Phytofiltration of arsenic from drinking water using arsenic-hyperaccumulating ferns

Arsenic contamination of drinking water poses serious health risks to millions of people worldwide. Current technologies used to clean arsenic-contaminated water have significant drawbacks, such as high cost and generation of 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. Hydroponically cultivated, two arsenic-hyperaccumulating fern species (Pteris vittata and Pteris cretica cv. Mayii) and a nonaccumulating fern species (Nephrolepis exaltata) were suspended in water containing As-73-labeled arsenic with initial arsenic concentrations ranging from 20 to 500 mug L-1. The efficiency of arsenic phytofiltration by these fern species was determined by continuously monitoring the depletion of As-73-labeled arsenic concentration in the water. With an initial water arsenic concentration of 200 mug L-1, P. vittata reduced the arsenic concentration by 98.6% to 2.8 mug L-1 in 24 h. When the initial water arsenic was 20 mug L-1, P. vittata reduced the arsenic concentration to 7.2 mug L-1 in 6 h and to 0.4 mug 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 mug 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 nonaccumulating 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.