Peculiarities of Recent Sedimentation in Lake Ladoga

The bulk of sedimentary material is supplied to Lake Ladoga in the form of suspension in river water. Rivers annually deliver 1.2 Mt of sedimentary material. A significant portion of clastic material in the sedimentation basin is also related to shore and bottom abrasion. Average sedimentation rate in the lake is 0.4 mm/yr for the last 10 ka. The wide grain size spectrum of lacustrine sediments is caused by textural inhomogeneity of Quaternary rocks, which are the main source of sedimentary material. Variably-grained relict sands at the depth of 12–20 m originated during a relatively low lake level. Silt, sand, and clay at 30–75 m are formed as a result of integration of the relict and newly supplied material. The sediment composition is principally defined by Cambrian–Ordovician rocks in the southern part of the lake, morainal and postglacial deposits in the eastern part, and crystalline basement rocks and their derivatives in the northern and western parts. Textural, mineral, and petrographic transformations of the surficial sediments take place under the influence of waves, induced currents, and gyres. Waves and induced currents mainly produce mature sediments, whereas gyres lead to the integration of materials supplied from different sources and the formation of petrographicaly mixed deposits. Based on the comprehensive analysis of sedimentological information, conditions of sedimentation and main features of lithodynamics are characterized. The results obtained may serve as a basis for the creation of a conceptual model of sedimentogenesis in Lake Ladoga.     

Level of Lake Lahontan during deposition of the Trego Hot Springs tephra about 23,400 years ago

The Trego Hot Springs tephra bed is a silicic tephra about 23,400 yr old, found at several localities in pluvial lake sediments in northern Nevada, southern Oregon, and northeastern California. It has been characterized petrographically, by the major and minor element chemistry of its glass, and by its stratigraphic position with respect to other tephra layers. At a newly described locality on Squaw Creek, northwest of Gerlach, Nevada, at the north end of the Smoke Creek Desert, Trego Hot Springs tephra has been found in sediments of the Sehoo and Indian Lakes formations. The depositional environments of these sediments show that when the tephra fell, pluvial Lake Lahontan stood between 1256 and 1260 m, and that immediately thereafter the lake rose to at least 1275 m. These data corroborate earlier findings by Benson (Quaternary Research9, 300–318) from radiometric dating of calcareous tufa. However, the Lake Lahontan area has been affected by isostatic subsidence and rebound in response to changing water loads, so that caution is required in the use of lakeshore elevations in correlation.     

Age and provenances of sandstones from the Riphean Priozersk and Salmi formations in the eastern Pasha-Ladoga basin (southern margin of the Baltic Shield)

The data on the age of sediments and their sources were first obtained by isotopic methods and lithological-petrographic observations for the Priozersk and Salmi formations in the northeastern Pasha-Ladoga basin. Wide development of coarse-grained terrigenous rocks and peculiar structures point to the proximity of provenances and dominant sedimentation in terrestrial settings. U-Pb dating of 168 detrital zircons revealed that approximately 87% of all grains are Early Riphean in age, while other grains are dated back to the Early Proterozoic. Archean age is documented for only two zircon grains. It is established that detrital material of sandstones from the Priozersk and Salmi formations largely originate from the Salmi Massif (1.55–1.53 Ga) and secondarily from the Svecofennian intrusions of the northern Ladoga region aged approximately 1.88 Ga, which is confirmed also by Sm-Nd data. The occurrence of detrital zircons dated at approximately 1480–1490 Ma indicates development of coeval magmatic bodies in the immediate proximity to the sedimentation basin, which remain undiscovered. The concordant age obtained for the youngest detrital zircon grain points to the onset of sedimentation in the basin after 1477 ± 8 Ma ago. Thus, Riphean sedimentation on the eastern slope of the trough commenced only 20 Ma prior to the emplacement of the Valaam Sill.     

