Continental run-off

The fractionated igneous and sedimentary rocks in Figure 20 have Rb/Sr and Eu/Sr ratios that are much higher than those in current estimates for the upper continental crust. The latter can be constrained by the strontium isotope ratios of continental run-off (—0.712), and its model neodymium age (—1.8 Ga). According to this method, a minimum time-integrated upper crustal Rb/Sr ratio of 0.14 is indicated. 

The surface waters of the ocean are the largest sink for tritium. Transfer into the surface ocean occurs by water vapor exchange, precipitation and continental run-off (e.g., Weiss et al. 1979 Weiss and Roether 1980). Most of the nuclear weapons tests were performed in the northern hemisphere, leading to a strong asymmetry in the global north-south distribution of bomb tritium in the ocean surface waters. Concentrations in the northern hemisphere are relatively high compared to those in the southern hemisphere (Weiss and Roether 1980 Fig. 1). 

Assuming a steady-state system in the continental run-off and the deposition of minerals in the ocean, the residence time of the elements in sea water can be estimated from the yearly rate of transport in the rivers and their average concentration in ocean water. For elements such as Zn, Cu, Ni, and Ti, the mean residence time in sea water before incorporation in solid phases is of the order of 10 years. 

Baumgartner, A. and Reichel, E. (1975). "The World Water Balance Mean Annual Global, Continental and Maritime Precipitation and Run-Off." Elsevier Scientific Publishers, Amsterdam. 

New scientific topics in the near-shore waters of the Russian continental shelf will include a broad range of studies from the biogeochemical fate of organic material contributed to the Arctic Ocean by shoreline erosion and river run-off" to the social and biological impacts of changes in sea ice distribution. 

Baumgartner A. and Reichel E. (1975) The World Water Balance— Mean Annual Global, Continental, and Maritime Precipitation, Evaporation and Run-off. Elsevier, Amsterdam, 179pp. 

F12 sediments from continental water bodies River run-off to oceans 136 122 104 104 104... 

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