Cores depth

Station Water Depth (m) Core Depth Range (cm) Sedimentation Rate (cm yr SD) Equation of Line ... 

One approach to elucidating the contribution of natural variability to recent temperature trends is to examine markers for temperature over much longer time scales, prior to the industrial revolution. A major source of such data is ice cores (see also Section B.2a). These ice cores provide a record of climate and atmospheric composition for at least 110,000 years, for which there is agreement among various studies. Data are available for 250,000 years before the present (bp), but there is some uncertainty in the dating of the layers corresponding to these older ice core depths (Chappel-laz et al., 1997). 

FIGURE 14-60 Relationship of ice core depth to years before the present (bp) and to the type of ice for the Central Greenland Ice Sheet. The Holocene and Wisconsin periods are also marked (adapted from Gow et at., 1997). 

The bubbles found at larger depths therefore correspond to older atmospheres. Figure 14.60 shows the relationship between the ice core depth and age (in... 

By coupling flow field-flow fractionation (flow FFF) to ICP-MS it is possible to investigate trace metals bound to various size fractions of colloidal and particulate materials.55 This technique is employed for environmental applications,55-57 for example to study trace metals associated with sediments. FFF-ICP-MS is an ideal technique for obtaining information on particle size distribution and depth profiles in sediment cores in addition to the metal concentrations (e.g., of Cu, Fe, Mn, Pb, Sr, Ti and Zn with core depths ranging from 0-40 cm).55 Contaminated river sediments at various depths have been investigated by a combination of selective extraction and FFF-ICP-MS as described by Siripinyanond et al,55... 

The vertical variation of the ratios of Org. N/Org. H in the same core sample shows that with a few exceptions the ratios increase regularly with increasing core depth. This means the organic hydrogen is more easily decomposed than organic nitrogen in recent sediments. 

There has been one significant study of PBBs in sediment from the Great Lakes. Zhu and Hites [22] measured BB-153 in one sediment core from northern Lake Michigan and in one core from eastern Lake Erie. In both cases, the cores were dated (that is, core depths were correlated with particular years) and focusing factors were determined using the well-known lead-210 method. The concentrations (ng/g) of BB-153 are shown in Fig. 4 as a function of year of deposition for Lake Erie. At this location, BB-153 was found in the deepest layer, representing 1972 the concentrations reached a max-... 

The PBDE concentrations in the core from Lake Erie are shown in Fig. 11 as a function of deposition year. Data from the other lakes are similar except the resolution with depth is much less. In this Lake Erie core, BDE-209 was first observed at core depths corresponding to 1979. This date is similar to the result reported by Zegers et al. [52], who found BDE-209 first appeared in 1978 in a sediment core from Drammcnfjord, Norway. This advent date also coincides well with the increasing production of commercial deca-BDE beginning in the late 1970s [28]. Both the SPBDE and BDE-209 concentrations in this sediment core increased exponentially with time. This is consistent with the increasing demand for PBDEs in U.S. market over the last 30 years. 

Other elements of antWpogenic origin, such as mrcury, lead and tin, were found to have peaks around similar core depths of the sediments. These results showed that the concentration of bismuth in the sediment core may serve as one of the promising indices of anthropogenic activities. 

At site A in Table 16, concentrations of all metals in the second soil-core depth were higher than those in the first soil-core depth. Bismuth and antimony concentrations in the soil core under the second core depth were less than those of natural concentrations, 0.34 and 0.37 /rgg , respectively. At sites B and C, the profiles of metal concentrations were somewhat different from those in site A The difference is probably due to dissimilarities in pollution history, surrounding circumstances and properties of soil. 

Sediment cores were taken in the accumulation area of the dams during the winter of 2004-2005 and the summer of 2005. A small boat was be used and during the summer and during winter time the ice was used as a sampling platform. The sediments were cores with a diameter of 31.16 or 55.39 cm. and were sliced in 1 cm. The maximum possible core depth was generally around 35 cm corresponding to the time of construction. 

SiOj ALO, FejOa MgO CaO Na 0 K 0 TiO 1 MnO PjOs Total Core depth... 

Table II. Intensities of Resonances from Selected Spectral Regions with Core Depth, Intact Sediments.

It can be seen that about 70% of the calculated inventory of 339,240py and 2 Am are accounted for by the measurements. It seems unlikely that underestimate of the loss through the North Channel could account for the discrepancy. It is likely that Pu and Am penetrating below the 0.3 m core depth sampled by Pentreath et al. (1984), and perhaps additional... 

Core Depth (m) Distance Sellafield (km) from Cs 238pu 239.240py Am... 

Pretreatment samples taken prior to aldicarb application insured that the soil was free of aldicarb residues. Daily rainfall and pan evaporation for this site were obtained from a nearby weather station. Soil cores were obtained by bucket auger to a depth of 3 meters, separated into increments of 0-0.3 m, 0.3-0.6 m, 0.6-1.2 m, 1.2-1.8 m, 1.8-2.4 m, and 2.4-3.0 m. The plot was divided into four subplots, and four samples were taken per subplot and composited at each date of observation, resulting in a total of four samples per date per core depth. These four samples were... 

The influence of the sediment composition on the formation factor-porosity relation illustrates Figure 2.7 for six provinces in the South Atlantic. For each core porosities and formation factors were evaluated at the same core depths by wet and dry weights and volumes of discrete samples... 

Fig. 17. UV-photomicrographs of thin sections and cleansed sandstones. All depths are core depths. Scale bar = 100 pm. (a) Euhedral overgrowths on quartz grain from cleansed sand from 4186.75 m in the dry well 6506/11-1. (b) Same as (a), but with deeper focus, revealing a fluorescent inclusion with rather big ca. 50 vol%) gas bubble. Due to refraction in the quartz crystal, the inclusion appears as three individual inclusions. The large gas bubble signifies that the trap contained a high GOR fluid before caprock failure.

Figure 8. Fluid inclusion homogenization temperatures from the Death Valley salt core, depths of 186 m to 109 m ( 192 ka to I20ka). Ranges of fluid inclusion homogenization temperatures for different stratigraphic intervals are plotted. Note that the range of homogenization temperatures in the salt pan facies is higher than ip the perennial lake facies. (From Roberts et al., 1997, Fig. 14. p, 119).

Thompson 1977a). The ice-core depth to the H/W (Holocene/ Wisconsinan) transition occurs at different depths depending on the rate of accumulation of snow at each site. The H/W transitions in the Antarctic and Greenland cores occur at about the same time in the past which confirms the bipolar occurrence of continental glaciation (Adapted from Thompson and Mosley-Thompson 1981, Figure 6)... 

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