4+-N的吸附量与NH_4+-N的初始浓度大致呈线性关系,并且低浓度下表现出很好的吸附/解吸特征;滇池表层沉积物NH_4+-N的吸附解吸平衡浓度(ENC0)高于上覆水中NH_4+-N浓度,表明沉积物中NH_4+-N有向上覆水中释放的风险,沉积物在很长一段时间内起到水体污染"源"的作用;ENC0与沉积物中总氮、NH_4+-N含量呈显著正相关,本底吸附量和有机质总量呈显著负相关,沉积物吸附NH_4+-N主要受有机质的影响.     

The initial assessment of trace metal pollution in coastal sediments

Coastal sediments are important hosts for pollutant trace metals, but analytical difficulties can prevent them being included in routine environmental monitoring programmes. In order to identify a suitable approach to the problem, an established simple technique has been evaluated for the initial assessment of trace metal pollution in coastal sediments. The technique, which involves leaching the samples with cold 0.5 N HCl, has been applied to surface sediments from two Greek gulfs and has been shown to provide a rapid, inexpensive way of initially establishing the gross degree to which a sediment population has been subjected to trace metal pollution from the overlying waters.     

Generation of rhyolite magmas by melting of subducting sediments in Shodo-Shima island, Southwest Japan, and its bearing on the origin of high-Mg andesites

Abstract Geochemical characteristics of rhyolites from the Miocene Setouchi volcanic belt in the Southwest Japan arc were examined. The following observations may be best explained by the derivation of rhyolite magmas by melting of subducting sediments as follows. (i) Sr-Nd-Pb isotope compositions of Setouchi rhyolites are close to those of the local trench-fill sediments; (ii) major element compositions of rhyolites are identical to those of experimentally produced sediment melts; and (iii) concentrations of incompatible elements in rhyolites are consistent with partial melting of the local trench-fill sediments in the presence of residual garnet. Furthermore, trace element and isotope signatures of Setouchi high-Mg andesites can be also rationalized by interaction of such rhyolitic sediment melts with overlying mantle peridotites.     

Dissolved heavy metals in a lacustrine mine tailings deposit—Buttle lake,British Columbia

Dissolved Zn, Cu and Cd concentrations in interstitial waters collected from a lacustrine mine tailings deposit indicate that the tailings are not releasing heavy metals to the overlying lake water at present, and there is no evidence to suggest that significant oxidation is occurring in the deposit. The lake waters are enriched in metals from surface drainage, however, while pore waters in natural sediments are heavy-metal-depleted. Diffusion into the natural sediments therefore tends to buffer the lacustrine metal load, but only to a very limited extent.     

太湖入、出湖湖区磷的特征及其影响因素分析

为进一步了解人类活动及环境因子对太湖磷污染的贡献,揭示磷在太湖不同介质中的迁移转化规律,本文以太湖主要入湖湖区竺山湖、西部沿岸区、南部沿岸区和主要出湖湖区东太湖为对象,调查了表层水、上覆水、间隙水和沉积物中总磷(TP)分布的概况,分析了不同介质中磷的交换特征及其影响因素.结果表明,表层水和上覆水TP浓度基本相当,平均值均为0.10 mg/L,上覆水和间隙水TP差异较大,间隙水平均浓度约为上覆水的7倍,表层沉积物TP含量为474～2160 mg/kg.在本研究水域中,TP具有较强的沉积物吸附特性,沉积物作为“汇”的特征明显强于其“源”的特征,且磷的留存能力高度依赖于铁浓度.空间分布上,入湖湖区磷污染程度明显高于出湖湖区,竺山湖和西部沿岸区存在较大的底泥污染释放风险,但竺山湖外源污染影响较内源污染更加突出,应列为当前太湖磷治理重点关注的区域,建议以控源截污作为竺山湖周边区域的治理重点.西部沿岸区需注重外源和内源污染同步控制.南部沿岸区周边区域需妥善处理好未来经济发展与废水排放负荷的关系.     

