Average world river water

The concentration of Ni in the lithosphere is 55p.gg (Li, 2000) and the concentration of dissolved Ni in stream water is 2p,gL (Turekian, 1971). More recent data on the concentration of dissolved Ni in average world river water indicates the value to be 0.8 xgL (Gaillardet et al., 2003) and the Ni concentration in ocean water to be 0.47 xgL (Chester, 2000). Natural emissions of Ni to the atmosphere are dominated by windblown dusts while anthropogenic sources that represent 65% of all emission sources are dominated by fossil-fuel... 

Average world river water composition plots close to the cross point of calcite saturation line for Pco2 = 10 atm and electroneutrality line which is approximated as mncos = 2mca2+- This shows that river water with small runoff is in equilibrium with calcite. Therefore, it is inferred that chemical composition of river... 

The waters through which ships travel are categorized by their salt content. The following are approximate values seawater, 3.0 to 4.0% salt coastal brackish water, 1.0 to 3.0% river brackish water, 0.5 to 1.8% salty river water, 0.05 to 0.5% river water, <0.05%. Seawater mainly contains NaCl. The salt content is approximately 1.8 times the chloride ion content. The salt content of the world s oceans is almost the same. Different salt contents can occur in more enclosed seas [e.g., the Adriatic (3.9%), Red Sea (4.1%) and the Baltic (1.0%)]. Table 17-1 gives as an example average analyses for seawater and the Rhine River. 

Based on world average river water from Livingstone (1963), which is not corrected for pollution. 

Based on natural" world average river water. 

Input of river water to seawater is the most important process controlling chemical composition of seawater. Chemical composition of river water varies widely (Table 4.4). Thus, it is difficult to estimate average chemical composition of river water in the world. However, it can be regarded as average chemical composition of major river water in continent (Missippi, Naile, Yangtze river etc.). Chemical composition of major river water is determined by water-rock interaction, mixing... 

Figure 2. Comparison of dissolved metal concentrations in surface waters of the Rio Solimdes, the Rio Negro, and forested streams in Caraj with world river average (25).

River transport of clay minerals into the ocean is spatially and temporally variable. The global annual suspended load of river sediment into coastal waters currently averages 12.6 X 10 ton. This flux is approximately 10% less than was delivered before humans began damming rivers. (One notable exception is the Mississippi River, whose sediment load has increased due to very high rates of soil erosion. The riverine sediments deposited in the mouth of the Mississippi River form one of the world s largest deltas.)... 

The situation is more complex in the region of Asia and the Pacific. Water quality has many enemies there. First, sedimentation constitutes a major cause of pollution in Asian rivers, since sediment loads are four times the world average. Secondly, hazardous and toxic waste deteriorates the water quality. It is noteworthy that lead levels in Asia s surface water are about 20 times higher than those in OECD countries. Thirdly, eutrophication is faced due to the extensive use of fertilizers in the last 30 years. But the list of problems does not end here. Asian rivers contain three times as many bacteria from human waste as the world average. Finally, urbanization and the release of untreated sewage and industrial waste to the environment are expected to cause severe water pollution problems. 

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