Input biogenic

Let us define a two-box model for a steady-stafe ocean as shown in Fig. 10-22. The two well mixed reservoirs correspond to the surface ocean and deep oceans. We assume that rivers are the only source and sediments are the only sink. Elements are also removed from the surface box by biogenic particles (B). We also assume there is mixing between the two boxes that can be expressed as a velocity Vmix = 2 m/yr and that rivers input water to the surface box at a rate of Vnv = 0.1 m/yr. The resulting ratio of F mix/V riv is 20. 

Now that we have defined the biogenic model we can define two important properties. The first is the ratio of falling particles to the input to the surface. This property (g) is equivalent to the efficiency of bioremoval from surface waters ... 

Use of pollutant and biogenic markers as source discriminants of organic inputs to estuarine sediments 70... 

As mentioned, the type of concentration-depth profiles observed in oceans should also be observed in lakes. However, the vertical concentration differences in lakes are often not as pronounced as in the ocean. The reason for this is, that the water column in lakes is much shorter mixing and stagnation in lakes is much more dynamic than in the oceans. Due to the presence of high concentrations of different particles in lakes, the release of trace elements from biogenic particles may not be clearly observed, due to readsorption to other particles. This would mean that low concentrations are observed throughout the water column, but that concentration differences are small. Atmospheric inputs to the upper water layers may also make it more difficult to observe a depletion of certain elements in the epilimnion. 

From the perspective of the surface box, the biolimiting elements are supplied via river runoff and from upweUing. The elements are removed via the sinking of biogenic particles and downwelling. Since this model considers only the transport of materials into and out of the ocean and between the two reservoirs, details as to what happens to the elements while they reside in the boxes are not needed other than that they are present in a steady state. In such a case, the input rate of a biolimiting element will equal its output rate. For the surface-water reservoir, the mass balance that describes this steady state is given by... 

Sabkhat also form inland, where river input and saline groundwater seeps contribute salt and water, forming an evaporitic pan. As illustrated in Figure 17.6, these continental sabkhat are fer more isolated from the ocean than a marine sabkha. They also contain far less biogenic detritus. 

The delivery of PIC and POC to the sediments depends on biological production in the surface waters. The input of terrestrial carbon is relatively minor. The relative proportions of PIC and POC generated in the surfece waters reflect the species composition of the plankton, i.e., calcifiers versus noncalcifiers. The success of detrital PIC and POC in surviving the trip to the seafloor is also dependent on the species composition of the plankton. As discussed in Chapter 23.5.4, the presence of biogenic hard parts confers protection on POC, inhibiting its remineralization. 

The sum of EC and OM contributes another 20-27% (at urban sites) and 18-24% (rural) to the PM mass, with OM dominating EC at most sites. Like in the case of SIA, differences between rural and urban sites appear modest which is probably caused by a considerable natural (biogenic) input. A study by ten Brink et al. [13] on the presence of 14C in PM filter samples revealed that at least 64% of the organic carbon measured at an urban Dutch site was contemporary (i.e. emissions from biogenic material and biomass wood combustion). 

Betzer P.R., Byrne R.H., Acker J.G., Lewis C.S., Jolley R.R. and Feely R.A. (1986) Biogenic input to the oceanic carbonate system Mass fluxes of pteropods and foraminifera in tropical, temperate, and sub-arctic regions of the western North Pacific, (manuscript). 

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