Stabilization of fluorine in soil using calcium hydroxide and its potential human health risk

Abstract

This study assessed the stabilization of fluorine (F)-contaminated soil using calcium hydroxide (Ca(OH)2) and the consequent changes in human health risk. The bioavailable F decreased to 3.5%, (i.e., 57.9 ± 1.27 mg/kg in 6% Ca(OH)2-treated soil sample) from 43.0%, (i.e., 711 ± 23.4 mg/kg in control soil sample). This resulted from the conversion of water-soluble F to stable calcium fluoride, which was confirmed by XRD spectrometry. Soil ingestion, inhalation of fugitive dust from soil, and water ingestion were selected as exposure pathways for human health risk assessment. Non-carcinogenic risks of F in soils reduced to less than 1.0 after stabilization, ranging from 4.2 to 0.34 for child and from 3.0 to 0.25 for adult. Contaminated water ingestion owing to the leaching of F from soil to groundwater was considered as a major exposure pathway. The risks through soil ingestion and inhalation of fugitive dust from soil were insignificant both before and after stabilization, although F concentration exceeded the Korean soil regulatory level before stabilization. Our data suggested that substantial risk to human health owing to various potential exposure pathways could be addressed by managing F present in soil.

Bioaccumulation of Fluoride in Plants and Its Microbially Assisted Remediation: A Review of Biological Processes and Technological Performance

“…Guo et al [187] have observed that -OH ions replace the exchangeable fluoride ions in an alkaline environment. Jeong et al [188] analyzed the fluoride stability in soil using calcium hydroxides and reported that the bioavailability of fluoride was reduced after calcium hydroxide treatment. The solubility of fluoride ions significantly depends upon soil pH (<4.9) and increases the organic matter [177], which possibly contaminates the groundwater for coarse-textured soil packing and shallow aquifers.…”