Phytoremediation of Engineered Nanoparticles Using Aquatic Plants: Mechanisms and Practical Feasibility

Nanoparticles are defined as those entities having at least one dimension less than 100 nanometers. So-called engineered nanoparticles (ENPs) play important roles in a variety of applications including optics, electronics, pharmaceuticals, and personal care products. Laboratory and field measurements and mathematical models indicate that engineered nanoparticles escape to the environment during manufacture, use, and during sanitary sewer overflows. The majority of released ENPs eventually enter freshwater environments. Aquatic plants represent the base of the aquatic food web; some have been documented to flourish in the presence of significant water pollution. This research shows the feasibility of using green plants for treatment of nanoparticle-affected aquatic ecosystems. Laboratory-scale constructed wetlands were established and grown with cattails (Typha latifolia) and/or sedge (Carex camosa) in a growth chamber. The constructed wetlands were doped with selected nanoparticles including silver, titanium dioxide, zinc oxide, and others at varying rates. Plants were incubated with the ENPs for a total of 15 weeks. At weeks 1, 2, 5, 10 and 15, tissue was removed from actively growing plants, chemically digested, and analyzed for the content of nanoparticles. Analysis involved transmission electron microscopy and inductively coupled plasma-AES. In addition, plant health was assessed by measuring activities of plant enzymes nitrate reductase, and catalase. Chlorophyll content were also determined at each sampling date. Attempts were made to photograph nanoparticles remaining in water using scanning electron microscopy. This step was carried out to assess whether particles agglomerate (cluster) over time. The findings of the proposed study can provide useful data regarding the ability of common aquatic plants to remediate nanoparticle-contaminated aquatic ecosystems.