Phytoextraction of mercury-contaminated soils using legumes

Nadine Sommer is a PhD Student at the University of Hohenheim in Stuttgart, Germany. Her research focuses on the identification of mercury (Hg) tolerant plant species that are able to remediate soil by accumulating this heavy metal in their plant biomass. In Ghana, many soils are heavily contaminated with mercury, which is widely used in the amalgamation process of mining gold. Phytoremediation depends on the ion-accumulation capacity of plants. Hyperaccumulator plants can absorb high metal concentrations without visible or physiological symptoms. Until now, no Hg-hyperaccumulator has been reported. For this research, the indigenous legumes Acacia mangium, Leucaena leucocephala, Mimosa Pudica and Senna siamea and the crucifers Moringa oleifera and Brassica juncea were chosen. Brassica juncea was selected as reference plant because it is well-studied and is a known Hg-accumulator. To evaluate the physiological reactions of the experimental plants to mercury exposure, carbon assimilation and biomass production of the plants were measured. The experiment was conducted in containers in a greenhouse. Mercury (10 mg kg-1) was applied as mercury chloride (HgCl2) when plants were about 10 weeks old. Sixteen days after mercury exposure, plants were harvested, and mercury concentration was measured in the above ground biomass. The results showed no significant influence of the mercury concentration on the examined species under the tested conditions. Neither biomass production nor assimilation rate was significantly affected by the mercury treatment. Each of the examined plant species accumulated mercury in their above ground biomass with particularly high values found in shoots (46.45 mg kg-1) and leaves (46.45 mg kg-1) of S. siamea followed by leaves (42.2 mg kg-1) and shoots (28.85 mg kg-1) of A. mangium. Because these two plant species accumulated these high concentrations of mercury without observed symptoms, they may be candidates for phytoremediation of Hg contaminated soils in Ghana.

Nadine Sommer won the ISHS Prof. Jens Wünsche Young Minds Award for the best oral presentation at the IV International Symposium on Horticulture in Europe (SHE2021), which was held virtually in Germany in March 2021.

Nadine Sommer, University of Hohenheim, Dept. of Crop Physiology of Specialty Crops, Emil-Wolff-Str. 23, 70599 Stuttgart, Germany, e-mail: nadine.sommer@uni-hohenheim.de

The article is available in Chronica Horticulturae