Changes in Hg fractionation in soil induced by willow

Abstract

This study investigated the effect of willow (Salix viminalis · S. schwerinii) on soil characteristics, including changes in Hg fractionation in the soil solid phase, and Hg accumulation and distribution in pot-grown plants cultivated for 32 and 76 days in aged Hg-contaminated soil (30 mg Hg kg )1 DW). Changes in soil pH and organic carbon content as well as in Hg fractionation were monitored in both rhizospheric soil and in soil without plants. Mercury fractionation was performed by a 5-step sequential soil extraction procedure. Organic carbon content increased while pH decreased in the rhizospheric soil. Both chemically defined exchangeable Hg (0.1%) and Hg bound to humic and fulvic acids (1.1%) decreased in the rhizospheric soil, whereas plant accumulation of Hg increased with cultivation time. The sum of the decrease of these two soil Hg fractions after 76 days of cultivation was approximately equal to the amount of Hg accumulated in plants. Furthermore, the major Hg fractions (Hg bound to residual organic matter (53%), sulphides (43%), and the residual fraction (2.5%)) remained stable. Neither whole plant accumulation of Hg from the soil, approximately 0.2% of total Hg in soil after 76 days cultivation, nor the fraction of total plant Hg in the shoots, which accounted for about 3% of the total plant Hg pool regardless of the cultivation time, were high. The overall results suggest that plants might be suitable for phytostabilization of aged Hg-contaminated soil, where root systems trap bioavailable Hg and help to control both leaching of Hg and re-entrainment of Hg-containing particulates from a contaminated site.

Mercury accumulation and resistance to mercury stress in Rumex induratus and Marrubium vulgare grown in perlite

“…Around 7%-17% of the Hg accumulated by plants was stored in shoots, values being 3-to 20-fold higher than found in previous studies dealing with Hg uptake of willow grown in soil and hydroponic cultures (Wang and Greger, 2004;Wang et al, 2005). Marrubium vulgare translocated more Hg to shoots than R. induratus when subjected to the highest Hg doses, while R. induratus accumulated higher amounts of Hg per plant than M. vulgare (Tab.…”

“…1), indicating that this species can accumulate Hg more efficiently than M. vulgare. In the same way, willow plants decreased Hg available in the rhizosphere of contaminated soils (Wang et al, 2005).…”

Nickel bioaccumulation by the chosen plant species

“…When the concentrations of metal in the aboveground parts are lower than in roots, the plant is classified as a heavy metal excluder (Ahmad et al 2007;Boularbah et al 2006;Wang et al 2005). On the other hand, in the indicator plants metal content is approximate to the concentrations in soil or in their growth environment.…”

Soil‐ecological evaluation of willows in a floodplain

“…Very likely, the metal concentrations and mobility in the soils are influenced by the flooding and sedimentation dynamics (see Tab. 1), in situ transformations and uptake by plants (Vervaeke et al, 2004;Wang et al, 2005). According to the HM uptake by the willows (Tab.…”