Spatial distribution of major and trace elements in shallow reservoir sediments: an example from Lake Waco, Texas

 Sediment geochemistry of a shallow (6-m average) reservoir (Lake Waco) was evaluated for the spatial distribution of major and trace elements. Sixty bottom and core samples along a 21-km transect within the reservoir, 18 overbank sediment samples, and 8 rock types in the drainage area were collected and analyzed for major (Al, Ca, Fe) and trace elements (As, Ba, Cr, Cu, Hg, Mn, Ni, Pb, Sr, V, Zn). Elemental concentrations in the reservoir sediments closely correspond to concentrations in the regional rocks and represent a mixture of overbank sediment composition of the tributaries. Elemental concentrations were statistically regressed against Al concentrations in order to establish regional baseline levels and thereby distinguish natural from anthropogenic sources. Spatial geochemical trends, considered in terms of element-to-Al ratio versus V-to-Al ratio, relate to the natural and anthropogenic sources contributing to the elemental concentrations. The spatial elemental distribution in the reservoir, which receive sediments from two mineralogically contrasting basins, reflect textural and mineralogical transition within the reservoir and suggest a progressive mixing of sediment from the tributaries. The spatial elemental distribution and sediment texture suggest that the sediment-source, which determines the sediment-type, has a greater influence on the major- and trace-element distributions in shallow reservoir sediments than bathymetry. Received: 25 September 1997 · Accepted: 3 February 1998     

桥墩墩型对平衡冰塞水位影响的试验研究

冰塞的出现使上游水位壅高,极易诱发凌洪灾害。桥墩墩型是影响桥墩附近冰塞壅水的重要因素之一。通过模型试验,对不同墩型影响下的平衡冰塞水位增值过程进行研究,并与无桥墩条件和明流情况进行了对比。试验结果表明:在试验冰水流量比条件下,当Fr≤0.145时,无桥墩条件下平衡冰塞水位增值小于有桥墩;当Fr>0.145时,无桥墩条件下平衡冰塞水位增值大于有桥墩;桥墩墩型引起的平衡冰塞水位增值由大到小排序为长方形桥墩、尖端形桥墩、圆端形桥墩和圆柱形桥墩。易发生冰塞的河段,建造桥梁时应当尽量选用圆柱形、圆端形桥墩。     

Acid leached analyses of stormdrain and harbor sediments, New Zealand

 Sediments from stormdrain catchments in Wellington city and sediment traps from Wellington Harbor were sampled for trace metal content. Samples were analyzed for acid leached metal content by extraction with 0.11 mol acetic acid l^–1 and using ICP-MS. Cu and Zn levels in harbor sediment traps increased towards the periphery of the harbor, while Pb levels adjacent to a road almost doubled. In general, areas of light industry in the Inner City stormdrain catchments exhibited higher acid leached metal concentrations. However, large-scale renovation work probably contributed to point sources of high metal levels. The proximity of stormdrain outlets to recreational activities, such as wharf fishing and shellfish gathering, should be of prime concern to local authorities. Some positive correlations are found between acid leached and total metal levels. These may prove useful for assessing the biological impact of significant increases in total metal concentrations in the vicinity of Wellington Harbor. Significant savings in the time and costs of analyses may be achieved. Received: 27 February 1998 · Accepted: 27 April 1998     

弯槽段冰塞形成及其厚度分布的试验研究

河流冰塞是寒冷地区河流的共性问题,弯槽段易于卡封是客观存在的现象,但对其形成机理的认识尚有待探索.借助于实验室的试验水槽,通过改变水流条件和冰流量条件,研究了弯槽段冰塞形成和厚度分布的规律.结果表明:当弯槽段先铺有模拟冰盖时,初始冰塞头部向下游推进的速度随水流的Fr增加而增加;当在弯槽尾部加上模拟的初封条件时,水流条件的变化可以产生冰塞发展的两种不同顺序,提出了实验室条件下的弯槽段冰塞体形成与否的临界F_r数.     

