Spatial Variations of Trace and Rare Earth Elements in Tropical Lake Sediments

This study provides baseline concentrations of major, trace (TE), and rare-earth elements (REEs) in the tropical lake bottom sediments and links the spatial variability of the elements to the controlling geochemical factors. The surface bottom sediment samples were collected in 10 water reservoirs in the Dak Lak Province of Central Vietnam. The concentrations of 57 elements were determined by atomic emission and inductively coupled plasma mass spectrometry (ICP-AES; ICP-MS). The potential contamination of bottom sediments was evaluated by calculating the geo-accumulation index (Igeo) and enrichment factor (EFAl and EFFe). The special goal of this study was the calculation of the local enrichment factor (LEF). Cluster analysis (CA) and principal component analysis (PCA) were applied to the enrichment factor distribution in order to indicate the element associations and their geochemical sources in various lakes. The values of the geochemical indices suggest low pollution of the lake bottom sediments. The found LEF values may be used as a background for long-term monitoring of potential hazardous elements in the region. Multivariate analysis shows that high spatial variability of element concentrations in lake bottom sediments is related to mineralogical provenance rather than to the age of the water reservoir, organic matter, and granulometric fraction content. The results suggest that application of the selected multivariate analyses (CA and PCA) to enrichment factor (EFFe) distribution has potential as a tool for identifying risk-elements and fingerprinting geochemical provenance even if applied to the limited geochemical data set.