Search results for "Sediment"
showing 10 items of 1648 documents
COMPOSITION AND QUALITY OF FRESHWATER LAKE SEDIMENTS (BALVU AND PĒRKONU LAKES)
2019
Water quality, watershed basin and urbanization are key factors from the perspective of freshwater management; however, actual depth of waterbodies is often an overlooked element. Actual depth represents the overall depth of lake bed and depth of sediments. Some cases have been reported, where with increase of average depth of lake , it is possible to expect improvements of water quality when sediments are removed. If lakes are eutrophic, shallow, overgrown with macrophytes and contain high concentrations of biogenic elements water and lake ecosystem quality can be endangered. Removal of sediments can be an expensive procedure and also depends on the composition, structure, local conditions…
The abundance of Au, Pt, Pd, and the mode of heavy metal fixation in highly polluted sediments from the Rhine River near Mainz, West Germany
1984
The Au, Pt and Pd contents of the sediments of Ginsheimer‐Altrhine River, a channel of the Rhine river which drains one of the most industrialized regions of western Europe, have been determined by flameless atomic absorption spectrophotometry. The abundances of these noble metals range from 96–460 ppb Au; 734 ppb‐31 ppm Pt and 32 ppb‐4 ppm Pd. The extremely high concentrations, particulary those of Pt and Pd, are attributed to their use in industry and are due to the formation and concentration of metal‐organic complexes, mainly at the interface between an extremely reducing and an oxidizing aquatic environment. Differential thermal analyses of the polluted sediments in comparison to the p…
Organic chlorine compounds in lake sediments. II Organically bound chlorine
1990
Abstract Organically bound chlorine together with inorganic chloride was measured from dated bottom sediment layers of 18 lakes in Central Finland and compared to organic matter contents. Pulp mills were found to be the source of significant increase of the accumulation of all of these materials in the 20th century.
Sediment delivery processes and the spatial distribution of caesium-137 in a small Sicilian basin
1998
The sediment delivery processes occurring in a small Sicilian basin are modelled using the spatially distributed SEDD model recently proposed by Ferro and Minacapilli. The model is applied by using soil data (grain-size distribution, organic matter content, etc.) of 129 samples uniformly distributed over the study area and compiling the available information (topographic map, soil data, etc.) into a Geographical Information System. Finally, the predictive capability of the distributed sediment delivery approach is tested experimentally using the caesium-137 measurement technique. The comparison between calculated sediment yield and the corresponding measured caesium-137 loss is used to vali…
Iron oxide-based magnetic photocatalysts: Recent developments, challenges, and environmental applications
2021
Abstract Magnetic separation of the solid photocatalyst from the reacting suspension has received great interest in recent research because it offers a suitable way for removing and recycling the heterogeneous photocatalytic material particles preventing the agglomeration and sedimentation during and after their use. The use of iron oxides such as heterogeneous photocatalysts is an appropriate choice to obtain a suitable photocatalyst easily separable from the fluid. This chapter presents a detailed investigation of iron oxide-based magnetic photocatalysts (IOMPs). We will discuss the required conditions for the synthesis of these photocatalysts, followed by their applications for the remov…
Biogeochemical evaluation of historical sediment contamination in the Gulf of Palermo (NW Sicily): Analysis of pseudotrace elements and stable isotop…
2012
Abstract Sedimentary biogeochemical data from the Gulf of Palermo, which borders one of the major urban and industrial areas of the central Mediterranean, provide a decennial–centennial-scale record of the effects of human activity on this coastal environment. In this study we report trace elements (TE), C org /N tot ratios, δ 13 C org , and δ 15 N tot from dated ( 210 Pb) sediments collected in two coastal stations variably influenced by urban/fluvial loadings and illegal dumping and we compare them with published data for offshore sediments, in order to investigate at a large spatial scale the influence of on-land activities on sedimentary marine system. TE were generally low except for H…
Relationships between Suspended and Sediment Organic Matter in a Semi-Enclosed Marine System: The Stagnone Di Marsala Sound (Western Sicily)
1997
To gather information on the interactions between the sediment and suspended organic matter pools in the Stagnone di Marsala, water and sediment samples were collected, on a monthly basis, at 11 stations. Water temperature and salinity showed a clear seasonality whilst particulate and sediment organic matter did not show any clear seasonal pattern. Relative abundances of suspended and sediment organic matter, on the other hand, appeared to be site-dependent and controlled mainly by the dynamic balance between resuspension and sedimentation. High quantities of both suspended and sediment total organic matter were present, while very low algal biomasses (in terms of chlorophyll-a concentratio…
Photoautotrophic community changes in Lagunillo del Tejo (Spain) in response to lake level fluctuation: Two centuries of sedimentary pigment records
2009
Lagunillo del Tejo is a small doline lake in a karstic region of the Iberian Ranges (central-eastern Spain) that undergoes significant lake level fluctuation in response to changing aquifer influxes. In order to assess changes in the primary producer community in the lake over the last two centuries and to elucidate whether these were conditioned by climatic variability, photosynthetic pigments and their derivatives were extracted from the sediments and the data analysed using multivariate statistical techniques. Quantitative variations in total pigment concentrations through the sedimentary sequence are considered a result of changes in sedimentation rate, largely due to lake level fluctua…
Chemical speciation of polycyclic aromatic hydrocarbons in sediments: partitioning and extraction of humic substances.
2010
The primary objective of this study was to examine the chemical speciation of polycyclic aromatic hydrocarbons (PAHs) found in sediments endowed with different characteristics. To achieve this purpose and because the nature of the sediments influences the distribution of PAHs, we have analyzed four different types of sediments. To study the role of organic matter in the sequestration of PAHs, we fractionated humic substances into humic acids and humin–mineral fractions. After their separation and purification, the humic components were examined for their sorptive reactivity by extracting them with organic solvents; these extracts were subsequently subjected to GC/MS analysis. Our results sh…
Polycyclic Aromatic Hydrocarbons in Sediments of Marine Coastal Lagoons in Messina, Italy: Extraction and GC/MS Analysis, Distribution and Sources
2004
The content of 21 polycyclic aromatic hydrocarbons (PAHs) has been determined in 16 samples of sediments collected from Ganzirri and Faro marine coastal lagoons in Messina (Italy). Analysis was performed by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM) mode. The total concentration of polycyclic aromatic hydrocarbons (PAHs) ranged from 74 to 5755 ...g/Kg of dry matrix. The resulting distributions and molecular ratios of specific compounds have been discussed in terms of sampling location and origin of organic matter. The results obtained show that levels of contamination are not homogeneous throughout the stations, while the relative distributions of PAH are…