Mineralogical and geochemical composition of Late Holocene bottom sediments of Lake Onego

The analysis of both the mineralogical and geochemical composition and the stratigraphy of Holocene sediments of Lake Onego provided a novel interpretation of their genesis. Their mineral composition suggests that Holocene bottom sediments generally inherit the composition of terrigenous material that enters the lake with river runoff. The predominant authigenic minerals include biogenic opal from diatom skeletons, Fe-illite, and Fe-chlorite, which are the main iron mineral forms in bottom sediments of Lake Onego. Unstable suspension components (illite and chlorite) transform into their ferruginous varieties under humid climate conditions and high concentrations of iron and silicon in the lake waters. Both the presence of ferromanganese nodules in the uppermost part of bottom sediments of Lake Onego and their formation result from the location of the lake in the northern humid zone, geological composition of Fennoscandian crystalline rocks on the Lake Onego watershed, and the presence of an oxidative geochemical barrier into the lake sediment sequence. Late Holocene bottom sediments are represented by two types of sequences: 1) Fe-Mn enriched layers are formed near the sediment-water interface under oxygenated near bottom waters, and 2) such layers are not formed due to low concentrations of oxygen in water; but there are also non-laminated, homogeneous greyish-green silts, similar to those present in the lower parts of the first type of cores. Sedimentation rates (~0.10 cm y⁻¹) were determined by ²¹⁰Pb- and ¹³⁷Cs geochronologies.     

Spectrally based bathymetric mapping of a dynamic,sand‐bedded channel: Niobrara River,Nebraska, USA

Methods for spectrally based mapping of river bathymetry have been developed and tested in clear‐flowing, gravel‐bed channels, with limited application to turbid, sand‐bed rivers. This study used hyperspectral images and field surveys from the dynamic, sandy Niobrara River to evaluate three depth retrieval methods. The first regression‐based approach, optimal band ratio analysis (OBRA), paired in situ depth measurements with image pixel values to estimate depth. The second approach used ground‐based field spectra to calibrate an OBRA relationship. The third technique, image‐to‐depth quantile transformation (IDQT), estimated depth by linking the cumulative distribution function (CDF) of depth to the CDF of an image‐derived variable. OBRA yielded the lowest depth retrieval mean error (0.005 m) and highest observed versus predicted R² (0.817). Although misalignment between field and image data did not compromise the performance of OBRA in this study, poor georeferencing could limit regression‐based approaches such as OBRA in dynamic, sand‐bedded rivers. Field spectroscopy‐based depth maps exhibited a mean error with a slight shallow bias (0.068 m) but provided reliable estimates for most of the study reach. IDQT had a strong deep bias but provided informative relative depth maps. Overprediction of depth by IDQT highlights the need for an unbiased sampling strategy to define the depth CDF. Although each of the techniques we tested demonstrated potential to provide accurate depth estimates in sand‐bed rivers, each method also was subject to certain constraints and limitations.     

Strategies for management of contaminated sediments within the meuse river-system

The sediments in the Meuse valley are contaminated on a large scale by diffuse sources. The project ‘Maaswerken’ aims at the enlargement of the discharge capacity of the river Meuse. In the realization of the project, a full-scale clean-up operation would not be realistic and not effective because of recontamination and the enormous scale and costs involved. The concept of dynamic soil management offers a solution to this problem. This approach to remediation implies putting back contaminated sediments of indigenous quality within the river system. Preconditions are determined by risk assessment and local conditions. The first aim is improvement of the environmental quality of the river system. Other objectives such as the development of natural areas, the mitigation of geohydrological effects and the exploitation of sand and gravel can be realized by several forms of beneficial use of contaminated sediments. Dynamic soil management is expected to be a pragmatic and cost-effective solution for the problem of contaminated sediments.     

