Accumulation of mercury in selected plant species grown in soils contaminated with different mercury compounds
- Institute for Clean Energy Technology (ICET), Mississippi State University, 205 Research Blvd, Starkville, MS 39759 (United States)
The objective of our research is to screen and search for suitable plant species for phyto-remediation of mercury-contaminated soil. Currently our effort is specifically focused on mercury removal from the U.S. Department of Energy (DOE) sites, where mercury contamination is a major concern. In order to cost effectively implement mercury remediation efforts, it is necessary now to obtain an improved understanding of biological means of removing mercury and mercury compounds.. Phyto-remediation is a technology that uses various plants to degrade, extract, contain, or immobilize contaminants from soil and water. In particular, phyto-extraction is the uptake of contaminants by plant roots and translocation within the plants to shoots or leaves. Contaminants are generally removed by harvesting the plants. We have investigated phyto-extraction of mercury from contaminated soil by using some of the known metal-accumulating plants since no natural plant species with mercury hyper-accumulating properties has yet been identified. Different natural plant species have been studied for mercury uptake, accumulation, toxicity and overall mercury removal efficiency. Various mercury compounds, such as HgS, HgCl{sub 2}, and Hg(NO{sub 3}){sub 2}, were used as contaminant sources. Different types of soil were examined and chosen for phyto-remediation experiments. We have applied microscopy and diffuse reflectance spectrometry as well as conventional analytical chemistry to monitor the phyto-remediation processes of mercury uptake, translocation and accumulation, and the physiological impact of mercury contaminants on selected plant species. Our results indicate that certain plant species, such as beard grass (Polypogon monospeliensis), accumulated a very limited amount of mercury in the shoots (<65 mg/kg), even though root mercury accumulation is significant (maximum 2298 mg/kg). Consequently, this plant species may not be suitable for mercury phyto-remediation. Other plant species, such as Indian mustard (Brassica juncea), a well-studied metal accumulator, exhibited severe chlorosis symptoms during some experiments. Among all the plant species studied, Chinese brake fern (Pteris vittata) accumulated significant amount of mercury in both roots and shoots and hence may be considered as a potential candidate for mercury phyto-extraction. During one experiment, Chinese brake ferns accumulated 540 mg/kg and 1469 mg/kg in shoots after 18 days of growing in soils treated with 500 parts-per-million (ppm) and 1000 ppm HgCl{sub 2} powder, respectively; no visual stress symptoms were observed. We also studied mercury phyto-remediation using aged soils that contained HgS, HgCl{sub 2}, or Hg(NO{sub 3}){sub 2}. We have found that up to hundreds of ppm mercury can be accumulated in the roots of Indian mustard plants grown with soil contaminated by mercury sulfide; HgS is assumed to be the most stable and also the predominant mercury form in flood plain soils. We have also started to investigate different mercury uptake mechanisms, such as root uptake of soil contaminant and foliar mercury accumulation from ambient air. We have observed mercury translocation from roots to shoot for Chinese fern and two Indian mustard varieties. (authors)
- Research Organization:
- American Society of Mechanical Engineers (ASME), Three Park Avenue, New York, NY 10016-5990 (United States); Technological Institute of the Royal Flemish Society of Engineers (TI-K VIV), Het Ingenieurshuis, Desguinlei 214, 2018 Antwerp (Belgium); Belgian Nuclear Society (BNS) - ASBL-VZW, c/o SCK-CEN, Avenue Hermann Debrouxlaan, 40 - B-1160 Brussels (Belgium)
- OSTI ID:
- 21156325
- Resource Relation:
- Conference: ICEM'07: 11. International Conference on Environmental Remediation and Radioactive Waste Management, Bruges (Belgium), 2-6 Sep 2007; Other Information: Country of input: France; 22 refs.; Proceedings may be ordered from ASME Order Department, 22 Law Drive, P.O. Box 2300, Fairfield, NJ 07007-2300 (United States)
- Country of Publication:
- United States
- Language:
- English
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