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The objectives of this paper are to review the role of rivers as a pathway of chemical elements from the land to the ocean and to assess the significance of river input of pollutants to oceanic chemistry.The major importance of river suspended matter (R.S.M.) on the transport of chemical elements to the ocean is underlined. The relationship between river water/river suspended sediment partition coefficient and the electronegativity function QYO has been reassessed. A comparison between theoretical erosion and actual fluxes of material carried by rivers shows that for most chemical elements these two figures are similar. Additional fluxes are observed in rivers for some elements like Sb, Zn and Pb. This discrepancy is discussed in terms of steady state and non-steady state erosional processes.During estuarine mixing the discharge of riverine elements to the ocean is drastically modified. More than 90% of the R.S.M. settles with its associated colloidal material produced when river water mixes with sea water. Consequently, due to the strong association of chemical elements with R.S.M., only a small percentage of the continental material will reach the sea. However, the comparison of R.S.M. with deep-sea clay composition emphasizes the prime influence of river input on oceanic sediment composition 265 C. S. Wong et al. (eds.), Trace Metals in Sea Water

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A number of procedures are now available for calculating the effects of ionic inter-actions on the behaviour of solutions as complex as sea water (Whitfield, 1973 a). These procedures are able to give a good account of the properties of the major electrolyte components (Leyendekkers, 1973 a; Robinson & Wood, 1972; Whitfield, 19736) and of the colligative properties of sea water (Robinson & Wood, 1972; Whitfield, 1973 c, d). However, greatest interest centres around the possibility of predicting the effects of these major components on the multitude of ionic equilibria that influence the properties of the less abundant constituents that are of greater biological and geological importance. It is here that the newer approaches to marine chemistry are weakest because suitable thermodynamic data are lacking. One system of practical importance that can be studied using a variety of theoretical approaches is the acid ionization of ammonium ions represented by the equation The toxicity of ammonium salts to freshwater life has been shown to be strongly dependent on the pH in a manner that is consistent with un-ionized ammonia (NH3) being the most lethal fraction (see, for example, Wuhrmann & Woker, 1948; Downing & Merkens, 1955; Lloyd & Herbert, i960; Hemens, 1966; and Brown, 1968). These papers and many others have been thoroughly reviewed (EIFAC Technical Paper no. 11, 1970, Kemp, Abrams & Overbeck, 1971). The free base (NH3) has a relatively high lipid solubility because it carries no charge and is therefore able to diffuse quite readily across cell membranes (Fromm & Gillette, 1968).