Sediments elemental composition

In some sediments, downcore variations in the bulk chemical composition are interpretable as records of temporal shifts in the elemental composition of the sinking POM. Such shifts are caused by changes in the production of sinking POM, which are in turn the result of fluctuations in the abundance and diversity of the overlying plankton community. In nearshore sediments, fluctuations in river runoff and lateral transport can lead to shifts in the supply rate of terrigenous organic matter. An example of a nearshore sediment core in which such fluctuations have been recorded is shown in Figure 23.18. 

Elemental composition C 7.81%, Cl 92.19%. Carhon tetrachloride may be analyzed by GC or GC/MS. For GC determination, an FID or a halogen-specific detector such as ECD or HECD may he used. Trace concentrations in aqueous matrix or soil, sediments or sohd wastes may he determined by purge and trap or thermal desorption techniques followed hy GC or GC/MS measurements. The characteristic masses for identification of CCI4 by GC/MS are 117, 119 and 121. 

Elemental Analysis. The elemental analyses are presented in Table IV. The atomic ratios H/C for all drinking water samples (nos. 1-10) were between 1.28 and 1.39. These values were comparable to humic acid derived from lake sediments. However, H/C ratios were much lower when compared to the chlorinated model humic substances (e.g., 1.04-1.08 for CFH-1 and CFH-2). Bromine was present in almost negligible quantities, whereas Cl varied between 0.3 and 2.4, and S varied between 0.9 and 2.7 in the drinking water organic matter. All fractions from drinking water showed similar elemental composition. However, they differed from the elemental composition of the CFH samples in all respects, especially in chlorine content. 

High-resolution compositional measurements are possible through use of a variety of microanalytical methods. Ideally, these should be non-destructive, can be targeted on small areas of sample, and have low minimum detection limits. Electron-probe X-ray microanalysis (EPXMA) and proton-induced X-ray emission (PIXE) techniques have both been used successfully on archaeological sediment thin sections (19, 20). Both techniques yield elemental composition data for a range of elements. EPXMA has the advantage of being nondestructive, whereas PIXE when used on thin-section samples is typically destructive conversely the detection limit for PIXE is lower than EPXMA. 

Humic acid is composed of aromatic, aliphatic and carbohydrate carbon compounds. An average humic acid s elemental composition is 55.1% C, 5.0% H, 3.5% N, 35.6% O, and 1.8% S (Rice and MacCarthy, 1991). Its molecular weight distribution is typically broad, and it is a relatively high-molecular-weight material relative to the fulvic acid isolated from the same soil or sediment. It s predominantly functionalized by carboxylic acid and phenolic groups. At least some components of humic acid are surface-active, and these components have been shown to form micelles in concentrated, alkaline aqueous solutions (Piret et al., 1960 Visser, 1964 Wershaw et al., 1969 Tschapek and Wasowski, 1976 Chen et al., 1978 Rochus and Sipos, 1978 Hayano et al., 1982 Hayase and Tsubota, 1984 Guetzloff and Rice, 1994). 

Soil- and sediment-derived fulvic acid is also composed of aromatic, aliphatic, and carbohydrate carbon components, though it is generally believed to be more aromatic than the humic acid from that same environment. A typical fulvic acid s elemental composition is 46.2% C, 4.9% H, 2.5% N, 45.6% O, and 1.2% S (Rice and MacCarthy, 1991). The carboxyl group is the predominant functional group in... 

At one sampling point near the Technical University of Kosice (Slovakia) (see Fig. 7-13) sedimented airborne particulate matter was sampled by the above described BER-GERHOFF method (see also Section 7.2.1.1) over a period of two and a half years. Tab. 7-5 shows the analytical methods applied for the determination of the elemental composition of the dust samples. 

Murphy, D.M., Garbarino, J.R., Taylor, H.E., Hart, B.T. and Beckett, R. (1993) Determination of size and element composition distributions of complex colloids by sedimentation field-flow fractionation-inductively coupled plasma mass spectrometry. /. Chromatogr., 642, 459M67. 

The Nile River provides a good example of the similarities and differences between sediments from the same river. The common origin of these Nile sediments is confirmed by the high degree of correlation in the elemental compositions between different Egyptian Nile sediment samples (2). 

Quartz typically yields low concentrations of the elements when measured by this procedure, and therefore does not contribute significantly to the overall trace element composition of the bulk sediment samples. Thus, the presence of quartz in sediments acts as a dilutant to their overall trace element content. Unfortunately, Si cannot be measured by this INAA pro-... 

Fenaz, E. S. B., and A. N. Fernandes. 1995. "Trace Element Composition in Sediments of the Amazonian Lake Cristalino." Marine Freshwater Research 46 107—111. 

The preferred chemical estimates of the continental crust used throughout this chapter are listed in Table 1. The major element composition of the upper crust is well constrained, since this is the most accessible to sampling, both directly and via erosion and sedimentation, and different studies utilizing diverse databases have yielded remarkably similar results. Si02is —61%, and Mg number (Mg, molar Mg/(Mg - - Fe)) is — 55 for the bulk continental cmst, and so it is more differentiated than any magma in equilibrium with the upper mantle. Trace-element abundances are more variable, as are estimates for the composition and proportion of the middle and lower cmst. As we will see below, the latter are critical to any discussion of the mechanisms of cmst formation and differentiation. 

By virtue of where, when, and how the various organic matter inputs were formed and transported to the underlying sediments, it is possible to exploit specific chemical and isotopic characteristics to make inferences about the sources and composition of sedimentary organic matter. Much of this information is inaccessible at the bulk level. For example, bulk elemental compositions and stable carbon isotopic compositions are often insufficiently unique to distinguish and quantify sedimentary inputs. Abundances and distributions of source-specific organic compounds ( biomarkers ) can help to identify specific inputs. However, this molecular marker approach suffers from the fact that the source diagnostic marker compounds are... 

PETROEOGY, MINERAEOGY, AND MAJOR ELEMENT COMPOSITION OF CLASTIC SEDIMENTS... 

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