Mercury and trace element fractionation in Almaden soils by application of different sequential extraction procedures

Abstract

A comparative evaluation of the mercury distribution in a soil sample from Almaden (Spain) has been performed by applying three different sequential extraction procedures, namely, modified BCR (three steps in sequence), Di Giulio-Ryan (four steps in sequence), and a specific SEP developed at CIEMAT (six steps in sequence). There were important differences in the mercury extraction results obtained by the three procedures according to the reagents applied and the sequence of their application. These findings highlight the difficulty of setting a universal SEP to obtain information on metal fractions of different mobility for any soil sample, as well as the requirement for knowledge about the mineralogical and chemical characteristics of the samples. The specific six-step CIEMAT sequential extraction procedure was applied to a soil profile (Ap, Ah, Bt1, and Bt2 horizons). The distribution of mercury and major, minor, and trace elements in the different fractions were determined. The results indicate that mercury is mainly released with 6 M HCl. The strong association of mercury with crystalline iron oxyhydroxides, present in all the horizons of the profile, and/or the solubility of some mercury compounds in such acid can explain this fact. Minor mercury is found in the fraction assigned to oxidizable matter and in the final insoluble residue (cinnabar).

Quantification and fractionation of mercury in soils from the Chatian mercury mining deposit, southwestern China

“…To compare the Hg determined by the BCR protocol with in vivo bioavailable Hg, soil extractant results were usually expressed as a percentage of total Hg content. The average percentage of each Hg fraction extracted from the CMD soils with respect to the corresponding total Hg content, in parentheses, followed the trend: residual (85.77%) [ organiccrystalline iron oxides (12.44%) [ amorphous FeMn oxides (0.93%) C EXC (0.86%), which is in agreement with the findings of Gómez-Ariza et al (2000) and Sánchez et al (2005). This trend suggests that most of the Hg in the CMD soils remains in residual form and inside the soil mineral matrix.…”

“…On the other hand, SEPs have been widely used to study the chemical partitioning, mobility and bioavailability of heavy metals, including Hg in soils and sediments. Numerous SEPs based on the fractionation of heavy metals from soil and sediment samples have been described (Tessier et al 1979;Nirel and Morel 1990;Gómez-Ariza et al 2000;Sánchez et al 2005;Han et al 2006). They use different reagents or extractants that preferentially leach, step-by-step, precipitated, adsorbed or complexed metal, avoiding an attack on the lithogenic residual fraction.…”

Mercury distribution and mobility in contaminated soils from vicinity of waste incineration plant

“…However, there is no universal sequential extraction concerning the individual Hg fraction determination. Several approaches were demonstrated by many authors (Renneberg and Dudas 2001, Sánchez et al 2005, Han et al 2006, Liu et al 2006.…”

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

“…Mercury mobility is defined in terms of the mercury leached in the following three fractions: mobile (M), semi-mobile (SM), and nonmobile (NM) Han et al, 2003), with toxicity decreasing In order to assess the dynamics of mercury within the soil system it is of paramount importance better to understand the relationships between mercury species and soil properties. The fractionation of mercury in soils can be affected by clay minerals, metal oxides, organic matter and pH (Sánchez et al, 2005). Complexes formed by divalent mercury with soluble organic matter, chlorides and hydroxides may contribute to its mobility (Millán et al, 2006;Sánchez et al, 2005).…”

“…The fractionation of mercury in soils can be affected by clay minerals, metal oxides, organic matter and pH (Sánchez et al, 2005). Complexes formed by divalent mercury with soluble organic matter, chlorides and hydroxides may contribute to its mobility (Millán et al, 2006;Sánchez et al, 2005). Organic matter presence in soils can also lead to the formation of mercury complexes and inhibit mercury biomethylation processes (Bloom and Preus, 2003).…”