Impact of rainstorm-triggered landslides on high turbidity in a mountain reservoir

Typhoon-triggered landslides deliver huge amounts of sediment to the upstream channel of the Shihmen Reservoir in northern Taiwan. Observation data regarding landsliding, sediment discharge and water turbidity following five major typhoon events from 1985 to 2006 demonstrated that each time water turbidity in the reservoir area rapidly increased up to ten-fold from the river catchment drainage, and the weight of landslide debris exceeded total sediment discharge five-fold. The fact that huge amounts of landslide debris still remained on upstream slopes and water turbidity suddenly increased in the reservoir area but not in upstream channel implied that the increasing water turbidity in the Shihmen Reservoir was indirectly related to the large landslides occurring in the upstream catchment. The main cause of high turbidity in the reservoir area was that, during a typhoon event, high water discharge flowing into the reservoir scoured the fine fraction sediment at the bottom of the reservoir and formed hyperpycanl flow with high turbidity, which then ascended to contaminate the reservoir surface water.     

The variability of δ34S and sulfur speciation in sediments of the Sulejów dam reservoir (Central Poland)

The study was carried out on the Sulejów dam reservoir (Central Poland). Water and sediment samples were collected between February and October 2006. Sulfur compounds in the sediment were chemically extracted and subjected to isotopic analysis.Large variability of SO₄²⁻ concentration in the water column (from 10.3 to 36.2 mg/dm³) and the isotopic composition of sulfur (δ³⁴S from 2.1 to 5.4‰) was observed. The main identified sources of SO₄²⁻ were watercourses, surface runoff, and phosphorus fertilizers.Both oxidized sulfur species (SO₄²⁻) and its reduced forms were found in sediments. Particular sulfur forms were characterized by large variations in both, concentrations and the isotopic composition of sulfur. SO₄²⁻ in the sediment and in the water column had different genesis. Bacterial oxidation of organic sulfur and its binding in SO₄²⁻ were observed in the sediment. Under reducing conditions, oxidized and organic sulfur is converted to H₂S which reacted with Fe or other metallic ions leading to metal sulfide precipitation. Monosulfides were shown to have a very low concentration, ranging up to 0.07 mg/g of sediment. The transformation of elemental sulfur from sulfides through their chemical oxidation occurred in the sediment.     

Identifying water-quality trends in the Trinity River,Texas, USA, 1969–1992, using sediment cores from Lake Livingston

 Chemical analyses were done on cores of bottom sediment from three locations in Lake Livingston, a reservoir on the Trinity River in east Texas to identify trends in water quality in the Trinity River using the chemical record preserved in bottom sediments trapped by the reservoir. Sediment cores spanned the period from 1969, when the reservoir was impounded, to 1992, when the cores were collected. Chemical concentrations in reservoir sediment samples were compared to concentrations for 14 streambed sediment samples from the Trinity River Basin and to reported concentrations for soils in the eastern United States and shale. These comparisons indicate that sediments deposited in Lake Livingston are representative of the environmental setting of Lake Livingston within the Trinity River Basin. Vertical changes in concentrations within sediment cores indicate temporal trends of decreasing concentrations of lead, sodium, barium, and total DDT (DDT plus its metabolites DDD and DDE) in the Trinity River. Possible increasing temporal trends are indicated for chlordane and dieldrin. Each sediment-derived trend is related to trends in water quality in the Trinity River or known changes in environmental factors in its drainage basin or both. Received: 6 October 1995 · Accepted: 13 October 1995     

新疆天山北坡中段河流冰凌洪水特征分析

冰凌洪水(冰洪)是新疆天山北坡中段河流冬季的一种特殊洪水,其暴发主要受气温、逆温带范围、冬季河流来水量、冰情冰厚、地势.河道弯曲率和河床条件等多种因素影响."冰洪"具有随机性、规律性和不重复性三种特性,冰凌洪水的峰型类似于暴雨洪水具有陡涨陡落的特点,峰前陡峭而落峰则相对缓一些.以四棵树河为典型流域,对冰凌洪水的成因、发展和运动规律进行研究,并发现冰凌洪水具有"水鼓冰开"现象.对四棵树河1967-2006年冰洪流量的年内、年际分布情况看,20世纪70-80年代由于冬季气候寒冷,是"冰洪"发生最多的时期;自进入20世纪90年代以来由于受全球气候变暖等因素影响,冰凌洪水呈现衰退趋势,气候变暖对冰洪影响非常大.     

