Distribution of certain cations and anions in seaweeds and seawater of Saurashtra coast and their geochemical significance

Abstract

Na and Mg dominate over K and Ca respectively in seawater, but a reverse trend is observed in many seaweeds. This preferential accumulation of one element over another similar element is adjudged on the basis of differential percentage enrichment factor (DPEF). It is positive for K over Na (3986) and Ca over Mg (359). It reflects lower residence time (<img src='/image/spc_char/tow.gif' border=0>) values of K and Ca which are preferentially accumulated than Na and Mg possessing higher (<img src='/image/spc_char/tow.gif' border=0>). Cl and I are more in brown seaweeds than in red and green seaweeds. Br is generally high in red seaweeds followed by brown and green seaweeds. The halogen content of investigated seaweeds is in the order Cl is greater than Br is greater than I is greater than F, whereas in seawater the trend is CI &gt; Br &gt; F &gt; I [F values, <i>Indian J Mar. Sci.,</i> <b>13</b> (1984) 47]. Their concentration factors, CF (median values), in seaweeds are in the order I &gt; F &gt; Br &gt; CI. DPEF of I, F, Br and CI in seaweeds in relation to their other halogens of higher ralso show descending order:I over CI &gt; I over Br &gt; I over F &gt; F over CI &gt; Br over CI &gt; F over CI. The trend of concentration of halogens in seaweeds compared to ambient medium (median values) suggests their relative uptake rates pattern. BnF ratio in seaweeds indicates that the accumulation of one halide is independent of the other. In general, shorter the (<img src='/image/spc_char/tow.gif' border=0>), more is die CF of cationic and anionic elements in seaweeds.