Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2004
Publication Date: 6/15/2004
Citation: Huang, J.W., Poynton, C.Y., Elless, M., Kochian, L.V. 2004. Phytofiltration of arsenic from drinking water using an arsenic-hyperaccumulating fern. Environmental Science and Technology. 38:3412-3417. Interpretive Summary: Arsenic (As) contamination of soils and groundwater is becoming a serious environmental problem. Arsenic occurs naturally in the environment, but has also been anthropogenically elevated from the widespread usage of arsenic as a basis for pesticides used in the USA prior to 1968. Arsenic has been found to be contaminating groundwater in parts of the Indian sub-continent, South-East Asia and in the USA, and the US Environmental Protection Agency has recently lowered the Maximum Contaminant Level for drinking water from 50 to 10 ug As L-1. Phytofiltration is a potentially attractive alternative to energy-intensive, high-cost traditional methods for remediation of contaminated groundwater. This new technology employs the use of higher plants capable of accumulating high levels of contaminants in shoots. Following harvesting, the shoot biomass can be disposed of in a final repository after volume reduction (e.g., ashing). There is considerable current interest in As phytoremediation due to the recent discovery of As-hyperaccumulating ferns in the genus, Pteris. In this study, we showed that two different As-hyperaccumulating fern species were extremely effective in removing As (as radiolabeled As) from water. Over a wide range of As concentrations commonly found in groundwater, these ferns were able to rapidly lower the As concentration below the new drinking water limit of 10 ug L-1. This was accomplished due to the unique ability of these fern species to absorb As from water and rapidly translocate it and store it in the above-ground biomass. Our results demonstrate that this arsenic-phytofiltration technique may provide the basis for a solar-powered hydroponic technique that enables small-scale cleanup of arsenic-contaminated drinking water.
Technical Abstract: Arsenic contamination of drinking water poses serious health risks to millions of people worldwide and the current technologies used to clean arsenic-contaminated water are quite costly and generate large volumes of toxic waste. In this study, we investigated the potential of using recently identified arsenic-hyperaccumulating ferns to remove arsenic from drinking water. Two arsenic-hyperaccumulating fern species (Pteris vittata and Pteris cretica cv. Mayii) and a non-accumulating fern species (Nephrolepis exaltata) were suspended in water containing 73As-labeled arsenic with initial arsenic concentrations ranging from 20 to 500 ug L-1. At an initial water arsenic concentration of 200 ug L-1, P. vittata reduced the arsenic concentration by 98.6% to 2.8 ug L-1 in 24 h. When the initial water arsenic was 20 ug L-1, P. vittata reduced the arsenic concentration to 7.2 ug L-1 in 6 h, and to 0.4 ug L-1 in 24 h. At similar plant ages, both P. vittata and P. cretica had similar arsenic phytofiltration efficiency and were able to rapidly remove arsenic from water to achieve arsenic levels below the new drinking water limit of 10 ug L-1. However, N. exaltata failed to reduce water arsenic to achieve the limit under the same experimental conditions. The significantly higher efficiency of arsenic phytofiltration by arsenic-hyperaccumulating fern species is associated with their ability to rapidly translocate absorbed arsenic from roots to shoots. The non-accumulating fern N. exaltata was unable to translocate the absorbed arsenic to the shoots. Our results demonstrate that the arsenic-phytofiltration technique may provide the basis for a solar-powered hydroponic technique that enables small-scale cleanup of arsenic-contaminated drinking water.