Rare earth element distribution in tropical coastal wetland sediments: a case study from Vembanad estuary, southwest India

Rare earth element (REE) geochemistry of sediments from Vembanad Coastal Wetland, southwest India, shows that light rare earth elements (LREEs) are the more abundant compared to middle rare earth element (MREE) and heavy rare earth element (HREE). We suggest that the textural parameters and the biochemical processes lead to the REE variation in this coastal wetland environment. Variations in the REE abundance are mainly controlled by the source materials deposited by riverine input. REE records in sediments showed spatial heterogeneity due to the influence of the physico-chemical conditions like, sedimentological conditions, salinity and depositional flux of the sediments along the wetland. Enriched values observed along the northern and southern stations are due to the increased riverine input. The REE ratios and enrichment factor values suggest that the abundance is in the order of LREE > MREE > HREE. Positive Eu anomaly is linked to the source sediments brought down from the catchment areas of the Periyar River and Muvattupuzha River. However, Ce anomaly suggests no significant variation in the oxidation condition at the sites of deposition.