Sediment dynamics and pollutant mobility in rivers: An interdisciplinary approach

Characteristic dynamic features of sediment‐related processes in rivers include dramatic effects of stormwater events on particle transport, rapid and far‐reaching effects of sulphide oxidation during resuspension, and biological accumulation and potential release of toxic chemicals. Pollutant mobility is the net result of the stabilizing and mobilizing effects in both hydraulic and chemical fields. In practice, emphasis has to be given to fine‐grained sediments and suspended matter as these materials exhibit large surface areas and high sorption capacities. Organic materials are highly reactive. Degradation of organic matter will induce oxygen depletion and might enhance formation of flocs and biofilms. Study of variations of sediment and water chemistry should predominantly include changes of pH and redox conditions, competition of dissolved ions and processes such as complexation by organic substances. Major questions relate to the potential reduction of sorption sites on minerals and degradation of organic carrier materials. All these processes will influence solution/solid equilibrium conditions and have to be studied prior to modelling the overall effects of pollutants on the water body and aquatic ecosystems. With respect to handling and remediation of contaminated river sediments, either in‐place or excavated, a chemical and biological characterization of the material, of the (disposal) site and of the long‐term processes is crucial. Passive techniques (e.g. in situ stabilization, subaqueous capping) provide economic advantages as there are no operation costs following their installation. However, the success of these ecological and geochemical engineering approaches is mainly based on an in‐depth knowledge of the underlying processes.     

The Utility of Magnetic Properties as a Proxy for Mapping Contamination in Hamilton Harbour Sediment

Rapid, non-destructive, magnetic-property measurements are useful as a proxy for contamination in sediment, and as an indicator of disturbed sediments. Magnetic-property measurements on sub-samples from sediment cores taken from Hamilton Harbour define a boundary marked by a sharp increase in magnetic mineral content. At this boundary magnetic susceptibility (κ) increases by at least one order of magnitude. Confirmation that this represents the base of the industrial sediment is provided by concomitant increases in both polycyclic aromatic hydrocarbon (PAH) and trace metal content. Detailed correlation of these horizons allows for the distinction between undisturbed and disturbed sediments. A consequence of this work is the potential use of completely non-destructive measurements of κ as a tool for mapping the distribution of contaminated sediments in Hamilton Harbour.     

Modeling the Transport of Sediments and Hydrophobic Contaminants in the Lower Saginaw River

A study of processes that are significant in the transport and fate of sediments and hydrophobic contaminants in the lower Saginaw River over long periods of time, up to 25 years, has been made. The numerical model used in the analysis consists of a two-dimensional, vertically-integrated, time-dependent hydrodynamic and sediment transport model coupled (a) with a three-dimensional, time-dependent model of the dynamics of the sediment bed and its properties and (b) with a model of the transport and fate of hydrophobic contaminants. Calculations of sediment transport for different magnitude flow events demonstrate the variations in erosion and deposition at different sites and the dependence of this erosion and deposition on the flow rate. These calculations also illustrate the inherent variability, or uncertainty, in any long-term predictions since the results depend to a great extent on the times of occurrence of the largest flow events, times which can not be predicted but are only known statistically. The transport and fate of PCBs were also investigated with the emphasis on the effects of (a) large flow events, (b) incoming upstream PCB loads, and (c) burial of contaminated sediments by clean sediments with subsequent erosion of sediments by a large flow event. The analysis clearly shows that the major erosion of contaminated sediments occurs at the edge of the river channel with little erosion of contaminated sediments in the near-shore area.     

Non-steady state behaviour of heavy metals in contaminated freshwater sediments

The behaviour of heavy metals has been investigated in contaminated sediments of the river Meuse, The Netherlands. Due to temporal changes in temperature and degradability of organic matter, the depths of the redox boundaries fluctuate. This contributes to a non-steady state. As a result of oxidation processes, a distinct peak in heavy metal concentrations in pore water is measured at the sediment-water interface. Because the studied anoxic sediments contain low levels of sulphide, other solid phases are expected to be of importance in the binding of heavy metals. Furthermore, heterogeneity of the sediment and complexation with dissolved organic compounds may result in supersaturation of the anoxic pore waters with respect to discrete heavy metal sulphides, thus influencing heavy metal mobility. Calculations using concentration gradients of heavy metals indicate that diffusive fluxes between the sediment and the surface water contribute to concentrations in the surface water, although significant effects may be confined to specific locations.     

