Selecting efficient methodologies for estimation of As and Hg availability in a brownfield

Area of Science:

• Environmental Chemistry
• Soil Science
• Analytical Chemistry

Background:

• Soil metal(loid) availability assessment lacks standardized analytical methods, leading to inconsistent results.
• Brownfield sites often exhibit high concentrations of toxic elements like arsenic (As) and mercury (Hg).
• Understanding metal(loid) bioavailability is crucial for accurate environmental risk assessment.

Purpose of the Study:

• To compare the efficacy of nine single and four sequential extraction methods for assessing As and Hg availability in polluted soils.
• To analyze As and Hg concentrations in native plant species grown in these soils.
• To evaluate the influence of soil properties and extractant type on metal(loid) availability and plant uptake.

Main Methods:

• Nine single extraction methods (e.g., H2O, CaCl2, NaNO3, NH4NO3, DTPA, EDTA, HCl, LMWOA, TCLP) were employed.
• Four sequential extraction procedures (Tessier, BCR, Wenzel, Fernández-Martínez) were utilized.
• As and Hg concentrations were measured in soil extracts and in three native plant species (Lotus corniculatus, Betula celtiberica, Dactylis glomerata).

Main Results:

• Single extractants demonstrated varied capacities for As and Hg extraction, reflecting different bound forms.
• Metal(loid) availability was influenced by element characteristics, soil properties, extractant type, and pollution levels.
• Sequential extraction procedures provided distinct patterns for As and Hg, offering more detailed insights into potential bioavailability.
• Plant analysis revealed higher metal(loid) concentrations in roots than aerial parts, with species-specific uptake differences and higher bioaccumulation factors (BCFs) for Hg than As.

Conclusions:

• No single extraction method can fully capture the complexity of soil As and Hg availability.
• Sequential extraction procedures provide more comprehensive information for risk assessment, especially when using aggressive extractants.
• Plant species significantly influence metal(loid) uptake and bioaccumulation, highlighting the importance of considering plant-soil interactions in bioavailability studies.