Linking oral bioaccessibility and solid phase distribution of potentially toxic elements in extractive waste and soil from an abandoned mine site: Case study in Campello Monti, NW Italy

Abstract

Mining activities have led to the introduction of high levels of potentially toxic elements (PTE) concentrations in soils. This has attracted governmental and public attention due to their nonbiodegradable nature and hazards posed to human health and the environment. However, total concentrations of PTE are poor indicators of actual risk hazard to human health and can lead to overestimation of risk. In this study, oral bioaccessibility, the fraction available for absorption via oral ingestion, was used to refine human health risk assessment at an abandoned mine site from Campello Monti, northwest Italy. The solid phase distribution was performed to characterise the distribution and the behaviour of PTE within the extractive waste streams and impacted soil nearby. Mineralogical information was obtained from micro-XRF and SEM analysis used to identify elemental distibution maps. The results showed that the total concentrations of PTE were high, up to 7400 mg/kg for Ni due to the presence of parent material, however, only 11% was bioaccessible. Detailed analysis of the bioaccessible fraction (BAF) showed that As, Cu and Ni varied from 7 to 22%, 14 to 47%, 5 to 21%, respectively. The variation can be attributed to the difference in pH, organic matter content and mineralogical composition of the samples. The non-specific sequential extraction also showed that the non-mobile forms of the PTE were associated with the clay and Fe oxide components of the enviromental matrices. The present study demonstrates how bioaccessibility, solid phase distribution and mineralogical analysis can help decision making and inform the risk assessment of abandoned mine sites.

Risk assessment of Ni, Cr, and Si release from alkaline minerals during enhanced weathering

“…Hence, excessive use of alkaline minerals can be associated with these possible negative effects. The release of metals contained in the mineral composition during the weathering (e.g., Ni, Mn, Cr) may pose an environmental risk (Mehta et al 2019). For example, the dissolution of olivine is associated with Ni releases and plant uptake (ten Berge et al 2012).…”

Arsenic in Soils Affected by Mining: Microscopic Studies vs. Sequential Chemical Extraction

“…There are also some previous works [6][7][8][9][10][11][12] in which the results from sequential extraction are combined, generally in a wise way, with studies through conventional techniques in mineralogy: µ-X 2 of 13 ray diffraction, scanning, and transmission electron microscopy, electron probe microanalysis, etc. ; these investigations are in all cases carried out in relation to a specific case study (usually, historic metal mines).…”

Bioaccessibility of metals in soils surrounding two dismissed mining sites in Northern Italy

“…by the BCR protocol, Rauret et al 2000) are used to describe the status of toxic metals in a contaminated soil. However, these data provide only limited information on the metal mobility and may overestimate the exposure, thereby influencing risk assessment outcome and remediation choices (Bakircioglu et al 2011;Mehta et al 2019;Mehta et al 2020b;Reis et al 2014;Ruby et al 1999). Not all metal species are equally mobile and absorbed by organisms, as the solubility largely depends on the chemical species and the size of the soil particles to which the elements are associated (Pascaud et al 2014).…”