Accumulation of mercury by the aquatic plant Lemna minor

Abstract

We hypothesized that Lemna minor (Lemnaceae) would sequester mercury occurring at environmentally relevant concentrations in aquatic systems. Lake water was collected from Cedar Lake, Minnesota, USA and added to 18 experimental containers placed in an environmental chamber set to replicate summer growth conditions. Different amounts of mercury (Hg2+) were added to 12 experimental containers, resulting in final aquatic mercury concentrations of 1.7 ng/L Hg (control), 112 ng/L Hg (low Hg treatment), and 270 ng/L Hg (high Hg treatment). Nutrients and two grams of L. minor were added to 700 mL of lake water in each container. Plant mercury concentrations were assayed before and after the 14‐day experiment. Total mercury was determined by cold vapor atomic fluorescent spectrometry with single gold trap amalgamation. Mean plant tissue mercury concentrations were significantly higher in both treatments than in the control containers (p < 0.0001). The concentration of mercury in the plant material was positively correlated with the concentration of the mercury in the water. The ability of L. minor to sequester mercury within its biomass makes it a potential candidate for use in phytoremediation in waters with realistic levels of mercury contamination.