Arsenic bioaccessibility and fractionation in abandoned mine soils from selected sites in New South Wales, Australia and human health risk assessment

Abstract

Understanding the transport behaviour of arsenic (As) from soils to humans is critical when undertaking human health risk assessment and contamination control. This research examined As bioaccessibility in different As fractions and particle size fractions of As-enriched mine soils using different extractions. Bioaccessibility of As ranged from 0.24% to 32% for Solubility Bioaccessibility Research Consortium (SBRC) and Physiologically Based Extraction Test (PBET) methods, with extractable As (using 0.43 M HNO3) being 1.3–24.9%. The highest As bioaccessibility (19–32%) was consistently observed in the fine particle size fraction (< 53 µm) of all three extractions. Sequential extractions revealed that As fractions were mostly associated with crystalline (30–73%) and amorphous (9–59%) Fe/Al oxyhydroxides. The bioaccessibility of As in the gastric phase of SBRC and PBET methods highlighted a positive correlation (R2 = 0.83–0.88, p < 0.01) with exchangeable, surface and amorphous- bound As fractions, while the intestinal phase showed a strong positive correlation (R2 = 0.85–0.89, p < 0.01) with exchangeable and surface bound fractions. The study revealed that As bioaccessibility in soils can potentially be determined using the 0.43 M HNO3 extraction procedure. Health risk assessment confirmed that there was a strong increase in chronic daily intake, hazard quotient and cancer risk, with a reduction in particle size.