A STUDY OF THE SEISMIC SIGNATURES OF SEDIMENTATION MODELS USING SYNTHETIC SEISMOGRAMS*

In modern exploration for hydrocarbons there is a great emphasis on the location of stratigraphic traps and estimation of lithologic information like sand-shale ratios from seismic data. In order to investigate the possibilities of success in this endeavour we have studied the synthetic seismograms for wave form and spectral characteristic for four basic sedimentation models: (I) interbedded sand-shale model representing the sediments of generally fluviatile origin, (2) interbedded coal-shale model representing deltaic deposits, (3) sedimentary models representing transgression and regression of shore lines, and (4) a basal sand model. The results have shown that for the first two models a change in the sand-shale or coal-shale ratio results in a characteristically different seismogram. The nature of the seismogram, however, is also strongly dependent on how the sand-shale or coal shale layers are arranged to ultimately give the same number of total layers, thus implying the same coal-shale or sand-shale ratios. The transgression, regression, and basal sand models also produce characteristically different seismic signatures. The spectra of these seismograms show attendant characteristic changes. However, it seems that in the case of real data which are disturbed by noise and the effects of overlying layers these characteristic features may not always be distinguishable.     

Methane consumption in Cariaco Trench waters and sediments

Detailed measurements of CH₄ in the water column and sediments of the Cariaco Trench show that CH₄ is non-conservative in both environments. Concentration differences between the sediments and adjacent overlying water suggest that the sediments are the source of the water column CH₄. Co-metabolism of CH₄ by sulfate reducers appears to be the CH₄ sink in anoxic environments.     

非稳沉采煤沉陷区沉积物-水体界面的氮、磷分布及迁移转化特征

以淮南后湖非稳沉采煤沉陷区沉积物-水体界面为研究对象,分析该湖未开发区(A区)、水产养殖区(B区)和水生蔬菜种植区(C区)3个功能区上覆水-间隙水-沉积物体系中氮、磷分布及其迁移特征.结果表明,氮、磷在不同水体界面的分布差异较大.其中上覆水中氮、磷浓度表现为A区B区C区;间隙水中氮、磷分布差异不显著,然而各功能区间隙水的氮、磷浓度明显高于上覆水,氮、磷主要由间隙水向上覆水中移动;沉积物中氮、磷含量以C区最高.后湖采煤沉陷区水体表现出氮污染、磷限制的现象.     

动、静水条件下苦草(Vallisneria natans L.)对沉积物磷释放的影响

在浅水湖泊中,沉降在沉积物中的营养盐易受到水流的扰动再释放出来,而沉水植物可以在一定程度减少营养盐的释放.借助自主开发的生态水槽,在40 d的实验周期内检测动、静水条件下有、无苦草(Vallisneria natans L.)时沉积物、上覆水中磷含量变化,旨在为沉水植物对湖泊沉积物营养盐释放量的影响估算及水环境质量评价提供科学依据.结果表明:动水条件下,沉积物在没有苦草的保护下总磷含量下降21.8%,而有苦草的保护下总磷含量下降17.7%.苦草根系从周围沉积物中吸收磷,1~4 cm沉积物层的吸收量高于4~8 cm沉积物层.动水槽的上覆水中总溶解态磷浓度和总颗粒态磷浓度均大量增加,并且总颗粒态磷浓度相对于总溶解态磷浓度占较大比例.苦草减少了沉积物中磷的释放,并对上覆水中正磷酸盐有明显的吸收作用.     

双向环形水槽模拟变化水位和流速下洞庭湖沉积物氮释放特征

浅水湖泊生态系统中的沉积物—水界面是湖泊内源氮释放的重要界面,而水动力因素是改变沉积物氮释放的重要因素.三峡大坝修建以后,长江中下游通江湖泊的水动力条件发生了明显的变化.通过采集洞庭湖湖口区域的沉积物和水样,在双向环形水槽动力模拟装置内模拟湖泊水位和流速的变化,探讨湖泊沉积物氮在沉积物和水系统中的二次释放特征.结果表明,随着扰动强度的增加,上覆水悬浮物浓度增大,上覆水中总氮浓度增加,沉积物向上覆水释放氮的强度增强,水动力条件的改变所引起的沉积物内源氮释放不容忽视.在该模拟实验条件下,沉积物存在最适扰动水位(20cm),此水位下上覆水中悬浮物浓度最低,总氮浓度最小.水动力条件的改变对上覆水和沉积物—水界面处铵态氮和硝态氮浓度的影响并不明显,孔隙水中铵态氮与硝态氮之间发生形态的转化.     

