Mercury Speciation in Highly Contaminated Soils from Chlor-Alkali Plants Using Chemical Extractions
- Carmen-Mihaela Neculitaab,
- Gérald J. Zagury *ab and
- Louise Deschênesb
- a Department of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-ville, Montreal, QC, Canada H3C 3A7
b NSERC Industrial Chair in Site Remediation and Management, Chemical Engineering Department, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-ville, Montreal, QC, Canada H3C 3A7
A four-step novel sequential extraction procedure (SEP) was developed to assess Hg fractionation and mobility in three highly contaminated soils from chlor-alkali plants (CAPs). The SEP was validated using a certified reference material (CRM) and pure Hg compounds. Total, volatile, and methyl Hg concentrations were also determined using single extractions. Mercury was separated into four fractions defined as water-soluble (F1), exchangeable (F2) (0.5 M NH4Ac–EDTA and 1 M CaCl2 were tested), organic (F3) (successive extractions with 0.2 M NaOH and CH3COOH 4% [v/v]), and residual (F4) (HNO3 + H2SO4 + HClO4). The soil characterization revealed extremely contaminated (295 ± 18 to 11 500 ± 500 mg Hg kg−1) coarse-grained sandy soils having an alkaline pH (7.9–9.1), high chloride concentrations (5–35 mg kg−1), and very low organic carbon content (0.00–18.2 g kg−1). Methyl Hg concentrations were low (0.2–19.3 μg kg−1) in all soils. Sequential extractions indicated that the majority of the Hg was associated with the residual fraction (F4). In Soils 1 and 3, however, high percentages (88–98%) of the total Hg were present as volatile Hg. Therefore, in these two soils, a high proportion of volatile Hg was present in the residual fraction. The nonresidual fraction (F1 + F2 + F3) was most abundant in Soil 1 (14–42%), suggesting a higher availability of Hg in this soil. The developed and validated SEP was reproducible and efficient for highly contaminated samples. Recovery ranged between 93 and 98% for the CRM and 70 and 130% for the CAP-contaminated soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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