Heavy metals pollution on the sediments in lakes Dianchi, Erhai and Poyanghu and historical records

In this paper²¹⁰ Pb and ¹³⁷Cs dating methods were used to determine sedimentation rates of lakes Dianchi, Erhai and Poyanghu, and to establish the time scale of the sediments. Also based on geochemical records in the sediment column, the historical variation in heavy metal content over the past one hundred years was determined. Some element concentration increased rapidly after the 1970s, such as Cu, Zn and Mn in the sediments of northern Lake Dianchi, Cd and Mn in southern Lake Erhai and in the west central parts of Lake Poyanghu, Our investigations indicate that the increase in element concentration is caused by human activities. In order to understand the extent of the effect caused by human activities, we have calculated the flux of Zn, Cd and Mn. Results show that the flux caused by human activities is seven times greater than the natural one and the ratio is about 2 times in Lake Erhai and Lake Poyanghu.     

Sedimentation in the Lake of Tunis: A lagoon strongly influenced by man

The Lake of Tunis in northern Tunisia is a eutrophic marine lagoon covering 45 km² to an average depth of 1 m. Exchange of water with the Mediterranean Sea is restricted to a few canals. Bottom sediment is mainly calcareous sandy mud with much organic material. Sand-size grains commonly include quartz, dolomite, gypsum, and pyrite, as well as calcareous skeletal material dominated by molluscan fragments. Pyrite is the only important authigenic mineral presently forming. Principal sources of sediment are sewage sludge and fill, calcareous marine organisms, including abundant worm reefs, and local intermittent streams. The concentrations of Hg, Pb, Cd, Cr, Zn, Cu, and Fe are significantly higher in Lake of Tunis sediments than in sediments from Bahiret el Bibane, an unpolluted lagoon in the south of Tunisia. Man has affected the Lake of Tunis in four important ways. (1) Cultivation by early settlers, particularly the Romans, caused increased regional erosion and probably provided the sediment that encloses the lagoon. (2) In the mid-1800's the French constructed a ship canal which reduced intralagoonal circulation as well as exchange with the Mediterranean. (3) Nutrient pollution from sewage has encouraged the growth of circulation-restricting worm reefs, caused eutrophication and fish kills, and produced H₂S odor which permeates the city of Tunis during the summer. (4) Finally, man has significantly reduced the size of the lagoon by filling the lagoon and operating salt pans.     

Records of land use and medieval settlement history in Vuonninen,Dvina Karelia,Northwest Russia

Although the documented history of Dvina Karelia (northern Russian Karelia) does not begin until the second half of the 16th century, individual finds of prehistoric artifacts point to earlier human occupation. The present paleoecological study of the Vuonninen area is the first of its kind concerning prehistoric land use in Dvina Karelia, a large region extending from Finland to the White Sea. It is based on the pollen analysis of sediments from Lake Ylä‐Kuittijärvi near the old Karelian village of Vuonninen. In its general features, the picture of the early stages of cultivation and human activity in the village of Vuonninen is comparable to results from East Finland, the Karelian Isthmus, and the northern shores of Lake Ladoga. The first, minor indications of human influence appear in the sediments of the 4th–6th centuries A.D. in Lake Kuittijärvi. Distinct and unambiguous signs of human activity appear in the pollen record in the 12th century. This is particularly evident in the decreasing proportion of Picea, caused by the clearance of spruce forest. The beginning of cultivation is dated according to Secale pollen to the beginning of the 15th century. Intensive arable farming emerges in the early 19th century in the form of regular occurrences of Secale and Hordeum pollen. © 2010 Wiley Periodicals, Inc.     