Sedimentology and depositional environments of the Lund Diamicton, southern Sweden

The Lund Diamicton (earlier named Lund Till) in SW Skåne, S. Sweden, is a glacioaquatic sediment consisting of clay and massive and laminated diamictons. It is characterized by clasts derived from the Baltic depression and its depositional history can be summarized as follows: After deglaciation, large fields of stagnant ice remained in the area and a periglacial land surface with ice-wedge polygons and wind-abraded clasts was developed in ice-free areas. A transgression followed and a clay/diamicton sediment was deposited, partly on top of stagnant ice and against a coastal barrier of stagnant ice along large parts of the basin boundary. This sediment is the Lund Diamicton. The main depositional processes were: fall-out of clay from suspension, sediment gravity flow from stagnant ice and icebergs and rain-out of debris from floating icebergs. The unit was extensively deformed by escaping pore water, loading, flow and due to melting of buried ice. The Lund Diamicton is the equivalent in this area of the classical 'Low Baltic till', which has been interpreted as a basal till deposited by the 'Low Baltic ice stream'. The present study concludes that this unit is instead a glacioaquatic sediment deposited during a transgression in the Öresund area. Its boundary represents the highest coastline and not the margin of a glacier.     

LA-ICP-MS heavy metal analyses of fish scales from sediments of the Oxbow Lake Certak of the Morava River (Czech Republic)

Heavy metal concentrations were studied in the scales of recent and subrecent (2–25 years old) fish buried in the oxbow lake sediments of the Morava River. The samples were taken from two cores up to 4-m deep and analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and an electron microprobe analysis (EMPA). The results were compared with heavy metal concentrations of bulk samples of the embedding sediment. The study has revealed substantial differences in heavy metal contents existing between the recent and subrecent fish scales documenting an extreme rapidity of the diagenesis/fossilization processes. The most apparent features of the early fossilization include the quick loss of the mucous envelope, collagen and magnesium and an enormous increase in the heavy metal concentrations in particular iron, which is connected with a colour change. The variations in heavy metal contents in fish scales within a sample are attributed to variations in heavy metal content in the environment and variable amounts of organic matter in the embedding sediment. In contrast to the contamination of the embedding sediment, no general increase in heavy metal concentrations in fish scales was observed down to the cores. It is inferred that the rapid sorption stabilizes the biologic hydroxyapatite of the fish scales, which thus rapidly attain a thermodynamic equilibrium with the embedding water-saturated sediment. The results show that the processes of sorption, fossilization and stabilization of hydroxyapatite can act very quickly over a time scale of several years and represent thus a great advantage in the preservation of the original signals of the ancient environments.     

黄河封河期冰凌预警地电测试技术研究

黄河流域地形地貌相差悬殊,受西伯利亚和蒙古一带冷空气的影响,冬春季干、支流有不同程度的冰情出现.由于黄河凌情来势迅猛,水位急剧壅高,易决口成灾,开展冰凌预警研究是十分必要的.黄河封河期冰盖下流凌量及冰塞体的生长状况是黄河冰凌预警的关键要素,采用地电测试技术,对冰水两相流进行视电阻率测量,绘制电测深曲线,数字化模拟冰凌参数,评估冰塞体的生长及冰块堆积状况,为防凌减灾提供预警服务.测试结果表明,平稳流凌时,测深曲线经子波分解后阈值为10Ω·m左右,当出现局部冰塞时阈值达到100Ω·m左右,数值易于区分,基于电测深曲线的差异性进行冰凌预警的方法是可行的,可为防凌减灾提供预警服务.     

