Masayuki Sakakibara 1 Yuko Ohmori 1,2 Nguyen Thi Hoang Ha 1 Sakae Sano 3 Koichiro Sera 4 1 Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan 2 Taisei Kiso Sekkei Co., Ltd., Tokyo, Japan 3 Faculty of Education, Ehime University, Matsuyama, Japan 4 Cyclotron Center, Iwate Medical University, Takizawa-mura, Japan Research Article Phytoremediation of heavy metal-contaminated water and sediment by Eleocharis acicularis Phytoremediation is an environmental remediation technique that takes advantage of plant physiology and metabolism. The unique property of heavy metal hyperaccumu- lation by the macrophyte Eleocharis acicularis is of great significance in the phytoreme- diation of water and sediments contaminated by heavy metals at mine sites. In this study, a field cultivation experiment was performed to examine the applicability of E. acicularis to the remediation of water contaminated by heavy metals. The highest concentrations of heavy metals in the shoots of E. acicularis were 20 200 mg Cu/kg, 14 200 mg Zn/kg, 1740 mg As/kg, 894 mg Pb/kg, and 239 mg Cd/kg. The concentrations of Cu, Zn, As, Cd, and Pb in the shoots correlate with their concentrations in the soil in a log-linear fashion. The bioconcentration factor for these elements decreases log-linearly with increasing concentration in the soil. The results indicate the ability of E. acicularis to hyperaccumulate Cu, Zn, As, and Cd under natural conditions, making it a good candidate species for the phytoremediation of water contaminated by heavy metals. Keywords: Abandoned mine; Eleocharis acicularis; Field cultivation experiment; Heavy metals; Phytoremediation Received: November 16, 2010; revised: January 14, 2011; accepted: February 16, 2011 DOI: 10.1002/clen.201000488 1 Introduction Environmental contamination is one of the most important factors responsible for degradation of the surface environment on earth. Heavy metals play a dominant role in this destruction. The mining of precious metals, coal, and other commodities forms an important part of the economy in many countries. Mining activities affect human health via the contamination of water, depending on the method of extraction. Mining also harms the wider environment, such as beach erosion resulting from sand mining, and water con- tamination may have longer-term effects such as reduced biodiver- sity and declining fish populations. Heavy metals released into the environment contribute to a variety of toxic effects on living organisms as they pass through the food chain. Heavy metals and metalloids (e.g., Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb) are important environmental pollutants, particu- larly in areas under high anthropogenic pressure. Many of these elements are highly toxic in both elemental and soluble salt forms. Their presence in the atmosphere, soil, and water, even in trace amounts, can cause serious health problems for organisms [1]. In particular, the bioaccumulation of heavy metals in the food chain can be highly dangerous to human health. The most common route of human exposure to heavy metals is through ingestion of food and water sources [2]. Soils and water that pose a contamination risk have convention- ally been treated by physical/chemical means such as water shield- ing, dumping in a landfill, or neutral sedimentation. In fact, new physical/chemical treatment technologies continue to be proposed [3]. Nevertheless, the large quantity of existing waste soil and water requires semi-permanent disposal and control measures, especially when considering drainage from abandoned mines. Phytoremediation is a technology that involves the use of plants to remove pollutants from the environment. Besides being an eco- nomical, energy-efficient, and environmentally friendly method, phytoremediation can be applied to large areas and is useful for treating a wide variety of contaminants (metals, radionuclides, and organic substances) and growth media (soil, sludge, sediment, and water). Previous studies have attempted to advance this technology from laboratory and field trials [4] to molecular mechanisms [5, 6]. Plant species that are natural hyperaccumulators of elements can be effective in the phytoextraction of particular elements from contaminated or mineralized soils [7–11]. It may be possible to use aquatic macrophytes to extract heavy metals from freshwater environments. Such macrophytes have been shown to accumulate trace elements by absorption [12–26]. However, many studies have examined concepts for phytoextraction that we believe are not useful for contaminated or mineralized soils. These methods are inappropriate because of metal leaching by addition of chelating agents, or are impractical because of the choice of plants with no practical ability to selectively extract unusually high levels of metals from natural soil, or from mixtures of soil elements, in contrast to the abilities of true hyperaccumulator species [27]. The aquatic macrophyte Eleocharis acicularis, which belongs to the Cyperaceae family, was reported to be a hyperaccumulator of Cu in a pot experiment within a greenhouse [19, 20], a hyperaccumulator of In, Ag, Cd, and Pb in a laboratory experiment [26], and a hyperaccumulator of Pb in a field experiment [23], and is a candidate Correspondence: M. Sakakibara, Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan E-mail: sakakiba@sci.ehime-u.ac.jp Clean – Soil, Air, Water 2011, 39 (8), 735–741 735 ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com