Accumulation and risk of heavy metals in relation to agricultural intensification in the river sediments of agricultural regions

The enrichment characteristics and risk of heavy metals were studied in the sediments of Liucha River in Chao Lake Valley, where agricultural intensification has developed rapidly since the 1980s. The results revealed that Cd, Pb and Zn showed the lowest levels in the upper reaches and peak values in the lower reaches, increasing from 0.064, 7.75 and 59.75 mg/kg to 0.176, 12.33 and 96.82 mg/kg on average, respectively. Enrichment factor (EF) analysis showed that the EF values of Cd, Pb and Zn (maximum 4.76, 2.51 and 2.74, respectively) all increased from the upper reaches to the lower reaches (>1.5), while correlation analysis and cluster analysis showed that they primarily originated from the extensive use of phosphate fertilizer. In addition, the comprehensive potential ecological risk due to Cd, Cr, Cu, Ni, Pb and Zn in the sediments showed low degree, but Cd showed moderate and high risk at some sites. Therefore, heavy metal pollution due to agricultural intensification in the agricultural regions of Chao Lake Valley should be given great attention during management of the water environment.     

太湖北部底泥中氮、磷的空间变化和环境意义

以太湖底泥为研究对象，通过分析不同形态N，P的含量，揭示太湖北部底泥N，P的区域和垂向变化特征，探讨了主要营养元素的环境意义。太湖北部底泥N，P的高值区分布在五里湖，梅梁湾北部和竺山湖北部，有效氮的分布与总氮的分布一致。相关分析表明，有效磷与无机磷具有很好的正相关性，N，P的含量还与粘土矿物的含量成正比。柱状样的N，P垂直变化显示，数千年人类的活动并未明显影响底泥中N，P的含量，而在近代则明显增加。底泥中大量的N，P主要来自生活污水，其次是农田肥料和围网养殖。     

内蒙古乌梁素海湖泊地球化学特征与初步评价

通过内蒙古乌梁素海表层沉积物和深层沉积物的研究分析,对乌梁素海的湖泊沉积物特征有着明确的了解。乌梁素海深层沉积物中各元素与河套平原深层土壤中基本一致,而表层沉积物中各元素则具有明显的特征。湖泊表层沉积物中主要富集C、lCd、S、F、Sb、C、B、iAs、Li、MgO、CaO、Cu、N、iSn、W、Zn、Co、Mo、Au、Sc、Tl、Hg、I、Mn、U、Ce、La、Be、Se、Th等。湖泊表层沉积物与深层沉积物相比,在表层富集S、orgC、N、Se、I、Br、Sr、C、U、Mo、C、lCaO、Hg、P。在湖泊表层富集上述元素说明了黏土极易吸附这些元素,有些元素的富集主要是由于人类活动造成的结果。同时在表层土壤中pH明显低于深层土壤和河套地区土壤的pH,这与工业排放等人类活动紧密相关。垂直剖面结果也表明,人类活动对湖泊环境造成了严重影响。乌梁素海已出现富营养化和Hg、F污染,需对其进行治理。     

云蒙湖表层沉积物重金属分布特征及风险评价

为了解云蒙湖表层沉积物中重金属的污染状况,选取云蒙湖沉积物中6种重金属(Cu、Zn、Pb、Cr、Cd、As)作为研究对象,测定并分析其在云蒙湖表层沉积物中的分布、来源及生态风险,以期为云蒙湖沉积物中重金属污染治理及饮用水安全保障提供依据。采用富集系数法、相关性分析及聚类分析对重金属来源进行分析,并选用富集系数法、地累积指数法和潜在生态危害指数法对重金属污染程度及潜在生态危害进行了评价。结果表明:云蒙湖表层沉积物中6种重金属Cu、Zn、Pb、Cr、Cd、As平均含量分别为20.9、73.1、23.1、62.0、0.4和4.5 mg/kg;与临沂市土壤背景比较,Cd、Zn和Cr的含量超过临沂市土壤背景值,Cd污染最严重。重金属来源分析结果显示:Cd受人类活动影响较大,可能与区域农业和林业施肥有关;Cu、Zn、Pb、Cr和 As这几种重金属以自然来源为主。综合富集系数法、地累积指数法和潜在生态危害指数法3种评价方法的结果得出,云蒙湖表层沉积物中Cd 为最主要的污染元素,且具有较强的生态危害。     

Effect of metal pollution on the water quality in Taihu Lake

Heavy metals Cu, Zn, Cr, and others were carried though Liangxi River and Xiaomei River from Wuxi City and Huzhou City into Taihu Lake. Pollution of heavy metals in the water and sediments and chemical forms of Cu, Ph, Zn, Cd, Hg, Cr in the surface sediments were analysed to predict the effect of the pollution on water quality in Taihu Lake.     