Composition and origin of a lithalsa related to lake‐level recession and Holocene terrestrial emergence,Northwest Territories,Canada

Lithalsas of the Great Slave Lowland, Northwest Territories, occur within fine‐grained glaciolacustrine, lacustrine, and alluvial deposits. Detailed investigations of a lithalsa revealed that it is composed of ice‐rich sediments with ice lenses up to 0.2 m thick below 4 m depth. The observed ice accounted for about 2 m of the 4 m between the top of the lithalsa and adjacent terrain. The ice is isotopically similar to modern surface water, but enriched in δ¹⁸O relative to local precipitation. Total soluble cation concentrations are low in the basal, Shield‐derived and unweathered glaciolacustrine sediments of the lithalsa. Higher concentrations in the overlying Holocene‐aged lacustrine and alluvial deposits may be due to greater ion availability in Holocene surface waters. Increasing Cl^‐ and Na⁺ concentrations in clays at depth likely relate to exclusion and migration of these dissolved ions in pore water during ice lens formation though total soluble cations remain comparatively low. The lithalsa developed 700 to 300 cal yr BP. A conceptual model of lithalsa formation and landscape evolution illustrates that this feature and more than 1800 other lithalsas in the region have developed in association with Holocene terrestrial emergence following lake‐level recession. Copyright © 2017 John Wiley & Sons, Ltd.     

Transport and emplacement mechanisms of channelised long-runout debris avalanches,Ruapehu volcano,New Zealand

The steep flanks of composite volcanoes are prone to collapse, producing debris avalanches that completely reshape the landscape. This study describes new insights into the runout of large debris avalanches enhanced by topography, using the example of six debris avalanche deposits from Mount Ruapehu, New Zealand. Individual large flank collapses (>1 km³) produced all of these units, with four not previously recognised. Five major valleys within the highly dissected landscape surrounding Mount Ruapehu channelled the debris avalanches into deep gorges (≥15 m) and resulted in extremely long debris avalanche runouts of up to 80 km from source. Classical sedimentary features of debris avalanche deposits preserved in these units include the following: very poor sorting with a clay-sand matrix hosting large subrounded boulders up to 5 m in diameter, jigsaw-fractured clasts, deformed clasts and numerous rip-up clasts of late-Pliocene marine sediments. The unusually long runouts led to unique features in distal deposits, including a pervasive and consolidated interclast matrix, and common rip-up clasts of Tertiary mudstone, as well as fluvial gravels and boulders. The great travel distances can be explained by the debris avalanches entering deep confined channels (≥15 m), where friction was minimised by a reduced basal contact area along with loading of water-saturated substrates which formed a basal lubrication zone for the overlying flowing mass. Extremely long-runout debris avalanches are most likely to occur in settings where initially partly saturated collapsing masses move down deep valleys and become thoroughly liquified at their base. This happens when pore water is available within the base of the flowing mass or in the sediments immediately below it. Based on their H/L ratio, confined volcanic debris avalanches are two to three times longer than unconfined, spreading flows of similar volume. The hybrid qualities of the deposits, which have some similarities to those of debris flows, are important to recognise when evaluating mass flow hazards at stratovolcanoes.     

新建人工深水湖泊沉积物上覆水和孔隙水中溶解性有机质的光谱特征

为了揭示湖库内源性污染物的分布、来源、组成及垂向分布特征,以新建人工深水湖泊龙景湖为研究对象,采用紫外-可见光谱和三维荧光光谱技术,研究了该湖泊以成湖前用途划分的3个特征区域(原河道底部、新淹没区底部和新淹没区边坡)的沉积物上覆水和孔隙水中的溶解性有机质(DOM)的光谱特征.结果表明,孔隙水中的DOM芳香性和腐殖化程度高于上覆水;孔隙水中疏水组分含量大于上覆水,且水体中可能存在内源孔隙水释放的低分子量DOM.龙景湖上覆水和孔隙水中的DOM主要源于水体自身的微生物,自生源特征明显,且可能存在新近释放到水体的有机质.龙景湖沉积物上覆水和孔隙水中的DOM以类腐殖酸和类蛋白质为主,且随着深度增加,类腐殖酸峰强度增强,与龙景湖的建湖背景有明显联系.