Burial rates

This D value is IJbAwZ4, where UB, the sediment burial rate, is 2.0 x 10-7 m/h. It can be viewed as GBZB4, where GB is the total burial rate specified as Vs/tB where tB (residence time) is 50,000 h, and Vs (the sediment volume) is the product of sediment depth (0.01 cm) and area Aw. Z4, ZB4 are the Z values of the sediment solids and of the bulk sediment, respectively. Since there are 20% solids, ZB4 is about 0.2 Z4. There is a slight difference between these approaches because in the advection approach (which is used here) there is burial of water as well as solids. 

Clam, Macoma liliana juveniles held in sediments containing <1 (controls), 5, 10, 15, 25, 30, 50, 70, or 140 mg/kg DW. Effects on avoidance in 96 h, burial rate in 90 min, and survival in 10 days were measured... 

Based on these monitoring results and some estimations of volatilisation and sediment burial rates, Ferguson et al. concluded that the estuarine fate of APEO metabolites in Jamaica Bay is determined mainly by sorption processes, degradation in the water, and advective transport out of the estuary [15]. 

A box model fiar the marine silica cycle is presented in Figure 6.11 with respect to the processes that control DSi and BSi. An oceanic budget is provided in Table 16.3 in which site-specific contributions to oceanic outputs are given. This table illustrates that considerable uncertainty still exists in estimating the burial rate of BSi. Regardless, burial of BSi is responsible for most of the removal of the oceanic inputs of DSi, with the latter being predominantly delivered via river runoff. This demonstrates the importance of the biological silica pump in the crustal-ocean-atmosphere factory. 

Conversely, perturbations in the burial rate of BSi have the potential to alter the marine silica cycle. For example, changes in sea level affect the expanse of continental shelf Since BSi burial is more efficient in shelf sediments (because of better preservation), a topographic change that alters the spatial extent of this depositional environment has the potential to alter the size of the DSi reservoir. 

Some particles, particularly the biogenous ones, are prone to alteration as they settle onto the sediments and then imdergo burial. The likelihood of particle preservation is generally enhanced in settings where the trip to the seafloor is short and burial rates are fast. The time a particle takes to settle onto the seafloor is determined by water depth and particle sinking rates. The latter is a function of particle shape and density. Seawater... 

The burial rate of organic matter in marine sediments is a factor of 2 smaller (0.15 to 0.19PgC/y) than the known terrestrial input. This requires that greater than half of the terrestrial organic matter be remineralized prior to burial. Marine chemists have been unable to establish how and where in the ocean this remineralization occurs. Similarly... 

Table 25.1 Organic Carbon Burial Rates Regimes (Pg C/y). in Different Marine Sediment ...

Of particular concern are the impacts of seawater acidification on biocalcification and the burial rates of sedimentary carbon. Carbonate ion concentrations in the surface waters have already declined by 16%. Thus, it is not surprising that the abundance of tropical/subtropic planktonic foraminiferan species appears to have declined since the 1960s. This information was obtained by studying the rapidly accumulating sediments of the Santa Barbara Basins off the coast of California. 

Carbonate compensation The ocean s response to perturbations through shifts in its carbonate chemistry. These shifts require changes in the carbonate ion concentration that change the depth of the calcium carbonate compensation depth and hence lead to changes in the burial rate of carbon as biogenic calcium carbonate. 

Continental shelves and slopes comprise approximately 10 percent of the Earth s surface, and contain over half the sediments in the ocean (Heezen and Tharp, 1965 Gregor, 1985). Recent estimates of marine carbonate burial rates (e.g., Hay and Southam, 1977 Sundquist, 1985) indicate that between about 35 to 70 percent of Holocene carbonate deposition has taken place on continental shelves. In spite of their importance for carbonate accumulation and the global CO2 cycle, relatively few studies have been made on the chemical controls of calcium carbonate accumulation in these sediments, and most of these studies have been confined to near-shore environments. 

DeMaster, D.J., Thomas, C.J., Blair, N.E., Fornes, W.L., Plaia, G., and Levin, L.A. (2002) Deposition of bomb 14C in continental slope sediments of the Mid-Atlantic Bight assessing organic matter sources and burial rates. Deep-Sea Res. II. 49, 4667-4685. 

Tg year x. Lein and Ivanov [71] have estimated the total sulfide burial in the Black Sea of 2.4 Tgyear 1 including about 1 Tgyear-1 that is buried in the anoxic zone. Using these data and integrated over the upper 20 cm of sediment sulfate reduction rates, Neretin and co-authors [75] concluded that the annual sulfide flux into the water column from sediments of the anoxic zone is between 3 and 5 Tgyear x. The value is likely to be overestimated due to spatial differences in pyrite burial rates and possible sulfide diffusion downward into the deeper sediment layers. 

---