Hydrologic scaling for hydrogeomorphic floodplain mapping: Insights into human‐induced floodplain disconnectivity

Hydrogeomorphic approaches for floodplain modelling are valuable tools for water resource and flood hazard management and mapping, especially as the global availability and accuracy of terrain data increases. Digital terrain models implicitly contain information about floodplain landscape morphology that was produced by hydrologic processes over long time periods, as well as recent anthropogenic modifications to floodplain features and processes. The increased availability of terrain data and distributed hydrologic datasets provide an opportunity to develop hydrogeomorphic floodplain delineation models that can quickly be applied at large spatial scales. This research investigates the performance of a hydrogeomorphic floodplain model in two large urbanized and gauged river basins in the United States, the Susquehanna and the Wabash basins. The models were calibrated by a hydrologic data scaling technique, implemented through regression analyses of USGS peak flow data to estimate floodplain flow levels across multiple spatial scales. Floodplain model performance was assessed through comparison with 100‐year Federal Emergency Management Agency flood hazard maps. Results show that the hydrogeomorphic floodplain maps are generally consistent with standard flood maps, even when significantly and systematically varying scaling parameters within physically feasible ranges, with major differences that are likely due to infrastructure (levees, bridges, etc.) in highly urbanized areas and other locations where the geomorphic signature of fluvial processes has been altered. This study demonstrates the value of geomorphic information for large‐scale floodplain mapping and the potential use of hydrogeomorphic models for evaluating human‐made impacts to floodplain ecosystems and patterns of disconnectivity in urbanized catchments.     

长江源曲麻莱段河床沉积物分布特征

基于长江源通天河曲麻莱河段河床沉积物测量和分析,通过各参数的统计及对比,探讨沉积物粒度的基本特性及时空分布规律。结果表明:取样河段沉积物以沙砾石为主,由跃移质和悬移质成分组成,无滚动沉积,粒度参数和频率分布曲线特征显示长江源曲麻莱段河床沉积物分选较差,自然分布频率曲线多为双峰,是较典型的河流动力沉积物。而阶地沉积物则为多峰,分选差,应为河流与冰川共同作用的结果;同一断面河槽附近沉积物粒径较粗,与水流动力分布一致;洲滩沉积物粒径的垂向分布呈现粗细交替的基本规律,可反映不同历史时期河道水文节律以及青藏高原气候的定性变化。沉积物粒度的垂向分布可以为河流历史形态复原和水力反演提供基本数据。     

Flood inundation mapping using NOAA AVHRR data

The river Brahmputra flowing through the state of Assam (India) floods every year. The analysis of spatial extent and temporal pattern of flood-inundated areas is of prime importance for mitigation of floods. With the development of remote sensing techniques, flood mapping for large areas can be done easily. In case of flood affected area mapping of large area it will not be feasible to use high-resolution data, because the whole area will be covered in number of scenes. Therefore use of NOAA (National Oceaongraphic Atmospheric Administrative) data is quite useful in such type of studies. NOAA-AVHRR (Advanced Very High Resolution Radiometer) data have the potential for flood monitoring due to high frequency of global coverage, wide swath, high repetivity and low cost. In this study, NOAA-AVHRR data have been used for mapping of flood-affected area during the year 2003. On the basis of spectral characteristics of land and water, a methodology for water identification is presented. The maximum spatial extent of floods, generated by compiling the available cloud free maps, is informative about flood damages. Analysis of results reveals that in the months of July and August almost 25-30% of the area was flood affected. Also the result indicates that in some districts, the flood-affected area is very high.     

Bioaccumulation Potential of Sediment-Associated Polychlorinated Biphenyls (PCBs) in Ashtabula Harbor,Ohio

