Speciation of mercury in soil and sediment by selective solvent and acid extraction

Abstract

In order to characterize the mercury hazard in soil, a sequential extraction scheme has been developed to classify mercury species based on their environmental mobility and/or toxicity for either routine lab analysis or on-site screening purposes. The alkyl mercury species and soluble inorganic species that contribute to the major portion of potential mercury toxicity in the soil are extracted by an acidic ethanol solution (2% HCl+10% ethanol solution) from soil matrices as "mobile and toxic" species. A High-Performance Liquid Chromatography (HPLC) system coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) detection has been developed to further resolve the species information into soluble inorganic species (Hg(2+)), methylmercury(II) (MeHg(+)) and ethylmercury(II) (EtHg(+)) species. Alternatively, these species can be separated into "soluble inorganic mercury" and "alkyl mercury" sub-categories by Solid-Phase Extraction (SPE). A custom Sulfydryl Cotton Fiber (SCF) material is used as the solid phase medium. Optimization of the SCF SPE technique is discussed. Combined with a direct mercury analyzer (DMA-80), the SCF SPE technique is a promising candidate for on-site screening purposes. Following the ethanol extraction, the inorganic mercury species remaining in soil are further divided into "semi-mobile" and "non-mobile" sub-categories by sequential acid extractions. The "semi-mobile" mercury species include mainly elemental mercury (Hg) and mercury-metal amalgams. The non-mobile mercury species mainly include mercuric sulfide (HgS) and mercurous chloride (Hg(2)Cl(2)).

Extractability and mobility of mercury from agricultural soils surrounding industrial and mining contaminated areas

“…As observed by the same authors, alkyl and inorganic soluble mercury species contribute to the major portion of potential mercury toxicity in soil (Han et al, 2003). On the other hand, chemically stable species, such as mercuric sulfide (HgS) are considerably less mobile, and, therefore, less toxic (Han et al, 2003).…”

“…However, the speciation and the way the different species interact with the soil matrix cause changes in solubility, toxicity and bioavailability of the metal (Biester et al, 2002). Han et al (2003) highlighted the high mobility and toxicity of alkyl species, such as methylmercury (MeHg + ) and ethylmercury(II) (EtHg + ), and the high solubility and mobility of soluble inorganic species, such as mercuric chloride (HgCl 2 ), in comparison with other inorganic mercury species. As observed by the same authors, alkyl and inorganic soluble mercury species contribute to the major portion of potential mercury toxicity in soil (Han et al, 2003).…”

“…Han et al (2003) highlighted the high mobility and toxicity of alkyl species, such as methylmercury (MeHg + ) and ethylmercury(II) (EtHg + ), and the high solubility and mobility of soluble inorganic species, such as mercuric chloride (HgCl 2 ), in comparison with other inorganic mercury species. As observed by the same authors, alkyl and inorganic soluble mercury species contribute to the major portion of potential mercury toxicity in soil (Han et al, 2003). On the other hand, chemically stable species, such as mercuric sulfide (HgS) are considerably less mobile, and, therefore, less toxic (Han et al, 2003).…”

“…Knowledge of the chemical forms of mercury in soil can be accomplished by the application of sequential extraction methods (Bloom and Preus, 2003;Fernández-Martínez and Rucandio, 2003;Han et al, 2003) and is critical to evaluate its environmental risk. These sequence of extractions are used to subdivide the mercury content of soil samples into several operational defined groups of more or less soluble species (Rubio and Rauret, 1996).…”

Synthesis and characterization of isotopically enriched methylmercury (CH3201Hg+)

“…Most of the published methods for mercury speciation in environmental samples are based on the Westöö procedure 7 (an acid leaching method), solvent extraction, 8 -11 distillation, 8,12,13 or modification of Westöö methodology 14 (alkaline-based leaching) and supercritical fluid extraction. 15 The most widely used separation techniques are: gas chromatography (GC), high-performance liquid chromatography (HPLC) coupled with element-selective detection techniques such as atomic emission spectrometry (AES), atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma mass spectrometry (ICP-MS) or cold vapor AAS (CV-AAS).…”