桥墩影响下冰塞水位变化规律的试验

采用聚乙烯颗粒为天然冰模拟材料,对桥墩影响下的冰塞水位变化规律进行了探索性试验研究.试验发现,有桥墩时,冰塞演变可分为冰塞越过桥墩和未越过桥墩两种情况;冰塞动态演变过程中,桥墩附近冰塞底部存在冲刷现象,由此产生的冲刷输冰流量会引发较为复杂的冰塞水位演变过程.研究表明,有桥墩条件下,水力及来冰量条件对平衡冰塞时的水位增值影响规律与无桥墩时基本一致;水流条件和来冰流量相同条件下,当冰塞能越过桥墩达到平衡时,墩径较大时水位增值也较大,在断面阻塞程度相同条件下,双墩水位增值大于单墩.     

黄河下游凌情特征及变化

黄河下游冰情的基本特点和规律是:冬季有的年份封冻,有的年份不封冻;下游下段河道流凌封冻日期早,融冰、开河日期晚,封冻历时长,冰盖厚冰质坚;上段河道流凌封冻日期晚,融冰、开河日期早,封冻历时短,冰盖薄冰质酥。冰凌洪水特点是流量小,水位高且上涨快;凌峰流量自上而下沿程逐渐增大。近20年来,由于黄河下游河道水量大幅度减少,甚至发生连年断流,冬季气温持续偏高,加上水库调度等因素的共同影响,引起了凌情的相应变化。这些变化主要表现为:封开河日期提前,封河长度缩短、封冻冰量和槽蓄水量减少,冰塞冰坝发生次数减少,不封冻年频率增加等。     

Effect of changes in water level on sediment pore water redox geochemistry at a reservoir shoreline

Pore water samplers with high vertical resolution were used to evaluate the response of sediment redox geochemistry during transient hydrologic conditions at Lake Powell, a large reservoir in Utah and Arizona, USA. Samplers were deployed at two different yet proximal shoreline locations, White and Farley Canyons, before and after exposure of sediment to air and subsequent resubmersion, which resulted from fluctuations in the water level of the reservoir. Before exposure to air, an observed increase in dissolved Mn concentrations and, at Farley Canyon, an observed decrease in dissolved U concentrations across and immediately below the sediment–water interface indicated reducing conditions in the sub-surface. After exposure and resubmersion of the sediment, pore water profiles at each site differed distinctly from those observed before the fluctuation in water level. At White Canyon, an increase in U concentrations and a decrease in Mn concentrations in pore water after exposure and subsequent resubmersion are suggestive of oxidative processes occurring during the period of sediment exposure. Data from Farley Canyon suggest that the same processes may be occurring, but to a lesser extent. Depth profiles of As and Pb were also examined, but were relatively featureless compared to those of Mn and U. At both sites, sediment evaluated for pore water chemistry in the second sampling was only fully resubmerged for 2–5 days prior to the second sampling event, yet reducing conditions were clearly evident in the Mn pore water profiles. This suggests that the dynamics of the biogeochemical processes occurring in surface sediment at Lake Powell are responsive on the timescale defined by the fluctuating water levels in the reservoir.     

近30 a气温变化对黄河下游凌情影响分析

根据1951－1998年黄河下游代表站冬季气温资料，统计分析了近30a平均气温和气温过程变化特点及其对凌情的影响，并在分析负气温演变特点及其与凌情关系的基础上，建立了气温－凌情关系式，同时利用70年代以来气温、凌情资料，计算分析了气温变化和其它因素对凌情的影响。     

黄河河曲段冰塞水位的分析计算

本文根据黄河河曲段６年的实测资料，分析了该冰塞河段冰期水位的变化规律，讨论了该河段冰塞水位的变化与冰塞演变的相互关系。建立了冰塞水位变化的参数关系式，基于原型的观测研究，对试验室模拟冰塞的水位进行了分析研究，研究表明：试验室模拟冰塞水位的变化规律与天然河道中冰塞水位的变化规律相同。由此，可以进行冰塞水位的计算及其预报。     

Distribution and speciation of mercury in the Hongfeng Reservoir,Guizhou Province,China

