Sediment indicators

For each of the suggested water and sediment indicators, there are possible confounding environmental factors that are not related to changes in Hg loading, but that could result in responses in some of the indicators. Several of these confounding factors have been previously mentioned, but a general discussion of them is provided here. 

Polycyclic aromatic hydrocarbons (PAH) are produced by the combustion, under fuel rich conditions, of almost any fuel. Although a few PAH with vinylic bridges (such as acenaphthylene) are lost, most PAH are quite stable in the atmosphere and eventually accumulate in environmental sinks such as marine sediments. Spatial and historical measurements of PAH in sediments Indicate that these compounds are stable, conservative markers of man s energy producing activities. 

Transport by Calcite. The annual flux of calcite into the uppermost trap (29 m below the lake surface) was estimated to be 35 g/m2, and the mean measured P content of this phase was estimated at 1.05 mg/g. A comparison of the calculated 29-m P flux, 37 mg/m2, with estimates of deposition to bottom sediment, indicated that 5-16 mg/m2 (13-43% of upper-water-column flux) was returned to the water column. This relatively small regeneration flux was not detected in profiles of meta- and hypolimnetic... 

All measured profiles of sulfate reduction in sediments indicate that much sulfide production and, by inference, oxidation occurs in permanently anaerobic sediments (78, 73, 90,101). The two most likely electron acceptors for anaerobic sulfide oxidation are manganese and iron oxides. Burdige and Nealson (151) demonstrated rapid chemical as well as microbially catalyzed oxidation of sulfide by crystalline manganese oxide (8-Mn02), although elemental S was the inferred end product. Aller and Rude (146) documented microbial oxidation of sulfide to sulfate accompanied by reductive dissolution... 

Available information on concentrations of OCs, particularly OC pesticides in water, sediment, soil, and air has been summarized in Table 13.1. In most cases, larger data sets on OC concentrations in abiotic compartment are from the surveys conducted in recent years (1990s to the middle of 2000s), with particular concern on water and sediment (Table 13.1). A nationwide occurrence of OC pesticides in water and sediment indicate that the two major contaminants in the Indonesian environment are DDTs and HCHs (Table 13.1). Although, there is no report on the usage of HCHs, elevated levels of this compound in water and sediment confirm... 

Experiments conducted on the solubility behavior of the odlitic sediments indicated that they were not in metastable equilibrium with their pore waters. On the basis of equilibration rates, Bernstein and Morse (1985) estimated that the residence time of the pore waters in these sediments was only a few days or less. 

Although the above discussion does not constitute a rigorous verification of the model (21), the similarity of the simulations presented here to observed profiles of H2S, FeS and FeS2 in marine sediments indicates that the model may be of value in the study and interpretation of vertical patterns in sulfur diagenesis. Comprehensive multiparameter analyses of sediment profiles from a variety of sites will be required to validate the model. In this endeavor techniques will have to be devised to ascertain the molar surface areas of the various solid phase reactants. Eventually it may be possible to expand the model presented here to include processes in the aerobic zone so that the depth to the oxidized-reduced boundary can be predicted as well as the pH profile through this boundary. This achievement would constitute a truly compr ensive model. 

A simple test for wetting efficiency is to make up suspensions using the same concentration of powder but different wetting agents and allow the suspension to settle out. About a gram of powder dispersed in 10 ml of liquid is suitable. Slow settling, a clear interface between the clear liquid and the turbid lower layers and a small depth of sediment indicate the best... 

Claypool G. E. (2003) Ventilation of marine sediments indicated by depth profiles of pore-water sulfate and S " S. In Geochemical Investigations in Earth and Space Sciences A Tribute to Issac R. Kaplan, Elsevier, Amsterdam. 

Ruttenberg K. C. and Goni M. A. (1997b) Depth trends in phosphorus distribution and C N P ratios of organic matter in Amazon Fan sediments indices of organic matter source and burial history. In Proc. Ocean Drilling Program. Sci. Res. (eds. R. D. Flood, D. J. W. Piper, A. Klaus, and L. C. Peterson), vol. 155, pp. 505-517. 

The reactivity of MPa and BaP seems to have resulted in the alteration of their source compositional ratios during transportation/deposition, and thus may not be a reliable source indicator. In addition to the compositional attributes of the parental PAHs, the presence of methylated compounds and a UCM in the surface sediments indicates possible petrogenic inputs of PAHs to the Harbor. The UCM is generally indicative of petroleum and petroleum products, and is a widely used indicator of petrogenic contamination in sediments (Prahl and Carpenter, 1979 Volkman et al., 1992, 1997 Simoneit, 1998). It is commonly assumed that a UCM consists primarily of an accumulation of multibranched structures that are formed as a result of biodegradation reactions of petroleum (Volkman et al., 1992). Since no clear indication of petroleum-derived inputs can be discerned from the compositional ratios of the prominent PAHs in the sediments, it is apparent that the isomeric ratios of the prominent petrogenic PAHs are masked by pyrogenic-derived components. 

Clay, sand, and gravel deposits were mapped to determine likely sources of cave fill and relative flow system energy (Table 1). The vertical relationships between sediments indicate the sequence of sedimentation in most of the caves of Lime Creek. Older deposits are buried by younger ones, or can be preserved in pockets and cemented by calcite above current base level. Older deposits may have been completely removed by later stream activity, so a complete sediment record may not be preserved. 

Cranwell, P. A. Monocarboxylic Acids in Lake Sediments Indicators De-... 

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