Insights into mixed contaminants interactions and its implication for heavy metals and metalloids mobility, bioavailability and risk assessment

Abstract

Mobility of heavy metals at contaminated sites is mainly influenced by the soil physicochemical properties and environmental conditions, therefore assessing heavy metals (HMs) and metalloids fractionation can provide insights into their potential risk and the mechanisms that regulate bioavailability. A 12-months mesocosms experiment was setup to investigate the effect of physicochemical factors (pH, moisture, and temperature) and weathering (time) on HMs and metalloids fractionation in three different multi-contaminated soil matrices (low, medium, and high contamination) collected from a soil treatment facility located in the United Kingdom, and two rural contaminated soil samples. The study demonstrates that even though Pb and Zn were found associated with the exchangeable fraction in the soil with the highest contamination (total average Pb 3400 mg/kg, and total average Zn 2100 mg/kg in Soil C), neither the condition applied nor the weathering caused an increase in their mobility. Although it was expected that lower pH (4.5) would favours the dissociation of HMs and metalloids, no significant differences were observed, potentially due to the initial alkaline pH of the genuine-contaminated soil samples. The results show that even though total concentration of Pb, Cu, and Zn exceed the soil standards and guideline values, HMs were predominantly associated with the non-exchangeable fraction, while only 5% were dissolved in the pore water fraction (potentially bioavailable). In addition, the mobility and bioavailability of HMs remained constant over the 12 months monitoring, suggesting that these soils pose negligible risk to the environment.

Predicting bioavailability change of complex chemical mixtures in contaminated soils using visible and near-infrared spectroscopy and random forest regression

“…Extraction, identification, and quantification of total and bioavailable PHC, PAH, and ALK were performed by gas chromatography-mass spectrometry (GC-MS) as described by Cipullo et al . 28 .…”

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

“…Potentially toxic elements (PTE) are associated with the various components in soils and the mineral phases of solid wastes in different ways, and these associations can lead to variation in both mobility and availability (Cipullo et al, 2018). A wide range of soil properties can thus lead to variation in bioaccessibility of PTE such as mineralogy, soil pH, organic matter content, presence of clay, iron oxides alumino-silicates in matrix as reported in other studies (Ruby et al, 1999;Peijenenburg and Jager, 2003;Martin and Ruby, 2004;Basta et al, 2005;Palumbo-Roe and Klinck, 2007;Denys et al, 2009;Reis et al, 2014;Palumbo-Roe et al 2015).…”

Linking bioavailability and toxicity changes of complex chemicals mixture to support decision making for remediation endpoint of contaminated soils

“…A modification of the method reported by Cave et.al (2004) was used for the sequential extraction; approximately 2 g of soil was consecutively extracted each time with 10 mL of solutions with increasing concentrations of nitric acid from (0 to 5 M) and H202 (Cipullo et al, 2018).…”