Rivers fluxes

Froelich, P. N., Blanc, V., Mortlock, R. A., Chillmd, S. N., Dunstan, W., Udomkit, A., and Peng, T. H. (1992). River fluxes of dissolved silica to the ocean were higher during glacials Ge/Si in diatoms, rivers, and oceans. Paleoceanography 7, 739-767. 

Evaporation of river water will not make seawater. Instead, evaporation of the nearly neutral Na -Ca -HCOi" river water produces a highly alkaline Na-HCO -COf water such as foimd in the evaporitic lake beds of eastern California (Carrels and MacKenzie, 1967). In addition, on comparing the amount of material supplied to the ocean with the amoimt in the ocean, it may be seen that most of the elements could have been replaced many times (Table 10-12). Thus some chemical reactions must be occurring in the ocean to consume the river flux. 

The present sources to the ocean are the weathering of old evaporites (75% of river flux) and CP carried by atmospherically cycled sea-salts (25% of river flux). Loss from the ocean occurs via aerosols (about 25%) and formation of new evaporites. This last process is sporadic and tectonically controlled by the closing of marginal seas where evaporation is greater than precipitation. The oceanic residence time is so long for CP ( 100Myr) that an imbalance between input and removal rates will have little influence on oceanic concentrations over periods of less than tens of millions of years. 

A solution, still controversial, has been recently proposed. This is the loss of sulfate from seawater during hydrothermal circulation through mid-ocean ridges (Edmond et al., 1979). The flow of water through these systems is estimated to be about 1.4 x 10 L/yr, about 0.4% of the flow of rivers. However, sulfate is quantitatively removed, yielding a flux of 125 Tg S/yr, capable of balancing the river flux. The controversy is whether the chemistry involved in removing sulfate is the formation of... 

The evaporite source is characterized by covariation of sulfate (from gypsum) and chloride (from halite). That elements can be recycled from the ocean to land by movement of saltbearing aerosols (so-called "cyclic salts") has confused the interpretation of river flux data somewhat. While this cycling generally follows the ratio of salts in the sea, the S/Cl ratio is an exception. Taking the S/Cl ratio of the cyclic component to be 2 (based on compositional data for marine rains) and assuming that all chloride in rivers is cyclic, an upper limit for the cyclic influence can be calculated. 

Accepting these relative proportions from evaporites (2/3) and sulfides (1/3), the characteristic times, T of cycling of the evaporite sulfur and sulfide sulfur reservoirs can be estimated from the reservoir sizes (R,) in Table 13-3, and the river flux of sulfur. For evaporites ... 

A small flux is shown between the land and atmosphere. This represents the transport of dust particles to the atmosphere (F28) and the deposition of these particles back on land either as dry deposition or associated with atmospheric precipitation (F82). Similarly, fluxes that represent the transport of seasalt from the surface ocean to the atmosphere (Fss) and the deposition of soluble (F85) and insoluble (F81) atmospheric forms are also shown. As already discussed for the river fluxes, the insoluble particulate flux is represented as a direct transport of P to the sediment reservoir. 

Fig. 3.7. Comparison of hydrothermal fluxes and river fluxes (data from Table 3.7) (Elderfield and Schultz, 1996).

Table 4. Total flux of elements flowing into the sea and main transport forms for Chinese continental rivers(flux units ton) ...

The data presented in Table 11.1 indicate that the fluvial gross river flux is the major source of trace metals to the oceans and that most of this flux is in particulate form (fluvial gross particulate flux). But the majority of this particulate flux is trapped within estuaries, primarily via settling, and, hence, is not released into the open ocean. As a result, the fluvial net particulate flux is only about 10% of the fluvial gross particulate flux. In seawater, most of this particulate metal remains in solid form due to low solubilities. The particulate metals eventually settle to the seafloor and are subsequently buried in the sediments. In the case of iron, a small fraction of the particulate pool does dissolve. In the surface waters, solubilization of particulate iron can provide a significant amount of this micronutrient to the phytoplankton. 

Other average fertilizers made of wastes 3.7 Rhine River flux to the outlet of —... 

A recent study of rainwater DOC suggested that rain also may be a significant source of DOC to the open ocean. The DOC concentration of marine rain was reported to be 0.3 mg L 1 and the global rainwater DOC flux to the oceans was estimated to be 0.43 x 1012 gC yr 1, about the same magnitude as the river flux of DOC (Willey et al., 2000). 

Probst, J.L., Mortatti, J., and Tardy, Y. (1994) Carbon river fluxes and weathering CO2 consumption in the Congo and Amazon river basins. Appl. Geochem. 9, 1-13. 

During the second part of the 20th century, river flux of organic matter, nutrients and pollutants markedly increased. For example, increase in concentration of ammonia nitrogen is 2.5 times, of nitrites and nitrates 4 and 5 times respectively, of phosphate 2 times. Since the beginning of 1970s, the concentration of heavy metals and oil in river water has also increased [9]. Over the period 1996-2000, the input of the contaminants to the Black Sea with the Danube waters comprises oil 53 x 1012 t, Cu 1.2 x 1012 t, and Zn 3.3 x 1012t [9],... 

Listed are the central values reported by Galloway et al. (2004) (see Table 1 and Fig. 1 of their publication). Galloway et al. (2004) lists only the total river flux. I assumed that about two thirds of the total is PON, and one third is DON. 

At regional scales, there are also examples in which SGD of nitrogen equals or exceeds river fluxes. For example, DIN fluxes in groundwater discharges through salt marshes along the South Carolina coast are estimated to be equivalent to input from major rivers in this region ( 60 X 10 mol yr ) (Krest et ai, 2000) (Table 9.5). 

Table 9.5 Comparison of estimated N fluxes through submarine groundwater discharge (SGD) relative to river fluxes (modified from Slomp and Van Cappellen, 2004 sites with relatively large SGD inputs relative to river inputs were specifically selected for this table)...

Fresh MORE Units Bulk rock gains (+) and losses ( —) for extrusives Dikes Gabbros Average crustal gainsAosses Units Total flux from crust Units Hydrothermal fluxes from submarine vents (gyr ) River fluxes (g yr )... 

Table 6 Distribution of global land area (Mkm ) exposed to chemical weathering and to river transfer of soluble material. A percent of land area (nonglaciated area also contains alpine glaciers). B percent of weathering generated fluxes (e.g., DIC flux). C percent of river fluxes to oceans.

Lemarchand D., GaiUardet J., Lewin E., and AUegre C. J. (2000) Boron isotopes river fluxes hmitation for seawater pH reconstruction over the last 100 Myr. Nature 408, 951. 

Wadleigh M. A., Veizer J., and Brooks C. (1985) Strontium and its isotopes in Canadian rivers fluxes and global implications. Geochim. Cosmochim. Acta 49, 1727-1736. 

For the major ions in seawater, the input from rivers is generally the dominant source. The historical approach to estimate the river flux of... 

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