Ashtabula Harbor, Ohio is designated as a Great Lakes Area of Concern contaminated by PCBs. Information on the bioaccumulation of PCBs from sediments is important for sediment management strategies such as dredging to restore navigable depths in the harbor. To ascertain the bioaccumulation of these PCBs, the aquatic earthworm Lumbriculus variegatus was exposed in the laboratory to contaminated sediments collected from 15 areas in the harbor. Data from these bioaccumulation experiments were used to determine the bioaccumulation potential of PCBs through the calculation of Biota- Sediment Accumulation Factors (BSAFs). The results showed that the mean values of the experimentally derived BSAFs for individual harbor areas ranged from 0.27 to 1.69. The median BSAF for sediments in the lower river sector of the harbor (0.38) was significantly lower than that for upper river sediments (1.34), indicating that the high adsorptive properties of coal soot particles constrained PCB bioavailability in the lower river sediments. These results indicate that the origin of total organic carbon (TOC) has a major influence on the bioavailability of total PCBs in harbor sediments. Moreover, the empirical BSAFs were well below the 4.0 default BSAF value recommended in joint USEPA/USACE protocols that are used to evaluate the Theoretical Bioaccumulation Potential, or bioavailability, of neutral organic chemicals in Great Lakes sediments. These empirical values should be used to more precisely predict the bioavailability of total PCBs in Ashtabula Harbor sediments.     

黄河流域泥沙矿物成分与分布规律

黄河及其干支流经常产生高含沙水流,泥沙中矿物的成分及含量是影响高含沙水流性质的主导因素,粘土矿物颗粒含量对高含沙水流流变性质的影响,远大于颗粒粒径大小对流变性质的影响,粘土颗粒和阳离子之间的相互作用对高含沙水流的流变性质也有非常大的影响。通过对黄河及其支流地区12个地点进行采样分析,得出黄河及其支流地区泥沙基本来源于同一地区,次生矿物是在长期的、相同的环境条件作用下形成的。根据泥沙样本的粒径分布曲线和矿物成分及含量,建立了黄河及其支流泥沙粘土、非粘土矿物含量与中值粒径之间的关系,能够更方便、快捷、廉价地估算黄河及其支流粘土矿物的含量。     

Can we characterize river corridor evolution at a continental scale from historical topographic maps? A first assessment from the comparison of four countries

National historical map resources are assessed in four European countries to characterize river corridor features and associated channel changes, as well as identify issues limiting or promoting geomorphic assessment procedures at a continental scale. A geomorphic audit that launches potential data for diagnosis from reach to continental scales could offer a good resource for biology and ecology managers of river authorities or government agencies and engineers. The assessment compares the resources available by country in terms of period covered, spatial scale, history and chronology, and representation of the fluvial corridor features. We then applied the Historical Maps Vectorization Toolbox, initially developed for vectorizing river corridors from French maps, to detect and extract flow channels, unvegetated bars and riparian vegetation patches from historical topographical maps. We found that (a) it is difficult to apply an audit of channel changes to the whole continental scale because map legends differ between countries due to geographic and political specificity; (b) there exists an opportunity to get assessment information in all countries at reach or national scale where map resources are available; (c) the highest potential is observed in Switzerland and Belgium where there is high quality national map coverage from the 19th century; and (d) the algorithm Historical Maps Vectorization Toolbox applied to map resources works well with any of the countries, and its widespread application is encouraging.     

基于遥感数据的河冰过程解译及分析

鉴于河冰的野外观测受观测技术、条件及方法的限制而无法获得大尺度、长序列的河冰过程数据,而遥感技术可有效完成复杂时空尺度海量信息的收集处理,以Landsat8遥感影像为数据源,通过单波段信息量比较及相关系数、信息熵和最佳指数的联合分析,得到最佳波段组合;采用监督分类的最大似然法对黄河内蒙古段三湖河口河段2013—2014年冬季不同时期遥感卫片数据进行解译,并对解译结果进行分析,从而获得该河段不同时期河冰的生消演变过程及特性。结果表明:应用7、4、3波段组合获得了较高的河冰解译精度,解译影像可以反映大尺度下冬季河冰的生消演变及输移过程,结合气象、水文等数据可以解释典型河冰现象,为河冰的理论分析及机理研究提供数据支撑。     

