Rare earth elements and heavy metal distribution in estuarine sediments of east coast of India

Bed sediment samples collected from the Hoogly, Godavari, Krishna and Cauvery estuaries on the east coast of India were analyzed for rare earth elements (REEs), mainly lanthanides (La-Lu), Y, a number of metals (V, Cr, Co, Ni, Zn, Ag, Cd and Pb), using Thermal Ionization Mass Spectrometry. Continental weathering plays an important role in the distribution of REEs and metals. However, metals showed wide variation in concentration among estuaries, mainly due to varying salinity, which controls complex estuarine processes, and partly to anthropogenic inputs. Factor analysis of elemental data identified two major groups of elements: (i) LREEs, HREEs, Cd, Pb and Ag, revealing an association with detritals brought in by the rivers; and (ii) V, Cr , Co, Ni and Zn, indicating complex estuarine processes and human input. LREEs are more enriched than HREEs (LREE/HREE ratio varied between 12 and 40) reflecting silicate weathering of crustal materials, and a resultant increase in LREEs in detritals. We conclude that the estuarine system constitutes 70% of LREEs and 30% of HREE flux to the Bay of Bengal.[PUBLICATION ABSTRACT]