Bioaccessibility and availability of trace elements coprecipitated with aluminum-substituted iron oxides

Area of Science:

• Environmental Science
• Geochemistry
• Soil Science

Background:

• Iron oxides nanoparticles are key reservoirs for trace elements in soils and sediments.
• Trace elements can be sequestered by iron oxides via surface complexation or solid-phase incorporation.
• Understanding trace element behavior in iron oxides is crucial for environmental risk assessment.

Purpose of the Study:

• To evaluate the sorption stability and bioaccessibility of trace elements coprecipitated with iron oxides.
• To assess the influence of aluminum (Al) substitution and mercury (Hg) presence on trace element environmental mobility.
• To investigate the impact of trace element concentration on sorption stability.

Main Methods:

• Precipitation of iron oxides with arsenic (As), lead (Pb), antimony (Sb), cadmium (Cd), lanthanum (La), ytterbium (Yb), and mercury (Hg) in the presence and absence of aluminum (Al).
• Evaluation of sorption stability using sequential extraction procedures (BCR and SBET).
• Human risk assessment via oral intake bioaccessibility analysis.

Main Results:

• Arsenic, cadmium, and antimony showed low extraction percentages (<10%), indicating strong retention by iron oxides.
• Lanthanum, lead, and ytterbium exhibited higher extraction percentages (up to 86%), suggesting weaker adsorption and limited incorporation.
• Sorption stability decreased for cadmium and lead at higher concentrations. Arsenic and cadmium coprecipitated with Al-goethite were more stable than with lepidocrocite or Al-free-goethite.
• High bioaccessible arsenic content posed a health risk to children (HQ > 1) in all samples.

Conclusions:

• Iron oxides exhibit selective sorption for trace elements, with strong retention for As, Cd, and Sb, and weaker for La, Pb, and Yb.
• Aluminum substitution influences trace element stability, enhancing that of As and Cd with Al-goethite.
• The bioaccessibility of arsenic in iron oxides presents a significant human health risk, particularly for children.