Monitoring water quality in reservoirs with IRS-1A-LISS-I

An attempt has been made to quantify the relationship between the variation in IRS-IA-LISS-I (Indian Remote Sensing Satellite-1A Linear Imaging Self-Scanning System) radiance data and field measured change in secchi disc depth. Secchi disc depth was measured for 47 predetermined sampling locations on reservoir surface water. At extinction depth (secchi depth), water samples were collected from all the sampling locations. Suspended sediments of eight locations representing various reaches of the reservoir were selected for mineralogical, particle size and optical properties analysis. The LISS-I radiance value in band 1 (0.45–0.52µm) band 2 (0-52–0.59 µm) and band 3 (0.62–0.68 µm) were used in a regression analysis. The absorption infrared band 4 (0.77–0.86 µm) was not included in the analysis. In these, the dependable variable was secchi depth (SD) and the LISS-I-radiance data was the estimator variable. Forty-seven data sets of 20 October 1988 from Tawa reservoir surface water were used to obtain an estimator equation for SD. The verification of the estimator equation was tested by applying it to a data set of 21 measurements of 28 September 1988 for this reservoir. The coefficient of correlation between observed and estimated values for the 28 September 1988 data set wasr=0.92 for SD, indicating that the equation could accurately predict the water clarity (SD) for this reservoir on new occasions from IRS-IA-LISS-I spectral data. It is shown that mineral composition and optical properties of suspended sediments influence the reflected radiance of water quality. It is concluded that IRS-IA-LISS-I data provide a useful means of mapping water quality in reservoir.     

The Effect of Contaminated Sediments on Fecundity of the Brown Bullhead in Three Lake Erie Tributaries

Female brown bullhead (Ameiurus nebulosus) were collected from three Lake Erie tributaries (Ohio) from 8 to 25 May 1989, to determine the effects of contaminated sediments on reproductive potentials. Fish obtained from the Black and Cuyahoga rivers, which contain sediments with elevated concentrations of metals, PCBs, and PAHs, were compared with fish collected in Mud Brook, a tributary of the Huron River, which was selected as our reference site. Fecundity, egg diameter, fish length and weight, and the presence of external abnormalities were recorded for each fish. Brown bullhead from the contaminated sites were larger then those from the reference site and fecundity was significantly (P ≤ 0.05) different in all three river systems. Those from the most polluted river (Cuyahoga River) had the greatest number of eggs per individual female. The high frequency of external abnormalities observed on brown bullhead from the contaminated sites did not appear to have a detrimental influence on fecundity. These results suggest that fecundity of the brown bullhead was not adversely affected in ecosystems altered by the presence of contaminated sediments. Increased fecundity of the brown bullhead from impacted rivers may be the result of reduced competition for an abundant invertebrate food source and limited predation by other fish species whose numbers are largely depleted in these degraded systems.     

南水北调温博段倒虹吸混凝土浸蚀分析

南水北调工程温博段倒虹吸工程建成后,其混凝土受到临近工业污水的影响,表层沉积砖红色沉淀,可能对混凝土质量造成影响。通过钻芯取样、环境水分析及硫酸盐浸入深度分析等方式对混凝土受浸蚀状况进行分析,并对目前混凝土质量进行了评定。     

Temporal and spatial patterns based on sediment and sediment–water interface characteristics along a cascade of reservoirs (Paranapanema River, south-east Brazil)

Physical and chemical characteristics of the sediments in a cascade of eight reservoirs located in the Paranapanema River (south‐east Brazil) were analysed during two consecutive years during summer (January), autumn (April), winter (July) and spring (October) of 2000 and 2001, respectively. The granulometric texture, organic matter content and nutrient concentration (total nitrogen and phosphorus) were determined in the superficial sediment of 19 sampling stations, as well as the temperature, dissolved oxygen, pH, conductivity and redox potential in the bottom layer of the water column. Seasonal and spatial changes were observed for both years, especially for organic matter and nutrient concentrations. Three different areas could be identified along the river, which corresponded to the upper, middle and lower Paranapanema basin. The first area was characterized by an increase of nutrients and organic matter in the sediments and a decrease of temperature and dissolved oxygen in the downstream direction. The second one represented a region where fluctuations in nutrient and organic matter concentrations and a reduction in dissolved oxygen were observed. In the third area, there was an increase in nutrient and organic matter in the sediments and also an increase in temperature and dissolved oxygen towards the river mouth. The results of the principal components analysis, using water and sediments variables, showed the ordination of sampling stations by periods: wet (January–April) and dry (July–October) during 2000. This pattern was also verified during 2001, but with slight changes, probably due to the increase in the rains which would have produced certain homogenization effects along the river.     

