Sediment sample characteristics

The physico-chemical characteristics of the sediment sample significantly influence the fate of agrochemicals in a paddy field and a waterway system. Therefore, the factors that influence adsorption, retention, and degradation of agrochemicals are very important. As a minimum the characteristics of the sediment sample listed below should be described ... 

An important consideration prior to sample collection is transportation and storage. Samples should be treated so as to retain the integrity of the sample from the moment of collection to the time of analysis. The physico-chemical characteristics of a sediment sample change during drying, with effects on the sorption-desorption behavior of chemicals. 

A sample may be characterized by the determination of a number of different analytes. For example, a hydrocarbon mixture can be analysed by use of a series of UV absorption peaks. Alternatively, in a sediment sample a range of trace metals may be determined. Collectively, these data represent patterns characteristic of the samples, and similar samples will have similar patterns. Results may be compared by vectorial presentation of the variables, when the variables for similar samples will form clusters. Hence the term cluster analysis. Where only two variables are studied, clusters are readily recognized in a two-dimensional graphical presentation. For more complex systems with more variables, i.e. //, the clusters will be in -dimensional space. Principal component analysis (PCA) explores the interdependence of pairs of variables in order to reduce the number to certain principal components. A practical example could be drawn from the sediment analysis mentioned above. Trace metals are often attached to sediment particles by sorption on to the hydrous oxides of Al, Fe and Mn that are present. The Al content could be a principal component to which the other metal contents are related. Factor analysis is a more sophisticated form of principal component analysis. 

Spores may be transferred from soil and plants to the sea via rainwater, causing the prevalence in coastal waters of the same C. botulinum types as on the land. Such a correlation was observed in Great Britain, where the type B predominates both in soil and in bottom sediments. Similarly, 71% of fish and bottom-sediment samples collected in southern France were contaminated with type B, while C. botulinum type E was found only in 9.6% of samples (Each et al., 2002). However, it is commonly believed that non-proteolytic type E is characteristic for the marine environment. A distinguishing feature of type E strains is the ability to grow in low temperatures (about 3°C), which are typical for bottom layers of seas and oceans. Moreover, the bottom sediments provide anaerobic conditions for the outgrowth of Clostridium. Therefore, the marine environment promotes C. botulinum type E distribution. This has been further supported by the rate of fish and seafood contamination fish and seafood isolated in many countries are most frequently contaminated with C. botulinum type E (Dodds, 1993 a,b). Furthermore, epidemiological studies have shown that the majority of botulism cases linked to fish and seafood consumption reported between 1950 and 1996 in the U.S. were caused by C. botulinum type E (Centers for Disease Control and Prevention 1998). C. botulinum type F,... 

All sediments used in the studies reported in this article were selected from a group of well-characterized soil and sediment samples which were collected and air-dried for the U. S. Environmental Protection Agency by Hassett and co-workers (22) The characteristics of several of these are outlined in Table I. 

Below this baked zone, the characteristics of the organic extracts from each sediment sample could be used to estimate the temperature. For example, at — 1.93 m, the maximum proportion of aromatic compounds were found but no pigment was present. The first observation defines the upper temperature limit at about 773°K and the second— the minimum— at 600°K. 

Screening of estuarine and marine sediment samples by automated pyrolysis mass spectrometry combined with factor-discriminant analysis leads to a useful classification related to the geographical position and the sources of the organic matter. The mass spectral data give preliminary information about the organic matter composition. Analysis of the characteristic mass peaks m/z=86 and 100 by PMSMS and PGCMS points to bacterial poly-alkanoates in the mud fraction of the river sediments. 

The pyrolysis methods applied in this study are used as a tool for a general characterization of the organic matter from the sediments. We describe here the results from screening of estuarine and open sea sediment samples by automated pyrolysis low voltage mass spectrometry combined with factor-discriminant analysis. Characteristic mass peaks resulting from this procedure were investigated in more detail by pyrolysis-tandem mass spectrometry and pyrolysis-photoionization GCMS. 

Tab. 6 Summarized characteristics of the incorporation of individual contaminants into sediment samples of the Teltow Canal with respect to the frequency of detection and the release after different degradation procedures.

Twinch, A. J. 1987. Phosphate exchange characteristics of wet and dried sediment samples from a hypertrophic reservoir implications for the measurement of sediment phosphorus status. Water Res. 21 1225-1230. 

Variables that affect radionuclide concentrations in sediment are water movement, water quality, the presence of aquatic vegetation, and sediment characteristics such as clay and organic fractions. Sediment samples collected at time intervals should not be expected to have a consistent pattern of radionuclide concentrations because the location sampled previously is difficult to find precisely, sedimenf may have moved downstream, and older sediment may be covered by more recent deposits. 

The close link between lakes and their catchments was evident in a study of spatial variability in surface sediment composition in a small northern Swedish lake (Korsman et al., 1999). In this study, the information in the near-infrared spectra of surface sediment samples was used to determine how sediment composition varied over the lake bottom. The study showed that the NIR spectra per se provide information that can be used to study sediment characteristics as well as sediment focusing in a qualitative way. The variance in the NIR spectra (Fig. 7) was only to a minor extent explained by the variation in water depth or sediment organic content. More importantly, the spatial evaluation of the spectral data suggested that NIR analysis of lake sediments mainly reflects sediment properties that cannot be simply explained by water depth or amount of organic matter. Principal component modelling of NIR spectra from 165 coring sites, established along a 50m x 50m... 

The purpose of a strength-testing program is to define the sediment strength characteristics needed for developing a geotechnical model of a site. A schematic flowchart of the overall process of site evaluation is presented in Figure 6.24. The prediction of the in-situ characteristics of marine sediments based on disturbed samples can be accomplished... 

Classification of lake sediments by means of factor analysis and hierarchical clustering has been reported by Hopke et. al. C1103- For a set of 79 sediment samples, 32 characteristic properties were determined (e.g. concentration of 15 elements, percent organic matter, criteria of the particle size distribution, water depth). Cluster analysis detected a single cluster for samples from the centre of the lake and three different clusters for samples from near the shore. 

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