Assessment of potentially toxic and rare earth elements in surface soils of Dong Nai, Vietnam

Abstract

This study investigates the quantities of Rare Earth Elements (REEs) and Potentially Toxic Elements (PTEs) in Dong Nai Province's surface soils. Atomic Absorption Spectrometry (AAS) and Instrumental Neutron Activation Analysis (INAA) were used to determine element concentrations. To validate the concentration results, established reference materials (NIST 2711 and IAEA Soil-7) were used. Element concentrations followed a certain order, with Mn, Cr, V, and Zn dominating, except for Al, which were used to determine the enrichment factor. Arsenic (As) concentrations ranged from 0.8 to 37.5 mg/kg, exceeding global averages but below Vietnam quality standards. Cadmium (Cd) concentrations ranged from 0.03 to 0.16 mg/kg, below global averages and quality standards. Cobalt (Co) and chromium (Cr) concentrations ranged from 0.5 to 135.1 mg/kg and 18 to 844 mg/kg, respectively, with notable percentages of samples exceeding global averages. Copper (Cu) and lead (Pb) exhibited elevated concentrations, with varying proportions exceeding quality standards. Manganese (Mn) and antimony (Sb) exceeded global averages in a significant percentage of samples. Vanadium (V) concentrations surpassed the crustal average by over half of the sites. Zinc (Zn) concentrations were below reference values. REEs showed significantly higher concentrations than global soil averages, with a substantial proportion of samples exceeding reference values. Geo Accumulation Index (Igeo), Enrichment Factor (EF), and Pollution Load Index (PLI) analyses provided a detailed numerical assessment of contamination and soil quality. Statistical analysis showed correlations and clusters of toxic elements and highlighted the spatial distribution of samples based on elemental compositions.

Keywords: Atomic absorption spectrometry; Neutron activation analysis; Potentially toxic elements; Rare earth elements; Soil contamination.