Evolution of a provenance as revealed by petrographic analyses of Cretaceous formations in the Queen Charlotte Islands, British Columbia, Canada

Two contrasting marine sedimentary facies, the Haida Formation of sandy and argillaceous sediments and the conformably overlying Honna Formation of gravelly sediments were formed within different types of tectonic basins during mid- to Late Cretaceous time. The sediments of both formations were derived from the east. Sandstones from the two formations show characteristics of mature magmatic arc provenance and are classified as lithic and feldspathic arenites. However, the Honna sandstones are more feldspathic and less quartzose than the Haida sandstones. The Honna sandstones have many volcanic rock fragments (VRF) but the Haida sandstones do not. Feldspars of the VRF-rich Honna sandstones, however, do not seem to have been derived from the breakdown of volcanic rocks. The observed petrographic differences between the two formations can be ascribed to a process in which the volcanic cover and the basement rock denudation took place simultaneously in the source area during deposition of the Honna Formation.     

近50年来抚仙湖重金属污染的沉积记录*

文章以抚仙湖污染严重的北部和基本未受人类活动影响的中部为研究对象,分别采集了沉积岩芯FB和FZ,通过对岩芯的¹³⁷ Cs测年和重金属元素(Cu,Ni,Ti,Cr,V,Pb,Cd和Zn)的含量分析,研究了湖泊重金属来源和污染历史,并利用地质累积指数法评价了湖泊重金属污染程度。结果表明:抚仙湖北部的平均沉积速率约为2.0~2.8mm/a;20世纪80年代以前,湖泊北部和中部的重金属元素(Cu,Ni,Ti,V,Pb,Cd,Zn)以自然来源为主;80年代以后,抚仙湖受到人类活动的影响,但湖泊中部Cu,Ni,Ti,V,Pb,Zn以及湖泊北部Cu,Ni,Ti,V仍以自然来源为主;湖泊北部Pb和Zn地质累积指数值小于1,属无污染到中度污染;北部Cd地质累积指数为3~4,达强度污染;中部Cd地质累积指数为2~3,属中强度污染;且Pb,Zn和Cd污染程度有加速增大的趋势。     

太湖流域土壤重金属元素污染历史的重建:以Pb、Cd为例

太湖是位于长江下游的一个大型浅水湖泊,通过对4个代表太湖不同沉积环境的湖底沉积剖面的137Cs和210Pb沉积定年,重建太湖湖底沉积物和太湖来水流域土壤Cd、Pb的污染历史。结果显示:1980年以前,太湖底积物中Cd、Pb含量与流域内的自然背景含量相当,1980年以后,湖底沉积物中的Cd、Pb含量显著增高,这与我国大规模工业化进程的起始时间基本一致,推测工业化进程是湖底沉积物中Cd、Pb含量增加的主要原因。1900年以来太湖湖底沉积物中累积含有Cd和Pb分别为146t和25980t,其中苕溪来水提供的Cd和Pb分别为40t、6777t,宜溧河来水提供的Cd、Pb分别为36t、6023t,其他来水(洮、滆、运河)提供的Cd、Pb分别为71t、13179t,其他来水是太湖Cd、Pd累积的主要输入途径。Cd、Pb累积的高峰期为20世纪80—90年代,1980年以来,运河来水Cd、Pb的输出通量为28.26t、3419t;苕溪流域Cd、Pb的输出总量分别为13.70t、1585t,其中人为源的Cd、Pb为8.90t、610t,人为源输出的Cd、Pb通量占总输出量的64.96%和38.47%;宜溧河流域Cd、Pb的输出总量分别为10.09t、1063t,人为源的Cd、Pb分别6.96t和500t,人为源输出的Cd、Pb通量占总输出量的68.68%和47.08%,表明太湖流域人类活动所导致的Cd已超过自然剥蚀过程,因此削减工业化进程中的Cd、Pb排放总量,控制太湖运河来水的输出通量是改善太湖底积物Cd、Pb环境质量的关键措施。     

