Phytostabilization and Retirement of Mercury from Wet Ecosystems

DESCRIPTION (provided by applicant): Because environmental mercury poses significant challenges to global public health, reducing mercury levels in air, soil, and water is an international priority. Widespread distribution of mercury (Hg) by the atmosphere makes current methods of addressing Hg contamination, such as excavation and replacement of soil, too expensive to be practical given the typically large scale of remediation activity required. This Phase I SBIR proposal seeks to develop an innovative, low-cost method of extracting Hg from wet ecosystems using a recently-identified Hg-hyperaccumulating plant species. The accumulated mercury readily binds with reduced sulfur in the plant to form HgS, an extremely refractory (highly stable) chemical form that effectively retires the mercury from its global cycle. This process utilizes sulfur (S), a nutritionally essential trace element that is naturally accumulated by plants from soils to render the accumulated mercury biologically inactive. Because the accumulated mercury is trapped in an insoluble, non-bioavailable form, the mercury stored in the plant may then be allowed to remain on-site, thereby eliminating the need for harvest and disposal, reducing the burden on hazardous waste landfills. Following the Phase I demonstration of high plant accumulation of mercury, in planta conversion of environmental mercury to HgS, and decreased bioavailability as assessed in an insect feeding study, Phase II tasks will explore methods of increasing Hg uptake, assess speciation of sulfur from the rhizosphere through the plant, assess the mercury phytoextraction performance of the Hg- hyperaccumulator at two field demonstration sites, and conduct in situ ecological risk studies at each of these sites to confirm the lower risk to ecological receptors of plants storing its accumulated mercury as HgS. The end result of the project will be to establish the foundation for a low-cost, solar powered method of removing and stabilizing mercury over large areas of soil and large volumes of water. PUBLIC HEALTH RELEVANCE: This NIH Phase I SBIR proposal seeks to retire mercury from the environment by inducing the formation of insoluble mercury sulfide (HgS) in a recently identified Hg-accumulating plant species. If successful, large areas of soil contaminated with mercury can be remediated.