Sediments accumulation

These instruments, sometimes referred to also as sediment accumulation devices, weight the sediment as it accumulates on a weigh-pan at the base of the sedimentation column. The methods are cumulative ones. With the development of sensitive electro balances, the cumulative sedimentation technique is generally easier to perform and more accurate than is the incremental technique. The powder may be dispersed initially in the bulk of the fluid or added instantaneously at the top. An advantage of this type of equipment is the absence of the conical base, needed in sediment extraction devices, upon the walls of which some sediment may adhere. The danger of particles sticking to the vertical walls is however still present... 

Thomann RV, Mahoney JD, Mueller R. 1995. Steady-state model of biota sediment accumulation factor for metals in two marine bivalves. Environ Toxicol Chem 14 1989-1998. 

Often the expected change in 210Pb concentration with depth (obtained from the logarithmic plot of unsupported activity as a function of the overlying mass of dry sediment accumulated) shows variations which are outside the analytical errors expected from the measurement of radioactive decay. Possible reasons for these discrepancies are ... 

The 210Pb input from the atmosphere must have been constant over the past 150 years due to the relative constancy in the maritime climate (temperature and soil moisture influences the radon emanation rate) and the resulting constancy in the input source for 210Pb. Therefore, the deviations from a single log-linear relationship of the unsupported 210Pb activity with the dry mass of sediment accumulation must be due to some property of the watershed. The three different relationships shown in... 

Solution of equation (10) which involves sedimentation in the presence of mixing and that of equation (11) which contains the sedimentation term only, are exponential in nature. The major conclusion which arises from this is that the logarithmic nature of the activity-depth profiles by itself is not a guarantee for undisturbed particle by particle sediment accumulation, as has often been assumed. The effects of mixing and sedimentation on the radionuclide distribution in the sediment column have to be resolved to obtain pertinent information on the sediment accumulation rates. (It is pertinent to mention here that recently Guinasso and Schink [65] have developed a detailed mathematical model to calculate the depth profiles of a non-radioactive transient tracer pulse deposited on the sediment surface. Their model is yet to be applied in detail for radionuclides. )... 

Maruya, K.A. and R.F. lee. 1998. Biota-sediment accumulation and trophic transfer factors for extremely hydrophobic polychlorinated biphenyls. Environ. Toxicol. Chem. 17 2463-2469. 

Ferromanganese nodules found in freshwater lakes show concentric, alternating, iron- and manganese-rich bands radiating out from a central nucleus of detrital rock (e.g. Harriss Troup 1970). The nodules are found primarily in shallow (1-5 meters depth) regions of lakes, in regions with little to no finegrained sediment accumulation (e.g. Kindle 1935). 

Following an aviation kerosin spill, hydrocarbons were detected in trout stream sediments and fish up to 14 months after the spill [13]. After a fire at a weed treatment plant in 1970 a large area of mixed forested ecosystem became contaminated with polycyclic aromatic hydrocarbons and creosote [66], High polyaromatic concentrations in stream sediments adversely affected micro- and meiobenthic communities at all trophic levels. Stein et al. [67] have studied the uptake by bethnic fish (English sole, Parophrys vetulus) of benzopyrene and polychlorinated biphenyls from sediments. Accumulation of contaminants from sediments was a significant route of uptake by English sole. 

Hay BJ (1988) Sediment accumulation in the central western Black Sea over the past 5100 years. Paleoceanography 3 491-508... 

The slowest growth rates are found in the Fe-Mn oxides that have formed predominantly by precipitation of solutes from seawater, being on the order of 1 to a few millimeters per million years. Because of slow formation rates, these hydrogenous precipitates tend to form only in areas where sedimentation rates are slow, such as the abyssal plains of the mid-Pacific Ocean, or where bottom currents are strong enough to prevent sediment accumulation, such as on submarine seamounts and plateaus. 

Relative primary productivity, POC fluxes at 105 and 3000 m, and POC sediment accumulation rates versus latitude in the central equatorial Pacific Ocean. Data are normalized to the maximum value in each transect. Survey 1 was conducted during February-March 1992 under El Nino conditions and Survey 2 from August to September 1992 under non-El Nino conditions at longitudes ranging from 135 to 140°W. Ordinate scale is reset to 1.0 at each maximum, and the absolute magnitude (mmolCm ij-i) of each parameter is given next to its maximum. Source-. From Flernes, P. J., et al. (2001). Deep-Sea Research I 48, 1999-2023. 

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