Geophysical Research Abstracts, Vol. 7, 02199, 2005 SRef-ID: 1607-7962/gra/EGU05-A-02199 © European Geosciences Union 2005 Chloride dynamics across Australia R.G. Cresswell (1,2) (1) CSIRO Land & Water, Brisbane, Australia, (richard.cresswell@csiro.au ), (2) CRC for Landscape Environments and Mineral Exploration, Australia 1 Introduction The hydrologic cycle neatly describes the dynamics of water on the earth’s surface. The simple hydrochemistry, high solubility and conservative behaviour of chloride mean we can incorporate chloride directly into this simple dynamic construct. Further, the natural occurrence of a radioisotope of chlorine ( 36 Cl) in the environment is useful when studying salt, and thus water, dynamics on and within the earth’s surface. 2 Chloride dynamics We now have a good description of chloride accession across Australia (Keywood, et al., 1997; Farrington, et al., 1993; Blackburn and McLoed, 1983; Hutton, 1976; Hingston and Gailitis, 1976). Simply put: chloride entrained in sea-spray is carried up and washes out in rainfall. Chloride concentration in rainfall is therefore dependent on distance from the coast in the direction of the prevailing winds. Keywood, et al. (1997) describe this in terms of the sum of 2 exponential components: rapid fallout of chloride near the coast, presumably as dissolved salts; and a component that is transported further inland, possibly as dissociated chlorine gas. The precise equation (Keywood, et al., 1998) approximates to: y = 52.5 (-d/56) + 2.95 (-d/710) (1)