The water, pore water, sediment, and fish samples were collected from the Hongfeng Reservoir in November 2003 and February 2004 in accordance with trace metal protocols. The average concentrations of total mercury （THg）, dissolved mercury （DHg）, reactive mercury, dissolved gaseous mercury, total methylmercury, and dissolved methylmercury in the water columns were 8.00, 5.70, 0.63, 0.05, 0.16, and 0.07 ng/L, respectively. THg and DHg in the water columns, THg in pore water and THg in lake sediments of the Hongfeng Reservoir showed the level of mercury in the Hongfeng Reservoir was higher than in other natural waters in the world due to the loading of a lot of waste water with relatively high concentrations of mercury, whereas methylmercury concentrations in fish （wet weight） varied from 1.73-51.00 ng/g, much lower than in most remote lakes and reservoirs reported in northern Europe and North America. Methylmercury distributions in pore water and sediments showed methylation occurred mainly in the upper several centimeters of sediment cores in the Hongfeng Reservoir. The concentrations of dissolved organic carbon, total suspended particles, total Hg, and methylmercury were higher at Houwu than those at Daba in November 2003. It is suggested that other pollutants such as N and P from fishing farm and other waste water at Houwu, which resulted in deterioration of water quality, affected the concentrations and distributions of mercury species in the reservoir.     

Forecast of water level and ice jam thickness using the back propagation neural network and support vector machine methods

Ice jams can sometimes occur in high latitude rivers during winter and the resulting water level rise may generate costly and dangerous flooding such as the recent ice jam flooding in the Nechako River in downtown Prince George in Canada. Thus, the forecast of water level and ice jam thickness is of great importance. This study compares three methods to simulate and forecast water level and ice jam thickness based on field observations of river ice jams in the Quyu Reach of the Yellow River in China. More specifically, simulation results generated by the traditional multi-variant regressional method are compared to those of the back propagation neural network and the support vector machine methods. The forecast of ice jam thickness and water level under ice jammed condition have been conducted in two different approaches, 1) simulation of water level and ice jam thickness in the second half of the period of measurement using models developed based on data gained during the first half of the period of measurement, 2) simulation of water level and ice jam thickness at the downstream cross sections using models developed based on data gained at the upstream cross sections. For this reason, as the results of simulation and field observations indicated, the back propagation neural network method and the support vector machine method are superior in terms of accuracy to the multi-variant regressional method.     

Remediation of heavy metal-contaminated sediments by solid-bed bioleaching

 Weisse Elster River sediment from the Leipzig Lowlands region (Saxony, Germany) is anthropogenically polluted by heavy metals. Sediment dredged from a trap to the south of Leipzig was characterized in detail. When freshly dredged sediment contacts air, the material turns acidic because of oxidation processes, the heavy metals become soluble and the sediment poses an environmental risk. We are therefore developing a sediment-treatment process based on heavy metal removal by bioleaching. Leaching experiments were carried out in suspension and in the solid bed. The heavy metals were solubilized to nearly the same extent by H₂SO₄ dosage (pure chemical extraction) and addition of elemental sulphur (microbial oxidation of S⁰ to H₂SO₄). With increasing dosage of the leaching agent, Zn, Cd, Ni, Cu and Cr were more and more solubilized, whereas Pb was only dissolved in small amounts. The addition of 2% S⁰ is considered an optimum dosage. When 5% S⁰ was added to the sediment, the pH dropped to 1.76 and large amounts of undesirable compounds such as Ca, Al and Fe were solubilized. The higher the temperature, the faster the metals were solubilized in both suspension and the solid bed. The temperature optimum for activating the indigenous S⁰-oxidizing microbes of the sediment lies between 30 and 40  °C. Conditioning of freshly dredged sediment with plants makes it suitable for solid-bed leaching; the kinetics of heavy metal solubilization from sediment conditioned for 6 months with Phragmites australis was the same as from long-term stored sediment. Received: 26 November 1999 · Accepted: 5 May 2000     

冰塞水位分析

高纬度地区河流冬季常形成冰塞,冰塞堵塞过流断面,使湿周增加,致上游水位升高,常因此产生凌洪灾害,冰塞的解体、溃决又常使下游产生灾害。冰期水位是冰塞演变和发展的重要结果之一,对于防灾减灾具有重要的参考价值。依据实验室资料和黄河河曲段的实测资料,针对直道和弯槽,对比分析了不同冰流量、不同初始水深和流速时模拟冰塞和天然河道冰期水位的变化规律。