Terrestrial environments export

The magnitude of this loss is thus substantial, and comparable to flux estimates for the delivery of terrigenous OC to the oceans (Figure 1). However, while the above studies imply low burial efficiencies for fluvial POM in deltaic environments, it is uncertain whether the apparent losses of riverine POM reflect its complete mineralization or export to the ocean interior either in dissolved or particulate form (Edmond et al., 1981). Moreover, the extent of terrestrial OC export and burial from river systems that do not form deltaic deposits is less weU constrained. 

Several important studies have examined the transfer of P between terrestrial and marine environments (e.g., Froelich 1988, Berner and Rao 1994, Ruttenberg and Goni 1997), but more work clearly needs to be done to quantify the interactions between dissolved and particulate P forms and the aquatic/marine interface. The net pre-human flux of dissolved P to the oceans is 1 Tg P/year, with an additional 1-2 Tg P/year of potentially soluble P, bringing the total to about 2-3 Tg P/year. Thus, the residence time of biologically available P on land is about 40-60 kyr with respect to export to the oceans. It may be no coincidence that this residence time is of a glacial timescale—later I discuss the control of climate on the terrestrial P cycle. But clearly, the interaction between biologically available P on land and loss of this P to the oceans is relatively dynamic and speaks to the relatively rapid cycling of P on land. 

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