The behaviour of aluminium in waters of the Mandovi estuary, west coast of India

The concentration of dissolved Al in both the freshwater (similar to 0.08-0.23 mu M) and seawater (less than or equal to 0.07 mu M) endmembers of the Mandovi estuary is low, the former being always greater in magnitude than the latter. In high-salinity (> 10) waters an increase in dissolved Al levels is conspicuous while it is uniform at salinities similar to 1-10. Although a removal of Al from solution in the low-salinity region is apparent, the magnitude of this removal is, however, relatively small. On the contrary, a steady increase in concentration of dissolved Al downstream reveals a significant input of Al into the high-salinity waters of the mid-and lower estuary. The data indicate that the removal of dissolved Al onto riverine sediments tends to occur during the initial stages of estuarine mixing but with little or no net permanent loss, as the sediments on resuspension release sorbed Al into solution. These observations suggest that sorption exchange processes dominate the geochemical interactions of Al in estuarine waters.