Clean 2009, 37 (3), 203 – 208 N. T. Hoang Ha et al. 203 Nguyen Thi Hoang Ha 1 Masayuki Sakakibara 1 Sakae Sano 1 Rie S. Hori 1 Koichiro Sera 2 1 Graduate School of Science and Engineering, Ehime University, Ehime, Japan. 2 Cyclotron Research Center, Iwate Medical University, Iwate, Japan. Research Article The Potential of Eleocharis acicularis for Phytoremediation: Case Study at an Abandoned Mine Site Phytoremediation, a plant-based and cost-effective technology for the cleanup of con- taminated soil and water, is receiving increasing attention. In this study, the aquatic macrophyte Eleocharis acicularis was examined for its ability to take up multiple heavy metals and its potential application for phytoremediation at an abandoned mining area in Hokkaido, Japan. Elemental concentrations were measured in samples of E. acicularis, water, and soil collected from areas of mine tailing and drainage. The results reveal that Pb, Fe, Cr, Cu, Ni, and Mn accumulation in the plants increased over the course of the experiment, exceeding their initial concentrations by factors of 930, 430, 60, 25, 10, and 6, respectively. The highest concentrations of Fe, Pb, Zn, Mn, Cr, Cu, and Ni within the plants were 59500, 1120, 964, 388, 265, 235, and 47.4 mg/kg dry wt., respectively, for plants growing in mine drainage after 11 months of the experiment. These results indicate that E. acicularis is a hyperaccumulator of Pb. We also found high Si concentrations in E. acicularis (2.08%). It is likely that heavy metals exist in opal-A within cells of the plant. The bioconcentration factors (BCF: ratio of metal concentration in the plant shoots to that in the soil) obtained for Cr, Cu, Zn, Ni, Mn, and Pb were 3.27, 1.65, 1.29, 1.26, 1.11, and 0.82, respectively. The existence of heavy metals as sulphides is thought to have restricted the metal-uptake efficiency of E. acicularis at the mine site. The results of this study indicate that E. acicularis shows great potential in the phytoremediation of mine tailing and drainage rich in heavy metals. Keywords: Eleocharis acicularis; Heavy Metals; Hyperaccumulator; Mine Site; Phytoremediation; Received: January 17, 2009; accepted: February 23, 2009 DOI: 10.1002/clen.200900009 1 Introduction Mining, urban sewage, smelters, tanneries, and the textile and chemical industries are known to be sources of environmental con- tamination by heavy metals [1, 2]. Waste materials containing metal-rich sulphides pose a risk to the health of the natural environ- ment [3, 4]. Indeed, the contamination of soil, groundwater, and sur- face waters by heavy metals is one of the most serious problems encountered near abandoned mine sites [5]. Heavy metals, being persistent in nature, tend to accumulate in various components of the environment. The remediation of heavy metals must involve either the physical removal of contaminants from the system or conversion to a biologically inert form [6]. Various technologies have been investigated for the cleanup of contaminated water and soil, including the physical removal of soils from contaminated sites (later to be used as landfill or inciner- ated) and in situ stabilization by chemical treatment; however, these remediation technologies are generally costly, generate secon- dary waste, and result in significant additional damage to the envi- ronment. An interesting alternative approach to this problem is phytoremediation, a plant-based and cost-effective technology for site cleanup that does not necessarily disrupt the established soil profile and soil functioning. Phytoremediation has become a promising technology with the discovery of hyperaccumulators: plants that are able to tolerate, uptake, and accumulate high levels of certain heavy metals that are toxic to most organisms [7]. Hyperaccumulators are defined as plants with leaves able to accumulate at least 100 mg/kg of Cd; 1000 mg/kg of As, Cu, Pb, Ni, Co, Se, or Cr; or 10,000 mg/kg of Mn and Zn (dry wt.) when grown in a metal-rich environment [8 – 10]. Of more than 400 reported hyperaccumulating plants, different strains of the Brassica, Alyssum, Arabidopis, and Petrisis species are the most widely studied [7]. The most extensively studied hyperaccumulators include Thlaspi sp., Arabidpsis sp., and Sedum alfredii sp. [11]. Thlaspi sp. are known to hyperaccumulate more than one metal; i. e., T. Caerules- cens accumulates Cd, Ni, Pb, and Zn; T. Goesingense and T. ochroleucum accumulate Ni and Zn; and T. rotundifolium accumulates Ni, Pb, and Zn [12]. Correspondence: N. T. H. Ha, Bunkyo-cho 2-5, Matsuyama, Ehime 790- 8577, Japan. E-mail: nguyen_ha@sci.ehime-u.ac.jp Abbreviations: BCF, Bioconcentration factor; TF, translocation factor; TOC, Total organic carbon i 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com