Multi-element Signatures in Lake Bottom Sediments of Central Vietnam

This study provides baseline chemical composition of a tropical lake bottom sediments collected in previously unstudied ten water reservoirs in the Dak Lak province of Central Vietnam. The concentrations of 57 major, trace (TE) and rare-earth (REE) elements were determined by atomic emission and inductively coupled plasma mass spectrometry (ICP-AES; ICP-MS). To link the spatial variability of the elements to the controlling geochemical factors, a multivariate approach was implemented. The environmental status of bottom sediments was evaluated by calculating the local geochemical background (LGB), geoaccumulation index (Igeo), enrichment factor (EFAl and EFFe), and local enrichment factor (LEF). The selected multivariate analysis tools (cluster analysis (CA) and principal component analysis (PCA)) were used to indicate the multi-element associations and their geochemical sources in various lakes. The bulk and LGB results can serve as a baseline for further environmental analyses in the region. The average values of geochemical indices suggested low pollution (Igeo < 0; EFAl, EFFe, and LEF < 2). The LEF distribution highlighted pronounced spatial variability in the chemical composition of the lake bottom sediments. However, the elevated LEF values (> 2.5) of some potentially hazardous TEs (Sn, Sb, Cs, As, Ag, Hg, W, Pb, Bi, and U) in the individual lakes might indicate the possible anthropogenic point source that should be further monitored. The multivariate analysis allowed the identification of three multi-element signatures that were linked to three main geological structures of the Dak Lak province. Therefore, the main process controlling spatial element distribution is the grain size and mineralogical fractionation of the catchment sedimentary material. An approach combining geochemical background concept (LGB and LEF) with multivariate analysis (CA and PCA) has proved to be an efficient tool for fingerprinting geochemical provenance, even if applied to limited geochemical data.