ESTIMATING ANNUAL RIVERBANK EROSION RATES—A DENDROGEOMORPHIC METHOD

An accurate estimation of riverbank erosion rates is critical for the evaluation of the past, present, and future sediment regime of river systems. Understanding these relationships allows watershed managers and regulators to prioritize river restoration and contaminated site remediation projects. In this dendrogeomorphic study, changes in the anatomy of tree roots exposed between 1 and 31 years were used to estimate the average annual erosion rates of riverbank sediments on a large river in Michigan, USA. Exposed root samples from diffuse and ring‐porous hardwoods, together with buried ones as controls, were analyzed. Differences in the arrangement, size and frequency of vessels, fiber diameter, cell wall thickness, growth ring width, and scarring between the exposed and the buried samples were used to identify the first year of root exposure. Results of the regression analysis between the average annual erosion rate and the Bank Erosion Hazard Index (BEHI) indicated that the more recently exposed roots (less than 7 years in this study) explained more of the variance (R² = 0.67) than when all samples were included (R² = 0.38). Although the average erosion rates for long periods can be accurately determined from the dating of exposed tree roots, attempts to relate these rates using the BEHI for longer periods are less successful, as BEHI values can vary considerably over time as the riverbank erodes. Consequently, when using exposed tree roots to develop regression equations and erosion rate curves for the estimation of erosion rates based on BEHI scores, it is necessary to use roots that were recently exposed. Copyright © 2013 John Wiley & Sons, Ltd.     

The Effects of Topographic Map Scale and Costs of Land Surveying on Geometric Model and Flood Inundation Mapping

The quality of topographic datasets plays a key role in deriving terrain model and hydraulic simulation. In developing countries, data-sparse regions and most parts of the world, accessing to high-quality datasets is almost impossible and topographic maps with a specific scale should be used to derive the geometry of river bed and floodplains. For these areas, understanding the effects of map scale on the costs of land surveying/river projects and flood inundation mapping may lead to an appropriate flood modeling and reduce huge amounts of financial resources. This research addresses the effect of using topographic maps with different scales on the hydraulic properties and focuses on using the relationship between topographic map scale, the costs of land surveying and hydraulic properties. The results from the three river reaches (SojasRood and SafaRood rivers in Zanjan and Mazandaran provinces, respectively and Sarbaz river in Sistan-Baluchistan province, Iran) used in this study show that in small-scale rivers (SojasRood and SafaRood rivers), the effect of topographic map’s scale on water surface elevation (WSE) isn’t meaningful up to 1:4000 (4 K) map scale, while in the case of Sarbaz river WSE is approximately scale independent (even up to 1:10000 (10 K) map) and there is no considerable discrepancy between low and high-quality maps in predicting this important variable. For example, in SojasRood river the mean absolute error (MAE) in simulation of WSE for low-quality maps (5 K and 6 K maps) varies between 0.79 m and 1.78 m, while for high-quality maps (1 K, 2 K and 3 K) it restricts to only 0.25 m. Also, in the case of Sarbaz river, for maps with the scale of higher than 5 K (high resolution maps) the maximum values of MAE and RMSE statistics limit to 0.13 m and 0.16 m, respectively. Moreover, findings demonstrate that using the topographic maps with the scales of 2 K and 7 K instead of high quality maps (1 K and 2 K maps in small-scale rivers and Sarbaz river, respectively as base maps) lead to the same geometric model and the mean relative error (MRE) in simulating inundation extents is lower than 10%. These outcomes clearly indicate that by accepting some reasonable errors the low quality maps, that are cost-effective and not time-consuming, can be considered as alternative maps for flood simulation in low budget projects. Furthermore, assessing the costs of ground surveying shows that it highly depends on the scale of topographic maps and by using low quality instead of high quality maps the costs of topographic maps’ production significantly decreases. In addition, changes in hydraulic properties due to using these maps are not considerable when compared to the significant saved financial resources.