Sediment flux

A fundamental distinction among landscapes is whether the net sediment flux (the total load carried by the river) is limited by the ability of erosional processes to carry sediment (transport-limited environments) or the availability of erodible material (weathering-limited environments). In general, soil-mantled landscapes can... 

Hay, W. W. (1998). Detrital sediment fluxes from continents to oceans. Chem. Geol. 145,287-323. 

Figure 4. Plots of Thg/Nae, Ue/Nae and Bae/Nae versus sediment flux for a number of arcs. Modified from Plank (1993) and Plank and Langmuir (1993).

Wu, H.L., Shen, H.T., Yan, Y.X., Wang, Y.H. 2006. Preliminary study on sediment flux into the sea from Yangtze Estuary. Journal of Sediment Research, 6, 75-81 (in Chinese). 

Experimental measurements in each lake included particle concentration and size measurements in the water column, sedimentation fluxes in sediment traps, and chemical and size characteristics of materials recovered from sediment traps. The colloidal stability of the particles in the lake waters was determined with laboratory coagulation tests. Colloidal stability was described by the stability ratio (a). For a perfectly stable suspension, a = 0 for a complete unstable one, a = 1.)... 

Simple steady-state models may be used in order to relate quantitatively the mean concentration in the lake water column and the residence time of metal ions to the removal rate by sedimentation (for a detailed treatment of lake models see Imboden and Schwarzenbach, 1985). In a simple steady-state model, the inputs to the lake equal the removal by sedimentation and by outflow the water column is considered as fully mixed mean concentrations and residence times in the water column can be derived from the measured sedimentation fluxes. The binding of metals to the particles is fast in comparison to the settling. 

Dating and Sediment Accumulation. Stratigraphic Patterns Lead-210 profiles from profundal cores from each study lake show conformable declines in unsupported activity to an asymptote of supported 210Pb typically below 40-60 cm deep (Figure 3). Supported activity, attained at shallower depths in Thrush (28 cm) and Kjostad (36 cm), indicates slower linear rates of sedimentation at these sites. The activity profiles for several lakes, most notably Thrush and Kjostad, are almost perfectly exponential and thus indicate nearly constant sediment accumulation rates. Others, such as Cedar and Mountain, show flat spots and kinks that probably represent shifts in sediment flux. 

This study demonstrates the use of multiple-core methods to obtain whole-basin sediment fluxes from a suite of lakes and the application of these data to questions of atmospheric metal deposition. Multiple-core data can be economically produced by integrating longer core sections and reducing the number stratigraphic units for analysis. As few as three 210Pb analyses per core can yield a modern accumulation rate additional samples provide more historical detail. 

Lakes. Flux calculations based only on wet and dry particle deposition were close to measured sediment fluxes. PCA analysis confirmed that wet and dry particle deposition was much more important than dry vapor deposition, based on homolog patterns. 

Sorption-desorption from suspended particulates and sediment fluxes play a large part in controlling the nonconservative behavior of dissolved concentrations of Fe and Mn in estuaries. 

Progradation lateral outbuilding of strata in a seaward direction. Progradation can occur as a result of a sea-level rise accompanied by a high sediment flux. 

The continental slope represents a transit zone of the sediment fluxes supplied in the form of detrital matter from the rivers and the products of abrasion, as well as the sediments carried by turbidity flows. The continental slope is covered with compacted clayey oozes (grain-size fractions of 0.001-0.01 mm). At selected places on steeper parts of the slope, remains of mollusk fauna such as shells of Dreissena rostriformis have been encountered. At sites with gentle sloping, they are overlain by the Holocene and recent sediments [11]. 

A summary of physical and biochemical parameters for the Amazon shelf are presented in Table 17.1. These data were used to develop the mass balance calculations described in the remainder of the paper. The rate of Amazon River sediment discharge that is cited in most studies (Meade et al. 1985) characterizes the flux at Obidos, which is hundreds of kilometers from the river mouth. The sediment fluxes that have been documented for the Amazon coastal area are the fine-grained sediment accumulation rate on the shelf (6.3 x 10 g yr, Kuehl et al. 1986, 1996) and the advection rate of particulate material northward out of the study area, primarily in nearshore environments (-1.2 X 10 g yr, Allison et al. 1995). Because some sediment may be deposited between Obidos and the river mouth, we have chosen to use the sum of the shelf... 

Figure 18.12 Bar graph of N-recycling efficiency as a function of bottom water dissolved oxygen concentration. Bars were based on Chesapeake Bay data reported in Kemp et al. (1990) and Cornwell (unpublished data). Solid dots were based on data from Rysgaard-Petersen et al. (1994) collected from Vilhelmsborg So, Denmark. Terms in the recycling efficiency calculation (y-axis) are Ffjj — flux of N2 from sediments = flux of ammonium from sediments FjsjOj flux of nitrate from sediments.

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