Capability of Selected Crop Plants for Shoot Mercury Accumulation from Polluted Soils: Phytoremediation Perspectives

High-biomass crops can be considered as an alternative to hyperaccumulator plants to phytoremediate soils contaminated by heavy metals. In order to assess their practical capability for the absorption and accumulation of Hg in shoots, barley, white lupine, lentil, and chickpea were tested in pot experiments using several growth substrates. In the first experimental series, plants were grown in a mixture of vermiculite and perlite spiked with 8.35 μg g–1 d.w. of soluble Hg. The mercury concentration of the plants' aerial tissues ranged from 1.51 to 5.13 μg g–1 d.w. with lentil and lupine showing the highest values. In a second experiment carried out using a Hg-polluted soil (32.16 μg g–1 d.w.) collected from a historical mining area (Almadén, Spain), the crop plants tested only reached shoot Hg concentration up to 1.13 μg g–1 d.w. In the third experimental series, the Almadén soil was spiked with 1 μg g–1 d.w. of soluble Hg; as a result, mercury concentrations in the plant shoots increased approximately 6 times for lupine, 5 times for chickpea, and 3.5 times for barley and lentil, with respect to those obtained with the original soil without Hg added. This marked difference was attributed to the low availability of Hg in the original Almadén soil and its subsequent increase in the Hg-spiked soil. The low mercury accumulation yields obtained for all plants do not make a successful decontamination of the Almadén soils possible by phytoremediation using crop plants. However, since the crops tested can effectively decrease the plant-available Hg level in this soil, their use could, to some extent, reduce the environmental risk of Hg pollution in the area.