Composition sediment

Fig. 2. Mapping of sediment composition by government agencies provides a reference for exploration by mapping background, identifying problematic areas, and by providing examples of anomalies (Thorleifson et at. 2007).

The only significant 5 Mo variation in these samples is a small offset of 0.15%o seen between Paciflc and Atlantic crusts, just outside the 2a uncertainties of Siebert et al. (2003). A similar offset is seen in nodule data, although well within the analytical uncertainties of Barling et al. (2001). Such offsets seem unlikely to reflect variations in 8 Mo in seawater in view of the long ocean residence time and relatively invariant seawater concentrations of Mo. Systematic differences in sediment composition may play a role (Barling and Anbar 2004). 

SIMCA can be applied to the problem of classification when attempting to correlate measurable effect variables with composition of the classified samples. In correlation analyses one may wish to determine how other sample variables, such as sediment composition, organic content, lipid concentration, etc., influence the composition of measured residues or concentrations of PCBs. 

Ringwood, A.H., DeLorenzo, M.E., Ross, P.E., Holland, A.F. (1997). Interpretation of the Microtox solid-phase toxicity tests the effect of sediment composition. Environmental Toxicology and Chemistry. 1997, 1135-40. 

In most of the study lakes organic content is poorly correlated with lake depth, a feature that may be partially attributed to the fact that fine-grained sediments are only weakly focused in small shallow lakes (6, 18). Indeed, sediments do become somewhat more organic with depth in the two deepest lakes, Thrush and Kjostad. The perception of uniform sediment composition also results from sampling bias, because few littoral cores were actually retained for analysis. Visibly inorganic sediments were assumed to represent nondepositional sites for purposes of calculating a Hg flux and were simply mapped and discarded. 

Ward, L.G, Kearney, M.S., and Stevenson, J.C. (1986) Accretion rates and recent changes in sediment composition of estuarine marshes. Ches. Bay Sci. EOS 67, 998. 

Averages for the 27 bulk samples are given in Table II for some of the elements measured. These averages, called Nile River Sediment Composite (NRSC), are very similar to the averages for modern Nile sediments compiled by Tobia and Sayer (2). This similarity clearly confirms that, other than the variations due to grain size (sand content), the modern Nile silts are quite uniform in composition. 

Numerous biotic factors influence N processing within sediments, including the composition of the microbial, macrofaunal, and macrophyte communities, behaviors of the various infaunal communities, and trophic transfer of carbon and nitrogen between communities. Interactions between benthic communities may be physical, chemical, or biological in nature and, in turn, are influenced by the physical nature of the environment, sediment composition, and autotrophic dominance (Fig. 19.3). 

Jahnke R. J. and Jahnke D. B. (2002) Calcium carbonate dissolution in deep-sea sediments implications of bottom water saturation state and sediment composition. Geochim. Cosmochim. Acta (in press). 

The outcrops of very old Archean rocks are few and thus may not be representative of the original sediment compositions deposited. Nevertheless, it appears that carbonate rocks are relatively rare in the Archean. Based on data from the limited outcrops, Veizer (1973) concluded that Archean carbonate rocks are predominantly limestones. During the early Proterozoic, the abundance of carbonates increases markedly, and for most of this Era the preserved carbonate rock mass is typified by the ubiquity of early diagenetic, and perhaps primary, dolostones (Veizer, 1973 Grotzinger and James, 2000). In the Phanerozoic, carbonates constitute 30% of the total sedimentary mass, with sandstones and shales accounting for the rest. The Phanerozoic record of carbonates will be elaborated upon in the subsequent text. 

Aston S. R., Thornton 1., Webb J. S., Purves J. B., and Milford B. L. (1974) Stream sediment composition an aid to water quality assessment. Water Air Soil Pollut. 3, 321-325. 

After the testing and evaluation of the operational parameters of the sediment retrieval system, the ground-truth study of the CS system was initiated to determine whether the CS samples reflected the true sediment composition and, therefore, its ability to correctly and rapidly survey the seafloor sediment. 

The gradient approach requires a great deal to be known about the landscape of the watershed, airshed, or other division of the area under consideration. Ideally, it is nice to have data on land use, geology, the hydrology, soil types, sediment composition, types of contaminants, the history of disturbance, and other information available when deciding a sampling plan. These data may not be available, and this uncertainty should be reported. 

Arkona Sea, see Table 17.1). In addition, the stations differ in the sediment composition (organic content or grain size) as shown in Table 17.1. The depth ranges covered are between 22 to 48 m, with the deepest station in the Arkona Sea. 

Landrum PF, Faust WR (1991) Effect of variation in sediment composition on the uptake... 

Indeed, at site 8 concentrations of HHCB and AHTN are significantly higher and are still high at site 6. Possibly, conditions for accumulation of suspended matter in the sediment are favourable due to low flow velocities there. Sediments at sites 5 and 4 contain less HHCB and AHTN. This could be the consequence of less favourable accumulation conditions or lower input in the area further upstream. Obviously, it is difficult to relate compound concentrations in riverine sediments to specific input situations, because other factors such as flow velocities and sediment composition are also of great importance. 

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