环境地球化学国家重点实验室知识库

The uptake and transport of mercury (Hg) through vegetation play an important role in the biogeochemical cycling of Hg. However, quantitative information regarding Hg translocation in plants is poorly understood. In the present study, Hg uptake, accumulation, and translocation in 4 crops—rice (Oryza.sativa L.), wheat (Triticum L.), corn (Zea mays L.), and oilseed rape (Brassica campestris L.)—grown in Hoagland solution were investigated using a stable isotope (198Hg) tracing technique. The distribution of 198Hg in root, stem, and leaf after uptake was quantified, and the release of 198Hg into the air from crop leaf was investigated. It was found that the concentration of Hg accumulated in the root, stem, and leaf of rice increased linearly with the spiked 198Hg concentration. The uptake equilibrium constant was estimated to be 2.35 mol Hg/g dry weight in rice root per mol/L Hg remaining in the Hoagland solution. More than 94% of 198Hg uptake was accumulated in the roots for all 4 crops examined. The translocation to stem and leaf was not significant because of the absence of Hg2þ complexes that facilitate Hg transport in plants. The accumulated 198Hg in stem and leaf was not released from the plant at air Hg0 concentration ranging from 0 ng/m3 to 10 ng/m3 . Transfer factor data analysis showed that Hg translocation from stems to leaves was more efficient than that from roots to stems.