Deglaciation history of Lake Ladoga (northwestern Russia) based on varved sediments

Lake Ladoga in northwestern Russia is Europe's largest lake. The postglacial history of the Ladoga basin is for the first time documented continuously with high temporal resolution in the upper 13.3 m of a sediment core (Co1309) from the northwestern part of the lake. We applied a multiproxy approach including radiographic imaging, (bio‐)geochemical and granulometric analyses. Age control was established combining radiocarbon dating with varve chronology, the latter anchored to a correlated radiocarbon age from a lake close by. The age‐depth model reveals the onset of glacial varve sedimentation at 13 910±140 cal. a BP, when Lake Ladoga was part of the Baltic Ice Lake. Linear extrapolation of published retreat rates of the Scandinavian Ice Sheet provides a formation age of the Luga moraine close to Lake Ladoga's southern shore of 14.5–15.9 cal. ka BP, older than previously assumed. Varve sedimentation covers the Bølling/Allerød interstadial, the Younger Dryas stadial and the Early Holocene. Varve‐thickness variations, conjoined with grain‐size and geochemical variations, inform about the relative position of the Scandinavian Ice Sheet and the climate during the deglaciation phase. The upper limit of the varved succession marks the change from glaciolacustrine to normal lacustrine sedimentation and post‐dates the drainage of the Baltic Ice Lake as well as the formation of the Salpausselkä II moraine north of Lake Ladoga, by c. 250 years. The Holocene sediment record is divided into three periods in the following order: (i) a lower transition zone between the Holocene boundary and c. 9.5 cal. ka BP, characterized by mostly massive sediments with low organic content, (ii) a phase with increased organic content from c. 9.5 to 4.5 cal. ka BP corresponding to the Holocene Thermal Maximum, and (iii) a phase with relatively stable sedimentation in a lacustrine environment from c. 4.5 cal. ka BP until present.     

A statistical approach for determining the environment impact of surface sediments from the Dongting Lake area,central China

The Dongting Lake, the second biggest freshwater lake in China, consists of three wetlands of national importance, namely the East Dongting Lake, the South Dongting Lake, and the West Dongting Lake. Surface sedi-ments were sampled from 57 locations across the lake. Nutrient concentrations [total organic carbon (TOC), total N (TN) and total P (TP)] and 16 element concentrations (Al, As, B, Ca, Cd, Cr, Cu, K, Fe, Hg, Mn, Ni, Pb, Si, Ti and Zn) in the sediments were measured to investigate the impact of industrialization along the lake's coastline and sev-eral tributaries on the profiles of nutrients and heavy metals in the lake's surface sediments. R-mode cluster analysis (CA) was used to integrate geochemical data. The result showed that euthophication of the Dongting Lake resulted mainly from TN and TOC. The main polluting trace metals are Hg, As, Cd, Zn, Pb and Mn, which are largely ad-sorbed on clay minerals or Fe/Mn oxides, or deposited as carbonates. Principal component analysis (PCA) revealed the source of micropollutants. The worst affected district by heavy metals is the East Dongting Lake, the pollution sources may originate mainly from the Xiangjiang drainage area. The results demonstrated that multivariate methods are the potentially great tools for the interpretation of the environmental data on lake sediments.     

