Determination of mercury in vegetal tissues by microPIXE: Application to the study of hyperaccumulation by Spirodela intermedia (Lemnaceae)

Abstract

Background and aims: Aqueous mercury (II), Hg2+, is still nowadays a hazardous pollutant with a large dispersion. Phytoremediation strategies are an environmental friendly and low-cost alternative. In order to improve these processes, Spirodela intermedia, an autochthonous floating macrophyte, was used to remove Hg2+ from mineral water under laboratory conditions, studying the in vivo distribution of mercury and other elements by nuclear microprobe scanning mapping.

M&M: Exposures (1 and 10 mg.L-1 Hg2+ concentrations) were performed during at least 2 weeks. All the parameters from the bioremediation process as uptake rate, bioconcentration factors (BCFs) of mercury in roots and leaves and translocation factors (TFs), were achieved from microPIXE quantifications at Buenos Aires Tandar accelerator.

Results: For 1 and 10 mg.L-1 concentrations, S. intermedia can be considered as a hyperaccumulator. The highest BCFs (> 1000 in roots and >were measured, indicating that Hg2+ translocation is not taking place. High resolution spatial 2D maps of the in vivo distribution for different exposure conditions were established. It was observed that Hg2+ distribution in leaves is more heterogeneous than in roots. An important finding was the detection of Hg in chlorenchyma where its effects are more toxic. Correlation between mercury and calcium distribution and its relationship with physiological responses to intoxication have been examined.
Conclusions: Phytoremediation of Hg2+ by S. intermedia is a convenient alternative. Since the protocol was performed using a real water, it becomes an advisable tool at higher scale.