Geochemical characteristics of sediments from a reservoir (tank) ecosystem in Sri Lanka

Major, trace and selected high field strength element geochemistry of fresh-water sediments from the Malagane tank, Deduru Oya basin, Sri Lanka, has been investigated in this study. Sediment samples were collected from 13 locations and analyzed for their elemental distribution using the X-ray fluorescence technique. The sediments were characterized by relatively low organic matter, ranging from 4.8 to 16.9%. The elemental distributions were compared with those of the average upper continental curst, and it was found that, with a few exceptions, most of the studied elements are either comparable or depleted. Correlation and principal component analyses were applied to identify the relationships among studied elements. Major elements, most trace and light rare earth elemental distribution show strong positive correlation with Al2O3 and TiO2, which indicate that the phyllosilicates and heavy minerals in the sediments are the probable hosts for these elements. The results also indicate that the sediments in the Malagane tank are representative of the materials from the metamorphic rocks in the watershed and were subjected to changes within the tank ecosystem. The results obtained from this study are vital for future pollution management of tank ecosystems in Sri Lanka, since information on elemental distribution within the sediments of tank ecosystem is lacking.