The strontium isotope distribution in water and fish within major South African catchments

Abstract

Strontium has 4 naturally-occurring isotopes ( 84Sr, 86Sr, 87Sr, 88Sr) all of which are stable (Faure, 1986). /T_he correlation between the 87Sr/86Sr isotope ratio of lake water and /f_ish /f_in spine tissue was investigated in 23 lakes within 4 major South African catchments. Data showed that /f_ish within a speci/f_ic lake all have the same Sr isotope ratio in their /f_in spine tissue regardless of species, age, sex and condition. /T_he origin of the dissolved Sr fraction in lake water can be either from the natural weathering of upstream geological units or from an upstream anthropogenic source. /T_he Sr isotopic ratios of the water samples were, however, constant over a multi-year period suggesting that the main source may be the more consistent geological environment. /T_he Sr isotope ratio of river and lake water generally increases along the course of the rivers within the tertiary catchments of the areas investigated. In large rivers like the Vaal, where pollution also plays a role, the pattern is much more complicated.

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