Toward a standard stratigraphical classification practice for the Baltic Sea sediments: the CUAL approach

The Late Pleistocene and Holocene glacial and postglacial sediments of the Baltic Sea basin are conventionally classified into units according to the so‐called Baltic Sea stages: Baltic Ice Lake, Yoldia Sea, Ancylus Lake and Litorina Sea. The Baltic Sea stages have been identified in offshore sediment cores by fundamentally different criteria, precluding detailed comparisons of the sediment units amongst different sea areas and studies. Here, long sediment cores and reflection seismic and pinger sub‐bottom profiles were studied from an offshore area in the Gulf of Finland, northern Baltic Sea. The strata are divided on the basis of sedimentological criteria into three allostratigraphical formations with subordinate allostratigraphical members and lithostratigraphical formations, following the combined allostratigraphical and lithostratigraphical (CUAL) approach. Sedimentological features are recommended as the primary stratigraphical classification criteria because they do not require the palaeoenvironmental inferences of salinity and water level that are inherent in the conventional classification practice. The presented stratigraphical division is proposed as a flexible template for future stratigraphical work on the Baltic Sea basin, whereby lower‐rank allounits and lithounits can be included and removed locally, while the alloformations will remain at the highest hierarchical level and guarantee regional correlatability. The stratigraphical division is compatible with international guidelines, facilitating communication to the wider scientific community and comparison with other similar basins.     

Heavy metals in sediments as evidence for recent pollution and quasi-estuarine processes: an example from Lake Druzno,Poland

This article presents the results of a geochemical investigation of sediments from Lake Druzno (northern Poland), a reservoir fed by freshwater from the catchment, with periodic input of brackish water from Vistula Lagoon. This study analyzed the spatial variation in heavy metal content in surface sediments as well as the temporal changes in metal content in two sediment cores dated using the ²¹⁰Pb method. In the surface sediments, the highest metal concentrations were recorded in the northern part of the lake, with lower concentrations in the central and southern parts. Absolute values of metal concentrations in the cores were low, but normalization with respect to Al showed an increase during the second half of the 20th century. Mean enrichment factors (EF) in sediments from the second half of the 20th century ranged from insignificant (1–1.2) for Fe to (1.55–3.3) for Cu, Cd, Pb and Zn. The sediments deposited before 1950 had lower EF values (>1.5) and had low variability. Results from both the surface sediments and the cores indicate that the main source of lake pollution is brackish water intrusion from the Vistula Lagoon via the contaminated River Elbląg.     

藏北那曲盆地中—上侏罗统拉贡塘组浊流沉积特征及微量元素地球化学

藏北那曲地区中上侏罗统拉贡塘组发育典型的深水浊流沉积,根据浊积岩鲍马序列和粒度特征,可以进一步将其区分为近源砂质浊积岩和远源细屑浊积岩。微量及稀土元素地球化学研究表明,拉贡塘组浊积岩富集Cr、Co、Sc、Th等元素,无Ce负异常或负异常不明显,沉积物物源主要来自于变质岩区或再循环的沉积岩分布区。那曲盆地是冈底斯中生代多岛弧盆系统的组成部分之一,中上侏罗世深水浊流沉积形成于活动大陆边缘中的弧后盆地环境,该弧后盆地的形成与班公湖怒江中特提斯洋盆的洋壳向南的俯冲作用有关。     

典型内陆湖泊沉积物氮、磷和重金属分布特征及生态风险评价——以武汉市武湖为例

城市内陆型湖泊湿地对城市生态系统具有重要的作用。以武汉市武湖为例,采用数理统计、营养盐指数、地累积指数和潜在生态风险指数等方法,对武湖表层沉积物中的氮、磷、有机质和重金属的平面分布特征、影响因素、富集污染程度、生态风险进行评价。结果表明: 武湖西北部表层沉积物中总氮、总磷和有机质的含量明显高于东南部,武湖周边地表径流和农田是营养元素的主要来源,旱地较水田有利于沉积物中总磷的富集; 武湖沉积物中有机质为内源水生植物和外源陆生植物的混合来源,与总氮具显著正相关关系; 沉积物中重金属含量总体较低,局部呈现高镉,平面上总体北部高于南部; 沉积物中重金属富集程度和潜在风险较低,局部地区镉和铅为轻微富集,镉和汞具中等潜在风险; 沉积物的潜在生态风险为低至中等,潜在生态风险与沉积物中镉的分布高度一致。