Opportunities and Challenges Associated with Bioavailability-Based Remediation Strategies for Lead-Contaminated Soil with Arsenic as a Co-Contaminant—A Critical Review

Abstract

Purpose of Review The ubiquity of soil contamination by lead (Pb) and arsenic (As) has prompted the development of numerous techniques for its remediation. For human health exposure assessment, oral bioavailability-based methods are the most suitable to assess the efficacy of these treatment strategies, including in vivo relative bioavailability (systemic absorption relative to a toxicity reference) and in vitro bioaccessibility (dissolution in simulated gastrointestinal solutions). This paper provides a critical review of opportunities and challenges associated with the immobilization of Pb and As in contaminated soil. Recent Findings This review identified that the major inorganic and organic amendments used to reduce Pb and As exposure include phosphate, industrial by-products, metal oxides, organic matter, biochar, and treatment with iron sulphate to promote the formation of plumbojarosite in soil. In addition to RBA and IVBA assessment, investigating changes in Pb/As speciation in untreated vs treated soil can provide additional confirmation of treatment efficacy. The results of this review showed that immobilization efficacy may vary depending on amendment type, Pb, and As speciation in soil and the approach used for its assessment. Summary Reducing childhood exposure to Pb and As is a significant challenge, given the variety of contamination sources and treatment strategies. A lines-of-evidence approach using standardized methodologies is recommended for the assessment of immobilization efficacy to ensure exposure and risk reduction Graphical Abstract Bioavailability-based remediation strategies. Popular soil amendments to reduce Pb exposure include phosphate, industrial by-products, metal oxides, organic matter, and biochar; however, these may increase As exposure. The plumbojarosite formation technique has been recently developed to mitigate Pb and As exposure simultaneously. Multiple lines-of-evidence approach is recommended to assess treatment efficacy

Arsenic, cadmium, lead, antimony bioaccessibility and relative bioavailability in legacy gold mining waste

“…3C ). Organic matter bound Pb may exhibit moderate Pb solubility because organic molecules act as a complexing agent for Pb [ 62 ], while mineral sorbed Pb tends to solubilize readily when exposed to acidic pH (1.5) of the gastric phase of USEPA method 1340 [ 63 , 64 ]. Additionally, anglesite is highly soluble in both acidic and neutral pH (2− 7) [ 65 ].…”

“…Elevated concentrations of these co-contaminants in Victorian goldfields raise considerable concern because Pb, Cd and Sb exposure have been associated with attention deficit/hyperactivity and autism spectrum disorders [ 38 , 39 ], while co-exposure to Mn and Pb has been shown to exacerbate neurological impairment in children, particularly during the formative years [ 40 ]. Therefore, development of strategies for the effective remediation of mine waste (e.g., contaminant immobilization) need to focus not only on As, but also extend to co-contaminant stabilization, which often shows antagonistic effects with As immobilization outcomes [ 64 ].…”

“…Limited studies have investigated human health exposure to As and co-contaminants in gold-mining impacted wastes via in vitro bioaccessibility assay (IVBA: elemental dissolution using simulated gastrointestinal solutions) and/or relative bioavailability assays (RBA: elemental absorption into systemic circulation relative to absorption from a water-soluble form) [ 25 , 26 ]. Variability in IVBA and RBA of potentially toxic co-contaminants among different waste materials and factors contributing towards this variation remains an important knowledge gap for contaminated soil exposure assessment.…”

Lead in paint-contaminated residential soils with varying physicochemical properties from three large US cities: assessment of geochemical forms and recommendations on amendments for immobilization

“…Although total lead concentration in soil is an important parameter from the regulatory standpoint, various other soil properties play a significant role in determining what fraction of the lead can be considered bioavailable (Ruby et al, 1993;Saminathan et al, 2010;Kastury et al, 2023). The distribution of lead in the geochemical fractions of the residential soils collected from San Antonio, Baltimore, and Detroit are presented in Figure 2.…”